1 Who should have visual acuity testing?

Anyone. Measuring vision is like taking the vital signs of the eye: nothing intelligent can be said without it. Since normal vision requires not only intact ocular function but also integrity of its vascular and neurologic supply, visual acuity is an excellent tool for the evaluation of ophthalmologic complaints. And since it can detect painless loss of vision in one or both eyes, it should be part of the screening exam of all adults (visual loss is in fact painless, except for disorders presenting with a red eye). Note that, in children, vision should be measured early (usually after the third birthday) to allow early detection of amblyopia.

2 What is needed to measure visual acuity?

Snellen chart, pinhole occluder, and pocket-size near-vision test card. All are readily available.

3 What is a Snellen chart?

A standard, wall-mounted eye chart imprinted with lines of black characters (letters, numbers, or illiterate Es), ranging in size from smallest (bottom) to largest (top).

4 Who was Snellen?

Hermann Snellen (1834–1908) was a Dutch ophthalmologist who graduated from (and later taught at) the University of Utrecht. He created his famous chart in 1862 as a first attempt to standardize visual acuity measurements.

5 How is the Snellen chart used?

By asking the patient to cover one eye at a time and then read from a well-illuminated chart at a distance of 20 feet (6   m). Testing starts by convention with the right eye and is carried out with reading or distance glasses. Visual acuity is the smallest line on which the patient can distinguish >50% of all letters. The number of letters missed on the same line should also be recorded, such as 20/20 − 1 or 20/40 − 2.

6 What does 20/20 mean?

That the patient can read at a distance of 20 feet a letter that was indeed designed to be read at 20 feet; conversely, 20/40 means that the patient can distinguish at 20 feet a letter that could normally be read at 40 feet, and so on. The numerator of the visual acuity fraction represents the distance at which the chart is placed, whereas the denominator represents the distance at which the letter could be recognized by a person with normal acuity. The denominator also identifies the smallest line on the chart where the patient is able to read >50% of all letters.

7 Can visual acuity be better than 20/20?

Yes. Although 20/20 is normal, most people without ophthalmic disorders can do better than that. Hence, their vision should be recorded accordingly, as 20/15, 20/12, and so on.

8 What is a pinhole vision?

It is vision through a pinhole occluder. If visual acuity is less than 20/20 (i.e., the patient cannot read the 20/20 line), measurement should be repeated after placing a pinhole occluder over the tested eye. This is a device with a very small opening (pinhole), which admits only axial light rays while eliminating instead all the peripheral rays that blur vision through either refractive errors or imperfections/opacities of the cornea and crystalline (see also strabismus and diplopia). Hence, the occluder improves vision in refractive or ocular media problems, but does nothing for retinal or neurovisual disorders. Once distant visual acuity has been measured in both eyes, near visual acuity should be evaluated, too. This can be done with a modified Snellen chart, such as the Rosenbaum Pocket-Size Visual Screener. Hold the card 14 inches (35   cm) away from the patient’s eyes, one at a time, covering the other with your hand. Reading/distance glasses should be kept on. Visual acuity is the fraction notated at the right of the smallest legible line.

9 How do you measure vision in patients who cannot read any letters on the chart?

By reducing the distance between patient and chart. This should be recorded as the numerator of the new visual acuity measurement (e.g., 5/70), and the fraction then translated into a more conventional recording (e.g., 20/280). If the patient cannot read the largest letters on a Snellen chart at 3 feet, vision may then be measured in terms of counting fingers (the examiner records the distance at which counting is accurate). If even this measurement is not possible, vision may be measured as ability to see hand motions (HM) or a flashlight (light perception [LP]), or finally as no light perception (NLP).

10 How is vision measured in illiterate patients or children?

By using the single “E” chart and asking patients to designate the strokes’ direction.

11 How is vision measured in bedridden patients?

By using the Rosenbaum card, which can be found at any medical supply store.

12 What is the significance of reduced visual acuity?

It may indicate any of the following ocular processes:

13 How can one confirm the cause of reduced visual acuity?

14 What are the refracting problems that can be corrected by glasses?

15 When should you refer a patient with subnormal visual acuity?

16 What are color vision screening plates?

They are pseudoisochromatic tables (i.e., pseudo-similarly colored) that present numbers or figures against a background of colored dots. This color combination is confusing and illegible to a person with abnormal color discrimination.

17 How is color vision tested?

By consecutively presenting color plates to the patient, one eye at a time, and by then recording results as a fraction, with the numerator indicating the number of correct responses and the denominator the number of total plates presented. In testing for unilateral dyschromatopsia, a simpler but still reliable method is to ask the patient to cover the affected eye and look at a red object, such as the cap of a mydriatic solution bottle. Then the patient looks at the same object with the other eye (while the unaffected one is covered) and reports whether the red color appears the same. In dyschromatopsia, the affected eye will see the color red as being gray or washed-out.

18 What is dyschromatopsia?

From the Greek dys (abnormal), chroma (color), opsis (vision), this is an acquired deficiency in color vision, as opposed to congenital color blindness.

19 What causes dyschromatopsia?

Optic nerve diseases or toxic/degenerative processes of the macula.

20 Why is visual field testing important?

Because it may reveal significant neurologic or ocular diseases. Terminology and interpretation, however, are often confusing.

21 Describe the normal anatomy of the visual pathways.

This is quite complex and yet fundamental for the understanding of visual field defects (Fig. 4-1). Our visual world (i.e., visual field) is divided into right and left hemifields. Each eye gets information from both.

Figure 4-1 Neurologic visual pathways, and diseases originating from their interruption.

(From Mihailoff G: Crash Course Nervous System. St. Louis, Mosby, 2005.)

After originating in the photoreceptors of the retina, vision is transmitted via the optic nerve axons. These partially cross at the optic chiasm and then emerge as optic tracts, wrapping around the midbrain to finally reach the lateral geniculate nucleus (LGN), where they stop for synapsis. From the LGN, axons fan out through the deep white matter of the brain (parietal and temporal lobe) as optic radiations, ultimately reaching the primary visual cortex in the occipital lobes. The crucial aspect of this entire pathway is its inversion of images, insofar as the nasal retina of the right eye sees the right half of the world (i.e., the temporal half of the visual field), whereas the temporal retina of the right eye sees the left half of the world (i.e., the nasal half of the visual field). As a result, the right nasal retina and left temporal retina see very much the same aspect of the outside world: the right hemifield (i.e., if you drew a line through the world at your nose, they would see everything to the right of that line).

Because of all these crossings, a prechiasmal lesion will be very much akin to losing one eye (i.e., it will affect only one eye but both hemifields). Conversely, chiasmal lesions will affect parts of both eyes and both hemifields (i.e., inputs from the nasal retinas will be lost, thus causing loss of peripheral vision on both sides). Finally, postchiasmal lesions will affect parts of both eyes, but only one hemifield.

The anatomic distribution of the optic radiations follows a wide three-dimensional arc, which first dives into the temporal lobe (Meyer’s loop), then heads back though the parietal lobe, and finally terminates into the occipital lobe. Lesions involving Meyer’s loop (i.e., temporal lobe) cause loss of vision in the upper visual world, but only in the left hemifield. Lesions involving the parietal portion of the optic radiations cause loss of vision in the lower visual world, but only on one side (the left hemifield in this case). Finally, lesions affecting the occipital (visual) cortex cause loss of vision in one hemifield, but with macular sparing (i.e., notched hemifield). This sparing results from either overlapping blood supply or large cortical representation of the fovea.

22 How do you test visual fields?

By using either a static or a dynamic technique. Diagnostic accuracy for visual field defects is similar, with high specificity but low sensitivity, especially for anterior or chiasmal lesions (see later).

After detecting the field defect, the examiner should then identify whether this defect respects the vertical or horizontal meridian of the visual field (see later).

23 What are visual field defects?

They are abnormalities of peripheral vision, reflecting lesions at various levels of the visual pathways. They are described as hemianopias (from the Greek hemi, half; an, lack of; and opsis, vision) if the loss of vision involves one half of the visual field of each eye; quadrantanopias if it instead involves one fourth of the visual field of each eye.

24 How are visual fields defects classified?

As anterior or posterior:

25 What is the difference between anterior and posterior visual field defects?

26 What are the causes of visual field defects?

It depends on their location:

27 What is the most important step after finding a monocular visual field defect?

To test the visual field of the other eye. Monocular field defects are usually due to problems in the affected eye (prechiasmal), whereas binocular defects are usually caused by intracranial (neurologic) processes, either chiasmal or postchiasmal.

28 What are the other characteristics of prechiasmal (ocular) defects?

They typically affect only one eye, compromise vision, and may have an abnormal pupillary/retinal exam (such as an afferent pupillary defect, cupping or atrophy of the disc, drusen, and retinal findings). In addition, prechiasmal visual defects typically cross the vertical meridian. This is because retinal nerve fibers draining the temporal retina arch across the vertical meridian in order to exit through the optic disc and nerve (which are located on the nasal side of the retina).

29 What are the main types of prechiasmal defects?

(1) “Arcuate defects” of the visual field, shaped indeed like an arch, and caused by small lesions of the nerve fibers, and (2) “altitudinal defects,” typically characterized by a sharp horizontal border in the visual field and caused instead by larger lesions of the nerve fibers.

30 What are severely constricted visual fields? What are their causes?

They also are a form of anterior defect, characterized by a concentric “cut” of the most peripheral vision (in this regard they are exactly the opposite of a central scotoma, which is characterized by loss of central vision with preservation of the peripheral one). Note that both these prechiasmal defects are monocular; typically cross the vertical meridian; and are usually due to advanced glaucoma, retinitis pigmentosa, and other more uncommon conditions (even though they also may be related to malingering.) A central scotoma is instead usually caused by damage to nerve fibers originating in the macula.

31 What are chiasmal defects?

They are bitemporal hemianopias.

32 What is a bitemporal hemianopia?

It is the loss of vision of one half of the visual field of both eyes (from the Greek hemi, half; an, lack of; and opsis, vision), more specifically, the temporal fields of both eyes (bitemporal). This is typical of chiasmal tumors (gliomas and craniopharyngiomas in children, pituitary adenomas in adults).

33 What are postchiasmal defects?

Homonymous hemianopias or quadrantanopias. These typically involve both eyes but preserve vision and pupillary and retinal exam (see below).

34 What is homonymous hemianopia?

A visual defect affecting the same side (homonymous) of visual space in both eyes. For example, if the defect in the left eye involves the temporal region (the left portion of the left eye’s visual field), the defect in the right eye will affect the nasal region (the left portion of the right eye’s visual field). Homonymous hemianopia is typical of retrochiasmal lesions (optic tracts, optic radiations, and especially, the visual cortex).

35 What are the causes of inferior and superior quadrantanopias?

Diseases of either the parietal (causing inferior quadrantanopia) or temporal cortex (causing instead superior quadrantanopia). Still, lesions of the temporal and parietal cortex cause more commonly dense hemianopias. Note that the most common cause of an isolated homonymous hemianopia is a lesion to the occipital cortex, usually an ischemic stroke. In patients with other neurologic findings (hemiparesis, aphasia and, especially, an asymmetric optokinetic nystagmus), the most common cause is a parietal lesion.

36 What is an asymmetric optokinetic nystagmus?

A horizontal nystagmus that can be elicited by having patients look at a vertically striped tape that rapidly moves in front of their eyes, first toward one direction and then toward the other. Amplitude of horizontal nystagmus should be similar in the two directions. If not, it indicates a parietal lobe injury, since this typically reduces the nystagmus amplitude triggered by tape moving toward the same side of the lesion.

37 Why is examination of the pupils important?

Because attention to pupillary shape, size, and response to external stimuli provides extremely valuable clinical information. Figures 4-2 and 4-3 summarize the most common pupil abnormalities.

Figure 4-2 Pupil abnormalities.

(From Liporace J: Crash Course Neurology. St. Louis, Mosby, 2006, Fig. 6.3.)

Figure 4-3 Additional pupil abnormalities.

(From Mihailoff G: Crash Course Nervous System. St. Louis, Mosby, 2005.)

38 What is the size of a normal pupil?

It depends on age. Pupils are larger in children (7   mm of diameter at 10 years of age), but progressively smaller with aging (5   mm at 50, 4   mm at 80). In addition to being important for amateur astronomers and late-evening bird watchers, this pupillary characteristic also may explain why children are “cute,” something cunningly exploited by Japanese cartoonists, who always draw their characters with big eyes and humongous pupils. Big and cute pupils are also nature’s way to prevent us from killing our young, especially when the young are crying, incontinent, and totally dependent. Conversely, crying, incontinent and totally dependent octogenarians have small pupils. Hence they are not cute, and that is why we put them in nursing homes. Italian Renaissance women also were quite aware of this important property of the eye, since they used to dilate their own pupils with atropine (aptly named belladonna [i.e., nice-looking woman]) before going out on dates. This, however, often backfired since loss of accommodation led to embarrassing accidents and, ultimately, to the discontinuation of the practice.

39 How does one examine the pupils?

In a darkened room. Ask the patient to fixate the gaze on something in the distance while you shine a penlight from below to ascertain that the pupils are round and equal.

40 What major features should be identified in the pupil?

(1) Shape, (2) size, and (3) responses to external stimuli. These, in turn, include response to accommodation and light, both direct and consensual. “Direct reaction” is the ipsilateral response to a light stimulus; “consensual reaction,” the contralateral response.

41 What is unique about the light reflex?

It contains crossed pathways, which means that both pupillary sphincters receive the same input from the midbrain.

42 What is anisocoria?

Pupillary asymmetry—from the Greek an (lack of), iso (equal), and core (pupils). Anisocoria reflects asymmetric diseases of either iris of efferent connections (i.e., third nerve or sympathetic nerves). The latter causes different signals to reach the two pupillary sphincters. A flip side to this rule is that anisocoria is absent in afferent disorders (i.e., affecting the optic nerve or retina) because crossed efferent pathways supply both eyes with the same signal.

43 What is accommodation?

A reflex that allows the subject to focus on a near object by activating three effectors: (1) the pupillary sphincters (causing constriction of the pupils); (2) the medial recti muscles (causing convergence of the eyes); and (3) the ciliary bodies (causing accommodation of the lens). It is typically spared in the Argyll-Robertson pupil.

44 What are the most common abnormalities in pupillary shape?

45 What is hippus?

A physiologic and synchronous oscillation in pupillary size. This may occur spontaneously or in response to light shined directly onto the eye. The term derives from the Greek hippos (horse), chosen to convey the up-and-down movements of a galloping horse. Note that hippus is not an afferent pupillary defect (i.e., a Marcus-Gunn pupil).

46 How is the pupillary diameter controlled?

By a dual mechanism: parasympathetic (through the third nerve) for the constrictor muscle, and sympathetic (through the cervical chain) for the dilator. Hence, parasympathetic denervation will cause dilation (mydriasis), whereas sympathetic denervation will cause constriction (miosis).

47 What are the most common causes of anisocoria?

Figure 4-4 Horner’s syndrome, with ptosis and miosis on the left. Note that the left lower lid is higher than the right lower lid. This inverse ptosis is due to interruption of the sympathetic innervation to the analog of Mueller’s muscle in the lower lid.

(From Vander JF, Gault JA: Ophthalmology Secrets. Philadelphia, Hanley & Belfus, 1998.)

48 What is the most common cause of a third-nerve palsy?

Nerve compression against the free edge of the tentorium. This can be due to either a rapidly expanding aneurysm of the posterior communicating artery or herniation of the ipsilateral uncus(Hutchinson’s pupil). The latter typically occurs with a change in mental status, plus ptosis and ophthalmoplegia. Note that the expanding mass responsible for herniation is usually ipsilateral to the mydriasis (and also to the ptosis and ophthalmoplegia, since they all originate in the compression of the ipsilateral third). Ipsilateral is also the hemiplegia, which, however, derives from damage to the contralateral cerebral peduncle.

49 What is a posterior communicating artery aneurysm?

The most common of all cerebral aneurysms. As many as 96% of these patients will have either a partial or complete third-nerve palsy (i.e., mydriasis, ptosis, and ophthalmoplegia); 20–60% will just have ipsilateral mydriasis. This provides an important localizing clue for surgery, which is key for preventing rupture.

50 Who was Hutchinson?

Sir Jonathan Hutchinson was an English surgeon and pathologist (1828–1913) who described his homonymous pupil in 1865. A devout Quaker, Hutchinson became involved with many philanthropic missions, and in fact even planned a career as a medical missionary. Instead, he gained the friendship of Sir James Paget and became one of the most versatile clinicians of 19th-century medicine. Besides being an ophthalmologist, he was also a venereologist, a clinician to the City of London Chest Hospital, and a general surgeon to the London and Metropolitan hospitals. He developed a special interest in congenital syphilis and was said to have seen more than 1 million patients. He published 1200 medical articles, with contributions in congenital syphilis and skin diseases (he also was among the first to describe sarcoidosis in 1877). Although his intellectual attributes were unchallenged, he had his critics, too. One commented: “He was totally devoid of any sense of humour, and like most humourless men, incredibly obstinate in clinging to his opinions long after they had been demonstrated to be untenable.” Another added: “There was nothing scintillating about it, but nonetheless you felt he was speaking out of immense knowledge.” In his private life, Hutchinson had 31 years of happy marriage and many children but kept his family in a country home while spending most of his week in London. He died at 85, choosing as an epitaph: “A Man of Hope and Forward-Looking Mind.”

51 What is the pupillary response to a close-up target?

Constriction, but less than that resulting from a bright light suddenly flashed onto the eye. To test for it, ask the patient to look at a far-away point and then focus rapidly on a much closer object, such as your finger. The pupil should constrict 1–2   mm.

52 What is the pupillary response to light being suddenly directed onto the eye?

Constriction of 2–3   mm. The contralateral pupil will constrict by the same amount, provided there are no abnormalities in the parasympathetic innervation of the sphincter.

53 What are Argyll Robertson (AR) pupils?

Pupils that do not constrict in response to light, but do so when shifting fixation from a distance to a near target—i.e., accommodation. This phenomenon is called “light-near dissociation” and is typical of tertiary (neuro) syphilis. Still, it also can occur in diseases of the dorsal midbrain that present as Parinaud’s syndrome (vertical gaze palsy, lid retraction, and convergence-retraction nystagmus; typical of patients with multiple sclerosis, basilar artery strokes, and pinealomas). Light-near dissociation also may present in traumatic injury to the orbital ciliary ganglion or ciliary nerves, or in viral infections of those structures (Adie’s pupil, see later). It also can occur in diseases of either retina or optic nerve (which, in contrast to other causes of an AR pupil will also impair vision). Nowadays, a light-near dissociation is mostly encountered in diabetes, neurosarcoidosis, or Lyme disease. The location of the lesion that produces AR is unsettled, although most likely is somewhere in the dorsal midbrain (which would spare the nuclei of Edinger-Westphal that are responsible for accommodation).

54 What is “near-light” dissociation?

The opposite of light-near dissociation. It describes pupils that do constrict in response to light, but not in response to accommodation. It used to be typical of von Economo’s encephalitis lethargica, but nowadays reflects mostly an unwillingness of the patient to focus on close objects. Hence, the maneuver should only be tried for absent pupillary light reactions.

55 Who was Argyll Robertson?

Douglas M.C.L. Argyll Robertson (1837–1909) was a Scottish surgeon. An avid golfer who studied in Berlin with Von Graefe, he eventually returned to Scotland, where he founded ophthalmology at the University of Edinburgh, mentored Marcus Gunn, and described his homonymous pupil in 1868.

56 What is Adie’s tonic pupil?

A pupil that, like AR, responds not to direct light, but to near targets. Yet, unlike AR, Adie’s constricts to near vision only very slowly (over seconds), and similarly slowly redilates when fixation is shifted to a distant target. Hence, the term tonic pupil, which indicates its long-lasting constriction. Adie also is dilated at rest and mostly unilateral, whereas AR is instead small and usually bilateral. Moreover, Adie’s may create subjective problems with accommodation and is often oval (because of the segmental impairment of the iris sphincter). Finally, Adie’s constricts in response to diluted pilocarpine (0.125% eye drops), a supersensitivity phenomenon that is absent in the normal eye.

57 What is the significance of Adie’s pupil?

Dubious. Although permanent, Adie’s usually offers no disturbance of vision and is unassociated with other important neurologic abnormalities. It usually reflects a lesion to the ciliary ganglion and postganglionic fibers, with aberrant regeneration toward the eye. Normally, the ciliary ganglion sends 30 times more fibers to the ciliary body (accommodation) than to the iris (light reflex), but after injury the regeneration tends to prioritize the iris. Hence, the preservation in Adie’s of pupillary response during near vision (albeit sluggishly), but its loss to light stimulation.

58 What are the causes of Adie’s pupil?

The most common is idiopathic. Still, various injuries to ciliary ganglion and fibers can cause it, too: orbital trauma, tumors, and viral infections (ophthalmic zoster).

59 Who was Adie?

William J. Adie (1886–1935) was an Australian who studied medicine in Edinburgh and then graduated just in time for World War I. He fought with honor in France, where he even saved his platoon by improvising a gas mask with cloth soaked in urine. Then, thanks to a well-timed measles attack, he also managed to survive the subsequent slaughter of his entire regiment, thus returning to England, where he taught and practiced until his death. His name is linked not only to the description of the homonymous pupil (in 1931) but also to the first description of narcolepsy. Adie was a brilliant teacher, an avid skier, and an amateur ornithologist. He died prematurely at 49 of a myocardial infarction.

60 What is the swinging flashlight test?

A test of response to light used to screen for an afferent pupillary defect. It was introduced by Levatin in 1959 and is carried out by asking the patient to gaze at a fixed target in the distance. A penlight is then shone first in one eye, and then into the other, back and forth, holding it in front of each eye for no more than 1–2 seconds. In normal subjects, as the light swings from one eye to the other, each pupil remains unchanged or constricts very slightly. If one eye has an afferent defect (optic nerve lesion or massive retinal damage), the pupil will dilate as the light strikes it (Marcus Gunn pupil). Note that it is important to keep swinging the light between the two eyes, since lingering on the affected eye may bleach the retina and thus produce a spurious Marcus Gunn. To avoid this, use the mnemonic, one two switch, one two switch to provide an adequate lilt to the swinging.

61 What is a Marcus Gunn (MG) pupil?

The most common abnormal pupillary response, more than all others combined. It is characterized by a normal efferent, but an abnormal afferent optic circuitry. Because the stimulus from the contralateral eye is coming in much stronger than that from the affected eye, shifting the light from the unaffected to the affected eye will release the urge to constrict (since this is only provided by the good eye). Hence, shifting light from the normal to the affected eye will cause the affected pupil to dilate. The relatively reduced input of MG is due to an optic nerve or retinal lesion. In fact, it involves both eyes (the damaged and normal contralateral one), even though it is normally described as Marcus Gunn pupil (or an afferent pupillary defect, APD) only in reference to the eye the light shines on.

62 What is the response of an MG pupil when the light is shone on it first?

It depends. If the light is shone on the affected pupil first (step 1 of the swinging flashlight test), the MG pupil will constrict, albeit poorly. As the light is then swung back and forth, the MG pupil will dilate.

63 What is a common cause of an afferent pupillary defect (MG pupil)?

Any optic neuropathy (i.e., neuritis, ischemic neuropathy, or optic nerve compression by tumor) that causes problems with the afferent pathway. In these patients, the test has a sensitivity of 92–98%, higher than any other test of afferent dysfunction, such as evoked potentials, visual acuity, or funduscopy. A massive and unilateral retinal lesion, like a central retinal artery occlusion, also may cause this phenomenon. Conversely, cataracts do not produce MG, since the ipsilateral retina is still able to receive light. Because afferent lesions spare the light reflex, only the presence of MG will be able to identify them.

64 Who was Marcus Gunn?

Robert Marcus Gunn was a Scottish ophthalmologist and a contemporary of another famous Scot, Robert Louis Stevenson, whom he personally knew and befriended. He was inspired to study ophthalmology by Argyll Robertson and then became highly regarded for his ophthalmoscopic skills. He reported his finding in 1904, even though it was probably already known.

65 What are the pupillary manifestations of diabetes?

Beside evidence of dysautonomic control (small and sluggishly reacting pupils), diabetes may occasionally induce an AR pupil. It also reduces the amplitude of hippus.

66 Summarize the examination of the external eye.

Much of the external exam can be done with penlight and thoughtful observation of orbits, eyelid position, conjunctiva, anterior portion of the globe, and corneal/light reflex.

(1) Tear Film

68 How is Schirmer’s performed?

After anesthetizing the eyes with a topical anesthetic, insert a small strip of filter paper into the fornix (i.e., the recess of the lower lid). Place the strip either medially or laterally, but not in the center of the eyelid. Remove the strip after 5 minutes. Measure in millimeters the wetting produced by the tears. Normal wetting distances are 10 and 15   mm for subjects, respectively, above or below the age of 40. A distance <5   mm is usually diagnostic of decreased tear production, whereas a 5–10   mm distance is suspicious

(2) Eyebrows

(3) Eyelids and Orbit

71 What is an ectropion?

The eversion (i.e., outward rolling) of the lower eyelid, not uncommon in the elderly. This exposes a rim of tarsal conjunctiva to external stimuli, causing keratinization, corneal exposure, and eye irritation.

72 What is an entropion?

The inversion (i.e., inward rolling) of the lower eyelid. This may mechanically irritate the eye through contact with eyelashes. Often due to trachoma, but also to simple aging.

73 What is a sty (hordeolum)?

A focal, acute, and painful inflammation of either hair follicle glands (external hordeolum) or one of the sebaceous meibomian glands in the eyelid inner margin (internal hordeolum). Usually infectious (with Staphylococcus aureus being responsible of >90% of cases), hordeolum presents with the typical findings of redness, swelling, and eyelid tenderness. Given the different location, internal hordeola suppurate on the eyelid’s conjunctival surface, whereas external hordeola exude mostly from the eyelash rim.

74 What is a chalazion?

A painless and slowly enlarging eyelid nodule, due to subacute inflammation of the meibomian glands. This is a sequela of blepharitis, eventually causing glands’ obstruction by secretions, with formation of a lipogranulomatous cyst. Chalazions differ from hordeola insofar as they are slower and painless processes. They may spontaneously disappear, although usually they require treatment—even slower and excision.

75 What is blepharitis?

A diffuse inflammation of the eyelid margin, which becomes swollen, crusted, erythematous, and tender. Due to S. aureus (or S. epidermidis), blepharitis also may have a hypersensitivity component. There is often ciliary cuffing and a dry eye sensation.

76 What is ptosis?

It is the unilateral or bilateral drooping of the upper eyelid (from the Greek term for falling). This is usually due to neurogenic or myogenic causes.

77 What are the causes of ptosis? How can they be differentiated?

The most common are myogenic reasons, such as (1) aging, (2) surgery, (3) trauma, and (4) congenital ptosis. The less common, but more ominous, are instead neurogenic reasons, and include (1) myasthenia gravis, (2) Horner’s syndrome, and (3) third-nerve palsy. Less common reasons usually can be identified by their associated clinical findings, such as ophthalmoplegia and diplopia (third-nerve palsy), myosis (Horner’s syndrome), and weakness (myasthenia). Overall, an isolated ptosis does not need to be referred, but a ptosis with diplopia, myosis, or weakness has to be.

78 What is proptosis?

From the Greek term for falling forward, proptosis (or exophthalmos) is the abnormal protrusion of one or both eyeballs. This, too, may be unilateral or bilateral.

79 What is the most common cause of exophthalmos in adults?

Graves’ ophthalmopathy (Fig. 4-5). The next most common reason is a space-occupying lesion, such as a metastatic or primary tumor (benign or malignant). Unilateral exophthalmos is instead almost always due to a tumor. For other ocular manifestations of Graves’ ophthalmopathy, also see Chapter 8, The Thyroid, questions 70 and 71.

Figure 4-5 Thyroid-related ophthalmopathy with proptosis and lid retraction.

(From Vander JF, Gault JA: Ophthalmology Secrets. Philadelphia, Hanley & Belfus, 1998.)

80 What is the most common cause of unilateral exophthalmos in children?

Orbital cellulitis. Still, the most common space-occupying lesion responsible for unilateral exophthalmos in children is a rhabdomyosarcoma.

81 What is the difference between preseptal and orbital cellulitis?

82 What is a blow-out fracture?

A fracture of the orbital floor (which is also the roof of the maxillary sinus). This may entrap the inferior rectus muscle, thus making the patient unable to fully look up or down and causing diplopia in those gaze positions. Orbital floor fracture also may damage the infraorbital branch of the trigeminus, thus causing numbness on the ipsilateral cheek.

83 What is enophthalmos?

The opposite of exophthalmos (literally, a falling inward). The eye is sunken into the orbit, rather than protruding from it. Enophthalmos may result from a large blow-out fracture.

(4) Extraocular Movements

85 What is diplopia?

It is double vision. Due to ocular misalignment, typically from paralysis of one or more of the external ocular muscles (usually because of lesions of cranial nerves III, IV, or VI, but also myasthenia gravis or extraocular myopathy; see question 89). Note, however, that more than one half of all diplopias actually have no cranial nerve lesions.

86 What are the main forms of diplopia?

Three quarters are binocular (and thus resolve with occlusion of the “good” eye); one quarter is instead monocular and thus causes double vision in one eye that persists after the opposite is covered. Note that binocular diplopias tend to be much more serious than monocular diplopias, since they reflect a true neuromuscular misalignment of the eye. Binocular diplopias can be esotropic (when the involved eye is deviated toward the nose); exotropic (when the involved eye is deviated toward the temple); and hypertropic (when the involved eye is deviated upward). Finally, diplopia can be horizontal (when the two images are side by side) or vertical (when one of the two images is higher than the other).

87 What is heterotropia?

It is strabismus (i.e., a condition characterized by visual axes that are not parallel) (see later).

88 What are the causes of monocular diplopia?

They are either ocular or extraocular.

89 What is the approach to the patient with binocular diplopia?

The first step is to recognize diplopias that are not due to cranial nerve lesions, but instead to eye muscle disease (15% of all binocular diplopias). These include (1) the diplopia of myasthenia gravis (which typically worsens with progression of the day and may be associated with ptosis); (2) the diplopia of thyroid myopathy (which typically occurs with other signs of Graves’ disease, such as proptosis and lid edema–retraction lag); (3) the diplopia of orbital fracture (14% of all binocular diplopias) should be easily recognizable by the history of trauma; and (4) finally, presence of ptosis should suggest third-nerve palsy or myasthenia gravis, whereas presence of other neurologic findings would argue in favor of supranuclear causes (such as internuclear ophthalmoplegia and skew deviation, responsible for 7% of all binocular diplopias). Once these conditions have been eliminated, the physician should identify the weak ocular muscle(s) caused by cranial neuropathy (i.e., third-, fourth-, or sixth-nerve palsy), which is responsible for 40% of all binocular diplopias. Note that a third-nerve palsy can be the presenting manifestation of a posterior communicating artery aneurysm, which has suddenly expanded and is about to rupture (see questions 48 and 49).

90 How can one identify the weak ocular muscle(s)?

By asking the patient to track an object (usually the examiner’s finger) across the eight cardinal directions of gaze: up, down, right, left, left up, right down, right up, left down. One rule that can help interpret this simple maneuver (and narrow down the search of the weak muscle from 12 to two) states that diplopia (and strabismus) will worsen whenever the patient is looking toward the weak muscle. Hence, if the weak muscle is the left lateral rectus, diplopia and strabismus will worsen when the patient looks toward the left (the same will occur if the weak muscle is the right medial rectus).

(5) Nystagmus

92 How do you classify nystagmus?

Based on the direction of eye movement. Hence, nystagmus may be horizontal, vertical, and rotatory. Physiologic nystagmus is instead the quick-and-slow eye movement of travelers (typically train travelers), whose gaze is fixed on rapidly approaching objects, such as telephone poles. It is entirely normal and can be triggered by asking the patient to look at a rapidly rotating drum covered with vertical stripes (optokinetic nystagmus).

93 What is the clinical significance of nystagmus?

Congenital nystagmus often indicates a disorder of vision. Acquired nystagmus indicates instead dysfunction of the brain stem (cerebellum, vestibularis, or oculomotor system). Common causes are multiple sclerosis, tumors, medication toxicity, infections, and neurodegenerative and toxic-metabolic states.

(6) Sclera

95 How much bilirubin is needed to produce scleral icterus?

It depends on the amount of natural light illuminating the patient’s eyes. In bright daylight, one can probably detect icterus for bilirubin levels as low as 1.5–1.7   mg/dL. In artificial light, however, levels >4   mg/dL are necessary. The same is true for other areas of the body normally checked for jaundice, such as the roof of palate or the palm of the hands. Of note, the term “scleral” icterus is histologically inaccurate, and one that found its way into textbooks only during the mid-1940s, thanks to German studies published a decade earlier that had shown strong affinity of bilirubin for elastin. In reality, the sclera per se contains very little elastic tissue. Instead, it is the innermost layer of the conjunctiva (and its contiguous aspect of the sclera, i.e., the episclera) that has elastic fibers. Hence, scleral icterus is conjunctival icterus. As Osler had defined it in all the editions of his book: a yellow “tinting of the skin and conjunctivae.”

96 Does conjunctival icterus look any different in dark-skinned patients?

No. It is important, however, not to interpret as icterus the brownish color normally present in the bulbar conjunctiva of dark-skinned individuals. This is usually the result of sunlight exposure and should not be confused with hyperbilirubinemia. To separate the two, ask the patient to look upward, then inspect the inferior conjunctival recess. This should be entirely white in nonicteric subjects.

(7) Conjunctiva

98 What is a pterygium?

From the Greek pteros (wing), this is an excessive conjunctival growth, more extensive than the pingueculum, but similar in etiology and histology (albeit more vascular). A pterygium probably starts as pingueculum, since they are similarly located over the temporal or nasal aspect of the bulbar conjunctiva. Both may result from long-term exposure to ultraviolet light and thus be more frequent in the Sun Belt. And both may cause mild irritation, dryness, and a foreign body sensation. Yet, if advanced, they can compromise vision, especially if growing into the visual axis and cornea. If removed, they often grow back.

99 What is a subconjunctival hemorrhage?

A well-demarcated hemorrhage in the subconjunctival layer. Although often an impressive sight (and a common cause of red eye, too), a conjunctival hemorrhage remains a rather trivial problem, destined to turn yellow in a few days and eventually resolve. Note that the redness of a subconjunctival hemorrhage is typically confluent, and thus easily distinguishable from other forms of red eye.

100 What causes subconjunctival hemorrhage?

Mostly trauma, but sudden increase in venous pressure (like a coughing spell) can do it, too. Yet many cases remain unexplained, usually reflecting defects in hemostasis or fragility of the vessel wall (from aging or diabetes).

101 How does conjunctivitis present?

With vessel dilation, and conjunctival swelling, and discharge. Discomfort (usually a scratchy feeling of sand in the eye) is common, but true pain is typically absent (itchiness, on the other hand, is typical of allergic conjunctivitis, which in contrast to the purulent or viral forms is always binocular). Vision is always spared.

102 What is the significance of a palpable preauricular lymph node?

It indicates viral conjunctivitis. It is just anterior to the tragus and usually tender.

103 Can conjunctival discharge differentiate the various forms of conjunctivitis?

Yes, since it is typically purulent in the bacterial forms, watery in the viral (or chemical), and stringy/white/mucoid (but overall scanty) in the allergic ones. Conversely, “pus” is so common in the bacterial forms that its absence questions the diagnosis.

104 How can one differentiate the injected vessels of uveitis from those of conjunctivitis?

By looking for prominent pericorneal vessels at the limbus (i.e., the interface between cornea and sclera). This phenomenon is known as “ciliary flush,” and it is typical of uveitis (see questions 111–114). By contrast, conjunctivitis causes diffuse vascular prominence, plus a typical discharge.

105 What is chemosis?

It is edema of the bulbar conjunctiva. This may be severe enough to cause the conjunctiva to protrude anteriorly, thus encroaching on the cornea. From the Greek chemos, which means not only yawning but also cockle. Indeed, the opening of the affected eye is often reduced to a slit, like the gaping shell of a cockle. Chemosis is typical of allergic conjunctivitis.

(8) Iris

107 Can heterochromia occur in Horner’s syndrome?

Yes, and it usually indicates congenital Horner’s, with the affected iris being lighter than the other; in acquired Horner’s syndrome, on the other hand, heterochromia is rare to absent. Other less frequent causes include a ferrous intraocular foreign body, which causes the affected iris to appear darker, and Waardenburg syndrome (see Chapter 3, The Skin, question 123).

108 Can iris color be used as a paternity test?

Not really. There is no simple Mendelian inheritance in iris color. Hence, no valid paternity test can be based on it, except for being aware that blue eyes are usually phenotypically recessive, so that a brown-eyed child of two blue-eyed parents is a bit unusual but may still happen.

(9) Cornea

110 What is the significance of arcus?

In subjects older than 50, it is probably minimal, since prevalence simply increases with age (arcus senilis). In younger patients, on the other hand, it suggests the presence of type 2 and 3 hyperlipoproteinemia, and thus a higher risk for cardiovascular death.

(10) Anterior Portion of the Globe

112 How is uveitis classified?

As anterior, intermediate, and posterior. The anterior form also is termed “iritis” (if only the iris is involved) or “iridocyclitis” (if both the iris and ciliary body are involved). The intermediate form is sometimes called “pars planitis,” and the posterior form “choroiditis.”

113 What is a ciliary flush?

A congestion of conjunctival and episcleral vessels over the corneal rim. It is a feature of anterior uveitis, but also keratitis and acute glaucoma. Never seen in conjunctivitis.

114 What are the symptoms of uveitis?

It depends. In anterior uveitis the affected eye may have a smaller pupil, yet the predominant symptom is aching ocular pain and photophobia, often requiring the use of dark glasses. Uveitis is different from keratitis since its pain is unrelieved by topical anesthetics; it also is different from conjunctivitis since it has no discharge, and it is different from glaucoma since it has lower intraocular pressure. Note that intermediate or posterior uveitis causes no pain but rather blurred vision and floaters (see also questions 139 and 226).

115 What is a hypopyon?

A layer of white cells (in Greek pyon, pus) in the bottom (in Greek upo, lower) of the anterior chamber. This may be seen in infectious processes (such as endophthalmitis after cataract surgery) and noninfectious inflammatory conditions (such as Behçet’s disease).

116 What is a hyphema?

It is blood in the anterior chamber, typically from trauma (from the Greek hyphaimos, suffused with blood). When bleeding is significant, blood can even be seen with a penlight, as a dark red layer in the inferior portion of the anterior chamber (see also question 132).

117 What is an eight-ball hyphema?

A hyphema that entirely fills the anterior chamber, so that the eye appears black like an eight-ball. This does not clear with conservative management but requires evacuation.

118 What is the value of gauging the depth of the anterior chamber with a penlight?

Little. This procedure is extremely inaccurate without special instruments like a slit lamp biomicroscope. Fortunately, very few patients have anterior chamber depths shallow enough to predispose to acute angle closure glaucoma. Hence, it is safe to dilate the pupils without making any attempt to gauge the depth of the anterior chamber.

(11) Corneal Light Reflex

120 What is the Hirschberg test?

A bedside assessment of ocular alignment, devised by the Baltimore neurologist Leonard K. Hirschberg. To carry it out, ask the patient to fixate a light at a distance of 2–3 feet. Then see whether the corneal light reflex is deviated from the center of the pupil in one eye or both. If so, the eyes are misaligned.

121 What is strabismus?

A misalignment of the eyes. Congenital strabismus is often uncertain in origin, whereas the acquired form is due to cranial nerve dysfunction, neuromuscular disease, or myopathy.

122 What is pseudostrabismus?

An apparent, but not true, misalignment of the eyes. This often arises in children with prominent epicanthal skin folds that obscure part of the nasal sclera, thus making the eyes look like they are turned in.

123 How do you tell strabismus from pseudostrabismus?

By examining the corneal light reflection in both eyes (Hirschberg test). If the reflection is centered in the two eyes, then the diagnosis is pseudostrabismus.

124 Is ophthalmoscopy an important skill?

It is a fundamental skill. Practice, as always, is paramount.

(1) Technique

126 Who should undergo ophthalmoscopy? When?

All comprehensive examinations should include ophthalmoscopy, especially in patients (1) complaining of altered vision, (2) older than 40 (because of the higher incidence of glaucoma with age), (3) suffering from neurologic disorders that may lead to increased intracranial pressure, or (4) with systemic diseases (such as diabetes and hypertension) that may be associated with vascular degeneration.

127 How does one perform ophthalmoscopy?

By dimming room lights and dilating the patient’s pupils. Contact lenses may stay in place, but glasses should always be removed (including your own). As patients gaze at a target straight ahead, approach their eyes from the temporal side (never from the front). This is necessary to avoid direct (and painful) stimulation of the macula. Look into the patient’s right eye by holding the ophthalmoscope in your right hand and using your right eye. Afterwards, view the patient’s left eye by using your left eye (and left hand).

128 How close should one get?

Start 2–3 feet away from the eye, so that you can visualize the red reflex and any abnormalities of the clear media. For proper viewing of the fundus, you should follow Robert Capa, the famous World War II photographer who once said, “If a picture is not good enough, it is because you did not get close enough.” Hence, to adequately see the fundus, get as close to the patient as possible. In fact, if you are not uncomfortably close, you are not close enough. As a measure of proximity, place your hand on the patient’s forehead, and then touch your hand with your head. While doing so, continuously adjust the focus of your ophthalmoscope, dialing the knob until the retina is in focus. Then, follow the vessels inward (using the natural “arrows” formed by their bifurcations), until they merge into the optic disc. Departing from the optic disc, explore the four quadrants of the eyeground (superior temporal, superior nasal, inferior nasal, and inferior temporal). Finally, examine the macula. Remember that ophthalmoscopy is a dynamic process, requiring continuously refocusing and repositioning.

129 What is the best way to examine the macula?

The traditional method consists in asking patients to look into the light. Yet this is not only painful (it causes intense photophobia) but also wrong, since the corneal glare is so bright that it interferes with macular inspection. Instead, approach the macula from the disc, by rotating the ophthalmoscope a few degrees temporally. Since this area is light sensitive (and its inspection always a bit painful), examine it at the end, and quickly.

130 How can one dilate the pupils?

By applying mydriatics. The two most commonly used are tropicamide (Mydriacyl), 0.5% or 1%, and phenylephrine (Neo-Synephrine), 2.5%. Phenylephrine 10% is no longer used because it may raise blood pressure or cause arrhythmias.

131 Do mydriatics have systemic effects?

Yes. All topically administered ophthalmic drugs are absorbed into the systemic circulation via the conjunctival, lacrimal, nasal, or oropharyngeal mucosa. Hence, the hypertensive effects of phenylephrine, an alpha₁-adrenergic agonist. If concerned about a cardiovascular reaction, use tropicamide (a short-acting antimuscarinic agent).

132 Are there any local contraindications to dilation of the pupils?

Very few. The absolute contraindication is the need to monitor pupillary signs in patients with suspected neurologic disease or trauma. Another one is the presence of an old intraocular lens implant in patients who have undergone cataract extraction (such implants, no longer used, were supported by the iris and thus tended to dislocate after pharmacologic mydriasis). A relative contraindication is narrow-angle glaucoma. Yet the precipitation of an attack of acute angle closure glaucoma may actually help a previously undiagnosed patient, since it may unmask an important but treatable condition.

(2) Red Reflex

134 How is the red reflex viewed?

Through an ophthalmoscope, by observing the pupils from a distance of 1–2 feet, focusing the instrument until a bright red pupil is clearly visualized.

135 What is leukocoria?

From the Greek leukos (white) and core (pupils), this is a condition characterized by total loss of the red reflex—hence, a white pupil. In children, it usually indicates a serious underlying condition, like a retinoblastoma, even though it also might result from a cataract, severe intraocular inflammation, retinopathy of prematurity, and other congenital lesions. Leukocoria also can be seen in retinal detachment. Its detection should prompt immediate referral to an ophthalmologist.

136 What common conditions may cause an abnormal red reflex?

All those causing opacity in the light-transmitting media of the eye. Of these, the most common affect anterior eye structures (lens or cornea). Posterior opacities are instead rare.

(3) Anterior Eye Structures

(4) Posterior Eye Structures

139 What are the most common opacities of the vitreous?

Hemorrhages and white blood cell clusters. A vitreous hemorrhage usually results from proliferative retinopathy (due to diabetes, hypertension, blood dyscrasias like thrombocytopenia and sickle cell disease, retinopathy of prematurity, and many other conditions) or from tearing of a retinal vessel. It may appear acutely and be either massive (totally obliterating the red reflex) or subtle (consisting of only a few erythrocytes, presenting usually as “floaters” in the vitreous gel). A vitreous hemorrhage is a reason for immediate referral to an ophthalmologist because it may accompany serious disorders, such as retinal detachment. White blood cell clusters result instead from inflammation of the choroid or retina, and may be part of an intraocular infection.

140 After visualization of the red reflex, which eye structures should be examined?

The optic disc, retinal blood vessels, retinal background, and macula.

141 What is the optic disc?

It is the point where axons of retinal ganglion cells form the optic nerve (nerve head).

142 How does one find the optic disc?

By closely approaching the patient’s eye while focusing the ophthalmoscope on the retina. Then follow its blood vessels toward the disc. To find it, you may need to refocus throughout, and also rotate the scope slightly around its vertical axis.

143 In following vessels toward the disc, how do you know the direction is right?

By noticing that the caliber of the vessels increases. Another way is to follow the “arrowheads” formed by the bifurcations of the retinal vessels (Fig. 4-6).

Figure 4-6 Arrowheads formed by the bifurcations of the retinal vessels.

144 What does a normal optic disc look like?

Like an oval, with sharp margins and a yellowish-pinkish color.

145 Are there any optic disc anatomic variants?

Some people may have a hypopigmented crescent surrounding the optic disc (particularly in its temporal side, as commonly encountered in myopic patients). This is usually caused by the failure of pigmented layers (retina and choroid) to extend onto the optic disc margin. Other people may have an excess of pigment, which usually appears as a darker rim surrounding the disc.

146 What is the optic cup?

The whitish central excavation of the disc. It is also the site where the retinal vessels enter and exit the eye. The diameter of this physiologic cup should not be greater than 50% of the diameter of the optic disc. If greater than that, suspect glaucoma.

147 What pathologic changes can be detected in the disc?

“/>Changes in (1) color (either pallor or hyperemia); (2) size of the cup (i.e., cupping, as in glaucoma); (3) elevation of the disc (papilledema or papillitis); and (4) the presence or absence of retinal venous pulsations.

(1) Changes in Color

149 What causes pallor of the disc?

Usually the death of retinal ganglion cells’ axons. The paleness is due to loss of supplying blood vessels, which, no longer needed after the axons’ demise, die too.

150 Does pallor of the disc always suggest a disorder of the optic nerve?

No. It often represents a normal variant, particularly in myopic eyes.

151 What are the common causes of optic atrophy?

Conditions causing damage to the retina, optic disc, optic nerve, optic chiasm, or optic tracts, which eventually result in axonal death. These include (1) previous optic neuritis (such as that of multiple sclerosis); (2) previous ischemic optic neuropathy (e.g., from temporal arteritis); (3) compression of the nerve by a mass (tumor, meningioma, or aneurysm); and (4) drug toxicity or toxins (e.g., ethambutol, ethylene glycol, methanol).

(2) Changes in Cup Size

153 What is the normal intraocular pressure?

Between 10 and 21   mmHg.

154 What is glaucoma?

A condition characterized by inadequate drainage of aqueous humor at the trabecular meshwork, resulting in increased intraocular pressure. This eventually causes neuronal death in the optic disc, and thus, loss of vision.

155 Why “glaucoma”?

The term was first introduced to indicate the peculiar shining of the eyegrounds in patients blinded by the disease (glaukos means sparkling in Greek), as opposed to the eyegrounds’ opacity (from loss of the red reflex) in blinding by a cataract.

156 What is chronic (or open-angle) glaucoma? What are its symptoms?

It is a different condition from acute (closed-angle) glaucoma, since the angle here is not closed, but simply not working well. This results in a slow drainage that is typically chronic and with no symptoms in its early stages. In this (most common) form of glaucoma, visual loss progresses slowly, compromising initially only the peripheral field, so that patients do not usually notice the deficit. Hence, the need to screen for glaucoma. The diagnosis is made by finding pathologic optic disc cupping (see question 159) and characteristic visual field loss. Elevated intraocular pressure also may be present.

157 What are the symptoms of acute (or angle-closure) glaucoma?

Pain (because of increased intraocular pressure), nausea, abnormal visual acuity, and a red, teary eye. Patients may even have vomiting, and often report seeing halos around lights. Vision is usually foggy (because of corneal swelling). All these manifestations result from rapid build-up in intraocular pressure, as the iris blocks the aqueous outflow channel (the trabecular meshwork).

177 What is the normal organization of the retinal circulation?

The retinal circulation includes branches of the central retinal artery and central retinal vein. The arterial branches originate at the optic disc, move centrifugally toward the four retinal quadrants, and distribute themselves in the superficial nerve fiber layer. The venous branches are arranged similarly but follow an opposite direction, converging centripetally toward the optic disc. Because there is a blood–eye barrier, just as there is a blood–brain barrier, retinal vessels autoregulate flow in response to changes in blood pressure, just like vessels in the central nervous system.

178 How can one differentiate retinal veins from retinal arteries?

Retinal veins are darker and larger than arteries (the normal vein-to-artery diameter ratio is 3:2). Arteries, on the other hand, have a more glistening light reflex.

179 Can the retinal arterial light reflex predict disease?

Yes. Changes in light reflex (and arterial width) may result from hypertensive changes or the arteriosclerosis of aging. As hypertension becomes more chronic, the anterior walls progressively thicken, causing the walls to reflect more light (increased light reflex), resembling at first copper wires and eventually silver wires.

180 What is hypertensive retinopathy?

The effect on retinal vessels of either acute or chronic hypertension. In poorly controlled hypertension, the vessels leak serum (hard exudates) and blood (dot, blot, and flame hemorrhages), eventually closing off and thus causing retinal microinfarcts (cotton-wool spots). In a hypertensive crisis, the leakage from optic disc vessels also may cause the optic disc to swell. In chronic hypertension, on the other hand, the arterial walls thicken, taking on first a copper and later a silver wire appearance. As walls thicken, they may indent and thus deviate retinal veins at arteriovenous crossings (“AV nicking”).

181 Does AV nicking revert with control of hypertension?

No, it is permanent. Hence, it provides valuable and indelible information about the patient’s medical history. AV nicking also may help understand the timing of a hypertensive disease. For example, since the changes take years to develop, a hypertensive patient presenting with renal failure but no AV nicking is more likely to have primary nephropathy with secondary hypertension than primary hypertension with secondary renal failure.

182 What are the manifestations of central retinal artery occlusion (CRAO)?

Profound and painless loss of vision in one eye. On funduscopy, there is retinal pallor and swelling, except for the macula, which appears instead cherry-red. This bright red spot is a diagnostic finding, caused by visualization of the preserved choroidal circulation through the fovea. The affected eye also demonstrates an afferent pupillary defect.

183 What are the causes of CRAO?

The most common is an embolus from the carotid artery or the heart, although giant cell arteritis or local thrombosis can do it, too, albeit less commonly.

184 What are the manifestations of central retinal vein occlusion (CRVO)?

CRVO also may cause an acute, painless loss of vision in one eye. Common fundus findings include (1) venous engorgement and dilation, (2) multiple intraretinal dot or flame hemorrhages splattered in all quadrants of the retina, (3) microaneurysms close to the retinal veins, (4) multiple cotton-wool spots, and even (5) optic disc edema.

185 What causes CRVO?

Usually a central retinal vein thrombosis at the level of the lamina cribrosa. This is often accompanied by atherosclerotic and hypertensive changes, but hyperviscosity syndromes (e.g., blood dyscrasias and dysproteinemias) also may cause CRVO.

186 What are the funduscopic findings in branch retinal vein occlusion (BRVO)?

Presence of flame hemorrhages and cotton-wool spots, but only over the retinal quadrant corresponding to the occluded vein. The vein distal to the occlusion is dilated and tortuous.

187 What causes BRVO?

Arterial compression of the vein (e.g., from arteriovenous crossings) is believed to be the main cause of BRVO. This would lead to turbulent flow, which, in combination with preexisting endothelial vascular damage (from hypertensive, atherosclerotic, inflammatory, or thrombophilic disease) would result in intravenous thrombus formation. Up to two thirds of BRVOs occur in the supertemporal quadrant, and the condition is not rare. In fact, retinal vein occlusions (branch and central) are the second most common retinal vascular diseases in the United States after diabetic retinopathy.

188 What is a Hollenhorst plaque?

A bright yellow, refractile arteriolar deposit usually wedged at the bifurcation of a peripheral arteriole (and thus causing a branch retinal artery occlusion). This often appears larger than the artery where it sits, and at times may even be seen migrating down the vessel. Migration may be facilitated by gently massaging the eyeball. It represents an arterial cholesterol embolus originating from the ulceration of an atheromatous plaque in a more proximal artery, usually the internal carotid.

189 What is the clinical significance of a Hollenhorst plaque?

It indicates severe generalized atherosclerosis. In fact, Hollenhorst patients are much more likely to die of stroke or myocardial infarction, with 10-year survival rates that are only half of age-matched controls. Hollenhorst plaques also are a complication of carotid endarterectomies, occurring in 14% of the cases.

190 What is retinal neovascularization?

The formation of new retinal vessels. It is always pathologic. New vessels tend to cluster around the disc but also may begin in the peripheral retina. They are often friable and may bleed into the vitreous.

191 What conditions cause neovascularization?

The most common is diabetes mellitus (see questions 216–222). In addition, other conditions that lead to retinal ischemia (such as hemoglobinopathies) also may cause neovascularization.

192 What retinal lesions can be identified by ophthalmoscopy?

Three groups: (1) yellow-white spots, (2) red spots, and (3) brown-black spots.

(1) Yellow-White Retinal Spots

194 What are cotton-wool spots?

Often misnamed soft exudates, these are round or oval patches on the superficial (inner) retina. They are white, ill-defined, and with indistinct borders. Since they are superficial, cotton-wool spots may obscure nearby vessels. They represent small retinal infarcts (and swellings) of the nerve fiber layer of the retina, due to microvascular disease.

195 What are the causes of cotton-wool spots?

Usually, conditions that damage the retinal microvasculature, such as (1) diabetes; (2) hypertension; (3) leukemias/lymphomas; (4) collagen vascular diseases (e.g., systemic lupus erythematosus); (5) infections (including bacterial endocarditis and, rarely, cytomegalovirus retinitis in patients with AIDS); (6) increased intracranial pressure with papilledema; (7) microembolic disease; and (8) severe anemia. As for the latter, cotton-wool spots are encountered in as many as one third of all patients with hemoglobin <7   gm/dL.

196 What are hard exudates?

They are small, yellowish/whitish, and well-demarcated retinal lesions. They are deeper in the retina than cotton-wool spots and are always due to microvascular retinal disease. As opposed to cotton-wool spots, however, they are not produced by microinfarcts, but instead by leaky and damaged vessel walls. Leakage of serum residues and various lipid aggregates eventually causes accumulation of lipoproteins in the middle retinal layers; hence, the waxy and often glistening look of these lesions.

197 What are the causes of hard exudates?

The same ones causing cotton-wool spots (i.e., processes affecting the retinal microvasculature, such as [1] diabetes and [2] hypertension).

198 What are drusen?

From the German term for geode (due to their glittering appearance), drusen are discrete, round, and yellowish lipoproteinaceous deposits in the retinal pigment epithelium (RPE, Fig. 4-7). First described by Donders in 1854, they are a normal byproduct of aging, often located in the macular region, but rarely causing visual disturbances. Yet, when in great number and large size, they are the earliest finding of age-related macular degeneration. They are totally unrelated to Optic Disc Drusen, which are instead globular deposits located on the optic nerve head (optic disk), found in 1–3% of the population, made of mucoproteins and mucopolysaccharides, often calcifying, and possibly representing a clue to the presence of retinitis pigmentosa.

Figure 4-7 Drusen are the byproduct of retinal metabolism and manifest as focal yellow-white deposits deep to the retinal pigment epithelium. They serve as a marker of nonexudative, age-related macular degeneration.

(From Vander JF, Gault JA: Ophthalmology Secrets. Philadelphia, Hanley & Belfus, 1998.)

199 What are chorioretinal scars?

Lesions of the retina and choroid, but not of the sclera. They may result from inflammations, trauma, surgery, or laser photocoagulation, although more typically they are encountered as sequelae of toxoplasmosis.

200 What are myelinated nerve fibers?

They are congenitally myelinated (i.e., medullated) axons of retinal ganglion cells. Myelination of these fibers is normally present only posterior to the lamina cribrosa, but not on the retinal surface. Occasionally, however, patches of the nerve fiber layer within the eye become myelinated. These have a bright white color and varying size; they also have feathery borders and, since they are superficial, often obscure blood vessels. They represent a congenital variant, with no pathologic significance.

(2) Red Spots

202 What causes retinal hemorrhages?

Leaky and damaged retinal capillaries, as may be encountered in chronic microvascular diseases like diabetes.

203 What other lesions may be associated with red spots?

Yellow-white spots, especially hard exudates in the perimacular region. These are due to damaged retinal vessels, leaking not only blood (responsible for red spots) but also plasma (causing hard exudates—see questions 196 and 197).

204 Why do red lesions have different shapes and sizes?

Shape and size depend on the location of the hemorrhage:

205 What are microaneurysms?

They are small, round, well-demarcated, red dots representing saccular outpouchings of the retinal capillaries (from the Greek aneurysma = dilation). They may be seen in association with other manifestations of microvascular disease and are almost always associated with diabetes mellitus.

206 What diseases present with dot-and-blot hemorrhages?

The most common is diabetes; but these lesions also may be encountered in (1) severe hypertension, (2) collagen vascular diseases, (3) infections, and (4) various hematologic disorders (leukemias or severe anemia).

207 Which processes are associated with flame and splinter hemorrhages?

It depends on location. When clustered around the disc, splinters and flames usually suggest a major ophthalmologic or neurologic emergency, such as (1) increased intracranial pressure with papilledema, (2) intracranial hemorrhage, or (3) poorly controlled glaucoma. When localized outside the disc, they have instead the same differential diagnosis of dot-and-blot hemorrhages, albeit linked more to hypertension than diabetes.

208 What are white-centered hemorrhages?

Red spots with white centers, often called Roth spots (even though Roth did not really describe them). They represent hemorrhagic microinfarcts of the retina with a fibrinous (e.g., whitish and pale) center They are typical of endocarditis, even though they also may occur in diabetes, intracranial hemorrhage, anemia, thrombocytopenia, leukemia, and various infectious processes.

209 Who was Roth?

Moritz Roth was a Swiss pathologist (1839–1914) who studied and taught in his native Basel. In addition to his retinal spots, he wrote a well-received biography of the Renaissance pathologist Andreas Vesalius.

(3) Brown-Black Spots

211 What is retinitis pigmentosa?

A degenerative disease of the retina. In the United States, 19% of all cases are autosomal dominant; 19% are autosomal recessive; 8% are X-linked; 46% are isolated, and 8% are undetermined. Only a few cases are due to known diseases and thus treatable. Among these is retinitis pigmentosa from vitamin A deficiency.

212 How does retinitis pigmentosa present on funduscopy?

With aggregations of pigment on the retina, usually arranged in a bony spicule formation. The pigment, however, may not always be present. In fact, 10% of the cases have no pigment at all. Note that bony spicules are usually in the midperipheral retina and thus difficult to visualize under direct ophthalmoscopy.

213 What is retinal pigment epithelium hypertrophy?

A congenital “grouped” pigmentation that results from hypertrophy of pigment cells in the retinal pigment epithelium (the same cells responsible for the red-orange color of the retinal background). Note that the color of the normal retinal background is also the result of choroidal blood and pigment. In fact, the darker fundus of pigmented races is due to the increased choroidal pigment of their fundi. Still, retinal pigment epithelium hypertrophy is often seen in Gardner’s syndrome, for which multiple bilateral pigmented lesions have a 78% sensitivity and a 95% specificity.

214 How does retinal pigment epithelium hypertrophy present ophthalmoscopically?

With many (>4) and bilateral retinal pigmented lesions. These have different sizes and shapes and are never larger than an optic disc. Hence, they usually do not compromise vision. Their typical grouping resembles animal tracks (bear track lesions). Their number is key to the diagnosis of retinal pigment epithelium hypertrophy, since normal subjects never have more than four pigmented lesions. These are usually in the peripheral retina and thus difficult to see ophthalmoscopically.

215 What are choroidal melanomas and benign nevi?

216 What is the relevance of diabetic retinopathy?

It is the most severe of all ocular complications of diabetes. A major cause of blindness.

217 Is there any correlation between diabetic retinopathy and nephropathy?

A strong one. Diabetic nephropathy (i.e., the glomerular disease of Kimmelstiel-Wilson) is almost always associated with diabetic retinopathy. Thus, absence of retinal disease in patients with changes suggestive of diabetic nephropathy should call into question the very diagnosis. Conversely, patients with diabetic retinopathy may not have glomerulopathy, since retinopathy usually precedes nephropathy.

218 What are the findings of diabetic retinopathy?

It depends on whether the patient is in the earlier and preproliferative stage (previously referred to as background) or in the full-blown proliferative stage. The difference between the two is that nonproliferative changes occur within the retina, whereas proliferative changes occur on the retina (or in the vitreous). Earliest signs of nonproliferative involvement include microaneurysms and dot intraretinal hemorrhages, occurring in nearly 80% of type 2 diabetics after 20 years of disease and in nearly all type 1 diabetics of the same duration. Both lesions reflect incompetent capillaries, resulting in bleeding and exudate formation. Progression of nonproliferative retinopathy is then characterized by an increase in number and size of intraretinal hemorrhages (both dot and blot), often accompanied by hard and soft exudates. Eventually, patients will develop venous beading (retinal veins resembling a string of beads) and intraretinal microvascular abnormalities (IRMA) (i.e., new or preexisting tortuous vessels that are contained within the retina).

219 What is proliferative diabetic retinopathy (PDR)?

The most advanced stage of diabetic retinopathy. It consists of chronic retinal ischemia resulting in new vessel formation (neovascularization) on the inner surface of retina, optic disc, or vitreous (Fig. 4-8). If untreated, this may lead not only to preretinal or vitreous hemorrhage, but also to tractional retinal detachments. The new vessels appear tiny, irregular, and often with a fibrous component. They may develop quite rapidly, even within 1 year after the initial appearance of an isolated cotton-wool spot. They often resemble the spokes of a wheel, insofar as they radiate outward toward a circumferential vessel. Neovascularization of the disc carries a worst prognosis than new vessel formation in other areas. Yet, all patients with PDR are at risk of losing vision, and thus should be candidates for photocoagulation. Patients with diabetes should be referred at least once a year for ophthalmologic evaluation.

Figure 4-8 Background diabetic retinopathy with exudate, hemorrhages, and edema.

(From Vander JF, Gault JA: Ophthalmology Secrets. Philadelphia, Hanley & Belfus, 1998.)

220 What are the late manifestations of PDR?

New vessels may extend into the drainage system of the anterior chamber angle of the eye, and thus lead to neovascular glaucoma.

221 What are the best predictors of proliferative retinopathy?

Intraretinal microvascular abnormalities, venous beading, and the extent of microaneurysms and hemorrhages. Soft exudates are not as predictive, and hard exudates even less. The extent of retinopathy at the initial visit is instead a good predictor of disease progression (and so is pregnancy, which accelerates progression). Note that all PDR changes can be detected by retinal examination. Yet, in the hands of generalists, ophthalmoscopy has only a 53–69% sensitivity, even when carried out with dilation (91–96% specificity; positive likelihood ratio [+LR] = 10.0). Since detection of proliferation is higher for specialists (particularly macular edema, which is almost never detected by the direct ophthalmoscopy of generalists), current guidelines call for referral of diabetics to an ophthalmologist, with frequency of follow-up to be determined by stage of disease.

222 What is macular edema?

Another important manifestation of progressive diabetic retinopathy. It is characterized by the breakdown of the blood–retinal barrier, with leakage of plasma into the central portion of the retina (macula), resulting in swelling. Hence, patients will not lose vision entirely, but only its central component. Resorption of plasma fluid by the vessels (but not of lipoproteins and lipids) will subsequently lead to their deposition as hard exudates. In a large population-based study, the incidence of macular edema over a period of 10 years is 20.1% in type 1 diabetics, 25.4% in type 2 diabetics on insulin, and 13.9% in type 2 diabetics not on insulin. Tighter blood glucose control may decrease its incidence. Macular edema is almost never detected by generalists when using direct ophthalmoscopy; hence, the need for subspecialists’ evaluation. Indirect clues to its presence include rings of hard exudates (often surrounding the edematous area) and diminished visual acuity. Note, however, that normal visual acuity should not rule out macular edema, since vision may often be spared.

K. Retinal Detachment

226 How does retinal detachment present?

With three “F’s”: floaters, flashes, and field loss. The most common initial complaint is the sudden appearance of floaters (i.e., opacities that float in the vitreous of the affected eye). These represent either clusters of red cells released at time of retinal tear or a fibrous condensation in the vitreous. Subsequently, there will be flashes of light (i.e., phospheni, from the Greek phos, light, and phaino, to show). These “shows of light” represent mechanical activation of the sensory retinal layer, stretched by traction from the vitreous. Eventually, with progression of the detachment, a “curtain” will gradually obscure the vision (field loss). This may occur as early as few hours or as late as few weeks since the initial event (see Fig. 4-9).

Figure 4-9 Horseshoe retinal tear with a bridging vessel.

(From Vander JF, Gault JA: Ophthalmology Secrets. Philadelphia, Hanley & Belfus, 1998.)

227 What are the ophthalmoscopic findings in retinal detachment?

It depends. If the entire retina is detached, there will be loss of the red reflex. Conversely, if only part of the retina is detached, the affected section will appear whiter, with fine folds on its surface. Most often, however, retinal detachment is difficult to visualize under direct ophthalmoscopy, except when performed with special instruments that allow better visualization of the peripheral retina (see Fig. 4-10).

Figure 4-10 Bullous rhegmatogenous retinal detachment with mobile, corrugated appearance.

(From Vander JF, Gault JA: Ophthalmology Secrets. Philadelphia, Hanley & Belfus, 1998.)

L. Macula

M. Red Eye