5. Test the eye movements (Figure 13.4). Look also for fatiguability of eye muscles by asking the patient to look up at a hat-pin or finger for about half a minute. In myasthenia gravis the muscles tire and the eyelids begin to droop.

6. Test colour vision if acuity is not poor. Ishihara test plates (where coloured spots form numbers) can be used. Red desaturation (impaired ability to see red objects) can occur with optic nerve disease. Red-green colour blindness affects 7% of males (X-linked recessive).

7. Test the corneal reflex. Consider the possibility that the patient may have a glass eye. This should be suspected if visual acuity is zero in one eye and no pupillary reaction is apparent. Attempts to examine and interpret the fundus of a glass eye will amuse the patient but are always unsuccessful.

8. Perform fundoscopy. Successful ophthalmoscopy requires considerable practice. It is important that it be performed in reduced ambient lighting so that the patient’s pupils are at least partly dilated and the examiner is not distracted. It can be easier to perform the examination, especially of the fundi, through the patient’s spectacles. Otherwise, the patient’s refractive error should be corrected by use of the appropriate ophthalmoscope lens. The patient should be asked to stare at a point on the opposite wall or on the ceiling and to ignore the light of the ophthalmoscope. Patients will often attempt to focus on the ophthalmoscope light and should be asked not to do this.

Figure 13.4 The cranial nerves III, IV & VI: voluntary eye movements

(a) ‘Look to the left.’ (b) ‘Look to the right.’ (c) ‘Look up.’ (d) ‘Look down.’

Begin by examining the cornea. Use your right eye to examine the patient’s right eye, and vice versa. Turn the ophthalmoscope lens to +20 and examine the cornea from about 20 cm away from the patient. Look particularly for corneal ulceration. Turn the lens gradually down to 0 while moving closer to the patient. Structures, including the lens, humour and then the retina at increasing distance into the eye, will swim into focus.

Examine the retinas (Figure 13.5; see also Figure 11.8, page 336). Focus on one of the retinal arteries and follow it into the optic disc. The normal disc is round and paler than the surrounding retina. The margin of the disc is usually sharply outlined but will appear blurred if there is papilloedema or papillitis, or pale if there is optic atrophy. Look at the rest of the retina, especially for the retinal changes of diabetes mellitus or hypertension.

Figure 13.5 Retinal photographs

(a) Retinitis pigmentosa. (b) Central retinal artery occlusion.

There are four types of haemorrhages: streaky haemorrhages near the vessels (linear or flame-shaped); large ecchymoses that obliterate the vessels; petechiae, which may be confused with microaneurysms; and subhyaloid haemorrhages (large effusions of blood which have a crescentic shape and well-marked borders; a fluid level may be seen). The first two types of haemorrhage occur in hypertensive and diabetic retinopathy. They may also result from any cause of raised intracranial pressure or venous engorgement, or from a bleeding disorder. The third type occurs in diabetes mellitus, and the fourth is characteristic of subarachnoid haemorrhage.

There are two main types of retinal change in diabetes mellitus: non-proliferative and proliferative. Non-proliferative changes include: (1) two types of haemorrhages—dot haemorrhages, which occur in the inner retinal layers, and blot haemorrhages, which are larger and occur more superficially in the nerve fibre layer; (2) microaneurysms (tiny bulges in the vessel wall), which are due to vessel wall damage; and (3) two types of exudates—hard exudates, which have straight edges and are due to leakage of protein from damaged arteriolar walls, and soft exudates (cottonwool spots), which have a fluffy appearance and are due to microinfarcts. Proliferative changes include new vessel formation, which can lead to retinal detachment or vitreous haemorrhage.

Hypertensive changes can be classified from grades 1 to 4:

Grade 1—‘silver wiring’ of the arteries only (sclerosis of the vessel wall reduces its transparency so that the central light streak becomes broader and shinier)

Grade 2—silver wiring of arteries plus arteriovenous nipping or nicking (indentation or deflection of the veins where they are crossed by the arteries)

Grade 3—grade 2 plus haemorrhages (flame-shaped) and exudates (soft—cottonwool spots due to ischaemia, or hard—lipid residues from leaking vessels)

Grade 4—grade 3 changes plus papilloedema.

It is important to describe the changes present rather than just give a grade.

Inspect carefully for central retinal artery occlusion, where the whole fundus appears milky-white because of retinal oedema and the arteries become greatly reduced in diameter. This presents with sudden, painless unilateral blindness, and is a medical emergency.

Central retinal vein thrombosis causes tortuous retinal veins and haemorrhages scattered over the whole retina, particularly occurring alongside the veins (‘blood and thunder retina’). This presents with sudden painless loss of vision which is not total.

Retinitis pigmentosa causes a scattering of black pigment in a criss-cross pattern. This will be missed if the periphery of the retina is not examined.

In retinal detachment, the retina may appear elevated or folded. The patient describes a ‘shade coming down’, flashes of light or showers of black dots. A diagnosis requires immediate referral to try to prevent total detachment and irrevocable blindness.

White spots occur in choroiditis which when active have a fluffy edge (e.g. in toxoplasmosis, sarcoidosis).

Finally, ask the patient to look directly at the light. This allows the examiner to locate and inspect the macula. Macular degeneration is the leading cause of blindness; central vision is lost. Drussen formation occurs in macular degeneration—small deposits are seen under the epithelium in the central retina. Macular degeneration may occur secondary to an atrophic or neovascularisation process.

9. Palpate the orbits for tenderness. Auscultate the eyes with the bell of the stethoscope—the eye being tested is shut while the other is open and the patient is asked to stop breathing. Listen for a bruit that may be a sign of an arteriovenous malformation or a vascular tumour.

10. Feel for the pre-auricular node (adenoviral conjunctivitis).

The causes of common eye abnormalities are summarised in Table 13.3.

TABLE 13.3 Causes of eye abnormalities

Cataracts

1. Old age (senile cataract)

2. Endocrine—e.g. diabetes mellitus, steroids

3. Hereditary or congenital—e.g. dystrophia myotonica, Refsum’s disease ^*

4. Ocular disease—e.g. glaucoma

5. Radiation

6. Trauma

Papilloedema vs papillitis

Papilloedema

Optic disc swollen without venous pulsation

Acuity normal (early)

Large blind spot

Peripheral constriction of visual fields

Large central scotoma

Pain on eye movement

Onset usually sudden and unilateral

Colour vision affected (particularly red desaturation)

Causes of papilloedema

1. Space-occupying lesion (causing raised intracranial pressure) or a retro-orbital mass

2. Hydrocephalus (large cerebral ventricles)

Obstructive (a block in the ventricle, aqueduct or outlet to the fourth ventricle)—e.g. tumour Communicating

Increased formation of CSF—e.g. choroid plexus papilloma (rare)

Decreased absorption of CSF—e.g. tumour causing venous compression, subarachnoid space obstruction from meningitis

3. Benign intracranial hypertension (pseudotumour cerebri) (small or normal-sized ventricles)

(a) Idiopathic

(b) The contraceptive pill

(d) Drugs—e.g. nitrofurantoin, tetracycline, vitamin A, steroids

(e) Head trauma

4. Hypertension

5. Central retinal vein thrombosis

Causes of optic atrophy

1. Chronic papilloedema or optic neuritis

2. Optic nerve pressure or division

3. Glaucoma

4. Ischaemia

5. Familial—e.g. retinitis pigmentosa, Leber’s disease,^† Friedreich’s ataxia

Causes of optic neuritis

1. Multiple sclerosis

2. Toxic—e.g. ethambutol, chloroquine, nicotine, alcohol

3. Metabolic—e.g. vitamin B12 deficiency

4. Ischaemia—e.g. diabetes mellitus, temporal arteritis, atheroma

5. Familial—e.g. Leber’s disease

6. Infective—e.g. infectious mononucleosis

Causes of retinitis pigmentosa

1. 1 Congenital (associated with cataract and deaf-mutism)

2. Laurence-Moon-Biedl syndrome ^‡

3. Hereditary ataxia

4. Familial neuropathy, i.e. Refsum’s disease

CSF = cerebrospinal fluid.

^* Sigvald Refsum, 20th century Norwegian physician.

^† Theodor von Leber (1840–1917), Göttingen and Heidelberg ophthalmologist.

^‡ John Laurence (1830–1874), London ophthalmologist; Robert Charles Moon (1844–1914), American ophthalmologist; and Arthur Biedl (1869–1933), professor of physiology, Prague.

Diplopia

Most cases of diplopia (about 60%) are not due to a cranial nerve abnormality. It is important to have an approach to the problem that will help work out the cause.

First find out whether the diplopia is monocular (25%) or binocular. Monocular diplopia persists when one eye is covered. It is usually due to an eye problem such as astigmatism, dislocated lens, uneven contact lens surface or thick spectacles. It disappears if the patient looks through a pin hole. Although it is said to be due to hysteria, this is a very rare cause.

If the diplopia is binocular, consider the common causes:

1. Cranial nerve palsy (III, IV or VI)—look for ptosis, pupil changes (III), abnormal eye movements.

2. Eye muscle disease (myasthenia gravis)—worse later in day, worse after prolonged upward gaze and associated with bilateral ptosis.

3. Thyroid ophthalmopathy—proptosis, lid lag, chemosis.

4. Trauma to the orbit—history or signs of trauma.

5. Internuclear ophthalmoplegia—associated neurological signs.

Horner’s syndrome

Examination anatomy

Interruption of the sympathetic innervation of the eye at any point (Figure 13.6) results in Horner’s syndrome^a (Table 13.4).

Figure 13.6 Left Horner’s syndrome, with partial ptosis and miosis

TABLE 13.4 Causes of Horner’s syndrome

1 Carcinoma of the apex of the lung (usually squamous cell carcinoma)

2 Neck

• Malignancy—e.g. thyroid

• Trauma or surgery

3 Lower trunk brachial plexus lesions

• Trauma

• Tumour

4 Carotid arterial lesion

• Carotid aneurysm or dissection

• Pericarotid tumours (Raeder’s syndrome)^*

• Cluster headache

5 Brainstem lesions

• Vascular disease (especially the lateral medullary syndrome)

• Tumour

• Syringobulbia

6 Syringomyelia (rare)

^* Sweating unaffected, as tumour localised to internal carotid artery.

Clinical approach

The syndrome includes partial ptosis (as sympathetic fibres supply the smooth muscle of both eyelids) and a constricted pupil (unbalanced parasympathetic action) which reacts normally to light (Figure 13.6). Remember the other causes of ptosis (Table 13.5).

TABLE 13.5 Important causes of ptosis

Cause	Associated features
Age-related stretching of levator muscle or aponeurosis	Common, often asymmetrical
Orbital tumour or inflammation	Orbital abnormality
Horner’s syndrome	Constricted pupil, reduced sweating
Third nerve palsy	Eye ‘down and out’, dilated pupil
Myasthenia gravis or dystrophical myotonica	Extraocular muscle palsies, muscle weakness
Congenital or idiopathic