Wilderness Eye Emergencies
Ocular Procedures
Examination of Pupils
Examine the pupils for size, equality, shape, and reaction to light.
1. Approximately 10% of the population has pupils of unequal size (anisocoria).
2. If light is shined in either eye, both pupils should constrict equally (consensual response). If one pupil is seen to be dilated compared with the other when a penlight is rapidly alternated from one eye to the other, this may indicate retinal or optic nerve dysfunction.
3. An irregularly shaped, tapered “teardrop pupil” suggests ocular penetration.
4. When evaluating a red or painful eye, a significant difference in size between pupils may provide a clue to diagnose iritis (constricted) or glaucoma (dilated).
5. Although somewhat rare, mid-dilation is noted in pupillary block/angle-closure glaucoma. Look for a mid-dilated pupil (5 to 7 mm), with pain and severe decreased vision in one eye. These patients tend to be farsighted and older than 50 years.
6. A widely dilated, nonreactive pupil is suggestive of contact with medicine (e.g., scopolamine patch) or a cerebral aneurysm. If increased intracranial pressure is causing anisocoria, the patient will be obtunded or comatose.
Estimation of Anterior Chamber Depth (i.e., Rule Out Narrow Angle, a Contributing Factor to Glaucoma)
Shine a small flashlight obliquely from the temporal side of the eye (Fig. 32-1, A).
FIGURE 32-1 Estimating depth of anterior chamber.
1. If the nasal iris is well illuminated, it suggests a normal anterior chamber.
2. If the nasal iris lies in shadow, it suggests a shallow anterior chamber (narrow angle) (Fig. 32-1, B).
3. This may be a difficult test to interpret. It is helpful to compare one eye with the other, or the patient’s eye with that of another person.
4. A history of being farsighted should raise suspicion; narrow angles accompany hyperopia and small anterior chambers (usually these individuals wear thick glasses that magnify their eyes on direct inspection).
Extraocular Muscle Testing
1. Have the patient follow a flashlight or finger through the extremes of gaze in six directions. Ask if the patient sees one image or two images.
2. Double vision in any field of gaze may represent extraocular muscle palsy.
3. Fourth cranial nerve palsies tend to occur after head trauma and are generally benign. The patient will have vertical diplopia.
4. Patients with sixth cranial nerve palsy will have horizontal diplopia.
5. When both eyes have lateral gaze limitation, this is a sign of increased intracranial pressure.
6. With a third cranial nerve palsy, the eye will be turned down and out. The patient may not complain of diplopia because of ptosis. If the same pupil is dilated, this is assumed to be from a posterior communicating aneurysm until proven otherwise. Evacuate the patient immediately.
7. Grossly limited extraocular motion (EOM) with proptosis suggests acute orbital inflammation or retrobulbar hemorrhage. Retrobulbar hemorrhage is usually accompanied by periorbital ecchymosis and subconjunctival hemorrhage following trauma.
8. If the eye appears sunken within the orbit and the patient exhibits limited upward gaze, suspect a blow-out fracture of the orbital floor. Fracture of the orbital floor with entrapment of the inferior rectus muscle causes vertical diplopia with limited gaze both up and down. Fracture of the medial orbital wall with entrapment of the medial rectus muscle causes horizontal diplopia and limited gaze both medially and laterally.
Visual Field Testing
1. Ask the patient to cover one eye completely and look directly at your opposing eye from a distance of about 1 m (3.3 ft).
2. Place your fingers outside the patient’s field of peripheral vision and slowly move them centrally.
3. Ask the patient to inform you when he or she can see your fingers. The patient’s fields are generally normal when they correspond with those of the examiner.
Upper Eyelid Eversion
1. Place the end of a cotton-tipped applicator horizontally above the tarsal plate while you pull the eyelashes and the lid margin down and out (Fig. 32-2, A).
FIGURE 32-2 Upper eyelid eversion.
2. Flip the lid up to evert it. Hold the everted lid in position by pressing the lashes against the superior orbital rim (Fig. 32-2, B).
Fluorescein Examination
1. Use fluorescein staining to evaluate any red or painful eye.
2. Wet the fluorescein strip with a drop of saline (artificial tears) or a drop of topical anesthetic.
3. When examining an eye with a possible infection, always use a separate fluorescein strip for each eye to avoid cross contamination.
4. Next, apply the wetted strip to the inside of the patient’s lower lid.
5. Ask the patient to blink, which will spread the fluorescein over the surface of the eye. Areas of corneal disruption stain brilliant green.
6. Use a small, blue filter placed over a penlight, which works well in the dark.
7. Outside during the day, simple sunlight often causes any significant corneal lesion to fluoresce.
8. Fluorescein permanently stains soft contact lenses, so instruct patients to remove these lenses before the fluorescein examination and leave them out for several hours after the examination.
9. If there is concern regarding a penetrating injury, fluorescein can be used to paint the area of concern. Observe if fluorescein dilutes by pinpoint leak of aqueous fluid (a positive Seidel test indicates an open globe).
Eye Patching
1. Use a pressure patch to hold the eyelid closed and thereby facilitate healing of a corneal defect. Protect the injured eye from bright light. Using a patch for healing is not always necessary, but may be a personal preference.
2. A (light) pressure patch is indicated in many common eye emergencies and whenever the surface of the cornea has been injured, especially with a large corneal defect. The patient will be more comfortable; however, pressure patching probably does not speed up corneal healing.
3. Small corneal defects may heal rapidly without patching.
4. After patching, the patient often experiences less pain and tearing.
5. Do not use patching when the corneal epithelial defect is secondary to an infection (e.g., conjunctivitis, corneal ulcer) or if injury was caused by or contaminated with organic matter.
6. Use caution if the patient is a contact lens wearer, especially extended-wear lenses, which contribute to increased risk for infection.
7. Never apply a pressure patch to an eye after a penetrating injury. After eye penetration or trauma, tape a protective cup (e.g., padded drinking cup) over the eye or fashion a cloth “donut” from a cravat or other cloth to avoid placing pressure on the eye or inflicting any further trauma during evacuation.
8. “Plano” (noncorrective) soft contact lenses are often used by ophthalmologists for patching corneal lesions. These might be considered if available.
Procedure
1. Before patching a corneal abrasion, apply both a drop or two of a mydriatic-cycloplegic solution and a thin ribbon of antibiotic-antiseptic ointment.
a. The cycloplegic relaxes ciliary muscle spasm that accompanies corneal abrasion.
b. Check the patient for a narrow anterior chamber before instilling the drops (see Estimation of Anterior Chamber Depth, earlier), although this is usually not realistic in the field.
2. Use antibiotic ointment for prophylaxis, although corneal abrasions rarely become infected.
3. For the patch to be effective, you must put it on just tightly enough to keep the eyelid shut. Do not put undue pressure on the eye.
a. Double the first patch by folding vertically, and place it over the closed lid. If a second patch is not available, this patch can be held in place with a single piece of tape.
b. Put the unfolded second patch over the first folded patch.
5. Prepare the skin near the eye with tincture of benzoin (if available) to help the tape adhere. Be careful to keep benzoin out of the eye.
6. Place the tape diagonally from the center of the forehead to the cheekbone. Make sure the tape completely covers the patch to minimize slippage but does not extend onto the angle of the mandible.
7. Remove the patch every 24 hours so that the eye can be reexamined and the patch changed. Using a clean patch every 24 hours helps to prevent infection.
8. Instruct the patient with an eye patch to rest the uninjured eye. Discourage reading because rapid involuntary movement of the patched eye occurs.
Locating a Displaced Contact Lens
1. The conjunctival fornix of the lower lid is easily examined by distracting the lens from the globe with gentle downward finger pressure applied to the lower lid.
2. If the contact lens has been displaced into the superior conjunctival fornix (usually the case), it may be more difficult to locate.
3. If visual inspection with a penlight and a handheld magnifying lens is not successful in finding the lens, gentle digital massage over the closed upper lid directed toward the medial canthus often results in the contact lens emerging at that location. Several minutes of massage may be required. A few drops of artificial tears, and topical anesthetic if available, often facilitate the process.
4. If this maneuver is unproductive, the eye may be anesthetized with a drop of topical anesthetic, the upper lid distracted from the globe with upward finger pressure, and the fornix swept with a moistened cotton-tipped applicator.
5. Alternatively, using a paper clip opened to a right angle to create a simple retractor, evert the eyelid after proparacaine (or other topical anesthetic) instillation, and then lift the edge of the tarsus with the rounded edge of the paper clip.
6. If the lens is not the last and can be discarded, it can often be easily located with fluorescein. Commonly, the missing contact lens will not be there, even in the presence of a persistent foreign body sensation.
Disorders
Sudden Loss of Vision in White, “Quiet” Eye
Acute and significant visual loss is an emergency. The common causes of acute visual loss are listed in Box 32-1.
Giant Cell (Temporal) Arteritis
Signs and Symptoms
Treatment
1. Because this disease can cause significant visual loss in the absence of effective treatment, initiate care immediately with a high-dose corticosteroid (e.g., prednisone, 80 to 100 mg/day PO).
2. Evacuate the patient so that a high-dose steroid can be administered intravenously.
3. When treated, symptoms often improve within 1 to 3 days. However, steroids are typically continued for many weeks.
Red Eye (Fig. 32-3 and Box 32-2)
Signs and Symptoms
1. Acute onset of severe pain and blurred vision
2. A red eye, often with the pupil slightly dilated and a “steamy” (edematous) cornea
3. The affected eye often feels appreciably harder than the unaffected eye (palpate through the lid gently and with extreme caution).
4. Symptoms beginning in low light
5. Possible nausea, vomiting, and generalized head pain
Treatment
1. Instill timolol 0.5% (Timoptic), 1 drop bid (caution if patient has asthma, chronic obstructive pulmonary disease, or history of heart block).
2. Instill pilocarpine 2% (Pilocar), 1 drop q15min × 4, then qid.
3. Administer acetazolamide 250 mg PO qid.
4. Arrange for immediate evacuation for emergency ocular surgery (laser iridotomy).
5. The other eye is also at risk; it is prudent to treat this eye with pilocarpine bid, prophylactically.
