It has been said the eyes are the windows to the soul. In emergency medicine, much can be learned from a routine eye examination. This article will review both techniques and evaluation of findings.
You arrive at a local nursing home to care for a patient who has become unresponsive. During your routine examination, you discover that both of his pupils are less than 1 mm wide, nonreactive and barely discernable.
It is neither possible nor desirable to conduct a complete eye examination in the field, since a complete eye exam requires an ophthalmoscope and other equipment not normally available or practical for use on the ambulance.
The goal of field examination is to determine whether there is injury to the eye or a condition resulting from either trauma or medical causes that is eliciting abnormal responses from the eyes.
A test for visual acuity usually involves the use of a Snellen eye chart, the familiar chart with the large “E” on it. During a typical ambulance call, this sort of test will not be possible, but visual acuity may be estimated by simply asking your patient to identify an item you hold up, like your watch.
The External Eye
Inspect the eyes for symmetry of eyelids, size, contour, alignment of the eyeballs and signs of traumatic injury. Look for eyelid droop (ptosis), dysconjugate gaze, exophthalmos (protruding gaze) and sunken eyes. Ask the patient to close his eyes and note whether the eyelids completely cover the eyes. Using your thumbs, gently retract the lower eyelids and look at the conjunctiva. It should be pink but not inflamed. Cyanosis of the lid may indicate anemia or shock. The sclera should be white—a yellow coloring in the sclera indicates jaundice. Elderly patients have a normal finding called arcus senilis, a clouding around the cornea caused by lipid accumulation. Do not confuse this with cataracts. It is normal and has no effect on vision.
Visual field is the area the patient can see with peripheral vision while looking at a fixed object. Test visual field with the confrontation test. While sitting or standing about 2 feet directly in front of the patient, ask him to cover his left eye while you cover your right eye. Then extend your left arm, hold up your first finger and move it toward the midline. Ask the patient to tell you when he first sees your finger as it moves inward. He should see it at the same time you do. Do this from several different angles, from 45 degrees above, 90 degrees, and 45 degrees below. Then repeat the test for the other eye. If your patient cannot see your finger at the same time you do, it suggests peripheral vision loss. This may be because of loss of vision in the upper, lower or outer half of the eye, or blindness in one eye.
Look at the size, shape, symmetry and reactivity of the pupils. Some patients have unequal pupils normally (anisocoria); pupils that react normally to light and are within 2 millimeters in size are normal in patients with anisocoria. However, larger differences coupled with nonreactivity may signal pressure on the oculomotor nerve (CN III).
Test for pupil reaction by shining a light into one eye. Advance it in from the side and look for constriction. Normal pupils will constrict rapidly. Repeat in the other eye, then repeat the process by shining your light into one eye and observing the other eye for constriction or consensual response.
Test for accommodation by having the patient focus on a distant object and then on your finger as you move it from a distance to the bridge of his nose. When he focuses on the distant object, his pupils should dilate, but as he focuses on the close object, they should constrict.
Then have your patient follow your finger in an H pattern as you move your finger in front of him to test his ocular muscle responses. Normal eye movements should be conjugate (together) and smooth. Jerky eye movements (nystagmus) may be normal at the extremes of movement, but when present across the whole field of movement may indicate either a normal condition or a number of other conditions. There are at least 11 types of nystagmus, some congenital, some acquired.1Drug or alcohol ingestion may cause nystagmus.