The health care provider, through careful questioning, elicits the necessary information that can lead to the diagnosis of an oph-thalmic condition. Pertinent questions to ask during the inter-view can be found in Chart 58-1.
After the patient’s chief complaint or concern has been identified and the history has been obtained, visual acuity should be assessed. This is an essential part of the eye examination and a measure against which all therapeutic outcomes are based.
Most health care providers are familiar with the standard Snellen chart. This chart is composed of a series of progressively smallerrows of letters and is used to test distance vision. The fraction 20/20 is considered the standard of normal vision. Mostpeoplecan see the letters on the line designated as 20/20 from a distance of 20 feet. A person whose vision is 20/200 can see an objectfrom
20 feet away that a person whose vision is 20/20 can see from 200 feet away.The patient is positioned at the proscribed distance, usually 20 feet, from the chart and is asked to read the smallest line that he or she can see. The patient should wear distance correction (eyeglasses or contact lenses) if required, and each eye should be tested separately.
The right eye is commonly tested first and then the left. If the patient is unable to read the 20/20 line, he or she is given a pinhole occluder and asked to read again using the eye in question. A makeshift occluder may be created by making a pinhole in an index card and asking the patient to look through the pinhole. Squinting produces the same effect. Patients should be encouraged to read more letters and to guess, if necessary. Often, patients avoid guessing and prefer not to try at all rather than to make a mistake. The patient should be encouraged to read every letter possible.
The visual acuity (VA) is recorded in the following way. If the patient reads all five letters from the 20/20 line with the right eye (OD) and three of the five letters on the 20/15 line with the left eye (OS), the examiner writes OD 20/20, OS 20/15-2, or VA 20/20, 20/15-2.
If the patient is unable to read the largest letter on the chart (the 20/200 line), the patient should be moved toward the chart or the chart moved toward the patient, until the patient is able to identify the largest letter on the chart. If the patient can recognize only the letter E on the top line at a distance of 10 feet, the visual acuity would be recorded as 10′/200. If the patient is unable to see the letter E at any distance, the examiner should determine if the patient can count fingers (CF). The examiner holds up a ran-dom number of fingers and asks the patient to count the number he or she sees. If the patient correctly identifies the number of fin-gers at 3 feet, the examiner would record CF/3′.
If the patient is unable to count fingers, the examiner raises one hand up and down or moves it side to side and asks in which direction the hand is moving. This level of vision is known as hand motions (HM). A patient who can perceive only light is de-scribed as having light perception (LP). The vision of a patient who is unable to perceive light is described as no light perception (NLP).
After the visual acuity has been recorded, an external eye exami-nation is performed. The position of the eyelids is noted. Com-monly, the upper 2 mm of the iris is covered by the upper lid. The patient is examined for ptosis (ie, drooping eyelid) and for lid retraction (ie, too much of the eye exposed). Sometimes, the upper or lower lid turns out, affecting closure. The lid margins and lashes should have no edema, erythema, or lesions. The ex-aminer looks for scaling or crusting, and the sclera is inspected. A normal sclera is opaque and white. Lesions on the conjunctiva, discharge, and tearing or blinking are noted.
The room should be darkened so that the pupils can be ex-amined. The pupillary response should be checked with a pen-light to be certain that the pupils are equally reactive and regular. A normal pupil is black. An irregular pupil may result from trauma, previous surgery, or a disease process.
The patient’s eyes are observed in primary or direct gaze, and any head tilt is noted. A tilt may indicate cranial nerve palsy. The patient is asked to stare at a target; each eye is covered and un-covered quickly while the examiner looks for any shift in gaze. The examiner observes for nystagmus (ie, oscillating movement of the eyeball). The extraocular movements of the eyes are sim-ply tested by having the patient follow the examiner’s finger or hand light through the six cardinal directions of gaze (ie, up, down, right, left, and both diagonals). This is especially impor-tant when screening patients for ocular trauma or for neurologic disorders.