Table of Contents
Ophthalmology Exam – the basic diagnostic procedures an ophthalmologist uses to assess the health of the eye and vision, and detect problems with the structures and functions of the eye. The standard ophthalmic examination includes several components.
For certain parts of the examination the ophthalmologist may place drops in the eyes that anesthetize the eye and dilate the pupils, to facilitate examining the structures of the back of the eye such as the retina and optic disk. Some people experience mild stinging when the drops first enter the eye.
There is otherwise no discomfort with an ophthalmic examination. The complete exam takes about 10 minutes.
The ophthalmologist begins with an examination of the orbital tissues, outer eyelids, inner eyelids, and conjunctiva (membrane lining the inner eyelids) of first one eye and then the other, checking to see that the eyelids open and close properly and looking for any growths or irritation.
The ophthalmologist then checks the movement of the eyes, typically by asking the person to follow the track of an object such as a pen. Using a small light, the ophthalmologist checks the reaction of the pupils. These procedures help the ophthalmologist to assess the basic neurologic aspects of the eye’s functions.
Visual Acuity and Visual Field
The familiar snellen chart test for visual acuity features lines of letters in differing sizes and order of presentation. Covering first one eye and then the other, the person reads the line with the smallest letters that appear clear.
The ophthalmologist records the result as a ratio that represents actual visual acuity compared to a standard of 20/20, with a score of 20/20 being what the normal eye sees at a distance of 20 feet. Diminished visual acuity may result from refractive errors such as myopia (nearsightedness) or hyperopia (farsightedness), or signal conditions of the eye such as cataract or glaucoma.
The ophthalmologist tests for basic visual field by having the person focus on an object in the distance and signal when he or she can see an object (such as a pen the ophthalmologist holds) that moves into the field of normal vision.
This test assesses peripheral vision and helps detect scotomas (small blind spots in the field of vision), which are both symptoms of glaucoma and retinitis pigmentosa.
Slit Lamp Examination
The slit lamp examination, also called a biomicroscopic examination, uses light focused as an elongated slit in combination with magnification. Slit lamp examination allows the ophthalmologist to closely examine the front structures of the eye including the sclera, cornea, iris, and lens.
The ophthalmoscope is a hand-held device that resembles a flashlight. It has narrowly focused beam of light and a magnifying lens. The ophthalmologist uses it to examine the inner structures of the back of the eye known collectively as the fundus: the retina, optic disk, and macula. The ophthalmologist usually dilates the pupil for ophthalmoscopy.
This test helps detect numerous problems of the eye including retinal detachment, retinopathy, optic nerve atrophy, and papillitis. Conditions such as glaucoma cause characteristic changes to the fundus.
The tonometer is a device that measures intraocular pressure (the pressure within the eye). The most simple variation involves measuring the force it takes for a puff of air to indent the cornea, a noncontact test.
For more accurate results the ophthalmologist numbs the eye with anesthetic drops and touches a tonometry probe against the surface of the eye to measure the pressure. Tonometry is a basic screening test for glaucoma, for which increased intraocular pressure is a key symptom.
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