The Eye Examination's Purposes

This is not a description of every eye examination but some of the purposes behind the eye examination in general.

The patient may well speak of long-standing or recent eye problems, and about occupational and recreational activities relevant to the eye (like using a computer).

Can both eyes focus on an object moving toward them? Can both eyes move easily from side to side and up and down?

How is the focussing of the eye, near and far?

How big are the pupils, and do they react quickly and adequately to changes in light?

The slit-lamp microscope gets a magnified view of the outer layers of the eye, which are carefully checked for signs of injury or disease.

An ophthalmoscope, the handheld device with a bright light, looks through the eye to the retina, checking the tiny blood vessels for damage due to high blood pressure or diabetes. It can illuminate a detachment of the retina from the back of the eyeball or blank spots on its surface.

The Snellen chart with letters allows the examiner to check for refractive errors.

A Phoropter, into which the examiner inserts different lenses, provides information about which corrective lenses are best. The same lens that gives the examiner the clearest picture of the retina should give the patient the clearest view of the outside world. The patient's answers confirm the visual information to the examiner. Contradictions between examiner and examinee lead to additional lenses used or repeat lenses to resolve the issue.

Tests for peripheral vision utilize moving objects, and color vision might be checked with a series of colored cards.

A tonometer tests for glaucoma. Tonometers use a fast puff of air and do not require drops. Eye drops anesthetize the eye and a probe touches the eyeball to determine intraocular pressure.

Once eye examiners inserted eye drops to enlarge the pupil and look into the eye. However, enlarged pupils can temporarily inconvenience the patient by making bright light uncomfortable and the eye might be irritated by the chemicals badly affecting other tests of functioning. Of course some tests, like cataract and retinal disease, may necessitate drops but usually they are avoided.

The eye examination may also reveal symptoms of diseases elsewhere in the body, such as blood disorders, diabetes, high blood pressure, and tumours of the pituitary. Arthritis and other connective tissue disorders also affect the eye.


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