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People often wonder what a comprehensive eye examination involves, what it tells the physician, and how the physician uses the results from an eye exam to devise a treatment program.

The first thing an ophthalmologist or optometrist checks are the eye's vital signs: visual acuity, eye pressure, and visual fields.

Visual acuity: Visual acuity is measured on an eye chart and recorded using numbers like 20/20 or 20/50. Looking through a single pinhole or multiple pinholes can give an estimate of the best vision that could be achieved if the lenses in a pair of eyeglasses were further optimized. This is an easy and useful method to assess whether a change in a lens prescription would be beneficial. Another technique for testing best visual acuity is called refraction. Here, different lenses are placed in front of the eyes to determine which would improve vision.

Eye pressure: This is measured using a special device called a tonometer. One form of this instrument is about the size of a fountain pen and is applied to the cornea for a few seconds to measure the pressure of the eye. This test screens for glaucoma and other eye health problems.

Visual fields: A test of visual fields measures peripheral vision. Macular degeneration affects central vision and usually spares peripheral vision.

The doctor will also take a patient's medical history. A complete examination is multi-stepped and includes gathering information about past medical and ocular disorders, medications, nutrition, allergies, history of smoking and alcohol use, and family medical problems. Then comes the actual eye exam.

Examination of the front portion of the eye
The front of the eye includes the parts we see in the mirror plus the lens which lies behind the pupil.

Motility of the eye: The doctor checks whether the eyes move freely and in alignment. The alignment is very important in order to avoid double vision.

Eyelids: The eyelids are checked for evidence of infection or malfunction.

Conjunctiva: The conjunctiva is a thin layer of cells covering the portion of the eyeball between the lids. Inflammation and redness of the conjunctiva can be a sign of infection or allergy.

Tear film: As we age, the tear film often becomes less capable of keeping the surface of the eye properly lubricated. This is called dry eye and is not related to the dry form of macular degeneration.

Cornea: The cornea is the clear front surface of the eye that is responsible for most of the eye's focusing power. In refractive surgery, lasers are used to change the curvature of the surface of the cornea so that eyeglasses or contact lenses are no longer needed. The doctor looks for evidence of corneal irritation, inflammation, and infection.

Lens: The other main component for focusing images is the lens. When the lens becomes cloudy it is called a cataract. A cataract that becomes cloudy enough to significantly impair vision can be removed and replaced with an artificial lens (called an implant). The lens is examined to determine if a cataract is present and to judge its severity.



Iris: The iris is the portion of the eye that gives it color. The iris controls the size of the pupil, enlarging it to allow more light to enter in low light situations and constricting it to reduce the light entering in bright light situations. Problems of the iris are relatively rare but can occur in certain situations including diabetic eye problems and certain types of inflammation.

Anterior chamber: The anterior chamber is the clear fluid filled space separating the cornea and iris. Signs of inflammation, infection, or hemorrhage can sometimes be early warning signals of a problem with the overall health of the eye.

Examination of the back inside portion of the eye
The back inside section of the eye contains mainly the vitreous gel, retina, and blood vessels.

Vitreous gel: The vitreous gel is a clear jelly-like substance filling the back portion of the eyeball and helping to give it form. In macular degeneration, the vitreous can on rare occasions contain blood that has leaked from under the retina.

Peripheral retina: A number of eye disorders involve the peripheral retina. While this area is generally not affected by macular degeneration, it is examined to be sure that other eye disorders are not involved.

Central retina or macula: Several components of the central retina or macula may be involved in retinal disease. Therefore, a retinal specialist will devote a great deal of attention to this part of an exam. The doctor may look for signs of dry macular degeneration (drusen, pigment, or thinning) and wet macular degeneration (fluid, blood, debris).

The components of the eye exam will vary depending upon the circumstances and the information needed by the eye doctor to provide the necessary care that a problem requires.