YAMOUT OPTICAL CENTER

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The Eye Examination

Whether you've had perfect vision all your life or wear prescription glasses or contact lenses, your vision can become worse. Your vision can deteriorate as you grow older for various reasons, such as spending significant amounts of time looking at a computer screen or having diabetes.


When you visit an eye doctor, you will take one or a series of visual tests. These include:

History—Although this is not actually a test, you will be asked several questions related to your health history. Although many patients find this cumbersome, it is very important that your physician be alerted to any previous medical illness, surgery, or injury, as this information will aid in the overall assessment of your eyes.

Visual acuity test—This test measures how well you see from a distance. Your vision will be tested at 20 feet (while looking across the room), and again at 14-16 inches away from the eye chart (while holding a reading card).

Refraction—Originally, refractions were performed using a trial frame or manual phoroptor. However, many offices now use an automated refracting machine which instantly measures the power and outer shape of the eye. Regardless of what method is used, you will have the opportunity to make sure that your prescription is comfortable during the subjective refraction. You will be shown different lenses of varying degrees of power: you will then be asked to choose which one appears clearest to you while reading the eye chart. Although many people dislike this portion of the refraction, it is necessary to determine whether or not the prescription is correct for you.

Binocular vision (extra-ocular muscle alignment test)—These series of tests determine how your eyes work together. You will be asked to focus on different objects at varying distances while the examiner observes your eye movements. The test is performed using an eye occluder, where one eye is covered alternately while focusing in the direction of an object.

Slit-lamp exam—The slit-lamp instrument is basically a microsope. It allows a close examination of the front structures of the eye and the lens. The slit-lamp is often used to diagnose contact lens problems. In addition, this instrument allows the examiner to find early cataracts, corneal scars, and other problems associated with the front structures of the eye.

Pupil dilation—Your eye doctor will place drops into your eye to widen the pupil. This allows a better view of the retina. The doctor will examine your retina for early signs of disease, including: leaking blood vessels; retinal swelling (such as macular edema); pale, fatty deposits on the retina (signs of leaking blood vessels); and damaged nerve tissue and blood vessel changes. After the examination, your close-up vision may remain blurred for several hours.

Tonometry—A standard test that determines the fluid pressure inside the eye. Elevated pressure is a possible sign of glaucoma, a common eye problem in people with diabetes.

Before a tonometry, you may have a topical anesthetic applied to your eyes. After the procedure, do not rub your eyes for 30 minutes. Here are various ways the procedure is conducted:

· Tonometry—The tonometer in the form of a contact lens is applied directly to your eye's surface.

· Noncontact tonometry—The tonometer does not touch your eye. Instead, it blows a puff of pressurized air into your eye and records the amount of pressure.

· Indentation tonometry—You lie on a table or in a chair with your head resting back while a manual Schiotz tonometer is placed on your eye, and a pressure reading is taken.

· Applanation tonometry—You sit upright with your head placed in the slit-lamp headrest. The tonometer is then placed against your anesthetized cornea.

Visual field tests (Perimetry)—These show field of vision (central and/or peripheral) and allow doctors to pinpoint the extent of vision loss. This test looks for glaucoma and other factors that may affect your fields of vision.

Ophthalmoscopy (Dilated Fundus Exam)—The retina is the only area of the body which allows the physician an external view of your body's vascular and arterioral system. For this reason, a thorough eye examination can provide clues about your overall health and signal evidence of many systemic diseases before their symptoms show up elsewhere in your body. The dilated fundus evaluation allows the practitioner to inspect the fundus, or back portion of the eye, which includes the retina, optic disc, retinal blood vessels and arteries. At the start of the procedure, medicated eyedrops are administered to dilate, or enlarge, the pupil and make the fundus easier to study. In a darkened examination room, the doctor will focus an ophthalmoscope in each eye, one at a time. This instrument projects a beam of light while the examiner looks through a magnifying lens to get a larger view of the back of the eye.

How Important Is A Dilated Exam?

The dilated fundus exam is considered to be one of the most valuable tests conducted during an eye examination because it can detect signs and physiological effects of various circulatory, metabolic and neurologic disorders such as high blood pressure, diabetes and some tumors. It can also aid in the diagnosis and assessment of the following eye disorders:

- Cataracts

This opacification of the normally clear lens of the eye mainly forms in older adults, but anyone is susceptible. Cataracts may result as a side effect of certain medications, or a complication of other systemic disease. Its typical symptoms of glare, hazy or blurry vision may be very slight during the early stages. A dilated exam can aid the evaluation of cataracts.

- Cloudy Vitreous

The vitreous is the clear, almost gelatinous substance that fills the main chamber inside the eyes. It, too, can become clouded and obscure vision by scattering light before it reaches the retina. Through a dilated fundus evaluation, the first signs of cloudiness may be seen so treatment can begin before vision is compromised.

- Retinal Tears and Detachment

A detached retina usually occurs when there is a tear, or hole, in the retina, allowing fluid to diffuse behind it and push the retina away from the wall of the eye. Depending on its size and location, the person may not have any symptoms in the early stages. Good outcomes are dependent on early detection and repair. A dilated eye exam may be the only means of detection in many cases.

- Optic Nerve Disease

The optic nerve is the bundle of nerves that transmits signals from the retina to the brain. When it becomes damaged or swollen from disease, sight is lost because the brain may not receive all of the necessary signals. The optic nerve can be better observed through the dilated pupil and evaluated for its health.

- Glaucoma

A leading cause of blindness, glaucoma results in damage to the optic nerve, usually associated with increased pressure within the eye. Because the disease is often asymptomatic, many people lose much of their sight before it is diagnosed. With early detection, most or all of a person's vision may be saved. Careful evaluation of the optic nerve is integral to the management of glaucoma.

- Diabetes

Annual eye examinations including a dilated fundus evaluation are a critical component of diabetic care. Diabetes causes changes in the vascular system: producing microaneurysms, hemorrhages and fluid leakage into body tissues, including the retina. Without dilation of the pupil, early stages of diabetic retinopathy may be missed. Through a dilated fundus evaluation, the changes that occur in retinopathy can be seen and monitored sooner. With early detection, these complications are more effectively managed.

- Other Diseases

Risk factors for other diseases, including hypertension and elevated cholesterol levels, are often identifiable in the eyes as well. Hypertension produces a narrowing of the arteries when blood pressure is significantly elevated. This can lead to hemorrhages in the retina. The appearance of retinal hemorrhages due to hypertension can be easily distinguished from hemorrhages due to diabetes during a dilated fundus evaluation.

Increased levels of lipids and cholesterol may result in plaques or clots in retinal blood vessels, indicating potential risk of stroke. These plaques may also be observed and detected during a dilated fundus evaluation.

Neurological disorders, such as Multiple Sclerosis and space occupying tumors in the brain often cause swelling and inflammation of the optic disc. Additionally, subtle changes in color vision, depth perception and peripheral vision may be early signs of neurologic disorder. Early detection and effective management of these potentially life threatening conditions can be facilitated through a thorough eye examination.