Most people with glaucoma do not experience noticeable symptoms. Therefore, it is important to schedule a comprehensive eye examination with an eye care professional. Detailed glaucoma evaluation is the only way to tell if you have glaucoma.
Below are some of the tests involved in a complete eye examination. This information will help you better understand what to expect during your eye examination.
The purpose is to establish patient history. Before examining your eyes, your doctor will ask you about your general health, medical conditions, and prior eye problems. It is important to provide accurate information as well as a listing of all medications (both tablets and eye drops) that you are using. This should include prescriptions and over the counter medicines.
Visual Acuity Test
This test is done to detect changes in vision. The first step in the actual examination of your eyes is to test your vision. Your ability to see sharply at a distance or up close for reading is referred to as visual acuity. For this test, you will be asked to read from an eye chart. If you wear glasses or contacts, you are familiar with this part of the exam.
Slit-lamp Examination for Glaucoma Evaluation
Slit-lamp examination is an extremely important part of the eye examination and is usually performed at each visit. The slit-lamp is a type of magnifying glass, or microscope, that is used to examine the eye. It is also known as a biomicroscope.
During the slit-lamp test, you are asked to place your head on a chin-rest and a magnified view of the eye is examined. A thin light beam illuminates the eye and gives your doctor a good view.
Eye Pressure Measurement – Tonometry
Measurement of eye pressure (intraocular pressure – IOP) follows the slit-lamp examination. This test, also known as tonometry, is important because eye pressure may be the single most important factor that affects the course of glaucoma. The accurate measurement of eye pressure is essential.
To measure eye pressure, an anesthetic (numbing) eye drop is placed on the eye. The drop may briefly sting. The surface of the eye is temporarily numbed within a few seconds. Eye pressure can then be measured with a device known as a tonometer. For this measurement, the tonometer is gently placed against the surface of the eye. You will not feel the tonometer on your eye. This procedure is quick, reliable and generally painless.
Several other methods of measuring eye pressure are sometimes used. One of these, an “air puff” tonometer, is less accurate, but eye drops are not required. This method of measurement is also generally painless.
Gonioscopy for Glaucoma Evaluation
The purpose is to evaluate the potential of drainage of the fluid in the eye. Gonioscopy is used to determine which type of glaucoma you may have. Once the surface of the eye has been numbed, your doctor will place a special contact lens on the eye. This special lens will allow your doctor to examine the eye’s drainage system.
Using the slit-lamp for magnification, your doctor can determine whether the drain is open or closed, check its color, and see if scar tissue is present. You might feel slight pressure on the eye as your doctor moves the lens, but this should not be uncomfortable.
Optic Nerve Examination
Glaucoma damages the optic nerve, but the damage is painless and difficult to detect. It is important for your eye doctor to carefully examine the back of the eye, where the optic nerve is located. Eye drops are used to dilate (widen) the pupil to give your eye doctor a better view of the optic nerve.
An ophthalmoscope is used for this examination. You may experience a mild blurring of vision, glare from bright lights, or difficultly reading for as long as 6 hours following pupil dilation. This examination can be somewhat uncomfortable.
Many other diseases besides glaucoma can cause loss of vision or damage to the optic nerve or the surrounding retina. Your doctor will use a variety of techniques, most of which use a bright light, to examine almost every aspect of your retina.
Visual Field Examination for Glaucoma Evaluation
The term visual field (peripheral vision) refers to the entire area you can see while looking at a fixed location. For example, while watching a stoplight, you might notice a car pulling up beside you in the next lane. Your peripheral vision helps you to perceive the car and its movement. The visual field is large when both eyes are working properly. With glaucoma, the field of view is often reduced.
The visual field test is an integral part of glaucoma evaluation. Visual fields are measured using a computerized instrument called Humphrey. During the visual field test, you will be asked to look straight ahead and indicate by pressing the button in your hand every time you see a flash of light. The light flashes appear randomly and in different areas of your visual field. Every time you see one, you press a button. This helps your eye doctor draw a map of your vision.
The eye examination is necessary for the proper diagnosis and treatment of glaucoma. Each part of the examination provides your eye doctor with information that will ensure you receive the best possible care.
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