Visual Field Testing

A perimeter is used to test your visual field. Your visual field includes both your central and side vision. During this test, while you are seated comfortably, you will be asked to look straight ahead at a central fixation target. You will be instructed to press a button when you become aware of a small shimmering light anywhere within your peripheral field. It’s important that you keep your eyes focused on the central target throughout this examination so that an accurate reading of your visual field is obtained.

This test can detect vision loss, even if the loss is far to the side or quite subtle. Even a large and profound vision loss in one eye’s visual field can go unnoticed by a patient because the visual field of the opposite eye overlaps it to a great extent. One eye simply “fill in” the area of vision loss present in the opposite eye. This is why the side-vision test is always administered to each eye separately.

The nerve pathways from the retina to the part of the brain where vision is interpreted are very uniform from person to person. Because of this uniformity, visual field analysis has a great deal of diagnostic value. Glaucomatous visual field loss usually follows a particular pattern. Other diagnostic patterns of visual field loss can indicate retinal detachment and neurological diseases, adding significantly to the value of this test. The nerve pathways for vision are long and cross over many brain structures on their route from the eye to the very back of the brain (visual cortex). Neurologists make great use of visual fields to help them determine where in the brain a tumor or other pathology is located.

Family History and Glaucoma

According to a study reported at the World Glaucoma Congress, the most efficient way to detect Primary Open-Angle Glaucoma (POAG), which is the most common form of glaucoma, is by knowing the medical history of close relatives with the disease. If you have a parent, sibling or child with POAG you have a greater than 25% chance of developing the disease. Others at risk include African Americans over 40, and anyone over 60, especially Mexican Americans. The earlier POAG is detected, the better the prognosis for retaining vision throughout one’s life. POAG occurs when the fluid that nourishes the eye cannot drain properly and the resulting increased pressure inside the eye damages the optic nerve. This is painless and not visually noticeable at first, but will lead to vision loss and blindness if left untreated. Increased pressure in the eye isn’t a sure sign of POAG, but it is a sign of increased risk for the disease. 

Early diagnosis is of utmost importance. Dr. Griffith examines different parts of your eye to determine if you have or are at risk for developing POAG. Detection and diagnosis relies on tests for pressure within the eye (Tonometry), corneal thickness (Pachymetry) and observation of the optic nerve (Ophthalmoscopy) and visual fields, including peripheral vision. Because of the increased risk among family members, a review of family history is also part of the screening. (Likewise, a positive diagnosis of POAG would be valuable information for close family members.)

Vision lost to glaucoma cannot be restored. The goal with treatment is to slow the disease progress and prevent further vision loss. The most common treatment is a prescription eye drop or pill meant to reduce pressure in the eye. It is important for Dr. Griffith to be aware of other medications you are taking in order to fi nd a compatible treatment for the glaucoma; fortunately there are usually several options. Additional treatment includes laser surgery or sometimes more traditional surgery; both physically alter and improve the drainage structure in the eye. In conclusion, regular eye examinations are a certain age is vital to prevent unnecessary vision loss. If you are newly diagnosed with POAG or any form of glaucoma, Dr. Griffi th can give you much more detailed information.