Q: My eye doctor thinks I may be developing glaucoma, and keeps making me take those “visual field” tests. I find those difficult and stressful to do. Is this really necessary?
A: In a word…..yes. Let me explain: visual fields are the area of your vision that each eye can see. Not how clearly or sharply you see, but the area in front of you that each eye can see. We use very sensitive technology to test and evaluate your field of vision for each eye in order to detect any change or defect.
Essentially, you will be shown tiny dots of light for each eye and your job is to respond when you see each dot. This is sort of like a hearing test…..you are given a stimulus and asked to respond every time you detect the stimulus. The test is very sensitive and can be challenging for some patients. The goal is to find any defect/s or problems in your field of vision very early. Visual field exams can usually find defects long before you would notice something missing in your regular vision!
Just for background, our eyes have far more nerve fibers in the optic nerves than “needed”. This over engineering means we can actually lose a lot of nerve fibers before we experience any defect in our visual field. In fact, by the time a field defect can be detected, we have already lost far too many optic nerve fibers. We naturally lose nerve fibers every year of life, but certain eye diseases can cause nerve death at a much faster rate. Our goal is to find and treat any eye disease long before you would notice any change or loss in your vision.
Likely the most common misconception about visual fields and eye diseases would be the thought the glaucoma first causes one to lose some “side vision”. This is not accurate. In reality, the earliest changes or defects in glaucoma affect our central vision. Technically, we find most early signs in the central 10 to 25 degrees of vision. So self evaluation of side vision is generally not of value.
There are certainly eye disorders and other vascular problems that do cause loss of side vision, but the most common reason most people have visual field testing would be suspicion or treatment of glaucoma. Some very good news……just this past year we now have a virtual reality headset testing instrument that is just as accurate as the traditional “big bowl” instrument, but patients find much easier and faster! These new virtual reality ( VR ) instruments are not universal, so if you have found the traditional method difficult or stressful, ask your eye doctor if they are using the new VR instrument?
Glaucoma diagnosis and control does require certain monitoring tests like eye pressures, visual fields, and optic nerve imaging. These tools allow us to intervene early and prevent any loss of vision for most patients!