Valuable tools to determine functioning vision
Your level of functioning vision is the most important aspect of your eyesight. Many patients relate to me that they can read letters on the eye chart but are still having trouble reading, seeing signs, driving at night etc. They also suffer from headaches and eyestrain. What is wrong with the visual system when you can see the letters on the eye chart but are unable to convert this acuity into functioning vision? Let’s look at two diagnostic steps that can help us understand why this limitation occurs.
Functional visual fields
|There are methods of evaluating the visual filed or peripheral vision. The first is static visual fields. A light of varying intensity is briefly flashed in the peripheral fields. No movement of the object is made just a flash of light. When you see the light, you respond by pushing a button. After responding to many test stimuli, a map is made of your peripheral fields. Most eye doctors test peripheral vision using this method. The problem with this test is does not measure our functioning visual field. Our visual system was designed to recognize motion.|
Recognizing a moving target more closely mirrors our functioning visual system. Our visual system was developed out of the need for protection and for hunting and gathering. We recognize a movement in the periphery and then we respond accordingly.
The second and more accurate test of functioning vision is the kinetic or functional visual fields. Objects of white, green, red, and blue are moved from the periphery toward the center. The field is measured once the perception of color is made. Many patients who have normal acuity and normal static visual fields will have a marked constriction of their functional or kinetic colored fields. This translates into major functional problems with reading, recognizing objects seeing signs etc. The functional fields can also reveal imbalances in the autonomic nervous system and neuroendocrine systems. Abnormalities in the red field are related to chronic problems such as high blood pressure and arteriosclerotic vascular disease of the retina and the optic nerve. Abnormalities of green relate to more focal acute problems such a localized infection in the body. Blue is found to be linked to abnormalities of the mental and emotional states. After this important diagnostic test, we are able to prescribe therapies to correct the constricted visual field any color abnormally. This test has become an important part of our evaluation and treatment of all of our patients
The second functional test is the VOSTAR.
This test measures how your eyes coordinate with each other and your perception of space. An example of a coordination problem might be that one eye has a tendency to deviate inward. This could result in eye strain or double vision when you are fatigued. The idea of perception of space is something new to me but it has become very valuable in evaluating and treating patients. A patient’s visual field might be normal and the acuity level very good but if the perception in space is deviated then functional vision will be limited. I have observed that many macular degeneration patients have their visual space pulled inward.
This inward pulling results in a decrease in peripheral vision. This can be a problem especially when a macular degeneration patient is loosing his central vision. This additional loss of peripheral vision can greatly limit the functioning ability. Once the peripheral vision is expanded, the quality of the functioning vision greatly improves.