Today’s guest blogger is Dr. Mary VanHoy. Dr. VanHoy practices in Indianapolis, Indiana. Her practice is limited to behavioral/developmental and neuro-rehabilitative optometric care. She has been practicing for over 30 years and hopes to practice for another 30 years!
This summer I became acutely aware of a growing number of adult patients, predominately female, either self-referred or referred by other health care offices, with complaints of blurred vision, dizziness, disorientation, double vision, and difficulties adjusting to their bifocals or reading lenses. A careful health history did not reveal any remarkable clues such as a change in medication or recent health challenges. Some noticed an increase in myopia (nearsightedness) along with the need for a bifocal yet they could not adjust to the bifocal portion. Another interesting observation was that their ages ranged from the early 40s to early 50s.
Clinical testing usually revealed unaided or correctable 20/20 visual acuities and good ocular health but in carefully evaluating their ability to maintain convergence, it became clear that this particular population had been relying primarily upon their accommodative convergence rather than utilizing fusional convergence to maintain clear, single, binocular (two-eyed) function.
When accommodative convergence is used, the extraocular muscles are being stimulated to point inward by a neurological link to the muscles that control the crystalline lens of the eye in order to change of focus from far to near. When fusional convergence is used, the extraocular muscles are being stimulated to point inward in order to avoid double vision. Perhaps these patients have relied upon their accommodative systems all their lives and this may account in part for their myopia. However, their difficulties and symptoms arose when they began to lose the flexibility of their crystalline lens due to aging (presbyopia) and their ability to call upon their focusing system to maintain clear, single, binocular vision began to fail them.
Clinical evaluation of these patients will show that while their eye muscles are certainly strong enough to converge, they do not fully utilize their fusional convergence system but instead rely upon their accommodative convergence system. Paradoxical findings such as the ability to pass the convergence range tests but difficulties with divergence (relaxing eyes outward) range and the inability to look through plus lenses and still maintain single, binocular vision are definite indicators of this syndrome. These findings clearly indicate their reliance upon their focusing system rather than their eye teaming system or fusional convergence system. Using this ineffective response to try to maintain single vision would explain blurred vision, double vision, and dizziness. They are straining their poor eyes but the over-exertion no longer works for them due to normal aging processes of the eyes.
The good news is that even as adults in their 40s and 50s, the ability to learn how to utilize their fusional convergence system is still viable. Specific guided visual activities and procedures through optometric vision therapy will allow this population to learn to become aware of where their eyes are pointing and how to aim them closer for near viewing without over-focusing to accomplish this. So, it is not a matter of building stronger eye muscles but of improved eye muscle coordination and the use of the proper visual system to maintain clear, single, binocular vision for all their visual needs.
Read more about convergence insufficiency: