Throughout my first 20 years of practice, I diagnosed about 15% of the patients who came to our office with binocular vision dysfunction (BVD). Most were children, as I would perform binocular vision testing on adults only if they had double vision (and most adults were not interested in vision therapy). For those with diplopia or double vision, I usually prescribed static or standard prism.
An Improved Method Improves Symptom Relief
Symptoms of BVD may include headaches, migraines, neck and shoulder tension, jaw pain, and motion sickness, and the extent of symptom overlap with other conditions is broad. Because many patients are not symptomatic, they come in for an eye exam, either not realizing that their symptoms are related, or having been symptomatic for so long that they don't believe a viable solution exists.
Once we began looking for BVD and asking the right questions, we realized that BVD is quite common. Over the last few years, I've seen such an amazing range of symptom improvement with contoured prism lenses, so now I test everyone for BVD, rather than only those registering as highly symptomatic on a questionnaire.
Evaluating Binocular Vision in the Past
Previously, I would perform cover test and phoria testing with the phoropter. Although cover test requires no subjective input from the patient, observing slight eye movements as we move the paddle from one eye to the other can be more difficult if the patient is not concentrating or is looking around. Because of this, the results of cover test can be variable, making it difficult to prescribe off of the results.
With phoria testing at the phoropter, I would often get inconsistent outcomes because of the subjective nature of the test. So many factors—such as fatigue, difficulty following directions, patients accommodating, or the near card being too close or too far—can affect the results of subjective testing.
In the past, when comparing results from year to year, it was not uncommon for me to get vastly different outcomes. Because of the inconsistent results, I would start my prescription with a low prism value, usually 1 prism diopter. If a patient's misalignment was larger, I might start out with 2 prism diopters. If the patient continued to be symptomatic at a follow-up visit, I would bump up the prism value. If they were still symptomatic the next year, I would bump them up again, and so on.
In reviewing a patient's notes annually, I might find, for example, that they had 5 exo at near one year and 2 eso at near the next. Were they currently eso? Or did they have a bad day, and, in over-accommodating, the over-convergence showed an eso deviation? It was hard to get a consistent value.
In short, evaluating BVD used to be more of an educated guess about what to prescribe. Some patients would get symptomatic relief, but only partly. Cover test and phoria testing with the phoropter were the two binocular vision tests I relied on for over 20 years, before we got the Neurolens Measurement Device Gen 2 (NMD2), which measures eye alignment more reliably.
Evaluating Binocular Vision Today
The NMD2 takes a lot of pressure off of the doctor. It's an eye-tracking system that's accurate down to a hundredth of a prism diopter, which is more granular than we can prescribe and also a lot more consistent, even from year to year. I use the diagnostic information that it provides to make decisions about the appropriate prescription for each patient we test.
Normal eye alignment changes depending on if one looks at distance, at a computer, a book, or a cellphone. Contoured prism lenses are designed with the precise amount of prism required at each distance, bringing the images closer together. This takes some of the strain off of the brain and the visual system, so patients don't have to work as hard, thereby providing symptomatic relief. In contrast, standard static prism lenses provide only one type of prism at all distances, which is a limitation that can lead to patient dissatisfaction.
The relief for patients who wear contoured prism lenses comes not only in terms of physical pain, but also economic costs. I had one patient with frequent migraines who would need to decide each time if her headache was bad enough to take a very expensive medication. With contoured prism lenses, she is not only having headaches far less frequently, but they are also not as severe. She has saved over $700 in her medication costs alone and no longer experiences the side effects that the drugs gave her.
Another patient in her 60s is now on the office kickball team after a lifetime of being considered clumsy and uncoordinated. She spent her whole life not being able to enjoy playing sports, and now with appropriate vision correction, she has begun to enjoy a more active lifestyle.
Solutions Within Sight
We must tell patients that we have options to treat their symptoms and that they can find relief from their glasses, without the potential side effects from medications. We can make potentially profound, life-altering results by adding contoured prism to their prescription. The past 3 years of prescribing Neurolenses have been exciting, and I now eagerly look forward to the next patients whose lives will be changed by this technology.
Troy White, OD provides a comprehensive range of services at Dr. Troy White Eyecare, an independent optometry practice offering treatment for dry eye, ocular disease, and emergencies in addition to comprehensive eye exams, pediatric eye care, eyewear, and contact lenses in Chattanooga, TN. Website: https://www.drtroywhite.com/ Contact: [email protected]