Revisiting BOP and BIM – Part 3: The Role of Accommodation
Treating the beast that is the Accommodation/Vergence relationship can be daunting, but by breaking down the moving parts and gaining a finer understanding of how each area can be addressed, the beast shrinks significantly. Understanding the progression that leads into the BOP/BIM work from the accommodative side is half the battle, and is today’s focus, if you’ll pardon the pun. Let’s be sure we know “how to get there” when treating accommodation. There are many moving parts to consider, and following a solid hierarchy when treating a patient, certainly would yield the finest results.
Many offices utilize plus and minus lenses in Vision Therapy only after the patient has successfully completed a range of real space activities, including a series of near to far jumps as well as a series of activities designed to help the patient understand the differences in feeling tone between convergence and divergence. Once these activities have been mastered, plus and minus lenses usually are introduced. Considering the physiological connection between accommodation and vergence, both plus and minus lenses can be used to strengthen accommodative vergence and fusional vergence, as well as increase the overall flexibility between the two systems. Plus lenses decrease the amount of accommodative demand (relax accommodation), thereby asking the patient to stimulate fusional convergence to maintain a clear and single image. Conversely, minus lenses increase the amount of accommodative demand (stimulate accommodation), while asking the patient to relax fusional convergence to maintain a clear and single image.
In most cases, our patients will begin with monocular lens work. When lenses are used monocularly, the patient is able to stimulate or relax accommodation without a concern for the performance of vergence. When a patient is having difficulty with stimulation of accommodation, they may be asked to perform monocular tasks with a near target while placing and removing a minus lens from in front of their eye. The patient’s primary concern and goal in this activity is for a clear image. Under these monocular circumstances the vergence system will still be active; however, the vergence demand and input is removed because the patient is not allowed to gather information under binocular conditions.
If a patient is having trouble specifically with relaxation of accommodation in real space, the same monocular conditions can be arranged with a plus lens. The patient is asked to perform monocular tasks with a near target while placing and removing a plus lens from in front of their eye. The primary goal in this activity is for a clear image, and since the patient is patched, there is no need to be overly concerned with the performance of the vergence system just yet. This way, patients can be encouraged to practice relaxing accommodation without concern for diplopia. The level of difficulty on this activity can be increased with higher powers of lenses, both plus and minus, as well as an increase in the frequency of shifting from one power to another.
The next step in most Vision Therapy programs is for binocular lens work with suppression controls. Since we are now introducing vergence, the demand of both plus and minus lenses is far greater and requires coordination and integration of the two systems under binocular conditions. For instance, if a patient is performing a binocular reading task with a pair of +/- 2.00 flippers, the plus lenses will cause he accommodative system will be relaxed, thereby requiring the patient to stimulate or maintain vergence at the plane of regard in order to maintain clear and single vision. The minus lenses will cause the accommodative system will be stimulated, thereby requiring the patient to relax or maintain vergence at the plane of regard in order to maintain clear and single vision. In a Vision Therapy setting, binocular accommodative skills can be performed while the patient is seated and reading for pleasure, with print and material that is age appropriate. The +/- 2.00 flippers can be “flipped” at the end of every sentence, at the end of every line of print, or even after every few words. The more frequent the “flip” from minus lenses to plus lenses, the greater demand on the patient to maintain flexibility between accommodation and vergence and the greater need for increased stamina in shifting from one posture to the other. Other ways to increase load, or demand, would be to choose a smaller font size, choosing a higher power of lens flippers (i.e. +/- 2.50), as well as making the “flips” from one power to another more frequent. In these circumstances, the demand of the patient is raised as the level of difficulty is increased.
The American Heritage Dictionary defines binocularity as “relating to, used by, or involving both eyes at the same time”. The key ingredient in a successful binocular accommodative rock procedure is to have a suppression control in place to ensure both eyes are being used “at the same time”. Suppression controls are always necessary to ensure patients are truly using both eyes equally and at the same time to gather information. Some methods for suppression control might be red/green bar readers with red/green glasses or stereo strips with a pair of orthogonally arranged, polarized lenses. With either of the aforementioned anti-suppression methods, the patient is able to receive direct feedback as to whether they use both eyes equally. If this is not the case, the patient will be unable to see the corresponding area with eye that they are neglecting. This is important because as the accommodative vergence demand is raised and lowered through the use of plus and minus lenses – BOP and BIM – and the involvement of both eyes together will be challenged and fine tuned.
As therapists, helping our patients build strong visual skills that will transfer into the real world should always be atop our list. In order to ensure these accommodative skills do transfer, we should always look to build a solid foundation under monocular conditions, eventually progressing into increasing the accommodative vergence flexibility while building stamina within the accommodative vergence system.