Meet Dale, a 61 year-old female who was referred to me by her internist who had successfully undergone vision therapy in our office. Dale reported first experiencing double vision about eight years ago. Actually, as she puts it, she didn’t realize she was seeing double until acquaintances pointed out to her that she was periodically closing her left eye.
Her main concern was that the prism glasses she had received last year were no longer satisfactory, and she was frequently seeing double, particularly when reading or using the computer. Although the prism didn’t totally resolve the double vision last year, they had made reading and computing much more tolerable than it had been in years.
We neutralized Dale’s glasses, and they had 3.5 prism diopters base down in the right eye and 4.5 prism diopters base up in the left eye. Here are her Van Orden Star and Cheiroscopic Tracings respectively, done without her glasses on. (Dale reported that she was too uncomfortable and con-fused with the glasses on to do the procedures.) The vertical imbalance is quite apparent.
On Red Maddox Rod testing in free space, Dale measured 16 prism diopters of right hyperphoria at both distance and near in primary gaze. She was however able to fuse a Worth 4 Dot at distance with only 2^ BD OD and 2^ BU OS. At near she was able to fuse a Random Dot E with 2.5^ BU OD and 3.5^ BU OS.
I advised Dale that contrary to what we had both expected, her prism glasses were no longer getting the job done because they were too strong, not because she needed more prism power. She would actually do better if we lessened the power of the prism rather than increase it. Dale asked me if it was unusual for the type of eye muscle imbalance that she had to improve this much in a year’s time, and I agreed that it was. So I asked her if there we any systemic issues that might be contributory – for example, a problem in her blood sugar level that had improved. Or any known neurological conditions that were getting better. Or medications that she may have been taking that were discontinued during the past year. The answers were all negative, but when I broadened the questions and asked about any significant lifestyle changes involving diet, nutrition, exercise, or stress reduction, her face lit up.
About six months ago, Dale had begun to undertake yoga in earnest. She also began a disciplined exercise program which consisted mainly of walking steep hills. The issue is not whether I would have prescribed yoga and hill climbing as exercises to proactively reduce vertical phoria. It’s that Dale’s history and the timeline strongly support the conclusion that eye muscle control is a head-to-toe affair. Whatever can be done to improve postural control in the vertical plane of the body may also improve vertical eye muscle posture. When I told Dale this, she said: “My yoga teacher is going to love you!”
Although Dale’s measured vertical phoria at distance and near were the same, she was very clear that maintaing single vision for near activities was more challenging than distance. When Rxing prism for vertical phoria, we prescribe the minimum amount of prism to achieve maximum comfort and performance. One can double check this by taking vertical vergence ranges around the point of fusion at both distance and near. We derived the following prescription for distance:
OD: -0.25 -0.50 cx 85/ 2^ BD
OS: +0.50-1.25 cx 90/ 2^ BU
And we derived the following prescription for computer and reading:
OD: +0.75-0.50 cx 85/add +1.50/ 2.5^ BD
OS: +1.50-1.25 cx 90/add +1.50/ 3.5^ BU