DW is an 85 year-old who has increasingly begun to close his left eye when driving. I hadn’t seen him yet this calendar year, so his acquired left exotropia was something I knew to be relatively new. As we talked about it, he was aware of his tendency to close his left eye in bright sunlight – which helped him cope better when driving. While this phenomenon has been widely reported in intermittent exotropia, we might paraphrase Buffalo Springfield and say “there’s somethin’ happenin’ here; what it is ain’t exactly clear”.
As I examined him and we talked further, he acknowledged that he was seeing double periodically but, other than driving, he seemed quite stoic about it. Of course when he closed his left eye while driving he solved one problem (eliminating diplopia) but created another (collapsing his visual field). I was anticipating that we could use some base-in prism to help him fuse, but the rule for acquired exotropia in the golden years is to presume non-comitancy until proven otherwise. Sure enough, DW has classic “V” pattern exotropia.
DW has bilateral IOLs and is emmetropic at distance. He enjoys his freedom from glasses and wasn’t enthusiastic about using prism unless I felt it was absolutely necessary. I probed the influence of both base in prism and yoked prism bases up, but it turned out that counseling him on the dramatic improvement in fusion if he elevates his chin slightly was much more dramatic than anything I could do with prism. He had no idea that his fusion varied so widely in the vertical plane.
We further discussed alternative approaches including spot or uni-temporal occlusion of the left lens, strabismus surgery, and optometric vision therapy. Ultimately DW was happy just becoming aware of the slight adjustment he needed to make in head posture to comfortably maintain fusion. We agreed on a little mantra that he could practice when he got in the car to remind himself to slightly lower his gaze: “Head’s up when driving”.