A Medical Mystery Posed by Blurred Lanes

“Are you practicing 80 mph slalom turns?” my wife asked.

Road conditions were normal. Our SUV had new tires. But the stripes often seemed to merge together. Sometimes the bands converged late in the afternoon, sometimes early. Sometimes under the scorching sun; sometimes in the fog. If I closed one eye, the paths became separate again.

What’s happened? I’ve worn myopia glasses since the fifth grade; During the year I visited my optometrist; my prescription was up to date. When we got to Tahoe, I went to the optometrist before I unpacked my skis. She said that everything was fine with my eyes, but advised me to do an MRI to rule out brain hemorrhage or a tumor. It happened a few days later.

She also advised me to see a neuro-ophthalmologist, an increasingly rare specialty. There are only about 600 of them nationally, and since many of them are in academic research or general ophthalmological practice, only 250 of them are full-time clinicians. According to an article last year in the Journal of Neuro-Ophthalmology, there are no medical practitioners in six states.

An optometrist in Tahoe warned that it could take months to make an appointment with one of the few medical practitioners in the area. But my brother, a Stanford surgeon, helped me get an appointment at Stanford Medical Center, a four-hour drive away, in Palo Alto, California, next week. Dr. Heather Moss performed a 90-minute examination, taking measurements that included the degree of correct centering of my eyes.

My diagnosis is esotropia, which means turning one or both eyes inwards.

When Dr. Moss placed a triangular plastic strip in front of each eye, the bouncing stopped. The piece of plastic was a collection of prisms, varying in strength from top to bottom. She alternated prisms until we got it right.

Wayward eyes can turn outward, up or down. These are all forms of strabismus, and double vision is the main symptom in adults, whose brains are used to receiving two slightly different images. (Without them, you wouldn’t have depth perception or the ability to see in 3D.) Someone with symptoms of strabismus receives two images. But they are not in order, because the eyes are displaced, and the brain does not compensate for the anatomical and mechanical defect.

Usually congenital, most often diagnosed in children whose symptoms show up in “lazy eye” because the brain suppresses images from the weak eye. Some children wear a strong eye patch to retrain the lazy eye. Many children have surgery to reposition the muscles that control the weak eye.

Strabismus comes from Strabo, the Greek word for strabismus, which accurately describes the reaction of adults who compensate by closing either eye. This eliminates conflicting binocular images from both eyes that the brain cannot overcome. According to the journal Ophthalmology, it affects about 4 percent of adults. But it often goes undiagnosed and people unwittingly live with imperfect vision. “Most conventional ophthalmologists just look at the eyes, not the movement of the eyes,” said Dr. Mark Dinkin, a neuro-ophthalmologist at Weill Cornell Medicine in New York.

Larry Froman, a professor at New Jersey’s Rutgers School of Medicine and executive vice president of the North American Society for Neuro-Ophthalmology, said the specialized field attracts fewer physicians because it requires an additional year of formal training beyond neurology or ophthalmology.

While surgery is sometimes the solution to this problem in adults, prisms are a common remedy. They can permanently fit into lenses, displacing light and shifting the position of what the eye sees, tricking the brain into correctly interpreting images from both eyes. Choosing the right degree of correction can be difficult. Prisms range in strength from 1 to 40 diopters (1 being the weakest), although they are rarely given more than 15 diopters due to the distortion they can create.

Dr. Moss recommended that I try temporary vinyl Fresnel lenses that are pressed onto the inside of the glasses with water. These one-millimeter-thick lenses allow patients to experiment with different strengths. The problem is that they can fall off, and plastic with thin etched lines on the surface is not as clean as lapped prisms. I tried lenses with 1 diopter, then 2 diopters before settling on 3 diopters for the next three months.

Driving was no longer excruciating, but my eyesight was far from perfect and even seemed to regress a little. When I returned to the East Coast, Dr. Dinkin of Weill Cornell took over. In his examining chair, I finally got double vision.

When there was a big “A” hanging on the wall and I removed the Fresnel lens from my glasses, I saw two “A”s. When I looked through his manual prism, the A’s magically merged together. What I called interstate 80 jumping images were actually separate images my brain was trying to put together. At the time, I didn’t think I was seeing double because the middle lane looked almost the same as the left lane. Actually, I saw two left lanes.

Dr. Dinkin increased the power of my prism to 10 diopters. He divided the prisms into lenses for both eyes – 5 and 5 (with light deviating in different directions). By the end of spring, Dr. Dinkin said it was time to put a correction in a pair of permanent lenses.

The new glasses worked well, although there was another problem. Lenses with permanent prisms are thicker at the edges, resulting in distortion that creates the effect of a mirror in a funny house. It is especially problematic to go down the stairs. So I got another pair of glasses, with slightly weaker prisms – 4 and 4 diopters. I try to use them most of the time, leaving 5 and 5 points for driving or when I need to improve my eyesight.

How did I end up diagnosed with strabismus as an adult? Dr. Dinkin and Dr. Moss agreed that I probably had it all or most of my life, although the displacement of my left eye is almost imperceptible. Before, no doctor found a problem, because no one was looking for it, and I did not make any complaints. My eyes themselves did not change their position. The symptoms of this condition appeared with age and fatigue.

My misery with vision was another of the dangers of growing up. Near the end of our stay in Tahoe, I fell off my skis for the first time in 20 years, spraining my left thumb and right shoulder. No big deal – they get better with ice, rest, a splint, and 15 weeks. But along with my eyes, I began to wonder about my long-term chances. Good thing I’m not a racehorse.