Stereopsis improves after LASIK correction of anisometropia

Orlando-In a small interventional case series, more than two-thirds of patients undergoing LASIK for correction of a high degree of anisometropia had improved stereopsis following surgery, according to Scott E. Olitsky, MD.

Dr. Olitsky, ophthalmology section chief at Children's Mercy Hospital and Clinics, Kansas City, MO, and associate professor of ophthalmology, University of Missouri-Kansas City, presented a poster on the study at the annual meeting of the American Academy of Pediatric Ophthalmology and Strabismus.

The principal investigators were Mai Hong Phan, MD, Yen Hai Tran, MD, and Tuan Ngoc Luong, MD, of Ho Chi Minh City Eye Hospital, Ho Chi Minh City, Vietnam, who recruited patients and performed the surgeries.

"They had talked to me about LASIK in these patients as a way to help their binocular vision," Dr. Olitsky said. "We discussed the fact that the effect of LASIK in this population of patients was not really known. They had data on one or two patients, and I suggested we collect data from a series of patients that they were treating to understand the effects better."

Goal of emmetropia

The study included 30 adults (ages 18 to 48) with anisometropia of 3 D or more and best spectacle-corrected visual acuity of 20/30 or better in each eye. After being tested for stereopsis with the Titmus test, the patients were treated with LASIK with the goal of emmetropia, Dr. Olitsky said. Refraction and stereopsis were checked 1 to 3 months postoperatively.

Twenty-three of the 30 patients had improved stereopsis, including five patients who had no preoperative stereopsis. Preoperative stereopsis ranged from 80 seconds of arc to none, while the range of postoperative stereopsis was 40 to 400 seconds of arc in 27 patients. In addition, 10 patients displayed high-grade stereopsis postoperatively, including one who had no stereopsis before surgery. Three patients continued to have no measurable stereopsis following LASIK.

Preoperative anisometropia ranged from 3 to 13.375 D; following surgery, anisometropia was less than 1 D in all subjects.

Dr. Olitsky, who is unaware of any studies conducted in the United States on the effect of LASIK correction of anisometropia on stereopsis, said that the results of the case series were unexpectedly strong.

"It was certainly surprising to me to see some patients start with no demonstrable stereopsis and end up having excellent levels of binocular function. I don't think any of us expected that," he said.

He added that he would be interested in starting a clinical trial in the United States to substantiate the findings and investigate further. For example, it is not known which patients in the case series had acquired or congenital anisometropia. Additional studies could be performed in a setting where such details are available.