Surgical strategy varies in youths with high AC/A ratios

Take-Home Message

Alignment at distance and patient age are factors contributing to treatment approaches for juvenile patients with high accommodative convergence-to-accommodation ratios.

Dr. Kushner

By Lynda Charters; Reviewed by Burton J. Kushner, MD

Madison, WI-Adolescents with high accommodative convergence-to-accommodation (AC/A) ratios should be treated differently based on whether the patient is aligned at distance and depending on patient age.

“If the patient is aligned in the distance, my experience influences my recommendations,” explained Burton J. Kushner, MD. He is the John W. and Helen Doolittle Professor, Department of Ophthalmology and Visual Science, University of Wisconsin School of Medicine and Public Health, Madison, where he is the director of the Pediatric Ophthalmology and Adult Strabismus Clinic.

A review of 374 patients with high AC/A ratio esotropia by Dr. Kushner revealed that 99% of patients who maintained good distance alignment outgrew the need for bifocals by age 18.

A high AC/A ratio is one in which the near esotropia exceeds the distance esotropia by 10 prism diopters (PD) or more and is approximately equal to the distance esotropia with added plus lenses at near.

Dr. Kushner dichotomizes his treatments based on two different parameters. He uses a different approach if optical correction achieves satisfactory alignment at distance than if the distance alignment is unsatisfactory.

For his purposes, he defined satisfactory alignment as being within 8 PD of straight. He also adjusts his treatment depending on the patient age-i.e., a young teenager at age 13 versus an older teenager at age 18.

Patients not aligned at distance

In this patient group, most surgeons agree that surgery is a necessary option, Dr. Kushner explained.

Common treatment options are:

• Recessions of the medial rectus (MR) muscle for the near angle with or without prism adaptation.

• MR recession with posterior fixation.

• MR recession for the accommodative component, e.g., the angle without glasses.

• MR recession for the distance deviation with 1 mm added to both of the MR recessions as was advocated by Marshall Parks, MD.

When MR recession recommended

MR recession and posterior fixation work, however, the procedure is less predictable and less reversible compared with other approaches, according to Dr. Kushner.

“Importantly, it is not predictable and easily reversible and its mechanism of action is unclear,” he said.

Dr. Kushner said he also does not recommend MR recession for the angle without glasses, because this approach is not physiologic, and no long-term studies have proven the efficacy and stability of the procedure. Regarding MR recession for distance deviation with 1 mm added, he reported a substantial number of undercorrections in his experience and many patients remained in bifocals.

He said he prefers to perform MR recessions that target the near angle when patients are wearing their full cyclolegic distance correction. In 22 patients in whom Dr. Kushner used this approach, he found that after 15 years of follow-up, the results were good and the patients were stable.

Dr. Kushner’s total experience includes 234 patients, 53 of whom were teenagers; 86% were aligned within 10 PD of esotropia. He reported that 42% required glasses for visual purposes; 31% needed single-vision glasses for control.

“Only 4% needed to continue using bifocals over the long term,” he said. “Only two patients had an exotropia at distance, yet were aligned at near. The results were similar for the teenage subset. No patients underwent prism adaptation.”

He recounted his findings with 374 patients with high AC/A esotropia. Of these, 67% were initially aligned; the remainder was not and underwent surgery. Slightly more than half of those who were aligned initially remained so, whereas 44% had a decompensated distance angle and underwent surgery.

Among the patients who remained aligned at distance, 99% outgrew the need for bifocals by age 18; two patients did not and underwent MR recession for the near angle at age 18 and did well.

The importance of age

Of the patients who outgrew the need for bifocals, 23% still needed a bifocal by age 13, and 94% of those subsequently outgrew that need by age 18, according to Dr. Kushner.

“Only two patients still needed bifocals, despite the fact that a large number of these patients needed bifocals when they were younger,” he said. “This is why I am surgically conservative when operating just for the purpose of eliminating the need of a bifocal for near alignment.

“In teenagers with esotropia at distance that is greater than 10 PD while wearing full plus correction, recess the MR muscles bilaterally operating for the near angle in the full distance optical correction,” Dr. Kushner advised.

“I do not think prism adaptation is needed,” he said.

If younger teenagers are aligned at distance but need a bifocal for near alignment, continue to treat them optically as most will outgrow the need of the bifocal, he continued.

“If the patient is close to 18 years, you can safely operate for the near angle in the full distance-plus without using prism adaptation,” Dr. Kushner concluded.

Burton J. Kushner, MD

E: bkushner@wisc.edu

Dr. Kushner has no financial interest in any aspect of this report.

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