Amblyopia recurrence after occlusion therapy studied

Chicago-An inverse correlation between age and recurrence of amblyopia following cessation of occlusion therapy was found in a large retrospective chart review, reported Rahul Bhola, MD, fellow, Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City.

"There is a clinically significant risk of amblyopia recurrence with the decrease or cessation of occlusion therapy. This risk is inversely correlated with the patient's age at the time of cessation or decrease of therapy," Dr. Bhola said. "These data may provide useful guidelines for physicians or parents when making a decision with regard to withdrawing occlusion therapy."

Recurrence was as high as 50% in the first year of life, decreasing to about 11% at 10 years of age.

All patients in this study had strabismic and/or anisometropic amblyopia and were less than 10 years of age at the onset of treatment. In addition, all patients had 2 lines or greater interocular acuity difference by optotype or one eye that showed an unmaintained fixation pattern. All patients had two or more logMAR level improvements in visual acuity or a change in the fixation preference from maintained to unmaintained following occlusion therapy. None had concurrent treatment with optical or pharmacologic defocusing.

Retrospective analysis

Dr. Bhola and his colleagues conducted a retrospective analysis of a database of 1,651 patients treated for amblyopia at the University of Iowa from 1970 to 2004. Of these, 449 patients met eligibility criteria and were included. Outcome measures included recurrence of amblyopia, defined as a two or more logMAR level reduction of visual acuity in the amblyopic eye or a change in the fixation preference from maintained to unmaintained within 1 year of decrease or cessation of occlusion therapy.

They also studied the association of amblyopia recurrence with patient age and the best-corrected visual acuity of the amblyopic eye at the time of decrease or cessation of occlusion therapy.

The occlusion treatment consisted of full-time occlusion to improve vision and part-time occlusion to maintain vision. An occlusion trial was defined as three or more episodes of full-time occlusion without change in the visual acuity or until equal vision was attained in both eyes, followed by either no occlusion until recurrence or no occlusion for at least 1 year without recurrence.

In the study, 653 occlusion trials were conducted among the 449 patients; of these, 459 were based on optotypes and 194 on the fixation preference test. The mean age at the onset of occlusion was 3.62 years, and the majority of patients had amblyopia secondary to strabismus.

Of the 653 trials, 179 (27%) resulted in recurrence of amblyopia. "The recurrence showed an inverse correlation with age, which was found to be statistically significant for both the combined fixation of the optotype groups as well as the optotype test only," Dr. Bhola said, adding that the recurrence showed no significant association with the BCVA of the amblyopic eye.

An inverse correlation was also found between age and recurrence in optotype occlusion trials only.

To check the validity of the fixation preference test as a means of testing amblyopia, investigators compared the recurrence of amblyopia in the fixation and optotype groups between the ages of 2 and 4 years. The difference between the two was not statistically significant.

There was a trend toward a higher rate of recurrence in patients who had more than one line of interocular visual acuity difference compared with those who had 1 line or greater interocular difference. However, the difference was not statistically significant.