Nancy A. Melville

April 07, 2014

PALM SPRINGS, California — In children with esodeviation, the strongest predictor of a successful outcome after surgery is age at disease onset, according to a new study.

"Older age at onset of esodeviation in partially accommodative esotropia appears to be the main factor affecting postoperative outcomes," said lead author Yiannis Iordanous, MD, from the Ivey Eye Institute at the University of Western Ontario in London, Canada.

"Unfortunately, this is a nonmodifiable factor; however, it may help physicians trying to predict surgical outcomes in this patient population," he said.

The study results were presented here at the American Association for Pediatric Ophthalmology and Strabismus 2014.

The retrospective review involved patients who underwent strabismus surgery for acquired partially accommodative esotropia.

Of the 57 patients, 24 (42%) achieved a high level of stereopsis, defined as a final stereopsis of 100 s of arc or better.

Children who achieved a high level of stereopsis at a mean follow-up of 2 years were older than those who did not (31.8 vs 23.8 months; P = .01).

In children with an age of onset of at least 36 months, 92% went on to develop stereopsis and 69% had 100 s of arc or better.

"Our results suggest that for every month delay in onset of esodeviation, a child with acquired partially accommodative esotropia is 6.5% more likely to regain stereopsis equal or better than 100 seconds of arc postoperatively," Dr. Iordanous reported.

Previous research has linked a longer period of misalignment with poorer outcomes, suggesting that patients with a duration of misalignment shorter than 4 months tend to do the best.

In contrast, this study found no significant difference in the duration of misalignment between those who achieved stereopsis of 100 s of arc or better and those who did not (30.1 vs 27.3 months; P = .6).

On regression analysis, only older age at onset was predictive of better postoperative binocular single vision (odds ratio, 1.065; 95% confidence interval, 1.014 - 1.118).

"Surprisingly, duration of misalignment did not appear to be related to final stereoacuity outcomes in this patient population," Dr. Iordanous said.

"The children all had a duration of misalignment much longer than 4 months — close to 30 months, on average — yet 42% had excellent results," he reported.

"Our results suggest that children with an older age of onset do well despite a long duration of misalignment," he noted. "However, for younger patients, duration of misalignment could still play a role."

In addition, greater improvement was seen in children with glasses that more correctly matched to their refractive error.

"Children who developed a higher level of stereopsis were more likely to present to our clinic from the referring physician or optometrist with glasses that had a power closer to their actual refractive error," he said.

On average, undercorrection was 1.0 diopter in children with stereopsis of 100 s of arc or better and 1.5 diopters in those who did not develop a high level of stereopsis.

"In addition, those with A- or V-pattern deviations — that is, an esotropia that varies in size on up and down gaze — also tended to do better," Dr. Iordanous explained.

The results also show that presentation with dense amblyopia appears to be correlated with worse postoperative outcomes.

The study design could account for the findings on the duration of misalignment, said Burton Kushner, MD, from the Department of Ophthalmology and Visual Sciences at the University of Wisconsin in Madison.

"This issue highlights the main flaw I see in this study," he explained.

"The definition of the duration of the deviation as being from onset until surgery could, in fact, include years of the patient being straight in glasses or intermittently straight or maybe constantly tropic," Dr. Kushner said. "That confounds the data analysis because what's probably most important is the number of months of constant deviation."

The analysis is further confounded by the fact that the mean duration until surgery was 30 months in the group with the best outcomes and 27 months in the group with the poorest outcomes. "That's a very long time if these patients were tropic. Both groups may have been harmed equally by long delays until surgery," he noted.

However, "I think this is a well-done study. It does not suggest that delaying surgery has no adverse effect," it simply does not address that issue, explained Dr. Kushner.

Dr. Iordanous said he agrees that the long duration of misalignment could have had an equally negative effect on the 2 groups.

"If the duration of misalignment had been a lot shorter — such as less than 4 months — we may have seen even better postoperative results than we reported," he said.

"A possible way to examine this is to conduct another study that stratifies patients by duration of misalignment — long vs short — and examine their outcomes," said Dr. Iordanous.

Dr. Iordanous and Dr. Kushner have disclosed no relevant financial relationships.

American Association for Pediatric Ophthalmology and Strabismus (AAPOS) 2014. Abstract 4. Presented April 3, 2014.

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