Persistent esotropic amblyopia related to delay in referral, anisometropia

May 7, 2007

Newly identified risk factors that increase the risk of development of persistent esotropic amblyopia are delay in referral and anisometropia in children with infantile or accommodative esotropia, said Eileen Birch, PhD, from the Pediatric Eye Research Laboratory, Retina Foundation of the Southwest, and the University of Texas Southwestern Medical Center, Dallas.

Newly identified risk factors that increase the risk of development of persistent esotropic amblyopia are delay in referral and anisometropia in children with infantile or accommodative esotropia, said Eileen Birch, PhD, from the Pediatric Eye Research Laboratory, Retina Foundation of the Southwest, and the University of Texas Southwestern Medical Center, Dallas.

"Amblyopia is associated with both infantile and accommodative esotropia," Dr. Birch said. "However, factors that might increase the risk for amblyopia have not been identified. Identifying these factors may provide guidance in determining which patients with esotropia might benefit from frequent visits to promote early detection and prompt treatment of amblyopia."

Ninety-one patients with infantile esotropia and 39 patients with accommodative esotropia were enrolled. The children were subdivided into groups based on whether they had never developed amblyopia, recovered from amblyopia, or had persistent amblyopia. The children were followed for a mean of 9.5 years.

Potential risk factors that Dr. Birch and colleagues evaluated were age of onset of esotropia; delay in referral; age at surgery; initial refractive error; and initial anisometropia.

Dr. Birch reported that delayed referral and anisometropia, among all of the risk factors, proved to be associated with the development of persistent esotropic amblyopia.

"Despite treatment, 22% of children with infantile esotropia and 33.3% of children with accommodative esotropia developed persistent amblyopia," Dr. Birch said. "A significant linear trend for delay in referral was found among the amblyopia groups, for both children with infantile and accommodative esotropia (infantile esotropia: never, 1.8 months; recovered, 2.7 months; persistent, 4.3 months, p = 0.0003; accommodative esotropia: never, 1.7 months; recovered, 3.6 months; persistent, 5.4 months, p = 0.001). All pair-wise comparisons were statistically significant (p

"The relative risk for amblyopia that persisted despite treatment was more than doubled if the delay in referral was 3 months or longer," Dr. Birch added.

A significant linear trend for anisometropia was found among the amblyopia groups (infantile esotropia: never, p = 0.01; accommodative esotropia: never, p = 0.002).

"Interestingly, anisometropia was related to the delay in referral, with greater anisometropia in children who had a delay in referral of 3 months or longer," Dr. Birch said.

"Amblyopia developed at some point in follow-up [for more than] 70% of patients with infantile and accommodative esotropia," Dr. Birch said. "The average point of diagnosis was 10 to 11 months after the onset of esotropia. Most amblyopia was treated successfully, but it persisted in more than 20% of children despite treatment.

"Delay in referral and anisometropia significantly increased the risk of development of persistent amblyopia; these factors may be interrelated," Dr. Birch concluded. "Early detection and treatment may prevent persistent amblyopia."