The April 2009 issue of the American Journal of Ophthalmology reported the results of a study by a team led by Dr. William V. Good of Smith-Kettlewell Eye Research Institute designed to learn whether electrophysiological changes indicating amblyopia occur even in the absence of clinically recognizable amblyopia.

As summarized in the free abstract of the article provided by the publisher, the study evaluated four infants between 7 and 19 months of age with unilateral periocular vascular lesions that intermittently obstructed vision in the affected eye but no clinical evidence of amblyopia. No child had anisometropia greater than 0.50 diopter in the greatest meridian or strabismus. Sweep visual evoked potential vernier acuity was measured under monocular viewing conditions with the fellow eye tested as the control.

The results of the study showed that response amplitudes and acuity thresholds were significantly diminished in the affected eyes. A phase analysis showed slowing of the response in the affected eyes compared with the control eyes.

The researchers concluded that an amblyopia-like effect on vernier acuity occurred in infants with unilateral periocular vascular birthmarks when the lesion caused intermittent occlusion of the eye. While the researchers acknowledged that whether long-term effects will occur is unknown, they recommended that children with no clinically apparent amblyopia in the setting of a vascular mark or other cause of intermittent occlusion of the visual axis be followed since the electrophysiology findings in the study suggest amblyopia may be present.

Science Mode (which reported on the study ^[1]) quoted Dr. Good as observing:

“This study has implications for the management of children with intermittent occlusion, who may develop amblyopia even when the clinical assessment is negative. It is likely that these findings extend to other eyelid problems, including congenital ptosis, where amblyopia may be present even in the absence of clinical features for amblyopia.”

Purchase the full article here ^[2].