blind-spot esotropia

Blind-spot esotropia is an esotropia whose angle places the retinal image of the fixated object on the optic disc of the deviating eye. The condition is also called the blind spot syndrome or blind spot mechanism.¹ The physiologic blind spot lies about 15 degrees temporal to fixation and slightly below it.²

Patients were thought to use the blind spot of the deviating eye to avoid diplopia. The first patients described had accommodative esotropia with good vision in each eye, normal correspondence and good fusional potential.³ Later descriptions added patients with amblyopia, anomalous correspondence and suppression.³

The existence of the syndrome is disputed. The optic disc is small and the deviation changes with fixation distance, so the image would keep slipping off the blind spot and cause intermittent diplopia.³ No known physiologic mechanism keeps a retinal image locked onto the optic nerve head. Testing with Bagolini striated glasses showed that anomalous retinal correspondence explains the absence of diplopia in these patients, and the investigators concluded that the blind spot syndrome does not exist.³