asymmetry of the motion VEP response, which appears to be associated with foveal suppression [4].

One possible explanation for this lack of motor evidence of the long-term image decorrelation in MFS is that the motor signs such as pursuit asymmetry are present, but subclinical.Another possibility is that the angle of strabismus is so small in primary MFS that the cortex does not recognize the decorrelation and the motor pathways develop normally. A third possibility is that it is the high quality of the binocular vision that is present in MFS that somehow prevents the development of these motor sequelae. This is yet another query to be added to Parks’ long list of questions about The Monofixation Syndrome.

Summary for the Clinician

■The MFS has much to teach us about both normal and abnormal binocular vision. Even as some answers begin to reveal themselves, more questions arise.

■Monofixation may be preventable if the cause of the image decorrelation is detected and repaired promptly, probably within 60–90 days of onset.

■Once monofixation is present, attempting a cure is unwise. MFS, particularly with small angle esotropia,is relatively stable and allows for good binocular vision so there is little to be gained.Antisuppression and anti-ARC therapies designed to restore bifoveal fixation typically result in intractable diplopia. Attempted repair of the associated strabismus with surgery or prism will not create bifixation once monofixation is established.

■MFS can decompensate with time, even in the presence of good binocular vision. Patients with this condition should be followed periodically, and any changes in acuity or refractive error addressed promptly to minimize the risk of deterioration with loss of binocular vision.

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