Clinicians who treat strabismus are cognizant of the tendency to close 1 eye that some patients display when performing complex or detailed visual tasks. Although the eye closure is frequently attributed to an attempt to alleviate binocular diplopia, it may occur even in the absence of double vision. A plausible explanation for this tendency in patients without diplopia is subnormal binocular summation or binocular inhibition.1 Scarce information is available regarding eye closure in ophthalmic conditions other than strabismus.