Apparent foveal displacement in normal subjects and in cyclotropia.

The average location of the fovea in relation to the optic nerve head was determined on fixation photographs from both eyes of 50 non-strabismic subjects. It was found to be 0.3 disc diameters below a horizontal line extended through the geometric center of the optic disc. The range of interocular and inter-individual variations from this position has been described. With the availability of this information, ophthalmoscopy and fundus photography have become useful ancillary tools in the diagnosis of cyclodeviations.