Visual acuity was assessed objectively by inducing a pendular eye movement and recording it on an eye movement monitoring device (Eye-Trac). By this method, the acuity threshold is more easily determined than when using the optokinetic nystagmus. The measurements were carried out on two groups of subjects: one in the laboratory, where variations of acuity were induced by ophthalmic lenses, and the other on patients in the clinic. The correlation between the acuity measured subjectively with a Snellen chart and that measured objectively was very high for the laboratory group, thus supporting the validity of the technique, and less high for the clinical group due to the customary variations encountered in a clinical population. The discrepancy between the objective and subjective acuity findings is discussed.
Millodot M, Miller D, Jernigan ME. Evaluation of an Objective Acuity Device. Arch Ophthalmol. 1973;90(6):449-452. doi:10.1001/archopht.1973.01000050449008