The effect of off-the-visual-axis retinoscopy on objective refractive measurement

Abstract

PurposeTo determine the effect of off-axis retinoscopy on objective refractive measurement. DesignProspective experimental study. MethodsEight volunteers underwent cycloplegic retinoscopy of their right eye on-the-visual-axis, and 5, 10, 15, and 20 degrees off-the-visual-axis in adduction. A single masked examiner performed all retinoscopy with random order of the patient and axis refracted. ResultsThe average spherical retinoscopic value at 0, 5,10,15, and 20 degrees of off-axis alignment was −0.40, −0.90, −1.00, −1.38, and −1.80 diopters, respectively. The average spherical equivalent retinoscopic value obtained for each of the above positions of eye alignment was −0.02, −0.59, −0.45, −0.64, and −0.98 diopters, respectively. The induced cylinder power increased by an average of 3% for each degree of off-axis retinoscopy, though the axis of the cylinder was not predictable. ConclusionObjective refractive measurement by retinoscopy is significantly altered by off-the visual-axis retinoscopy. The induced error may be clinically important even with small degrees of eccentricity.