Retinoscopic reflexes: theoretical basis and effects of monochromatic aberrations

Current literature describing retinoscopy does not provide a full description of the pupil reflexes observed in retinoscopy or of the effects of monochromatic aberrations. The intent of the study was to develop a geometrical model of retinoscopy that provides a more complete analysis. The model can take specific aberrations and predict the succession of reflexes observed in retinoscopy for an eye with these aberrations.

Theoretical predictions were compared with observations using a hand-held streak retinoscope. CCD-based retinoscopy was performed on subjects with known aberrations.

Reflexes observed in retinoscopy can be computed by modeling a light source whose eccentricity from the retinoscope sight-hole is varying in position. Results from study calculations show that the succession of reflexes observed in retinoscopy can be thought of as a measure of the transverse aberration of the eye. Both qualitative and quantitative measures showed agreement between theoretical and experimental results. Transverse aberration of the eye can be observed and measured using retinoscopy.

Monochromatic aberrations have significant and predictable effects on retinoscopy. The best way for a retinoscopist to avoid such aberrations and provide a proper refraction is to neutralize the reflex across the largest visual zone possible and ignore the reflex motion at the edges of the pupil.