Photo-Cell Device for Slit-Beam Adjustment to the Optical Axis of the Eye in Scheimpflug Photography

Abstract
In the photographic documentation of lens findings according to Scheim-pflug’s principle, a good reproducibility of the camera adjustment to the patient’s eye is prerequisite for quantitative densitometric evaluations. To ensure reproducible adjustment, the camera was equipped with a green blinking target for patient fixation, and with two phototransistors. These are stimulated by the slit light reflected from the patient’s cornea and trigger an acoustical signal when the slit beam is perpendicular. When the patient fixates the target light, and the pitch of the acoustical signal indicates a perpendicular alignment, the slit passes through the optical axis of the eye. Such adjustment makes it possible to take photos of a reproducible central optical section of the lens.