Refractometer for the automatic objective determination of the refractive condition of an eye

US4266862A · kind A · utility

Assignee

• Carl Zeiss Stiftung · DE

Inventors

• Otto Trotscher · Aalen, DE
• Erwin Wiedmann · Oberkochen, DE

Key dates

• Filing date: Nov 21, 1977
• Grant date: May 12, 1981
• Expiry date: Nov 21, 1997

Classification

• Technology area (CPC A): Human Necessities
• CPC primary: A61B3/103
• WIPO field: Medical technology
• WIPO sector: Instruments

Abstract

The invention contemplates a refractometer that images a test mark on the retina and is automatic in its determination of both refractive-power and astigmatism parameters, for the eye under examination. An imaging lens serves both (1) to project the test mark to the retina and (2) to convey that image for refocus external to the eye, to a scanner having the ability to digitally establish the eye's focal length. In the process of establishing the eye's focal length, the instrument automatically positions the imaging lens to best serve infinity viewing by the eye, and a prism then rotates the test mark while the scanner photoelectrically tracks the refocused image for the angles at which response is at a maximum, thus establishing astigmatism parameters. The instrument provides selective direct indication or print-out of the automatically determined parametric values.