Eye examination apparatus employing polarized light probe

• US 5,787,890 A
• Filed: 04/18/1994
• Issued: 08/04/1998
• Est. Priority Date: 12/16/1991
• Status: Expired due to Term

• Current Assignee: Carl Zeiss Meditec Incorporated (Carl-Zeiss-Stiftung)
• Original Assignee: Laser Diagnostic Technologies, Inc. (Carl-Zeiss-Stiftung)
• Inventors: Reiter, Klaus, Dreher, Andreas W.
• Primary Examiner(s): Smith, Ruth S.
• Application Number:
  US08/229,151
• Time in Patent Office: 1,569 Days
• Field of Search: 128/653.1, 128/665, 128/745, 351/200, 351/205, 351/206, 351/214, 351/215, 351/221
• US Class Current: 600/476
• CPC Class Codes: A61B 3/1225 using coherent radiation

Abstract

Apparatus is provided for determining the topography, thickness, and fiber orientation of the nerve fiber layer at the fundus of the eye by measuring the polarization shift induced in a return beam of polarized light which is reflected at the ocular fundus from an incident beam of a known polarization state. A corneal polarization compensator effectively cancels the birefringent effects of the cornea and other portions of the eye anterior to the fundus, so that clinically meaningful results are produced.

Claims

1. An apparatus for analyzing an eye having an anterior portion and a posterior portion, comprising:

(a) a polarized light source for producing an incident diagnostic beam of known state of polarization;

(b) an optics system transmitting said incident diagnostic beam into an eye through the pupil, where it is reflected from the interior of the eye as a return diagnostic beam, the optics system collecting said return diagnostic beam and directing same to a polarization sensitive detection device;

(c) a polarization sensitive detection device for collecting and transducing information about the state of polarization of said return diagnostic beam into an electrical signal, the electrical signal being representative of the state of polarization of the return diagnostic beam whereby the electrical signal can be used to indicate the state of polarization of the return beam; and

(d) a corneal polarization compensator positioned and configured for modifying the polarization of at least one of said diagnostic beams to thereby facilitate assessment of any alteration of the polarization state of said return diagnostic beam caused by the polarization properties of the posterior portion of the eye.

2. Apparatus according to claim 1 and including means to modulate the polarization of at least one of said diagnostic beams.

3. Apparatus according to claim 1, wherein said optics system includes a light detector and wherein said optics svstem focuses said incident diagnostic beam on one focal point in the eye and including a point orifice diaphragm positioned conjugate to said focal pcint in front of said polarization sensitive detecting device to restrict said light detector to detecting only light reflected from objects at said focal point from said incident diagnostic beam.

4. Apparatus according to claim 1 wherein said optics system includes a diagnostic scanner to scan said incident diagnostic beam across the ocular fundus of the eye.

5. Apparatus according to claim 4 wherein said optics system includes a focusing means to change the focal point of said incident diagnostic beam.

6. Appartatus according to claim 1 wherein said polarization sensitive detecting device comprises an ellipsometer.

7. Appartaus according to claim 1 wherein said polarization sensitive detecting device comprises at least two detectors for detecting at least two different polarization components of said return beam.

8. An apparatus according to claim 1, further comprising a source of electrical power, wherein said corneal polarization compensator is electrically connected to the source of electrical power such that the corneal polarization compensator is powered and requires power to modify the polarization state of at least one of said diagnostic beams at a power useage rate correlated to the level of said alteration of the polarization state of said return diagnostic beams that is required to neutralize the polarization effects of said anterior portion on said at least one diagnostic beam, and including means operative with said compensator to monitor and record said power usage to provide an indicator of the condition of said anterior portion.

9. An apparatus according to claim 1 wherein said polarization sensitive detecting device comprises an array of polarizers of different pre-determined states of polarization, a deflecting device for scanning said return diagnostic beam sequentially onto said polarizers, collector means for sequentially receiving light from said polarizers, and at least one detector receiving light from said collector means and transducing the intensity of said return diagnostic beam into electrical signals of intensity corresponding to the polarization of the light from said polarizers.