Glaucoma testing from observations of optokinetic nystagmus

• US 5,295,495 A
• Filed: 05/13/1992
• Issued: 03/22/1994
• Est. Priority Date: 05/13/1991
• Status: Expired due to Term

• Current Assignee: Australian National University
• Original Assignee: Australian National University
• Inventors: Maddess, Teddy L.
• Primary Examiner(s): Pellegrino, Stephen C.
• Assistant Examiner(s): SCHMIDT, JEFFREY
• Application Number:
  US07/882,111
• Time in Patent Office: 678 Days
• Field of Search: 128/898, 128/745, 128/645, 351/209-211, 351/221, 351/222, 351/237, 351/239, 351/246
• US Class Current: 128/898
• CPC Class Codes: A61B 5/4863 Measuring or inducing nystagmus

Abstract

Optokinetic nystagmus is the rhythmical scanning of the eyes when primates attempt to stabilize constantly moving visual scenes. If a pattern having distinct vertical features is projected onto a screen and is drifted to the left or to the right, variations of certain parameters associated with optokinetic nystagmus of a subject observing the drifting pattern from the values of those parameters for persons having normal, healthy vision provide an indication of damage to M-type ganglion cells due to the presence of glaucoma in the subject. Such variations occur at an early stage of glaucoma, before other positive indications of the disease are present. Preferably the projected pattern is a coarse sinusoidal grating with vertical striations, which is temporally modulated by a rapid movement or flicker.

Claims

1. A method for diagnosing the occurrence of glaucoma in a subject, said method comprising the steps of:

(1) presenting to the subject a regular pattern, having distinct vertical features, and causing the pattern to move laterally to either the left or the right, at a constant rate;

said distinct vertical features comprising a relatively low spatial frequency, or a collection of relatively low spatial frequencies, and having a contrast which is modulated at a relatively high temporal frequency, said modulation being effected by a translation of the pattern image across the subject'"'"'s retina and/or by direct contrast modulation of the pattern features, at a frequency which is sufficient, or nearly sufficient, for a frequency doubled visual illusion to be perceived by a person of normal vision who observes said pattern;

(2) monitoring an optokinetic nystagmus of the subject during the movement of the pattern and determining at least one of the parameters in the group consisting of

(a) standard deviation of optokinetic nystagmus slow phase velocity;

(b) standard deviation of an optokinetic beat duration;

(c) mean optokinetic nystagmus heat duration for optokinetic nystagmus beats having a slow phase which is well represented in a graphical display by a straight line;

(d) standard deviation of the optokinetic nystagmus beat duration for optokinetic nystagmus beats having a slow phase which is well represented in a graphical display by a straight line;

(e) 95 percent confidence limit in a mean duration of optokinetic nystagmus beats for beats which have a slow phase eye position with time which is well represented in a graphical display by a straight line;

(f) standard deviation of optokinetic nystagmus beats which occur within contiguous clusters of beats;

(g) mean rate of optokinetic nystagmus beats which occur within contiguous clusters of beats;

(h) mean eye deflection per optokinetic nystagmus beat of optokinetic nystagmus beats which occur within contiguous clusters of beats; and

(i) relative total variation in optokinetic nystagmus beat velocity for optokinetic nystagmus beats which have a slow phase that is well represented by a straight line; and

(3) comparing each of the determined parameters with a value of that parameter expected for a person with normal, healthy vision.

2. A method as defined in claim 1, in which at least the parameters (a), (b), (e), (g) and (h) are determined and are compared with the values of these parameters expected for a person with normal, healthy vision.

3. A method as defined in claim 1, in which said pattern is a sinusoidal grating pattern with substantially vertical striations.

4. A method as defined in claim 3, in which the lateral movement of said pattern is at a rate within the range of from 4 pattern cycles per second to 10 pattern cycles per second.

5. A method as defined in claim 1, in which the lateral movement of said pattern is at a rate within the range of from 4 pattern cycles per second to 10 pattern cycles per second.

6. A method as defined in claim 1, in which said pattern is described by the function I(x,t) defined by the relationship

7. A method as defined in claim 6, in which:

C(t) is a square wave, modulated at the rate of 27.2 Hz;

the spatial frequency is 0.25 cycles per degree of the subject'"'"'s vision; and

the lateral movement of said pattern is at the rate of 6.79 Hz.

8. A method for diagnosing the occurrence of glaucoma in a subject, said method comprising the steps of

(1) presenting to said subject a grating pattern having sinusoidal striations or other distinct periodic features extending in a first direction and causing the pattern to move in a second direction at a constant rate, said second direction being orthogonal to said first direction;

said striations or periodic features having a relatively low spatial frequency, or a collection of relatively low spatial frequencies, and having a contrast which is modulated at a relatively high temporal frequency, said modulation being effected by a translation of the pattern image across the subject'"'"'s retina and/or by direct contrast modulation of the pattern features, at a frequency which is sufficient, or nearly sufficient, for a frequency doubled visual illusion to be perceived by a person of normal vision who observes said grating pattern;

(2) monitoring an optokinetic nystagmus of the subject during the movement of the pattern and determining at least one of the parameters in the group consisting of

(a) standard deviation of optokinetic nystagmus slow phase velocity;

(b) standard deviation of an optokinetic beat duration;

(c) mean optokinetic nystagmus beat duration for optokinetic nystagmus beats having a slow phase which is well represented in a graphical display by a straight line;

(d) standard deviation of the optokinetic nystagmus beat duration for optokinetic nystagmus beats having a slow phase which is well represented in a graphical display by a straight line;

(e) 95 percent confidence limit in a mean duration of optokinetic nystagmus beats for beats which have a slow phase eye position with time which is well represented in a graphical display by a straight line;

(f) standard deviation of optokinetic nystagmus beats which occur within contiguous clusters of beats;

(g) mean rate of optokinetic nystagmus beats which occur within contiguous clusters of beats;

(h) mean eye deflection per optokinetic nystagmus beat of optokinetic nystagmus beats which occur within contiguous clusters of beats; and

(i) relative total variation in optokinetic nystagmus beat velocity for those optokinetic nystagmus beats which have a slow phase that is well represented by a straight line; and

(3) comparing each of the determined parameters with a value of that parameter expected for a person with normal, healthy vision.

9. A method as defined in claim 8, in which at least the parameters (a), (b), (e), (g) and (h) are determined and are compared with the values of these parameters expected for a person with normal, healthy vision.

10. A method as defined in claim 9, in which the lateral movement of said pattern is at a rate within the range of from 4 pattern cycles per second to 10 pattern cycles per second.

11. A method as defined in claim 8, in which said pattern is described by the function I(x,t) defined by the relationship

12. A method as defined in claim 11, in which C(t) is a square wave, modulated at the rate of 27.2 Hz;

the spatial frequency is 0.25 cycles per degree of the subjects vision; and

the lateral movement of said pattern is at the rate of 6.79 Hz.

13. A method as defined in claim 8, in which the lateral movement of said pattern is at a rate within the range of from 4 pattern cycles per second to 10 pattern cycles per second.