APPARATUS AND METHODS FOR DIAGNOSIS OF STRABISMUS

• US 20150265146A1
• Filed: 10/02/2013
• Published: 09/24/2015
• Est. Priority Date: 10/02/2012
• Status: Active Grant

• Current Assignee: University Hospitals of Cleveland (University Hospitals Health System Incorporated)
• Original Assignee: University Hospitals of Cleveland (University Hospitals Health System Incorporated)
• Inventors: Inmann, Andreas, Bloom, Jeffrey, White, Kevin, Peters, Ryan
• Granted Patent: US 9,968,252 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 3/0008 provided with illuminating means A61B3/117 takes precedence; goniolenses used for laser treatment A61F9/009; illuminating means for optical instruments G02B27/00
• CPC Class Codes: A61B 3/0025 characterised by electronic signal processing, e.g. eye models
• CPC Class Codes: A61B 3/0075 provided with adjusting devices, e.g. operated by control lever manipulators B25J
• CPC Class Codes: A61B 3/0091 Fixation targets for viewing direction
• CPC Class Codes: A61B 3/085 for testing strabismus
• CPC Class Codes: A61B 3/145 by video means

Abstract

An apparatus for diagnosing and/or quantifying the degree of strabismus is disclosed. The apparatus includes a beam that supports at least two targets, a video camera, a light source for generating Purkinje reflexes, and a computer. The patient gazes at the targets while the video camera captures the patient'"'"'s eyes. The frames of the video are then analyzed as described herein to determine the location of the pupil and the first Purkinje reflex. With this information, strabismus can be diagnosed, as well as the angle of deviation, which is useful for surgically correcting the strabismus. Methods of analyzing the frames are also discussed herein.

Claims

1. An apparatus for diagnosing strabismus in a patient, comprising:

a zero target and a secondary target, wherein the secondary target is located a first distance to one side of the zero target;

a single video camera mounted proximate the zero target;

a light source fixed in place relative to the video camera; and

a computer for analyzing data captured by the video camera.

2. The apparatus of claim 1, wherein the secondary target is a left target, and the apparatus further comprises a right target located a second distance to the other side of the zero target;

wherein the zero target, the left target, and the right target are present on a front surface of a beam, the first distance and the second distance being equal;

wherein the single video camera and the light source are mounted on a surface of the beam; and

wherein the zero target, the light source, and the single video camera are centered on a line perpendicular to a line connecting the zero target, the left target, and the right target.

3. The apparatus of claim 2, wherein the zero target, the left target, and the right target each include a first light and a second light, the two lights being of different colors.

4. The apparatus of claim 2, wherein the beam can be rotated between a horizontal position and a vertical position, and the beam can be fixed in place in any location between the horizontal position and the vertical position.

5. The apparatus of claim 2, wherein the beam is mounted upon a stand, the stand is mobile, and the stand is adjustable in height.

6. The apparatus of claim 2, wherein the left target is located 30°

to the left of the zero target relative to a fixed point about 1 meter in front of the zero target, and the right target is located 30°

to the right of the zero target relative to a fixed point about 1 meter in front of the zero target.

7. The apparatus of claim 2, having three speakers, a first speaker being located behind the zero target, and a second speaker located to a left side of the zero target, and a third speaker being located to a right side of the zero target, each speaker being located closer to the left or right target than the zero target.

8. The apparatus of claim 1, wherein the zero target, the single video camera, and the light source are contained in a first physical module;

and the secondary target is contained in a second physical module.

9. The apparatus of claim 8, wherein either:

(a) the first physical module and the second physical module are mounted onto a common transverse beam

(b) the first physical module is mounted on a vertical stand, the second physical module is mounted on a transverse beam extending from the vertical stand, and the transverse beam can be rotated around the vertical stand;

or

(c) the first physical module and the second physical module are mounted on two separate stands.

10. The apparatus of claim 1, wherein the zero target and the secondary target are mounted on a flexible surface;

wherein the single video camera and the light source are contained in a physical module mounted on a vertical stand;

wherein the secondary target is a left target, and the apparatus further comprises a right target located a second distance to the other side of the zero target on the flexible surface; and

wherein the apparatus further comprises a vertical stand and a crossbar extending transversely from the vertical stand, the physical module being mounted on the vertical stand and the crossbar supporting the flexible surface.

11. The apparatus of claim 1, further comprising a metering system for measuring the distance from the video camera to the head of an associated patient, and wherein the apparatus does not include any equipment for fixing the head of an associated patient in place relative to the video camera.

12. The apparatus of claim 1, wherein the single video camera is a monochrome camera.

13. The apparatus of claim 1, wherein the zero target, the light source, and the single video camera are centered on a line perpendicular to a line connecting the zero target and the secondary target.

14. The apparatus of claim 1, wherein the zero target and the secondary target are present on a front surface of a beam, the beam being mounted upon a mobile stand.

15. The apparatus of claim 14, wherein the beam can be rotated between a horizontal position and a vertical position.

21. The method of claim 1, wherein the brightest points in the frame are identified by processing to remove noise, thresholding to locate possible bright points, and then applying a size filter and an eccentricity filter to identify the brightest points;

and

wherein the pupil is identified by using an edge detection method and thresholding to detect possible edges, applying a size filter and an eccentricity filter to identify potential pupil edges, and using a curve fitting algorithm to identify the pupil.

16. A method for determining and quantifying the angle of strabismus in a patient, comprising:

using a video camera and a light source to capture a series of frames containing the patient'"'"'s eyes as the patient'"'"'s head remains in a stationary position relative to the camera and the eyes gaze at a zero target and at least one additional target;

locating the Purkinje reflex and the pupil of a given eye by;

in each frame, identifying the brightest points in the frame to designate potential Purkinje points for a given eye in the frame;

defining clusters based on the potential Purkinje points from all of the frames, wherein each cluster includes a potential Purkinje point and the number of frames containing the potential Purkinje point, and designating the cluster with the highest number of frames as identifying the Purkinje reflex for the given eye;

for each frame, based on the location of the Purkinje reflex for the given eye, identifying a region of interest in the frame for the given eye; and

within the region of interest, identifying the pupil for the given eye;

subsequently sorting the frames into at least four different groups corresponding to each eye and which target the eye was gazing; and

calculating the angle of strabismus.

17. The method of claim 16, wherein the angle of strabismus is calculated by using linear regression to determine the y-intercept of the group corresponding to the zero target for the given eye;

and

further comprising calculating the Hirschberg ratio for each eye, wherein the Hirschberg ratio for a given eye is calculated by;

identifying a known angle for each group of the given eye;

calculating a displacement between a centroid of the Purkinje reflex and a centroid of the pupil for each group of the given eye;

plotting the known angle versus the displacement for the three groups of the given eye; and

using linear regression to determine the slope of a best-fit line for the plot, wherein the slope is the Hirschberg ratio for the given eye; and

18. The method of claim 16, wherein the patient'"'"'s head is not fixed in position relative to the video camera.

19. The method of claim 16, wherein two additional targets are used, the two additional targets being a left target and a right target, and wherein the left target and the right target are independently located at an angle of 15°

to 45°

to opposite sides of the zero target relative to the patient'"'"'s head.

20. The method of claim 19, wherein the left target is located 30°

to the left of the zero target relative to the patient'"'"'s head, and wherein the right target is located 30°

to the right of the zero target relative to the patient'"'"'s head.