# US 9,872,615 B2 · Systems and methods for improved ease and accuracy of gaze tracking > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,872,615 B2 - Document ID: US9872615B2 - Status: Granted - Kind: B2 - Application number: 14/919,491 - Filed: 2015-10-21 - Published: 2016-02-11 - Granted: 2018-01-23 - Earliest claimed: 2013-02-28 - Assignees: Carl Zeiss Meditec AG - Applicants: Carl Zeiss Meditec, Inc. - Inventors: Harihar Narasimha-Iyer; Vincent Michael Patella; Goran Anders Johansson - Web page: https://patentgrep.com/patent/US9872615B2 ## CPC - A61B 3/113: for determining or recording eye movement - A61B 3/0008: {provided with illuminating means (A61B3/117, A61B3/14 take precedence)} - A61B 3/0025: {characterised by electronic signal processing, e.g. eye models} - A61B 3/0091: {Fixation targets for viewing direction} - A61B 3/024: for determining the visual field, e.g. perimeter types - A61B 3/032: Devices for presenting test symbols or characters, e.g. test chart projectors (A61B3/036 takes precedence) - G06F 3/013: {Eye tracking input arrangements (G06F3/015 takes precedence)} - G06V 40/19: Sensors therefor - A61B 3/0041: {characterised by display arrangements} - A61B 3/0083: {provided with means for patient positioning} - A61B 3/04: Trial frames; Sets of lenses for use therewith - A61B 3/14: Arrangements specially adapted for eye photography - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING ## Abstract Methods for improving gaze tracking are presented. These methods eliminate the need for a separate initial calibration step to determine whether the subject is properly centrally fixated during testing. In one embodiment, whether the subject is centrally fixated is determined by identifying inlier and outlier gaze descriptors; the inliers are assumed to be associated with central fixation. This reduces the total time required for testing. These methods also improve the accuracy of gaze tracking during testing without the need for individual subject calibration. Instead, a database of reference eyes is used. The subject's eye can be compared to the reference eyes, and the mapping function for one or more reference matches can be used to estimate the subject's gaze direction. In another embodiment, previous calibration data from the same subject can be used to determine whether the subject is properly centrally fixated and/or the direction of the subject's gaze. ## Claims ### Claim 1 A method for performing a visual field test on a subject using a perimeter, wherein the subject has been instructed to fixate their gaze on a specified location throughout all or a portion of the test, said method comprising: displaying a series of test stimuli to the subject; collecting responses to the stimuli from the subject; analyzing the responses to determine the sensitivity of the subject's visual field; with a camera, collecting information on the gaze direction of the subject during the displaying of stimuli; determining deviations in the subject's fixation from the specified location using the collected gaze information, wherein characteristics of the subject's gaze associated with fixation on the specified location are determined from the gaze information and wherein the determination assumes that the majority of the responses collected during the visual field test occurred when the subject was fixated on the specified location and generating a calibration vector based on that assumption and wherein the deviation in the gaze direction from the specified location is determined by comparing the gaze direction information associated with each stimuli to the calibration vector; and for any response to a stimuli wherein the determined deviation in gaze direction exceeds a threshold, performing one of the following steps: (a) disregarding the response; (b) flagging the response to the clinician; or (c) reassigning the response to a different location. ### Claim 2 (depends on 1) A method as recited in claim 1, wherein the test stimuli are displayed on a screen and the specified location is the center of the screen. ### Claim 3 (depends on 1) A method as recited in claim 1, wherein the characteristics of the subject's gaze associated with fixation on the specified location are made by determining inliers and outliers within the gaze information. ### Claim 4 (depends on 1) A method as recited in claim 1, wherein the characteristics of the subject's gaze associated with fixation on the specified location are determined using a subset of the collected gaze information. ### Claim 5 (depends on 1) A method as recited in claim 1, wherein the magnitude of deviations are determined. ### Claim 6 (depends on 1) A method as recited in claim 1, wherein the direction of deviations are determined. ### Claim 7 (depends on 1) A method as recited in claim 1, wherein the gaze information comprises a series of images of the eye collected while using one or more light sources to create one or more reflections from ocular surfaces that are detectable in the images. ### Claim 8 (depends on 7) A method as recited in claim 7, further comprising determining a gaze descriptor for each stimulus using the gaze information. ### Claim 9 (depends on 8) A method as recited in claim 8, wherein the gaze descriptor for each test stimulus is determined based on the relationship between the locations of the pupil center and the one or more reflections from an ocular surface. ### Claim 10 (depends on 9) A method as recited in claim 9, wherein the characteristics of the subject's gaze associated with fixation on the specified location are contained in a fixation gaze descriptor determined by analyzing inlier and outlier gaze descriptors. ### Claim 11 (depends on 10) A method as recited in claim 10, further comprising comparing the fixation gaze descriptor to the gaze descriptors of test stimuli to determine which gaze descriptors are associated with deviations in fixation from the specified location. ### Claim 12 (depends on 11) A method as recited in claim 11, further comprising disregarding stimuli responses associated with fixation deviations. ### Claim 13 (depends on 11) A method as recited in claim 11, further comprising determining the overall proportion of the number of stimuli displayed during the test with fixation deviations versus the total number of stimuli displayed during the test and reporting the proportion along with the visual field sensitivity determination. ### Claim 14 (depends on 10) A method as recited in claim 10, further comprising: using a fixation gaze descriptor from a previous test as an estimate of a fixation gaze descriptor for the current test. ### Claim 15 (depends on 14) A method as recited in claim 14, further comprising: refining the estimate of a fixation gaze descriptor for the current test based on the determination of inlier gaze descriptors.