WO2019173878A1

WO2019173878A1 - Method and system for detecting vision deficiency and simulating vision defects

Info

Publication number: WO2019173878A1
Application number: PCT/AU2019/050233
Authority: WO
Inventors: Michael Peter Halley JAMIESON
Original assignee: Neural Metrics Pty Ltd
Priority date: 2018-03-16
Filing date: 2019-03-15
Publication date: 2019-09-19

Abstract

A method of simulating an eye condition, comprising: displaying visual stimuli to a subject, using a headset mounted on the subject's head; receiving responses to the stimuli from the subject; determining a vision deficiency, if any, of the subject, based on the subject responses; modifying an image to reflect any determined vision deficiency of the subject; and displaying the modified image.

Description

METHOD AND SYSTEM FOR DETECTING VISION DEFICIENCY AND

SIMULATING VISION DEFECTS

Field

The invention relates to the field of eye testing for vision deficiencies, and creating simulations of those deficiencies.

Background

Eye diseases have a devastating effect on people of all ages, if left untreated. Worldwide, the leading cause of irreversible blindness is due to glaucoma. Early detection is critical as glaucoma treatment typically cannot reverse the damage, but can save the remaining vision. Glaucoma detection is complex and requires a multitude of tests to establish a diagnosis and severity of the disease.

One of the key tests is a visual field test as glaucoma initially causes peripheral vision loss that is not usually noticed by the patient. This test is performed in a clinic and requires a dedicated room for the testing machine. The light levels in the room must be closely controlled to ensure the test accuracy. As part of the test, the patient has to place their chin on a chin rest of the testing machine. The actual test involves testing each eye separately. A testing technician flashes a series of small lights in the periphery and the patient presses a button in response to the stimuli. In the case where the patient wears glasses, the technician needs to place handheld lenses in front of the patient's eye to be able to be tested with current standard testing machine.

Visual field testing should be repeated regularly to detect any progression of vision deficiency. The physical constraints of this test mean that people with mobility issues (especially bed or wheelchair bound) might find it difficult to access the doctor's office and perform the test. Furthermore, people with musculoskeletal factors such as kyphosis and/or arthritis might find it difficult and uncomfortable to gain access to the chin rest of the testing equipment. The test process creates a logistics problem within healthcare clinics. As standard testing time is between 15 to 25 minutes in total, this may mean an extra wait time for a patient requiring visual field testing if the test unit is currently occupied. In a situation where several patients in sequence require a test, the serial nature of this test can add up a substantial additional total wait.

The current test requires a skilled clinical technician to perform a number of functions. The technician monitors the light levels in the testing room. They also operate the testing equipment and provide instruction to the patient. Furthermore, when switching between the eyes it is the role of the technician to place an eye patch on the eye that is not tested. As mentioned above, the technician also is required to determine and place correct handheld lenses in front of the patient's eye instead of glasses. The presence of the technician may introduce human errors and thus result in an incorrect assessment.

The results of the test are usually presented numerically and graphically on a computer printout indicating areas of the central and peripheral vision and any detected vision loss. This printout is complex and intended for interpretation by skilled clinicians. It is only meaningful to laypeople including patients, relatives, carers and friends if accompanied by significant explanation from a clinician. Conditions causing reduced vision, particularly glaucoma, can vary considerably in severity from barely noticeable peripheral impairment to severe‘tunnel -vision’ or total blindness. Existing methods to simulate the vision defects to peripheral and central vision for educational purposes include adding shading to a still photograph or using glasses with frosting applied in a generic way to the peripheral glass.

The present invention aims to reduce or ameliorate some or all of the disadvantages of standard visual field tests, or provide an alternative method of testing. Summary of the Invention

In a first aspect of the present invention, there is provided a method of simulating an eye condition, comprising:

displaying visual stimuli to a subject, using a headset mounted on the person's head; receiving responses to the stimuli, from the subject;

determining a vision deficiency, if any, of the subject, based on the subject's responses;

modifying an image to reflect any detected vision deficiency of the subject; and displaying the modified image.

The visual stimuli are preferably light stimuli. In a preferred embodiment, the visual stimuli may comprise luminances at specified locations having an eccentricity of a visual angle. This makes use of current testing protocols for testing for vision deficiencies such as glaucoma. However, the present invention is not bound to a specific testing protocol.

In a preferred embodiment, the method may include a first step of measuring a luminance threshold for an eye, preferably each eye, preferably separately. Preferably, the luminance threshold is measured throughout the central and peripheral vision for the or each eye. The luminance threshold may be measured by displaying visual stimuli to a subject, using a headset mounted on the person's head. In an alternate embodiment, the luminance threshold may be measured by analysing a report from another visual field device.

In a preferred embodiment, the method of the present invention may include the further step of generating a degradation mask, preferably for each eye (right and left). This may be achieved, for example, by applying an algorithm to the visual field test results.

In a preferred embodiment, the method of the present invention may include the further step of combining one or more degradation masks to a camera feed, preferably a real-time camera feed. Preferably, the camera feed is acquired from a camera on the headset mounted on the person's head. Preferably, the camera is front facing. Preferably, combining the degredation masks and camera feed creates the modified image, preferably for the right and left eyes, to reflect any detected vision deficiency of the subject. Preferably, the modified image is a live image. Preferably the modified image is a modified camera feed.

Accordingly, in a particularly preferred embodiment, the present invention provides a method of simulating an eye condition, comprising:

measuring a luminance threshold for the eye, by either:

analysing a report from another visual field test device, or

displaying visual stimuli to a subject, using a headset mounted on the subject's head;

receiving responses to the stimuli, from the subject;

generating a degradation mask for the eye;

combining the degradation mask with a camera feed acquired from a camera on the head-mounted device to create a modified camera feed to reflect any detected vision deficiency of the subject; and

displaying the modified camera feed.

Preferably, the visual stimuli are light stimuli.

Preferably, the luminance threshold is measured for eye, preferably separately. Preferably, the luminance threshold is measured throughout the central and peripheral vision for the or each eye.

Preferably the degradation mask is generated for each eye (right and left). Preferably, the degradation mask is generated by applying an algorithm to visual field test results. In other words, the degradation mask is generated using a software algorithm based on the results of a subject’s visual field testing. This field testing may be performed either using the methods or devices of the present invention, or using other commercially available devices. Other commercially available devices may reference calibration information from the methods or devices of the present invention. Preferably, the camera feed is a real-time camera feed. Preferably, the camera feed is acquired from a camera on the headset mounted on the person's head. Preferably, the camera is front facing. Preferably, the modified camera feed displays modified images for the right and left eyes, to reflect any detected vision deficiency of the subject. Preferably, the modified image is a live image.

Because the present invention makes use of a headset (such as a virtual reality headset), it avoids the need for dedicated testing rooms or locations, and avoids requiring patients to adopt awkward or uncomfortable testing postures. This leads to improvements in patient comfort and patient access (e.g. for bed or wheelchair bound patients, as well as patients who have difficulty traveling or who have musculoskeletal conditions that make it hard to use conventional testing equipment). Consequently, the present invention allows for more efficient and accessible testing procedures.

Furthermore, the display of results improves the ability of patients and relatives or carers to understand the test results, and the vision deficiency that may be detected by the testing procedures. The image may, for example, be displayed with a shadow overlaid, or a degradation mask, reflecting the subject's vision deficiency.

Thus the present invention allows for performing a vision assessment and then a simulation, for example using the same portable device to reproduce the quantified visual defect overlaid on a real-time video feed of the immediate surroundings. For example, the present invention may improve awareness of patients’ visual deficits by using an algorithm to selectively degrade aspects of a real-time live video feed for the right and left eye separately in a portable head-mounted device, according to the individual visual field test results for a patient, to provide a realistic simulation of that patient’s visual experience.

In a second aspect of the present invention, there is provided a method of assessing vision of multiple subjects and/or providing simulations of the vision of multiple subjects, said method comprising: displaying visual stimuli to multiple subjects, using a headset mounted on each subject's head;

receiving responses to the stimuli, from the subjects;

wherein the responses are received and feedback coordinated by a centralised processor.

In a preferred embodiment, the method may include the further steps of generating a degradation mask for each subject; combining the degradation mask with a camera feed acquired from a camera on the head-mounted device to create a modified camera feed to reflect any detected vision deficiency of each subject; and displaying the modified camera feed.

These steps may be performed by methods as hereinbefore described.

This enables multiple subjects to be tested simultaneously, with the results received and processed centrally. This enhances the efficiency of the testing procedures, and reduces wait times for access to dedicated testing facilities (which can be a problem when using conventional equipment).

The headset may communicate with the centralised receiver via a wireless connection.

The step of assessing vision of multiple subjects may include simulating an eye condition, as hereinbefore described.

In a third aspect of the invention, there is provided a system for simulating an eye condition, comprising a headset configured to perform the method of the first aspect of the invention.

In a fourth aspect of the invention, there is provided a system for assessing vision of multiple subjects, comprising:

a plurality of headsets; and

a centralised processor in communication with the headsets; wherein the headsets are configured to provide subject response data to the centralised processor in accordance with the method of the second aspect of the invention.

A detailed description of one or more embodiments of the invention is provided below, along with accompanying figures that illustrate by way of example the principles of the invention. While the invention is described in connection with such embodiments, it should be understood that the invention is not limited to any embodiment. On the contrary, the scope of the invention is limited only by the appended claims and the invention encompasses numerous alternatives, modifications and equivalents.

For the purpose of example, numerous specific details are set forth in the following description in order to provide a thorough understanding of the present invention. The present invention may be practiced according to the claims without some or all of these specific details. For the purposes of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the present invention is not unnecessarily obscured.

Brief Description of the Drawings

Embodiments of the invention will now be described with reference to the accompanying drawings wherein:

Figure 1 is a perspective view of a headset suitable for use in accordance with an embodiment of the invention.

Figure 2 is a screenshot from a screen displayed by the headset during use of an embodiment of the invention.

Figure 3 is a Gamma curve from experimental luminance measurements measured through an embodiment of the invention.

Figure 4 depicts the visual calibration of an embodiment of the invention.

Figure 5 is a screenshot from a control console according to an embodiment of the invention. Figure 6 depicts triangulation lines calculated for a 24-2 pattern visual field test performed according to an embodiment of the invention.

Figure 7 depicts a shadow generated from a right eye test result file.

Figure 8 is a screenshot displayed reflecting a vision deficiency, in accordance with an embodiment of the invention.

Figure 9 is a schematic depiction of a system according to an embodiment of the invention.

Detailed Description

System Overview

In accordance with an embodiment of the invention, a system is provided for assessing and simulating an eye condition. The system, as generally depicted in Figure 9, includes at least one headset 100, and a centralised console in communication with the headset(s).

In this embodiment, the headset(s) 100 are virtual reality headset(s) - namely, Samsung Gear VR headset(s), as depicted in Figure 1. These headsets are commercially available off the shelf. However, various other headsets may be used - either off the shelf headsets, or dedicated headset designs. The system of this embodiment is interoperable with other headset solutions and the software is designed to support all currently produced virtual reality headsets (including HTC Vive, Oculus Rift and PSVR).

Each headset 100 can be worn by a subject, generally the person who is being tested for the eye condition, but in some cases also to simulate the eye condition to another person (such as a friend, relative or carer).

A network-connected smartphone 200 or other type of digital display screen can be mounted within the headset 100. The system further includes a control device 300 in the form of a bluetooth connected button, as shown in Figure 1, for recording patient responses and/or alternating between healthy and diseased versions of the simulated vision defect.

A central console (ie centralised processor) 400 is also provided, in communication with the smartphone 200 in headset 100.

Visual field testing software is installed on the smartphone, and can be configured to display visual stimuli to the subject. The visual stimuli may be presented in accordance with existing testing protocols. For example, for testing for glaucoma, the software may coordinate the display of visual stimuli at selected luminances at specified locations defined by their eccentricity in visual angle. Standard testing involves brief 0.2 second flashes of white stimuli with a dimmer white background. However, different embodiments of the invention may use other stimuli, such as moving stimuli (‘kinetic testing’) and different colours/images. Essentially, different target stimuli may be used to test for different eye conditions.

Calibration

For glaucoma testing, the invention utilises a calibration method to calibrate both luminance output and visual angle measurements.

The luminance output is calibrated by taking mean values of multiple luminance measurements using a photometer directed through the assembled virtual reality headset at 21 step brightness setting levels. These measurements can be used to derive the gamma curve for the display, as seen in Figure 3. Calibration of the device is performed for a series of luminance levels and eccentricities of visual angle, for purposes including increasing fidelity of testing and of simulation.

Calibrating the brightness setting to luminance output can then be performed in multiple different ways. In one example, a polynomial trendline can be fitted to the datapoints using standard regression techniques. Alternatively, in a preferred method, localised gradients can be calculated using linear gradients from the nearest datapoints for any reference luminance value.

The visual angle of displayed luminances can be calibrated by referencing an image of the virtual reality headset display to an image of a known reference angle, and then calculating the ratio of visual angle in degrees to display pixels. Figure 4 depicts an example of such images - the left image in Figure 4 is of a known target visual angle, and the right image is of the virtual reality display with a width of 500 pixels. The ratio of visual angle to pixels can be calculated. In this case, the ratio is 18.42 (±0.41) pixels per degree.

Centralised administration console

The centralised communication console 400 takes the form of a computer (having a CPU in communication with a memory) that is connected via a wireless network to the display headset(s) 100. Multiple display headsets 100 can be simultaneously connected to one console 400. The console 400 may communicate via a local area network or via the Internet. The use of a centralised console 400 to facilitate the simultaneous testing or simulation of multiple subjects provides a far more efficient testing regime than conventional testing facilities.

In accordance with this embodiment of the invention, patient data is entered on the console 400 and the type of test to be conducted is selected. This information is then sent to the headset 100 (ie the smartphone app) and the test begins. At the conclusion of the test, a result file is transmitted back to the console 400. Throughout the test, information is sent to the console 400 including time taken, test locations complete, estimated time remaining and battery level.

The console 400 stores previous test result files in a database, and associates them with the tested subjects. Each subject may be identified within the database. The software running on the console 400 allows generation, display and printing of reports summarising test data. A profile can therefore be generated for a particular test subjects. This means that multiple tests can be analysed together to generate reports showing changes over time, which may indicate progression of disease. A screenshot of the standard console screen is depicted in Figure 5.

Simulation of Vision Deficiency

The test results for some patients may indicate a vision deficiency. In accordance with this embodiment of the invention, the system is also capable of simulating a detected vision deficiency (scotoma). Generally, this will involve generating a customised shadow or degradation mask from a patient’s visual field test result file. This shadow or mask represents areas of reduced central or peripheral vision.

By a“degradation mask” is meant simulation of an area of reduced vision, for example by blurring or another form of degradation of the image. In some cases, this may be a shadow. The simulation allows a subject to perceive 'missing' an area of vision, which may not only be perceived as, for example, a black shadowy area. This is because vision defects cause neural compensation based on an assumption of the colour and texture of the area based on any surrounding areas that retain normal vision. This results in a loss of perceptual information but not necessarily a black shadow. A degradation mask allows live video to be blurred or degraded in any manner that includes overlaying a black shadow on top in order to simulate reduced vision as well as blurred or degraded imaging.

The invention is also capable of generating a shadow or degradation mask from visual field test results derived from an alternative testing device, such as a Zeiss Humphrey Field Analyser. In this instance, the resulting printout is analysed using either pdf-file text extraction or convolutional neural network based image recognition of a scanned result file. A software algorithm combines the extracted test result values with calibration information (as mentioned above) for the headset to create an equivalent test result file to if the test had been performed on the headset itself. This test result file is then passed through the standard degradation mask generation algorithm. The shadow or degradation mask may be displayed (e.g. overlaid on an image either directly on the console display, or on a display associated with a headset 100 (which may be the same headset used for testing purposes, or an alternative headset). In one preferred embodiment, live input images (ie video) are taken from the smartphone camera, while the smartphone is installed in the headset. These video images are combined with the generated shadow or degradation mask to create a representation of how a patient views the world. Scotomata can be simulated for the right eye and left eye separately, or concurrently, as required. One significant advantage of the simulation is to communicate the extent of vision loss to patients and relatives.

In this embodiment, a generalised method can be utilised for developing a shadow from any type or pattern of visual field test, in accordance with the following steps:

1. Definition of test point locations (measured in degrees of visual angle) from data

2. Definition of visual function at each location, by referencing measured visual threshold data against population normal levels

3. Triangulation of the tested area (as seen in Figure 6), by:

a. Calculating a line from each test point to each other test point b. Removal of the longer of any two lines that are overlapping in a colinear fashion

c. Removal of the longer of any two lines that are overlapping in an intersecting fashion

d. Specification of triangles by collecting lines sharing endpoints e. Increasing the number of triangles, if necessary for smoothing, by creating extra nodes at the midpoint of longer lines and repeating the triangulation procedure

4. Calculation of 3-dimensional planes corresponding to each triangle, representing visual angle by x- and y- coordinates and visual threshold on the z-axis.

5. Calculating the necessary shadow-level at every point in an overlay image by referencing the z-values of the triangle containing that point. Points outside the tested area are averaged to the nearest threshold at the perimeter of the tested region. Figure 7 depicts a shadow generated from a right eye test result file, for a particular subject.

Figure 8 depicts a shadow or degradation mask overlaid on a live (realtime) camera feed. The camera feed is being actively modified by overlaying a shadow or degradation mask (as shown in isolation in Figure 7). The simulation demonstrates the loss of visual information on the right side of the scene due to a scotoma, and also some mild further peripheral degradation. The scotoma in the figure is representative of the physiological blind spot present in healthy vision, which may be enlarged in an eye or eyes associated with the disease of glaucoma or glaucoma associated peripapillary atrophy around the optic nerve.

Workflow Improvements

In addition to the ability to detect and simulate a vision condition, the present invention also provides an improvement in several aspects relating to the clinical administration of visual field testing.

Current technology requires a dedicated room for the testing machine and the light levels in the room must be tightly controlled to ensure the test is accurate. Typical testing time is between l5-25min total for both eyes. This introduces a significant extra wait time for a patient requiring visual field testing if the test unit is currently occupied. If several patients in sequence require a test, the serial nature of testing can add up a substantial additional total wait. However, the present invention allows multiple patients to be simultaneous tested with separate headsets 100, and alleviates the requirement for a dedicated dark room for each patient. The use of a centralised console 400 simplifies the management of multiple testing or simulating units.

In addition, the present invention can reduce the staff requirements for managing multiple tests. In this preferred embodiment, test instructions are provided to patients via the headset 100, which eliminates the need for specific patient instruction by a clinical staff member. A properly calibrated headset may also enable more accurate testing for eye conditions, in some embodiments.

Furthermore, the software can automatically switch testing procedures from one eye to the next, which removes the need for a staff member to replace an eye patch between tests and to manually re-start the test (which is required with currently used devices).

The optics of the virtual reality headset 100 can allow patients to use their normal distance glasses during testing. This removes the need for handheld lenses to be placed in front of a patient’s eye, which is required with current standard machines. The determination of the correct handheld lens is an additional element of workflow, and the lens can introduce test errors (commonly referred to as“rim artifact”). Both of these problems may be addressed in embodiments of the present invention.

Patients who are bound to a wheelchair or otherwise limited are able to be tested easily by this portable device. Many patients with such restrictions are often unable to be tested at all with standard equipment.

There are numerous other potential advantages of the present invention, which is capable of numerous variations and rearrangements without departing from the scope of the inventive concept. For example, the invention may provide the ability to conduct home testing and simulation of patients, using a portable headset 100. Testing instructions can be provided from the console 400 to the headset 100, via the Internet. Another option is to incorporate test results from other devices, and compare them to test results obtained by the present invention. Test results can be backed up to the cloud, from console 400.

In another variation, the present invention may provide the ability to control tests and simulations in progress using an app on staff members’ smartphone devices, in addition to using console 400. Further variations may include customisable options such as the playback of sound and video before, during and after test to give patients feedback, or to customise test patterns and programs for particular eye conditions, or particular subjects. In some variations, the invention may provide the capability to support eye tracking input data, obtained by tracking a subject's eyes while using the headset. This may be useful in detecting some eye conditions and in more authentic simulation by tracking the degradation mask to the subject’s direction of gaze. Throughout this specification and the claims which follow, unless the context requires otherwise, the word“comprise”, and variations such as“comprises” and“comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps, but not the exclusion of any other integer or step or group of integers or steps. The reference in this specification to any prior publication (or information derived from it), or to any matter which is known is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

1. A method of simulating an eye condition, comprising:

displaying visual stimuli to a subject, using a headset mounted on the subject's head; receiving responses to the stimuli, from the subject;

determining a vision deficiency, if any, of the subject, based on the subject responses; modifying an image to reflect any determined vision deficiency of the subject; and displaying the modified image.

2. A method of simulating an eye condition, comprising:

measuring a luminance threshold for the eye, by either:

analysing a report from another visual field test device, or

receiving responses to the stimuli, from the subject;

generating a degradation mask for the eye;

displaying the modified camera feed.

3. The method of claim 2, wherein the degradation mask is generated using a software algorithm based on results of a subject’s visual field testing.

4. The method of any preceding claim, wherein the visual stimuli comprise light stimuli.

5. The method of any preceeding claim, wherein the visual stimuli comprise luminances at specified locations having an eccentricity of a visual angle.

6. The method of claim 5, wherein the luminance output is calibrated for a series of luminance levels and eccentricities of visual angle.

7. The method of any preceding claim, wherein the eye condition is glaucoma.

8. The method of any preceding claim, wherein the subject is responding to a range of visual stimuli displayed on the headset.

9. The method of any preceding claim, wherein the subject's responses are received by utilising an actuator on a control device.

10. The method of any preceding claim, wherein the headset is a virtual reality headset.

11. The method of any preceding claim, wherein the responses are compared against a known reference to determine the vision deficiency or a change/deviation from the reference.

12. The method of any preceding claim, wherein a shadow or degradation mask is overlaid on the image or camera feed, respectively, to show an area of reduced vision associated with the determined vision deficiency.

13. The method of claim 12, wherein the overlaid image or camera feed is displayed using a headset.

14. The method of any preceding claim, wherein the shadow or degraded area represents an area of reduced central or peripheral vision.

15. The method of any preceding claim, wherein the image or camera feed comprises a real-time image and/or video, respectively.

16. The method of any preceding claim, wherein the headset comprises a mobile computing device with a screen for displaying the visual stimuli to the subject.

17. The method of claim 16, wherein the mobile computing device is a smartphone.

18. A method of assessing vision of multiple subjects and/or providing simulations of vision to multiple subjects, said method comprising:

displaying visual stimuli to multiple subjects, using a headset mounted on each subject's heads;

receiving responses to the stimuli, from the subjects;

19. The method of claim 18, including the further steps of generating a degradation mask for each subject; combining the degradation mask with a camera feed acquired from a camera on the head-mounted device to create a modified camera feed to reflect any detected vision deficiency of each subject; and displaying the modified camera feed.

20. The method of claim 18 or 19, wherein the headset communicates with the centralised receiver via a wireless connection.

21. The method of claim any one of claims 18 to 20, wherein the displaying and receiving steps are conducted simultaneously for the multiple subjects.

22. A system for simulating an eye condition, comprising a headset configured to perform the method of any one of claims 1 to 17.

23. A system for assessing vision of multiple subjects and/or of providing simulations of vision to multiple subjects, said system comprising:

a plurality of headsets; and

a centralised processor in communication with the headsets;

wherein the headsets are configured to provide subject response data to the centralised processor in accordance with the method of any one of claims 18 to 21.