FIELD OF THE INVENTION

The present invention relates to devices, systems and methods for addressing or compensating for partial loss of vision in a subject. More particularly, the present invention relates to a device, system and method for compensating for loss of part of the visual field (e.g. hemianopsia) by displaying in the surviving visual field a live video feed showing all or part of the lost visual field.

BACKGROUND OF THE INVENTION

Normal binocular visual field in humans extends up to approximately 90 to 100 degrees temporally (away from the nose in each direction) and approximately 50 to 60 degrees superiorly (upwards) and 70 to 75 degrees inferiorly. Visual field loss (loss of vision in a part of the visual field) may occur due to disease or trauma to the eye or brain (including the optic pathways). Several conditionals may cause loss of part of the visual field. For example, vision loss may occur when the optic pathways to the brain are damaged during as a result of a brain injury. The most common causes are stroke, brain tumour or trauma, although other causes have been reported. However, loss of part of the visual field may also arise due to near or total blindness in one eye or the loss of an eye.

Hemianopsia is impaired vision or blindness in part of the visual field. Most commonly, hemianopsia manifests itself as blindness in half of the visual field although blindness in more or less than half of the visual field is also possible. The most common types of hemianopsia include homonymous hemianopsia (blindness on the same side of the vertical mid line in both eyes, resulting in loss of one side of the visual field), heteronymous hemianopsia (loss of vision on different sides of both eyes, resulting in loss of the central or peripheral visual field), superior hemianopsia (loss of the upper half of the visual field in both eyes) and inferior hemianopsia (loss of the lower half of the visual field in both eyes), and quadrantic hemianopsia (loss of one quarter of the visual field in one or both eyes). Other proportions of the visual field may also be lost or lost to a different degree, depending on the location and severity of the brain injury and the resulting disruption to the optic pathways.

Current treatments for partial visual field loss include saccadic eye movement training, optical visual field expanders and vision restoration therapy.

Saccadic eye movement therapy involves teaching the patient to move their eyes to expand their field of vision by scanning the area of field that is missing. One of the drawbacks of saccadic eye movement therapy as a treatment for hemianopsia is that many patients with brain injuries resulting in loss of visual field may also struggle to perform the necessary eye movements for scanning.

Optical field expanders rely on prescription eyewear that expands the visual field of the patient using optical elements. Examples include peripheral prism visual field expanders, as described in “Community-based trial of a peripheral prism visual field expansion device for hemianopia”, Bowers et al, Arch Ophthalmol. 2008 May; 126(5): 657-64.

Vision restoration therapy (VRT) describes treatments that seek to restore the lost visual field by stimulation around the periphery of the region in which the visual field has been lost. Typically, such VRT requires the patient to focus of a focal point and respond whenever they perceive a light appear around the focal point. The lights are programmed to appear around the edge of the lost visual field. With time, the user trains the impaired but surviving visual function around the edge of the lost visual field, thus improving their overall visual field.

SUMMARY OF THE INVENTION

The present invention seeks to provide devices and methods that can at least partially compensate for the loss of part of the visual field in a subject.

In a first aspect of the invention there is provided a device for compensating for partial loss of visual field in a subject, the device comprising: a wearable frame comprising a first arm, a second arm and a bridging portion configured to extend between the first arm and the second arm and rest on the face of the subject; an image capture device supported by the wearable frame and configured to capture an image from a first region of the subject's visual field; a display unit configured to project the captured image onto a region of a retina of the subject corresponding to a second region of the subject's visual field; wherein the first region of the subject's visual field is identified as a region of the subject's visual field in which the subject's vision is impaired and the second region of the visual field is identified as a region of the subject's visual field in which the subject's vision is deemed non-impaired. Optionally, the display unit can be configured to crop the image based on stored cropping information before projecting the image onto the region of the retina of the subject, wherein the stored cropping information is based on patient information identifying the first region and the second region of the visual field.

In a second aspect of the invention there is provided a method for manufacturing a device for compensating for partial loss of visual field in a subject, the method comprising: providing patient information identifying (i) a first region of the subject's visual field in which the vision is identified as impaired and (ii) a second region of the subject's visual field in which vision is identified as non-impaired; providing a wearable frame comprising a first arm, a second arm and a bridging portion configured to extend between the first arm and the second arm and rest on the face of the subject; based on the identification of the first region, mounting an image capture device on the wearable frame to capture an image from the first region of the subject's visual field; based on upon identification of the second region, mounting an image display unit on the frame to project the captured image onto a region of the subject's retina that corresponds to the second region of the subject's visual field. Optionally, the display unit can be configured to crop the image based on stored cropping information before projecting the image onto the region of the retina of the subject, wherein the stored cropping information is based on patient information identifying the first region and the second region of the visual field.

In a third aspect of the invention, there is provided a method for compensating for partial loss of visual field in a subject, the method comprising: (a) providing patient information identifying (i) a first area of the subject's visual field in which the subject's visual field is identified as impaired and (ii) a second region of the visual field in which the subject's visual field is identified as non-impaired; (b) capturing an image from the first area of the subject's visual field using an image capture device; (c) projecting the captured image onto a region of the subject's retina that corresponds to the second region of the subject's visual field as identified in step (a). Optionally, the display unit can be configured to crop the image based on stored cropping information before projecting the image onto the region of the retina of the subject, wherein the stored cropping information is based on patient information identifying the first region and the second region of the visual field.

In a fourth aspect of the invention, there is provided an image display unit provided with at least one light source for delivery of photons to an eye for use in a method for the treatment of hemianopsia characterized in that the light source of the image display emits photons building up an image onto a region of a subject's retina that corresponds to a second region of the subject's visual field in which the subject's vision is identified as non-impaired, therewith compensating for partial loss of visual field in the subject, the method comprising: (i) identifying a first region of the subject's visual field in which the subject's visual field is impaired; (ii) capturing the image from the first region of the subject's visual field using an image capture device; (iii) displaying the image captured by the image capture device on the image display, wherein the displayed image is optionally cropped based on image cropping information relating to the first area identified in step (i); (iv) projecting the displayed image onto the region of the subject's retina that corresponds to the second region of the subject's visual field in which the subject's vision is identified as non-impaired. In at least some embodiments, the image display can be provided with at least one light source for delivery of photons to an eye, wherein the image display comprises at least one light emitting diode comprising the light source and wherein the light source is a semiconductor material such as a p/n semiconductor material.

In any of the above inventive aspects, the display unit can be configured to crop the captured image to correspond to the first region. In some embodiments, the cropped image can extend beyond the first region to provide at least one region of overlap with the second region. In such embodiments, the cropped image can comprise a first portion captured from the first region and a second portion captured from the second region, wherein the second region occupies between 5% and 20% of the area of the cropped image (e.g. 10% of the area of the cropped image).

The display unit can comprise a display configured to display the captured image and an optical element configured to project the image onto the region of the subject's retina. The display can comprise a screen and/or a projector. In at least some embodiments, the optical element can comprises a lens, a prism, a mirror or any combination thereof, configured to allow the user to focus on the image displayed by the display unit.

Preferably, the device further comprises a rechargeable power source. The rechargeable power source may comprise a battery rechargeable by inductive charging.

The image capture device can mounted on a central portion of the bridging portion of the wearable frame (e.g. in a region between the user's eyes) or the image capture device can be mounted to one side of the frame (e.g. on one of the support arms). In at least some embodiments, the wearable frame can comprise a frame for a pair of spectacles comprising a first lens supporting portion coupled to the first arm, a second lens supporting portion coupled to the second arm and a nose bridge portion connecting the first and second lens supporting portions. Alternatively, the frame can comprise a different structure configured to be worn by the user and display an image to the user in a perceivable manner. For example, the frame can comprise a single arm and an additional support portion configured to rest on the nose of the wearer. Other wearable frame configurations will be apparent to the skilled person.

In any of the above described aspects of the invention, the patient information can comprises a hemianopsia classification. A hemianopsia classification can include homonymous hemianopsia, heteronymous hemianopsia, superior hemianopsia and inferior hemianopsia, and quadrantic hemianopsia or other visual field loss classifications.

The patient information can also comprise an individualised visual field map identifying at least one of: (i) the first area of the subject's visual field in which vision is identified as impaired; and (ii) the second area of the subject's visual field in which vision is identified as non-impaired. The field map can be produced by monocular perimetry testing or binocular perimetry testing.

Methods according to aspects of the present invention can further comprise the step of mapping the subject's visual field and identifying (i) the first area of visual field in which vision is identified as impaired; and (ii) the second area of visual field in which vision is identified as non-impaired.

Method according to aspects of the present invention can further comprise the step of configuring the display unit to crop the captured image based on the patient information. The cropped image can corresponds to the first region (e.g. the captured image shows an image extending across the first (missing) region of the visual field but no further). The cropped image can extend beyond the first region to provide at least one region of overlap with the second region. The region of overlap can be between 5% and 20% of the area of the displayed image, e.g. 10%. The overlap between the captured image and the unimpaired visual field allows the user to correctly place the captured image relative to their surroundings.

In at least some embodiments of the above described aspects, the patient information can be stored in a storage medium comprises in the device. The device can comprise connection means (e.g. a wired or wireless connection) that allows patient information to be uploaded to the device. The device can further comprise processing means configured to appropriately crop the image and/or orient the camera based on the stored patient information.

For any of the above described aspects, the display unit can be configured to show a live video feed from the image capture device. In at least some embodiments, the frame can be formed using an additive manufacturing technique.

