A gonio camera without a slit lamp

Field of Invention

The invention generally relates to medical devices and more specifically assessment of angle structures of the eye for glaucoma and the status of the optic disc. It enables a non ophthalmologist to capture picture/ video of the angle structures for an assessment by an ophthalmologist either on the device or an app or a server from a remote location.

Background of Invention:

India has 1% of population being blind. Of these, 5.8% are due to glaucoma. PAC upto 4.2 % of adults and three undetected cases for every detected case. All need gonioscopy.

Angle closure glaucoma: 5-11% of blindness . 40% misdiagnosed as open anglel From 2010 to 2020, India: 3.7 million to 5.0 million patients Since by 2020, India accounts for 23.1%2 of angle closure glaucoma in the world. Globally: 5.3 million blind due to angle closure glaucoma by 2020 It is possible to predict the population prone for angle closure glaucoma by assessing the angle structures (gonioscopy). Once the proneness is confirmed, an iridotomy prevents blindness.

The key is to diagnose it early enough to prevent damage. The only method to predict this is by examining the angle structures to decide whether the angle can close. This is traditionally done on slit lamp by Van Herrick's method and by gonioscopy. Van Herrick's method of assesing can be done by a well trained optometrist and an ophthalmologist. However, gonioscopy needs a trained ophthalmologist to perform and interpret the test. Other methods are ultrasound biomicroscopy and optical computerised tomography. The first two methods need the help of a trained person and a slitlamp. The other techniques are very expensive and need an expert to examine and interpret.

Since ophthalmologists are not available in all hospitals, especially in remote areas, there is a need for an optometrist or a trained healthcare worker to assess ability of angles to close. Our equipment enables such a less trained person to perform gonioscopy without a slitlamp and even at patients home. This can send images to a centre or an app for further interpretation. Those with risk of developing angle closure glaucoma can be called to the hospital for further evaluation and treatment. This device is affordable, technically less demanding and can be used in remote areas with comparable results with gonioscopy with slit lamp by an ophthalmologist.

Objects of the Invention:

The principal object of this invention is to enable a non ophthalmologist to help in assessing the angle structures.

Another objective is to record the pictures or videos of angle structures for assessment.

Yet another objective is not to depend on slit lamp for assessment.

Yet another objective is to improve the depth perception and clarity by photo stacking.

Yet another objective is to take pictures of the optic disc.

Yet another objective is using an app or a reading centre or a facility or an expert of similar nature to interpret the angle structures based on the photo or video taken. Yet another objective is to make it a user friendly device.

Yet another objective is to make it affordable both for health care providers and patients to identify those with blinding disease.

Yet another objective is to enable to be used in remote areas.

Yet another objective is to prevent economic burden to the individual and the society.

Summary of the Invention

Thepresent invention enables a non ophthalmologist to assess angle structures and the optic disc. This device does not need a slit lamp and the person performing the test need not assess the structures in real time. The test can be performed at a less equipped centre/ patients's home instead of hospital or a clinic. This enables screening of wider population. The expert can interpret later at his convenience. It has a conical mirror or several plane mirrors inclined at such an angle to reflect images of angle structures of the eye on to a camera. These images are suitably magnified and focused to enable detailed observation. This may also include a view of the optic disc. It may also use photo stacking to get clear images and achieve depth perception. It may also have a software program to unwrap the image.

Detailed description of the invention

The gonioscope of the present invention is funnel shaped with smaller end sitting flush with the cornea and the sides angled appropriately. It is made from a material with such a refractive index that allows rays of light from the angle of anterior chamber to continue to the mirrored surfaceon the sides by overcoming total internal reflection at cornea- air interface. The mirrored surface is angled around 64 deg or in such a manner that the rays are reflected to the examiner. This makes angle structures visible. The mirrored surface may be a first or second surface or a total internal reflecting surface. There are marks on the mirror to identify anatomical positions. LED light either from the camera of a smart phone or another source with or without opticprovides slit and diffuse illumination. The slit is rotated either manually or using a motor to identify corneal wedge in different segments. The illumination beam has an occluderin the centre so that pupil is not illuminated to avoid its constriction. Once the view of angle structures with non constricted pupil is obtained, the occluder is removed to obtain view with constricted pupil view.lt uses such a magnification system so that a slit lamp is not necessary. The bottom diameter is less than that of cornea and the curvature is similar to that of cornea. Hence, coupling fluid is not required. It can take pictures with and without indentation. It isattached to a portable device like a smart phone or a microcomputer. Since it has a funnel shape, a 360 deg view is obtained without rotation of the device. However, theimage formed is distorted and a software is used to unwrap the image for interpretation.The image of angle of anterior chamber from the slit beam is superimposed on the image from diffuse beam to locate the corneal wedge. The depth of perception and clarity can be improved by photo stacking. OCT dimensions of the angle structures may be used to define the depth of focus and the optics of the instrument. We can convert a smart phone into a microscope and a slit lamp may be not necessary. This can be done by using a reverse mobile optic attached to the mobile camera and using an objective lens. Foam board or a similar material is used to ward off reflections. Options may be provided to obtain pictures of the optic disc. Analysis of disc for cd ratio, retinal nerve fiber loss and thinning of neuroretinal rim can also be done using appropriate illumination, for example red free light. These video or photos can be stored, modified, analyzed and transmitted to an ophthalmologist in a distant location through an app using a mobile phone camera or a similar device. The software in the app analyses it and grades whether the angle is capable of closure. Finally may suggest the patient to contact a nearby hospital or an ophthalmologist as soon as possible. Since ophthalmologists are not available in all hospitals, especially in remote areas, there is a need for an optometrist or a trained healthcare worker to assess ability of angles to close. Our equipment enables such a less trained person to perform gonioscopy without a slitlamp and even at patients home. It can also capture images of the optic disc. This can send images to a centre or an app for further interpretation. When combined with non contact tonometry, a combination of intra ocular pressure, gonioscopy and optic disc photos help the ophthalmologist to triage and schedule the patient's visit appropriately. Those with risk of developing angle closure glaucoma can be called to the hospital for further evaluation and treatment. This device is affordable, technically less demanding and can be used in remote areas with comparable results with gonioscopy with slit lamp by an ophthalmologist. Brief Description of drawings:

Fig. 1 describes the gonioscope as it is used on the eye

Fig. 2 describes the conical mirror arrangement in one of the embodiments

Fig.3describes the octagonal mirror arrangement in another embodiment Fig. 4describes flat mirror arrangement in another embodiment. Fig. 5 Lay out of optics of microscope and the gonioscope

Fig. 6 Illumination of the angle structures by direct illumination at an angle

Fig. 7 Illumination using a beam splitter. Detailed description of the drawings:

Fig 1 further explainsa paramedical worker holding our device and capturing the image of the angle structures. Those used to record intra ocular pressure with Perkin's tonometer would find our device comfortable to use.

Fig 2 further explains The gonioscope (l)has an optically transparent solid body (2), the distal end (3) has a viewing surface preferably orientedperpendicularly to the optical axis of the body, the proximalend (4)of the gonioscope has a transparent concave surface with a curvaturesimilar to the curvature of a patient's cornea. The body (2) of the gonioscope (1) tapers from the distal end (3) to the proximal end (4) at such an angle that the angle structures are visible. The angulation aids in total internal reflection within the transparent solid body (2). The shape of the transparent solid body (2) is conical.

Fig 3 further explains the gonioscope (l)has an optically transparent solid body (2), the distal end (3) has a viewing surface preferably orientedperpendicularly to the optical axis of the body, the proximalend (4)of the gonioscope has a transparent concave surface with a curvaturesimilar to the curvature of a patient' s cornea. The body (2) of the gonioscope (1) tapers from the distal end (3) to the proximal end (4) at such an angle that the angle structures are visible. The surface of the transparent body (2) has eight flat surfaces (5). The shape of the transparent body (2) is octagonal in cross section. Fig 4 further explains gonioscope (1) has a hollow body (6), the distal end (3) has a viewing surface preferably orientedperpendicularly to the optical axis of the body, the proximalend (4) of the gonioscope has a transparent concave surface with a curvaturesimilar to the curvature of a patient' s cornea. The body (2) of the gonioscope (1) tapers from the distal end (3) to the proximal end (4) at such an angle that the angle structures are visible. The surface of the hollow body (6) has eight flat surfaces or a conical surface in cross section. The internal surface (7) of the hollow body (6) may be mirror coated or arranged in such a way to elicit total internal reflection between the hollow part and the inner surface. A half ball lens or a similar lens (8) is placed on the distal surface of the proximal end to prevent total internal reflection between the cornea and the proximal end.

Fig. 5 further explains The rays of light emerging from the eye, especially from the angle of anterior chamber are collected by a convex lens, preferably an aspheric one to form an intermediate image between the gonioscope and the microscopic system (13). A beam splitter (12) may be interposed between the gonioscope and the lens microscopic optics. The combination of the lenses focuses the image on the sensor of the camera (13). The microscopic system may or may not have autofocus facility depending on the type of the camera.

Fig 6 further explains An LED illuminator (9) with suitable optics (10) which focuses on the iris, pupil and the angle structures directly or indirectly. This may be powered by AC or Alternatively, the angle of anterior chamber may be illuminated by sclerotic scattering occurring at the cornea. One or multiple LED illuminators may be used. The illumination beam may have an occluder/ mask (11) in the centre so that pupil is not illuminated to avoid its constriction. Once the view of angle structures with non constricted pupil is obtained, the occluder is removed to obtain view with constricted pupil view. This may help in distinguishing between oppositional closure and synaechiae

Fig 7 further explains the way in which the beam of illumination may be directed to the angle structures also when a two way mirror or a beam splitter (12) is used in the path of imaging rays. A slit (11) can be imaged on the angle structures after reflecting through the beam splitter. The slit is rotated through 180 deg and it clicks once the rotation is complete. Foam board or a similar material is used to ward off reflections. A suitably designed secondary LED lens may be used along with the primary lens and LED. Advantages:

The present invention is affordable and can be analysed using an app/ ophthalmologist pool.

Technicians can take videos and photos of angle of anterior chamber of the eye without using a slit lamp, large number of patients

General population can be screened for blinding disease of angle closure glaucoma and brought to a bigger centre for further evaluation and treatment.