Since the introduction of the modern self-illuminating binocular indirect ophthalmoscope (BIO) in the middle of the 20th century, developments have focused mainly on improving illumination without significant changes in the core optical system.1.2 The optical principle of BIO depends on reducing the examiner’s interpupillary distance (IPD) with the help of mirrors and/or prisms, so that the visual axis of both eyes of the examiner receives the light rays reflected through the patient’s pupil simultaneously. The light rays returning from the fundus are collimated by an indirect ophthalmoscopy lens to form a real, inverted and laterally inverted image between the patient and the examiner. Performing and anatomically interpreting the BIO examination is a skill that ophthalmology students develop during their residency training programs.3 Traditional BIOs cannot record videos and images of the examination. Video capable BIO devices are commercially available at a higher price, are more bulky, and enable 2D recording of videos and still images of the eye examination with an integrated digital camera.4–6 The limitations of currently available video-capable BIO devices include the possible decentralization of the recorded image from the examiner’s point of view, which requires frequent adjustments.4 and the lack of stereo vision of the recordings, as they provide two-dimensional (2D) rather than stereoscopic 3D images. Here we describe a novel design of a BIO prototype capable of fully digital video recording, which provides stereoscopic, three-dimensional (3D) recording of the fundus image with the possibility of real-time anatomical correction.
This prospective observational pilot study was approved by the Human Research Ethics Committee of the Eye Research Institute, Giza, Egypt, and was conducted in accordance with all local laws and the principles of the Declaration of Helsinki. Written consent was obtained from the study participants. The prototype used in this study consists of a generic LED light source and two side-by-side mini-cameras synchronized 15 mm apart. The mini-cameras are connected to a processor, data carrier (Samsung note-9 Android smartphone in the current prototype) and virtual reality kit (VISIONHMD Bigeyes H1 3D Video Glasses in the current prototype) (Figure 1). The synchronized dual cameras are configured to export the recorded video to the Samsung note-9 phone using a docking console (Samsung Dex Dock Station). A custom Android application was designed to capture test media from the dual camera, with the right camera projected to the right half of the screen and the left camera projected to the left half of the screen, creating a side-by-side image. stereogram. The software also allows for optional real-time anatomical correction of the examination view at the touch of an on-screen button or via a wired remote. The test media is then projected onto the virtual reality set so that the image from the right camera is projected onto the right side of the virtual reality goggles and seen by the examinee’s right eye, and the image from the left camera is projected onto the left side. on the side of the virtual reality glasses and seen by the examiner’s left eye.
Figure 1 (THE) A schematic diagram and (B) is the current prototype of a fully digital binocular indirect virtual video ophthalmoscope, which consists of two mini cameras, a light source, a virtual reality set, a connection console and a smartphone.
The prototype was first tested and adjusted on three different schematic eyes, including the Ocular Imaging Eye Model (Ocular Instruments Inc. Bellevue, WA, USA), the RetCam Digital Retinal Camera Practice Kit (Massie Research Laboratories Inc., Pleasanton, CA, USA ) and Reti Eye Model (Gulden Ophthalmics, Elkins Park, PA, USA). The LED lamp has been tested for light intensity and spectrum for safety to the human eye. The light intensity was 3.8 mW/cm2 (the safety limits are at least 1 order of magnitude below the safety limit defined by ISO15004-2.2, which is 706 mW/cm2)7,8 and the light spectrum fell entirely within the safe visible spectrum with no ultraviolet or infrared composition.
Binocular, stereoscopic indirect ophthalmoscopy was then attempted in 15 eyes of 15 patients in dim light after dilating the pupils with Tropicamide 1% eye drops, without digital real-time anatomical correction of the examination view. Attached video output was attempted to another virtual reality set for observer viewing in 10 patients and to an external monitor in 5 patients.
Binocular, virtual, stereoscopic indirect ophthalmoscopy can be successfully tested on the three schematic model eyes with this prototype, together with the +20 diopter indirect ophthalmoscopy lens.
Binocular video stereo ophthalmoscopic media could be obtained for all patients (n = 15). The anatomical correction of the examination view was successful in all patients (n = 15) (Fig. 2 and Additional Video). The adjunctive teaching view can be simultaneously streamed for each patient to a different virtual reality glasses (10 out of 10 patients) and a monitor screen (5 out of 5 patients).
Figure 2 Indirect retinal photography (THE) optical disc, (B) macula and (C) peripheral retinal pathologies.
The aim of this work was to investigate the feasibility of indirect binocular ophthalmoscopy with a newly designed fully digital binocular indirect ophthalmoscope that replaces the traditional optical system of BIO with two side-by-side mini-cameras. This achieves the goal of reducing the examiner’s IPD and enabling virtual binocular indirect simultaneous visualization through the subject’s pupil and projecting two images of the fundus view onto the corresponding screen of a virtual reality set. This allows the examiner to see the fundus virtually and binocularly in real time.
Traditional BIOs cannot record the examination in pictures or videos. Video-capable BIOs are significantly more expensive, larger in size, provide 2D recordings, and may be limited by decentralization of the camera’s view from the examiner’s view, requiring frequent adjustments.4 In our design, the video examination of the fundus seen by the examiner is simultaneously recorded in a stereoscopic 3D side-by-side format.
The image of the fundus seen by the examiner during the traditional BIO examination is inverted and turned sideways compared to the true anatomical orientation.1 With our described design, the anatomical correction of the examination view can be achieved during a real-time examination by digital horizontal inversion and vertical inversion of two side-by-side images of the fundus examination. Although the skill of anatomical interpretation of the BIO image is usually acquired during the years of residency training,3 providing the possibility of an anatomically corrected view can make this part of the BIO examination more comfortable.
Ophthalmology trainees can observe the results of the ophthalmology examination through an additional educational mirror attached to the front of the traditional BIO devices. These teaching mirrors provide a 2D image of the examiner’s view9 which the trainee can see in a narrow window between the examiner and the patient, which may be uncomfortable for the patient. In video-enabled BIOs, students can view test results in 2D, in real time or after the test on a connected monitor.5 Kong et al described the use of two additional cameras with traditional BIO to provide a 3D view to students.10 This makes the BIO bulkier, more difficult to wear, and does not prevent the students’ vision from being distracted from the view seen by the examiner. Our design provides ophthalmology students with a real-time stereoscopic 3D view of the eye exam, which is identical to the image seen by the examiner. The examination can be recorded in 2D or 3D for documentation and clinical education. Limitations of our current temporary prototype include the use of commercially available affordable mini-cameras and virtual reality headsets, as our goal at this point was only proof of concept. We believe that by further developing mini cameras and designing them individually, we can make the view even better and make the device more compact.
We describe the novel design of a BIO device suitable for video recording, which replaces the complex optical system of the traditional BIO with two mini cameras placed next to each other. Benefits of this novel design include optional real-time anatomical correction of the examiner’s fundus view and optional identical capture of the examiner’s BIO view in stereoscopic 3D and 2D, which can improve clinical documentation and education.
Data sharing statement
The data used in this study are available from the corresponding author upon reasonable request.
Ethics approval and consent to participate
This report was approved by the Research Ethics Committee of the Ophthalmological Research Institute and followed the principles of the Declaration of Helsinki. Written informed consent was obtained from all participating patients.
The design described in this article is related to an international patent pending by Dr. Omar Solyman (PCT # PCT/US2021/071604).
No funding to report.
Dr. Omar Solyman initiated the launch of ophthalmic hardware and software solutions for Wadjet: the Eye Gadget. The design of the prototype described in this article is related to a pending international patent by Dr. Omar Solyman (PCT # PCT/US2021/071604). The authors report no other conflicts of interest in this work.
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