Since the introduction of the modern self-illuminating indirect ophthalmoscope (BIO) in the mid-20th century, improvements have been directed primarily at improving illumination without significantly altering the underlying optical system.1And the2 The optical principle of BIO is based on reducing the examiner’s inter-pupillary distance (IPD) by means of mirrors and/or prisms to allow the examiner’s optic axes of both eyes to simultaneously receive light rays that bounce off the patient’s pupil. The light rays coming from the fundus are collimated by the lens of indirect ophthalmoscope to form a real, laterally inverted and mirrored image between the patient and the examiner. Taking and anatomically interpreting a BIO test is a skill that ophthalmological trainees develop during their residency training programs.3 Traditional BIOs cannot capture inspection videos and photos. Video-enabled BIO devices are commercially available at a higher cost, are larger and allow 2D video and still images to be captured for ophthalmoscopic examination by means of a built-in digital camera4-6 Limitations of the currently available video BIO hardware include the ability to modify the captured image from the examiner’s point of view which requires frequent adjustments4 and the lack of stereoscopic view of the recordings because they provide two-dimensional (2D) images rather than stereoscopic 3D images. Here, we describe a novel design of an all-digital video recording BIO prototype that provides stereoscopic three-dimensional (3D) recording of the fundoscopy image with real-time anatomical correction capability.
This observational pilot study was approved by the Human Research Ethics Committee of the Research Institute of Ophthalmology, Giza, Egypt, and was conducted in accordance with all local laws and in compliance with the tenets of the Declaration of Helsinki. Written informed consent was obtained from all study participants. The prototype used in this study consisted of a generic LED light source and two synchronized 15 mm microcameras spaced side by side. The tiny cameras are connected to a processor and storage media (Samsung note-9 android smartphone in current prototype) and a virtual reality suite (VISIONHMD Bigeyes H1 3D video glasses, in current prototype) (Figure 1). The synchronized dual cameras are configured to export captured video to a Samsung note-9 via a connected controller (Samsung Dex Dock Station). A dedicated android app is designed to capture inspection media from the dual camera so that the right camera is displayed on the right half of the screen and the left camera is on the left half of the screen to create a stereoscopic image side by side. The software also enables optional real-time anatomical correction of the scan view by touching a monitor button or via a wired remote shutter. The examination media is then projected onto the VR set so that the right camera image is projected onto the right side of the VR goggles and seen by the examiner’s right eye and the left image from the left camera is projected onto the left side of the VR goggles and seen by the examiner’s left eye.
The prototype was first tested and modified on three different schematic eyes including the Optical Imaging Eye Model (Ocular Instruments inc. Bellevue, WA, USA), RetCam Digital Retinal Camera Practice Kit (Massie Research Laboratories Inc., Pleasanton, CA, USA), and the Reti Eye Model (Gulden Ophthalmics, Elkins Park, PA, USA). LED light has been tested for safety for the human eye in terms of light intensity and spectrum. The light intensity was 3.8 mW/cm2 (The safe limits are at least one order of magnitude lower than the safety limit specified by ISO15004-2.2 of 706 mW/cm2)7And the8 The light spectrum is completely dipped in the safe visible spectrum with no UV or IR build-up.
Indirect stereotactic ophthalmoscopy was then attempted on 15 eyes of 15 patients in a dim light condition after pupil dilation using tropicamide 1% eye drop without and with real-time digital anatomical correction of the examination method. Lateral video output to another VR was attempted that observers were set to view in 10 patients and to an external screen in 5 patients.
Microscopic, virtual, indirect stereoscopic ophthalmoscopic examination can be tested on the three schematic model eyes using this prototype in conjunction with a +20 diopter indirect ophthalmic lens.
Media of stereoscopic videomicroscopy ophthalmoscopes could be obtained in all patients (n = 15). Anatomical correction of scan width was performed in all patients (n = 15) (Figure 2 And the Supplementary video). An educational side view can be broadcast simultaneously in all patients either to another set of VR glasses (10 patients out of 10) and to a monitor (5 patients out of 5).
Figure 2 Indirect retinal imaging showing (a) the optic disc, (B) macular and (cPeripheral retinal diseases.
The aim of this work was to investigate the feasibility of an indirect ophthalmoscope using a newly designed fully digital indirect ophthalmoscope that replaces the conventional optical system of BIO by two small side-by-side cameras. This achieves the goal of reducing the examiner’s IPD and allowing simultaneous indirect binocular virtualization by having the subject’s pupil and projection of two fundus view images on the screen corresponding to the virtual reality set. This allows the examiner to see the fundus virtually and speculum in real time.
Traditional BIOs cannot record scans in photos or videos. Video-enabled BIOs are available at a significantly higher cost, are bulkier in size, provide 2D recordings and may be limited by optimizing the camera view relative to the examiner’s viewpoint requiring frequent adjustments.4 In our design, the video examination of the fundus seen by the examiner is simultaneously recorded in a side-by-side stereoscopic 3D format.
The fundus image seen by the examiner is inverted and reversed laterally relative to the true anatomical orientation in a conventional BIO scan.1 Using our described design, anatomical correction of the examination view during real-time examination can be achieved by digitally inverting horizontally and inverting vertically each of the two adjacent fundus examination images. Although the skill of anatomical interpretation of a BIO image is usually mastered during years of residency training,3 Providing an anatomically correct viewing option may make this part of the BIO scan more convenient.
Ophthalmology trainees can monitor the results of an ophthalmoscopic examination with an attached teaching mirror attached to the front of the conventional BIO devices. These educational mirrors provide a two-dimensional image of the examinees’ point of view9 It can be seen by the trainee in a narrow window between the examiner and the patient which may be uncomfortable for the patient. In video-enabled BIOs, trainees can view 2D examination results in real time or post-examination on a connected monitor.5 Kong et al. describe the use of two cameras attached to a conventional BIO to provide trainees with a 3D view.10 This makes the BIO heavier, heavier in position and does not prevent a decent view of the trainees from the point of view seen by the examiner. Our design provides ophthalmic trainees with a real-time stereoscopic 3D view of an ophthalmoscope that is identical to the view seen by the examiner. Examination can also be recorded in 2D or 3D for documentation and for clinical education. Limitations of the current tentative prototype include the use of affordable, commercially available small cameras and virtual reality headsets since our goal at this point was only a proof of concept. We think the display can be made better than this and the device can be more compact if the small cameras can be upgraded and custom designed.
We describe a novel design of a video recording-enabled BIO that replaces the complex optical system of a conventional BIO with two small cameras adjacent side by side. Advantages of this new design include optional real-time anatomical correction of the examiner’s fundus perspective and optional mirror recording of the examiner’s BIO display in 3D and 2D stereoscopic image that can enhance clinical documentation and education.
Data sharing statement
The data used in this study are available from the corresponding author on reasonable request.
Ethical approval and consent to participate
This report was approved by the Research Ethics Committee of the Institute of Ophthalmological Research and followed the tenets of the Declaration of Helsinki. Written informed consent was obtained from all participating patients.
Thanks and appreciation
The design described in this article is associated with a pending international patent by Dr. Omar Suleiman (PCT # PCT/US2021/071604).
No funding to report.
Dr. Omar Suleiman initiated the launch of Wadjet’s ophthalmic hardware and software solutions: the Eye Gadget. The prototype design described in this article is associated with an international patent pending by Dr. Omar Suleiman (PCT # PCT/US2021/071604). The authors report no other conflicts of interest in this work.
1. Brockhurst RJ, Tour RL. Indirect modern ophthalmoscopy. I J ophthalmic. 1956; 41 (2): 265-272. doi: 10.1016/0002-9394 (56) 92021-9
2. Kothari M, Kothari K, Kadam S, Mota P, Chipade S. Conversion of a traditional wired halogen-illuminated ophthalmoscope to a cordless light-illuminated indirect ophthalmoscope in less than 1000 rupees. Indian J. Oyoun. 2015; 63 (1): 42-45. doi: 10.4103/0301-4738.151466
3. Rai AS, Rai AS, Mavrikakis E, Lam WC. Teaching binocular indirect ophthalmoscopy to novice residents using an augmented reality simulation. Can J Ophthalmol J Was Ophtalmol. 2017; 52 (5): 430-434. doi: 10.1016/j.jcjo.2017.02.015
4. Vantage Plus Digital Instruction Manual. Available from: https://support.keeler-global.com/_manuals/Indirect%20Ophthlmoscopes/Vantage%20Plus%20Digital%20(EP59-09863-art-F)/EP59-09863-art-F.pdf.
5. Sridhar J, Shahlai A, Mehta S, et al. The usefulness of structured instruction with indirect, ophthalmoscope-guided video instruction in improving the resident ophthalmologist’s confidence and ability. Retinal ophthalmology. 2017; 1 (4): 282-287. doi: 10.1016/j.oret.2016.12.010
6. Ho T, Lee TC, Choe JY, Nallasamy S. Real-time video evaluation from an indirect digital ophthalmoscope for telemedicine consultations in retinopathy of prematurity. J Telemed Telecare. 2020; 1357633X20958240. doi: 10.1177/1357633X20958240
7. Suleiman Um, Hamdi, Abdel Qawi, Hassan A. Investigating the flashlight (LED) properties of a sample of smartphones for their safety in indirect retinal imaging. Pan Afr Med J. 2022; 43:15. doi: 10.11604/pamj.2022.43.15.32963
8. Hong SC, Wynn-Williams G, Wilson G. Photographic integrity of the iPhone retina. J Med Eng Technology. 2017; 41 (3): 165–169. doi: 10.1080/03091902.2016.1264491
9. Saunders RA, Bluestein EC, Berland GE, Donahue ML, Wilson ME, Rust PF. Can non-ophthalmologists check for retinopathy of prematurity? J Pediatr Ophthalmol about strabismus. 1995; 32 (5): 302-304; discussion 305. doi: 10.3928/0191-3913-19950901-08
10. Kong HJ, Cha JP, Seo GM, Hwang GM, Chung H, Kim HC. Development of a cold-light indirect ophthalmoscope video system for sharing stereotactic imaging. Annu Int Conf IEEE Eng Med Biol Soc IEEE Eng Med Biol Soc Annu Int Conf. 2007; 2007: 2219-2222. doi: 10.1109/IEMBS.2007.4352765