An imaging-based autorefractor

Autorefraction consists of the automatic sensing of three parameters - spherical error, cylindrical error, slope of the principal meridian - that describe the deviation of the focusing properties of an ametropic eye with respect to an emmetropic state. Low-cost autorefractors would be highly desirable in resource-poor settings for the stratification of patients between those who can be treated in the community and those who need to be referred to specialist care. In the present paper, we describe the implementation of an autorefractor based on projecting patterns onto the retina of an eye and observing the projected pattern through an ophthalmoscopic camera configuration coaxial with the projection path. Tunable optics in the coaxial path, combined with appropriate image processing, allows determination of the three parameters. The simplicity and performance of the setup, measured on an eye simulator, shows promise towards clinical use in the community. Further work is needed to confirm the performance in vivo

Too many shades of grey : photometrically and spectrally mismatched targets and backgrounds in printed acuity tests for infants and young children

Purpose: Acuity tests for infants and young children use preferential looking methods that require a perceptual match of brightness and color between grey background and target spatial average. As a first step in exploring this matching, this article measures photometric and colorimetric matches in these acuity tests. Methods: The luminance, uniformity, contrast, and color spectra of Teller Acuity Cards, Keeler Acuity Cards for Infants, and Lea Paddles under ambient, warm, and cold lighting, and of grey-emulating patterns on four digital displays, were measured. Five normal adults’ acuities were tested at 10 m observationally. Results: Luminance and spectral mismatches between target and background were found for the printed tests (Weber contrasts of 0.3% [Teller Acuity Cards], −1.7% [Keeler Acuity Cards for Infants], and −26% [Lea Paddles]). Lighting condition had little effect on contrast, and all printed tests and digital displays met established adult test luminance and uniformity standards. Digital display grey backgrounds had very similar luminance and color whether generated by a checkerboard, vertical grating, or horizontal grating. Improbably good psychophysical acuities (better than −0.300 logMAR: (logarithm of the minimum angle of resolution)) were recorded from adults using the printed tests at 10 m, but not using the digital test Peekaboo Vision. Conclusions: Perceptible contrast between target and background could lead to an incorrectly measured, excessively good acuity. It is not clear whether the luminance and spectral contrasts described here have clinically meaningful consequences for the target patient group, but they may be avoidable using digital tests. Translational Relevance: Current clinical infant acuity tests present photometric mismatches that may return inaccurate testing results

Screen and virtual reality-based testing of contrast sensitivity

Contrast sensitivity is a key visual ability for everyday tasks, as well as a potential indicator of important optical and neurological diseases. Current clinical standards, based on visual discrimination performance on printed charts, present problems that could be bypassed using electronic devices. This work describes the development of new tests for contrast sensitivity, based on the detection of a moving target on a computer screen and in virtual reality headset. It presents preliminary evaluation of these innovations by comparison of their performance, using healthy adults with normal vision and by artificially altering their contrast sensitivity. The results demonstrate consistent correlation between all test modalities explored

Virtual consultation for red eye

This article was written with the aim of helping primary care doctors to reflect on their knowledge and skills in managing common ophthalmic condition such as red eye in the community via virtual consultations. Expert opinions (from both ophthalmologists and general practitioners) combined with the evidence from the literature were used to create this article. PubMed was searched for relevant articles related to virtual consultation and red eye using several key words, including “red eye”, “tele-medicine”, “virtual consultation”, “telephone consultation” and “video consultation”. Literature search was started on 15 December 2020 and last updated on 01 February 2021

3D reconstruction of the optic nerve head of a phantom eye from images obtained using a slit lamp fitted with low cost add-ons

Early detection and treatment are key in limiting vision loss from glaucoma, the second leading cause of blindness worldwide. The alteration of the optic nerve head’s (ONH) morphology, detectable early in the condition, is a key clinical indicator. The current gold standard is subjective observation through a slit lamp. If quantitative diagnostic devices to extract the topography of the ONH could be made objective and affordable, it could mean task shifting glaucoma diagnostics from specialist to primary/community care. A potentially cost-effective solution is to apply digital 3D reconstruction to stereo images obtained through a slit lamp, a mainstay of eye diagnostics, present in practically all ophthalmology and optometry practices. This works shows ONH reconstruction in an eye phantom through a common slit lamp fitted with extremely inexpensive cameras. Quantitative reconstructions, in close agreement with ground truths, were obtained

Synthetic stereo images of the optic disc from the CORD dataset

Advancement of techniques for 3D reconstruction of the optic disc could lead to affordable objective detection of glaucoma. Applying computer stereo vision techniques to image pairs is particularly promising. More data, along with the stereo camera calibration parameters and ground truths required for validation, could aid development. This work presents a method to generate, using a virtual environment, synthetic stereo images of optic discs from images in the CORD database and obtain the corresponding stereo camera calibration parameters and ground truths. Our own reconstruction technique was tested using data created using this environment and quantitatively validated

Clinical validation of a smartphone-based adapter for optic disc imaging in Kenya

Visualization and interpretation of the optic nerve and retina are essential parts of most physical examinations. To design and validate a smartphone-based retinal adapter enabling image capture and remote grading of the retina. This validation study compared the grading of optic nerves from smartphone images with those of a digital retinal camera. Both image sets were independently graded at Moorfields Eye Hospital Reading Centre. Nested within the 6-year follow-up (January 7, 2013, to March 12, 2014) of the Nakuru Eye Disease Cohort in Kenya, 1460 adults (2920 eyes) 55 years and older were recruited consecutively from the study. A subset of 100 optic disc images from both methods were further used to validate a grading app for the optic nerves. Data analysis was performed April 7 to April 12, 2015. Vertical cup-disc ratio for each testwas compared in terms of agreement (Bland-Altman and weighted κ) and test-retest variability. A total of 2152 optic nerve images were available from both methods (also 371 from the reference camera but not the smartphone, 170 from the smartphone but not the reference camera, and 227 from neither the reference camera nor the smartphone). Bland-Altman analysis revealed a mean difference of 0.02 (95%CI, −0.21 to 0.17) and a weighted κ coefficient of 0.69 (excellent agreement). The grades of an experienced retinal photographer were compared with those of a lay photographer (no health care experience before the study), and no observable difference in image acquisition quality was found. Nonclinical photographers using the low-cost smartphone adapter were able to acquire optic nerve images at a standard that enabled independent remote grading of the images comparable to those acquired using a desktop retinal camera operated by an ophthalmic assistant. The potential for task shifting and the detection of avoidable causes of blindness in the most at-risk communities makes this an attractive public health intervention

Phone-based ophthalmoscopy for Peek, the Portable Eye Examination Kit

Peek, the Portable Eye Examination Kit, leverages smartphone technology to provide a range of ophthalmic diagnostic tests in low-income settings, thus empowering health workers to diagnose eye diseases and to manage and monitor patients within the community. A low-cost adapter on the phone native camera provides Peek with retinal imaging functionalities. The intrinsic connectivity of the smartphone allows transmission of geo-tagged patient records and, potentially, diagnostic data. The ease of use and field of view of the Peek ophthalmoscope represents a seed change in handheld direct ophthalmoscopy. The intrinsic telemedicine capabilities show promise in remote diagnostics and in integration with screening programs

Peek: Portable Eye Examination Kit. The smartphone Ophthalmoscope

Purpose: Create hardware and software solutions allowing the smartphone to be used to visualise the retina. Methods: The target device under investigation is the Samsung Galaxy S3 (Samsung Group). Accompanying software was designed for the android platform to automate such features as optic cup:disc ratio calculation, with a view to aiding diagnosis of glaucomatous optic neuropathy. An adaptor clip was designed with Rhinoceros 3D (McNeel and Associates), and manufactured in PolyLactic Acid (PLA) by Fused Filament Fabrication using an Up! Plus 3D printer (PP3DP, China). The optics blanks were cut on a CTR E5 (CTR Lasers, UK) laser cutter and polished by hand using diamond lapping compound, to create a miniature prismatic solution re-routing light from the native flash to become coincident with the optical path. Results: Peek provides high-resolution images of the retina sufficient for clinical examination, with a greater field than conventional direct ophthalmoscopy. Images obtained with Peek, along with comparative images using conventional disc photography are demonstrated in Figure 1. The relative differences in field between Peek and other ophthalmoscopic modalities are demonstrated in Figure 2. Conclusions: Peek is a low-cost alternative to the direct ophthalmoscope, comprising a smartphone adaptor that circumvents many of the technically challenging aspects of fundoscopy. The technology takes advantage of the intrinsic auto-focussing features within the smartphone to provide a high-resolution view of the retina through an undilated pupil. The adaptor couples the native mobile LED flash to optical path of the camera, allowing clinicians access to a previously unobtainable view of the retina using a smartphone. The connectivity of smartphone devices adds capacity to transmit retinal findings to secondary care for more effective triage in cases of diagnostic doubt. This low-cost technology has been designed with a view to improving access to ophthalmic diagnostics in resource-poor settings. Trials are underway to assess the impact of the technology in the diagnosis of glaucomatous optic neuropathy in a related cluster randomised controlled trial based in Kenya

Travel optional for eye appointments? Live teleophthalmology decision support and remote vision testing

Telemedicine is introducing new paradigms in the delivery of ophthalmology services. This work will explore the Scottish experience in delivering remote live decision support and remote visual assessment