Automating the eye examination using optical coherence tomography

Optical coherence tomography (OCT) devices are becoming ubiquitous in eye clinics worldwide to aid the diagnosis and monitoring of eye disease. Much of this uptake relates to the ability to non-invasively capture micron-resolution images, enabling objective and quantitative data to be obtained from ocular structures. Although safe and reasonably quick to perform, the costs involved with operating OCT devices are not trivial, and the requirement for OCT and other imaging in addition to other clinical measures is placing increasing demand on ophthalmology clinics, contributing to fragmented patient pathways and often extended waiting times. In this thesis, a novel “binocular optical coherence tomography” system that seeks to overcome some of the limitations of current commercial OCT systems, is clinically evaluated. This device incorporates many aspects of the eye examination into a single patient-operated instrument, and aims to improve the efficiency and quality of eye care while reducing the overall labour and equipment costs. A progressive framework of testing is followed that includes human factors and usability testing, followed by early stage diagnostic studies to assess the agreement, repeatability, and reproducibility of individual diagnostic features. Health economics analysis of the retinal therapy clinic is used to model cost effectiveness of current practice and with binocular OCT implementation. The binocular OCT and development of other low-cost OCT systems may improve accessibility, however there remains a relative shortage of experts to interpret the images. Artificial intelligence (AI) is likely to play a role in rapid and automated image classification. This thesis explores the application of AI within retinal therapy clinics to predict the onset of exudative age-related macular degeneration in fellow eyes of patients undergoing treatment in their first eye. Together with automated and simultaneous imaging of both eyes with binocular OCT and the potential for low-cost patient-facing systems, AI is likely to have a role in personalising management plans, especially in a future where preventive treatments are available

Human Factor and Usability Testing of a Binocular Optical Coherence Tomography System

PURPOSE: To perform usability testing of a binocular optical coherence tomography (OCT) prototype to predict its function in a clinical setting, and to identify any potential user errors, especially in an elderly and visually impaired population. METHODS: Forty-five participants with chronic eye disease (mean age 62.7 years) and 15 healthy controls (mean age 53 years) underwent automated eye examination using the prototype. Examination included 'whole-eye' OCT, ocular motility, visual acuity measurement, perimetry, and pupillometry. Interviews were conducted to assess the subjective appeal and ease of use for this cohort of first-time users. RESULTS: All participants completed the full suite of tests. Eighty-one percent of the chronic eye disease group, and 79% of healthy controls, found the prototype easier to use than common technologies, such as smartphones. Overall, 86% described the device to be appealing for use in a clinical setting. There was no statistically significant difference in the total time taken to complete the examination between participants with chronic eye disease (median 702 seconds) and healthy volunteers (median 637 seconds) (P = 0.81). CONCLUSION: On their first use, elderly and visually impaired users completed the automated examination without assistance. Binocular OCT has the potential to perform a comprehensive eye examination in an automated manner, and thus improve the efficiency and quality of eye care. TRANSLATIONAL RELEVANCE: A usable binocular OCT system has been developed that can be administered in an automated manner. We have identified areas that would benefit from further development to guide the translation of this technology into clinical practice

Intravitreal injections: past trends and future projections within a UK tertiary hospital

Aims: To describe past trends and future projections for the number of intravitreal injections being administered at a large tertiary hospital in London, United Kingdom. Methods: Retrospective data from Moorfields Eye Hospital were collected using the electronic medical record system. Descriptive statistics were used to visualise overall trends. Time series forecasting was used to predict the number of injections that will be administered up to and including the year 2029. Results: The number of injections has increased nearly 11-fold from 2009 to 2019, with a total of 44,924 injections delivered in 2019. The majority of injections were given for the treatment of neovascular age-related macular degeneration. Aflibercept formed 87% of injections administered in 2019. The number of injections is predicted to continue to increase every year, with nearly 83,000 injections forecasted in the year 2029. Conclusion: The demand for intravitreal injections has increased substantially over the last decade and is predicted to further increase. Healthcare systems will need to adapt to accommodate the high demand. Other solutions may include longer-acting therapies to reduce the treatment burden

Automated Pupillometry Using a Prototype Binocular Optical Coherence Tomography System

PURPOSE: To determine the test-retest reliability and diagnostic accuracy of a binocular optical coherence tomography (OCT) prototype (Envision Diagnostics, USA) for pupillometry. DESIGN: Assessment of diagnostic reliability and accuracy. METHODS: Fifty participants with RAPD confirmed using the swinging flashlight method (mean age 49.6 years) and 50 healthy controls (mean age 31.3 years) were examined. Participants twice underwent an automated pupillometry exam using a binocular OCT system that presents a stimulus and simultaneously captures OCT images of the iris-pupil plane of both eyes. Participants underwent a single exam on the RAPDx (Konan Inc, USA), an automated infrared pupillometer. Pupil parameters including maximum and minimum diameter, and anisocoria were measured. The magnitude of RAPD was calculated using the log of the ratio of the constriction amplitude between the eyes. A pathological RAPD was considered to be above ±0.5 log units on both devices. RESULTS: Intraclass correlation coefficient was >0.90 for OCT-derived maximum pupil diameter, minimum pupil diameter, anisocoria. The RAPDx had a sensitivity of 82% and a specificity of 94% for detection of RAPD whereas the binocular OCT had a sensitivity of 74% and specificity of 86%. The diagnostic accuracy of the RAPDx and binocular OCT was 88% (CI: 80-94%) and 80% (CI: 71-87%) respectively. CONCLUSIONS: Binocular OCT-derived pupil parameters had excellent test-retest reliability. Diagnostic accuracy of RAPD was inferior to the RAPDx and is likely related to factors such as eye movement during OCT capture. As OCT becomes ubiquitous, OCT-derived measurements may provide an efficient method of objectively quantifying the pupil responses

Relationship between psychophysical measures of retinal ganglion cell density and in vivo measures of cone density in glaucoma

Purpose: Considerable between-individual variation in retinal ganglion cell (RGC) density exists in healthy individuals, making identification of change from normal to glaucoma difficult. In ascertaining local cone-to-RGC density ratios in healthy individuals, we wished to investigate the usefulness of objective cone density estimates as a surrogate of baseline RGC density in glaucoma patients, and thus a more efficient way of identifying early changes. Design: Exploratory cohort study. Participants: Twenty glaucoma patients (60% women) with a median age of 54 years and mean deviation (MD) in the visual field of –5 dB and 20 healthy controls (70% women) with a median age of 57 years and a mean MD of 0 dB were included. Methods: Glaucoma patients and healthy participants underwent in vivo cone imaging at 4 locations of 8.8° eccentricity with a modified Heidelberg Retina Angiograph HRA2 (scan angle, 3°). Cones were counted using an automated program. Retinal ganglion cell density was estimated at the same test locations from peripheral grating resolution acuity thresholds. Main Outcome Measures: Retinal cone density, estimated RGC density, and cone-to-RGC ratios in glaucoma patients and healthy controls. Results: Median cone-to-RGC density was 3.51:1 (interquartile range [IQR], 2.59:1–6.81:1) in glaucoma patients compared with 2.35:1 (IQR, 1.83:1–2.82:1) in healthy participants. Retinal ganglion cell density was 33% lower in glaucoma patients than in healthy participants; however, cone density was very similar in glaucoma patients (7248 cells/mm2) and healthy controls (7242 cells/mm2). The area under the receiver operator characteristic curve was 0.79 (95% confidence interval [CI], 0.71–0.86) for both RGC density and cone-to-RGC ratio and 0.49 (95% CI, 0.39–0.58) for cone density. Conclusions: Local measurements of cone density do not differ significantly from normal in glaucoma patients despite large differences in RGC density. There was no statistically significant association between RGC density and cone density in the normal participants, and the range of cone-to-RGC density ratios was relatively large in healthy controls. These findings suggest that estimates of baseline RGC density from cone density are unlikely to be precise and offer little advantage over determination of RGC alone in the identification of early glaucomatous change