Smart Devices in Optometry: Current and Future Perspectives to Clinical Optometry.

There is a huge unmet need for eye care with more than a hundred million people living without basic eye care services and facilities. There is an exigency to deploy adequate resources in terms of manpower and equipment to address this. The usage of smart devices in optometry and eye care practice has been gaining momentum for last half a decade, due to the COVID-19 pandemic and technological advancements in telemedicine. These smart devices will help facilitate remote monitoring of important visual functions, ocular signs and symptoms, thus providing better eye care services and facilities and promoting outreach services. Smart devices in optometry exist in the form of gadgets that can be worn in the wrist, and spectacle-mounted or head-mounted devices. On the other hand, with the ubiquitous nature of smartphones, a large number of smartphone applications have been developed and tested for advanced optometry and primary eye care practice, which may potentially reduce the burden of inadequate resources and the unmet need for eye care. This article aims to give an overview of the current trends and future perspectives on the application of such smart devices in optometric practice.

Light exposure profiles differ between myopes and non-myopes outside school hours.

PURPOSE: Considering the putative role of light in myopia, and variations in socioeconomic, lifestyle, educational and environmental factors across ethnicities, we objectively investigated light exposure patterns in Indian school children. METHODS: The light exposure profile of 143 school children (9-15 years, 50 myopes) recorded using a validated wearable light tracker for six continuous days was analysed. Additional data for non-school days were available for 87 children (26 myopes). The illuminance exposure levels, time spent outdoors and epoch (number of times participant is exposed to a predefined range of lux level per day) were compared between myopes and non-myopes across different light conditions: ≥1000, ≥3000, ≥5000 and ≥10 000 lux. For school days, light exposure profiles during (1) before school, school and after school hours; and (2) class, break and transition (when a student travels to and from school) time were analysed. RESULTS: The overall median (IQR) daily illuminance exposure level, time spent outdoors and epochs at outdoors (≥1000 lux) were 807 (507-1079) lux/day, 46 (30-64) min/day and 9 (6-12) times/day, respectively. The daily illuminance exposure on non-school days was significantly higher in non-myopes than myopes (6369 (4508-9112) vs 5623 (2616-6929) lux/day, p=0.04). During transition time (school days), non-myopes had significantly higher illuminance exposure (910 (388-1479) vs 550 (263-1098) lux/day, p=0.04), spent more time outdoors (25 (10-43) vs 14 (4-29) min/day, p=0.01) and had higher outdoor epochs (6 (4-11) vs 5 (2-8) times/day, p=0.01) than myopes. CONCLUSIONS: A small but significant difference in illuminance exposure, time spent outdoors and epoch was noted between myopes and non-myopes during transition time, which may have implications in myopia control.

Biometry-Based Technique for Determining the Anterior Scleral Thickness: Validation Using Optical Coherence Tomography Landmarks.

Purpose: Considering the potential role of anterior scleral thickness (AST) in myopia and the ubiquitous use of optical biometers, we applied and validated a biometry-based technique for estimating AST using optical coherence tomography (OCT) landmarks. Methods: The AST was determined across four meridians in 62 participants (aged 20-37 years) with a swept-source OCT and a noncontact optical biometer at a mean ± SD distance of 3.13 ± 0.88 mm from the limbus. The biometer's graticule was focused and aligned with the anterior scleral reflex, which led to the generation of four prominent A-scan peaks: P1 (anterior bulbar conjunctiva), P2 (anterior episclera), P3 (anterior margin of anterior sclera), and P4 (posterior margin of anterior sclera), which were analyzed and compared with the corresponding OCT landmarks to determine tissue thickness. Results: The AST measurements between biometer and OCT correlated for all meridians (r ≥ 0.70, overall r = 0.82; coefficient of variation [CV], 9%-12%; P < 0.01). The mean difference ± SD between two instruments for overall AST measures was 3 ± 2.8 µm (range, -18 to +16 µm; lower limits of agreement, -89 to +83 µm; P = 0.23) across all meridians. The mean ± SE AST with both instruments was found to be thickest at the inferior (562 ± 7 µm and 578 ± 7 µm) and thinnest at the superior (451 ± 7 µm and 433 ± 6 µm) meridian. The biometer demonstrated good intrasession (CV, 8.4%-9.6%) and intersession (CV, 7.9%-13.3%) repeatability for AST measurements across all meridians. Conclusions: The noncontact optical biometer, which is typically used to determine axial length, is capable of accurately estimating AST based on OCT landmarks. Translational Relevance: The high-resolution optical biometers can demonstrate wider application in the field of myopia research and practice to determine AST.

Association between relative peripheral refraction and corresponding electro-retinal signals.

PURPOSE: Considering the potential role of the peripheral retina in refractive development and given that peripheral refraction varies significantly with increasing eccentricity from the fovea, we investigated the association between relative peripheral refraction (RPR) and corresponding relative peripheral multifocal electroretinogram (mfERG) responses (electro-retinal signals) from the central to the peripheral retina in young adults. METHODS: Central and peripheral refraction using an open-field autorefractor and mfERG responses using an electrophysiology stimulator were recorded from the right eyes of 17 non-myopes and 24 myopes aged 20-27 years. The relative mfERG N1, P1 and N2 components (amplitude density and implicit time) of a mfERG waveform were compared with the corresponding RPR measurements at the best-matched eccentricities along the principal meridians, that is at the fovea (0°), horizontal (±5°, ±10° and ± 25°) and vertical meridians (±10° and ± 15°). RESULTS: The mean absolute mfERG N1, P1 and N2 amplitude densities (nV/deg2 ) were maximum at the fovea in both non-myopes (N1: 57.29 ± 14.70 nV/deg2 , P1: 106.29 ± 24.46 nV/deg2 , N2: 116.41 ± 27.96 nV/deg2 ) and myopes (N1: 56.25 ± 15.79 nV/deg2 , P1: 100.79 ± 30.81 nV/deg2 , N2: 105.75 ± 37.91 nV/deg2 ), which significantly reduced with increasing retinal eccentricity (p < 0.01). No significant association was reported between the RPR and corresponding relative mfERG amplitudes at each retinal eccentricity (overall Pearson's correlation, r = -0.25 to 0.26, p ≥ 0.09). In addition, the presence of relative peripheral myopia or hyperopia at extreme peripheral retinal eccentricities did not differentially influence the corresponding relative peripheral mfERG amplitudes (p ≥ 0.24). CONCLUSIONS: Relative peripheral mfERG signals are not associated with corresponding RPR in young adults. It is plausible that the electro-retinal signals may respond to the presence of absolute hyperopia (and not relative peripheral hyperopia), which requires further investigation.

Extent of foveal fixation with eye rotation in emmetropes and myopes

Purpose: This pilot study aimed to investigate the maximum extension of foveal fixation in the horizontal direction among young adults in both emmetropes and myopes.Methods35 participants (28 emmetropes and 7 myopes) were included. Participants with restricted extra-ocular mobility, end gaze nystagmus, and/or any other ocular pathology were excluded. Visual acuity (VA) was used as a surrogate measure of foveal fixation. VA was determined using a staircase procedure with 8 reversals. The average of the last 5 reversals was taken as the thresholds. VA acuity was measured at different gaze eccentricities along nasal and temporal visual field meridian. The eccentricity at which VA drops significantly was taken as the maximum extent of foveal fixation. A bilinear fit regression model was used to investigate the drop in the VA in both nasal and the temporal direction.ResultsEmmetropes can foveate up to 35 ± 2° in nasal and 40 ± 3° in temporal direction and myopes can foveate up to 38° in both nasal and temporal directions. Paired student t-test showed a significant difference in foveal fixation between nasal and temporal direction for emmetropes (P<0.001) but not in myopes (P = 0.168). An unpaired student t-test showed a significant difference in foveal fixation for nasal direction between myopes and emmetropes (P = 0.01). However, no statistically significant difference was found in foveal fixation for temporal direction between myopes and emmetropes (P = 0.792).ConclusionThe eye rotation does not necessarily match with the extent of foveal fixation at extreme eye rotation. Eyes can fixate only up to 35° nasally and 40° temporally maintaing their maximum visual acuity. (AU)

Asymmetric Peripheral Refraction Profile in Myopes along the Horizontal Meridian.

SIGNIFICANCE: The investigation of peripheral refraction profiles in Indian myopes showed relative peripheral hyperopic refraction in temporal retina and possible dominant role of hyperopic defocus signals from temporal retina in the development of myopia. PURPOSE: Considering that the peripheral refraction profiles were extensively reported to be associated with the central refractive error and vary among different ethnicities, we investigated the peripheral refraction profiles in Indians. METHODS: A total of 161 participants aged between 18 and 33 years were included in the study. All of the eligible participants underwent a comprehensive eye examination. Central and peripheral refractions were determined using an open-field autorefractor in 10° intervals up to ±30° in the horizontal meridian, and in 5° intervals up to ±15° in the vertical meridian. Axial length and central corneal radius were measured using a non-contact optical biometer. Peripheral refraction was compared between the different refractive error groups and myopic subgroups. RESULTS: Myopes showed a significant asymmetrical peripheral refraction profile along horizontal meridian with relative peripheral myopia at nasal 30° and relative peripheral hyperopia at temporal 30° (mean ± standard error at N30°: -0.37 ± 0.13 D vs. T30°: +0.56 ± 0.11 D, P < .05). Emmetropes and hyperopes showed relative peripheral myopia both in nasal and temporal eccentricities. Relative peripheral refraction was significantly different between the refractive groups and myopic subgroups along the temporal retinal eccentricities only (P < .05). Along the vertical meridian, relative peripheral myopia was seen among the three refractive error groups (P < .05). J0 and J45 significantly changed with retinal eccentricity along both the meridians in all the refractive error groups (P < .05). CONCLUSIONS: Myopes showed an asymmetric type of peripheral refraction with relative hyperopic defocus in temporal retina and myopic defocus in the nasal retina. Possible role of retinal hyperopic defocus along temporal retina in myopiogenesis needs to be explored.

Alterations in peripheral refraction with spectacles, soft contact lenses and orthokeratology during near viewing: implications for myopia control.

CLINICAL RELEVANCE: The peripheral refraction profile in myopes with different corrective modalities varies significantly for both distance and near viewing and will have implications in managing myopia. BACKGROUND: This study investigated how the magnitude of peripheral myopic defocus induced by Ortho-K varies with and without accommodation, and how this compares to single vision spectacles and soft-contact-lenses (SCL). METHODS: Relative peripheral refraction (RPR) of 18 young adults (spherical equivalent -1.00 D to -4.50 D) was determined along the horizontal meridian (±10°, ±20°, ±25°) during distance (3-metres) and near viewing (0.2-metres), and along vertical meridian (±10°, ±15°) for distance viewing alone. Measurements were obtained in an uncorrected state and with single vision spectacles, soft contact lens and Ortho-K. Changes in RPR and astigmatic components were compared between distance and near viewing with all different modalities. RESULTS: A significant interaction (p = 0.02) between relative peripheral refraction and the target distance (distance and near viewing) was found among different refractive modalities. Single overnight Ortho-K lens wear alone led to relative peripheral myopia for both distance (mean RPR ± SE: -0.92 ± 0.21D and -1.04 ± 0.22D) and near viewing (-0.71 ± 0.17D and -0.76 ± 0.20D). Comparisons of relative peripheral refraction between different corrective modalities at each eccentricity indicated statistical significance of RPR at extreme locations along both temporal and nasal meridian (±20 and ±25°, p < 0.05). RPR with soft contact lenses and spectacles were similar for both distance and near viewing (p > 0.05). CONCLUSION: Single overnight Ortho-K lens wear alone shifted the RPR in the myopic direction for both distance and near viewing in comparison with single vision spectacles and soft contact lenses. The Ortho-K lens designs that offer a large amount of mid-peripheral corneal steeping, in-turn leading to high relative peripheral myopia for both distance and near viewing and might offer beneficial effects on myopia control.

Extent of foveal fixation with eye rotation in emmetropes and myopes.

PURPOSE: This pilot study aimed to investigate the maximum extension of foveal fixation in the horizontal direction among young adults in both emmetropes and myopes. METHODS: 35 participants (28 emmetropes and 7 myopes) were included. Participants with restricted extra-ocular mobility, end gaze nystagmus, and/or any other ocular pathology were excluded. Visual acuity (VA) was used as a surrogate measure of foveal fixation. VA was determined using a staircase procedure with 8 reversals. The average of the last 5 reversals was taken as the thresholds. VA acuity was measured at different gaze eccentricities along nasal and temporal visual field meridian. The eccentricity at which VA drops significantly was taken as the maximum extent of foveal fixation. A bilinear fit regression model was used to investigate the drop in the VA in both nasal and the temporal direction. RESULTS: Emmetropes can foveate up to 35 ± 2° in nasal and 40 ± 3° in temporal direction and myopes can foveate up to 38° in both nasal and temporal directions. Paired student t-test showed a significant difference in foveal fixation between nasal and temporal direction for emmetropes (P<0.001) but not in myopes (P = 0.168). An unpaired student t-test showed a significant difference in foveal fixation for nasal direction between myopes and emmetropes (P = 0.01). However, no statistically significant difference was found in foveal fixation for temporal direction between myopes and emmetropes (P = 0.792). CONCLUSION: The eye rotation does not necessarily match with the extent of foveal fixation at extreme eye rotation. Eyes can fixate only up to 35° nasally and 40° temporally maintaing their maximum visual acuity.

Electroretinogram responses in myopia: a review.

The stretching of a myopic eye is associated with several structural and functional changes in the retina and posterior segment of the eye. Recent research highlights the role of retinal signaling in ocular growth. Evidence from studies conducted on animal models and humans suggests that visual mechanisms regulating refractive development are primarily localized at the retina and that the visual signals from the retinal periphery are also critical for visually guided eye growth. Therefore, it is important to study the structural and functional changes in the retina in relation to refractive errors. This review will specifically focus on electroretinogram (ERG) changes in myopia and their implications in understanding the nature of retinal functioning in myopic eyes. Based on the available literature, we will discuss the fundamentals of retinal neurophysiology in the regulation of vision-dependent ocular growth, findings from various studies that investigated global and localized retinal functions in myopia using various types of ERGs.

Does myopia decrease the risk of diabetic retinopathy in both type-1 and type-2 diabetes mellitus?

PURPOSE: To study the relationship between the severity of myopia and the severity of diabetic retinopathy (DR) in individuals with type 1 or type 2 diabetes mellitus (DM). METHODS: This retrospective study was conducted using data from electronic medical records from a multicentric eyecare network located in various geographic regions of India. Individuals with type 1 or type 2 DM were classified according to their refractive status. Severe nonproliferative DR (NPDR), PDR, or presence of clinically significant macular edema (CSME) with any type of DR was considered as vision-threatening diabetic retinopathy (VTDR). RESULTS: A total of 472 individuals with type-1 DM (mean age 41 ± 10 years) and 9341 individuals with type-2 DM (52 ± 9 years) were enrolled. Individuals with a hyperopic refractive error had a significant positive association with the diagnosis of VTDR (odds ratio (OR) 1.26; 95%CI 1.04-1.51, P = 0.01) and moderate nonproliferative DR (OR 1.27; 95%CI 1.02-1.59, P = 0.03) in type-2 DM; however, no significant association was found in type-1 DM. After adjusting for age, gender, anisometropia, and duration of diabetes, the presence of high myopia (< - 6 D) reduced the risk of VTDR in type 2 DM (OR 0.18; 95% CI 0.04-0.77, P = 0.02), but no association was found in type 1 DM. Mild and moderate myopia had no significant association with any forms of DR in both type-1 and type-2 DM. CONCLUSION: Hyperopic refractive error was found to increase the risk of VTDR in persons with type 2 DM. High-myopic refractive error is protective for VTDR in type 2 DM, but not in type-1 DM.

Ambient light level varies with different locations and environmental conditions: Potential to impact myopia.

PURPOSE: Considering that time spent outdoors is protective for myopia, we investigated how ambient light levels reaching the eye varies across 9 outdoor and 4 indoor locations in 5 different environmental conditions. METHODS: Illuminance (lux) was recorded using a lux meter under conditions of weather (sunny/cloudy), time of a day (7:00,10:00,13:00, and 16:00 hours), seasons (summer/winter), and sun protection (hat and cap) in outdoor and indoor locations. Nine outdoor locations were "open playground", "under a translucent artificial-shade", "under a porch facing east", "under a porch facing south", "under a big tree", "between three buildings", "within 4 buildings", and "canopy". As a ninth outdoor location, "Under a glass bowl" in the outdoor location was used as a simulation for "glass classroom model" and measurement was taken at the floor level only to determine in overall the illuminance conditions with glass covered on all sides. The 4 indoor locations included "room with multiple large windows", "room with combination light source", "room with multiple artificial lights", and "room with single artificial light". RESULTS: The overall median illuminance level (median; Q1-Q3) recorded in 9 outdoor locations was 8 times higher than that of all indoor locations (1175;197-5400 lux vs. 179;50-333 lux). Highest illuminance in outdoor locations was recorded in "open playground" (9300;4100-16825 lux), followed by "under a translucent artificial shade (8180;4200-13300 lux) and the lowest in "within 4 buildings" (11;6-20 lux). Illuminance under 'Canopy', 'between three buildings' and 'within four buildings' was similar to that of indoor locations (<1000 lux). Time of the day, weather, season, sensor position and using sun protection did not alter illuminance to change from high to low level (>1000 to <1000 lux). Among indoor locations, illuminance in "room with multiple large windows" crossed 1000 lux at a specific time points on both sunny and cloudy days. CONCLUSIONS: Illuminance levels in outdoors and indoors varied with location type, but not with other conditions. Given the variation in illuminance in different locations, and the impact it may have on myopia control, appropriate detailed recommendations seems necessary while suggesting time outdoors as an anti-myopia strategy to ensure desired outcomes.

Myopia progression varies with age and severity of myopia.

OBJECTIVE: To investigate annual myopia progression in individuals from South Indian states across different age groups, and its association with age of onset and severity of myopia. METHODS: This retrospective study included the data of 6984 myopes (range: 1-30 years), who visited at least twice to LV Prasad Eye Institute and on whom a standard retinoscopy technique was performed to determine refractive error. Based on spherical equivalent (SE) refractive error, individuals were classified into mild, moderate, high and severe myopic groups. Myopia progression was calculated as difference between SE at 1-year follow-up visit and at baseline. To determine the age-specific myopia progression, individuals were further categorized as myopes who are at least 15 years or younger and those who are above 15. RESULTS: The mean annual progression of myopia was influenced by both the age group (p < 0.001) and severity type of myopia (p < 0.001). The overall mean myopia progression ranged from -0.07 ± 0.02 D (standard error) to -0.51 ± 0.02 D across different age groups with maximum change in refractive error noted in children aged 6-10 years and the least in adults aged 26-30 years. Myopia progression was greater in severe myopes, followed by high, moderate, mild myopes and in individuals aged ≤ 15 years compared to those aged >15 years (-0.45 ± 0.01 vs. 0.14 ± 0.01, p < 0.001). Severe myopes alone had similar annual myopia progression rate irrespective of age (i.e ≤15 and >15 years, p = 0.71). Early onset of myopia was associated with high myopia in adulthood. CONCLUSION: The magnitude of myopia progression in children from South Indian states is comparable to that of Caucasians and Chinese. The greater progression in 'severe myopes' across different age groups emphasize the need for regular follow-ups, monitoring axial lengths, and anti-myopia strategies to control myopia progression irrespective of the age and degree of myopia.

Optical mechanisms regulating emmetropisation and refractive errors: evidence from animal models.

Our current understanding of emmetropisation and myopia development has evolved from decades of work in various animal models, including chicks, non-human primates, tree shrews, guinea pigs, and mice. Extensive research on optical, biochemical, and environmental mechanisms contributing to refractive error development in animal models has provided insights into eye growth in humans. Importantly, animal models have taught us that eye growth is locally controlled within the eye, and can be influenced by the visual environment. This review will focus on information gained from animal studies regarding the role of optical mechanisms in guiding eye growth, and how these investigations have inspired studies in humans. We will first discuss how researchers came to understand that emmetropisation is guided by visual feedback, and how this can be manipulated by form-deprivation and lens-induced defocus to induce refractive errors in animal models. We will then discuss various aspects of accommodation that have been implicated in refractive error development, including accommodative microfluctuations and accommodative lag. Next, the impact of higher order aberrations and peripheral defocus will be discussed. Lastly, recent evidence suggesting that the spectral and temporal properties of light influence eye growth, and how this might be leveraged to treat myopia in children, will be presented. Taken together, these findings from animal models have significantly advanced our knowledge about the optical mechanisms contributing to eye growth in humans, and will continue to contribute to the development of novel and effective treatment options for slowing myopia progression in children.

What Public Policies Should Be Developed to Cope with the Myopia Epidemic?

The epidemic of myopia in urban Asian cities has increased over recent generations and has become a significant public health concern. Considering the potential role of time outdoors in myopia prevention, and the differences in behavioral attitudes of individuals living in Urban East Asian (more indoor-centric) and Western countries, public policies should be developed in different countries accordingly to encourage children to go outdoors to counteract myopia. This is a short manuscript (presented at the International Myopia Conference-2015 by Prof. Seang Mei Saw) about public policies that should be developed to cope with the "myopia epidemic."

Axial Length/Corneal Radius of Curvature Ratio and Myopia in 3-Year-Old Children.

PURPOSE: This study investigated the association of axial length (AL) to corneal radius of curvature (CRC) ratio with spherical equivalent (SE) in a 3-year old Asian cohort. METHODS: Three-hundred forty-nine 3-year old Asian children from The Growing Up in Singapore towards Healthy Outcomes (GUSTO) birth cohort study underwent AL and CRC measurements with a noncontact ocular biometer and cycloplegic refraction using an autorefractor. The ratio of AL to CRC (AL/CRC) was calculated for all the participants, and subsequently AL, CRC, and AL/CRC were analyzed in relationship to SE. RESULTS: The SE showed better correlation with AL/CRC (Spearman's correlation coefficient, ρ = -0.53; 95% confidence interval [CI]: -0.66; -0.49; P < 0.001) compared to either AL or CRC alone ([ρ = -0.36; 95% CI: -0.51 to 0.51; P = 0.01] and [ρ = 0.05; 95% CI: -0.04 to 0.17; P = 0.34], respectively). Mean AL/CRC was 2.91 ± 0.06 among myopes and decreased to 2.79 ± 0.06 among hyperopes. Axial length to corneal radius of curvature was strongly correlated with SE in myopes (ρ = -0.78; 95% CI: -3.76; -0.79; P = < 0.001), but not in emmetropes and hyperopes ([ρ = -0.39; 95% CI: -10.73; -0.57; P = 0.01] and [ρ = -0.18; 95% CI: -17.28; 12.42; P = 0.38], respectively). Linear regression adjusted for gender and ethnicity showed a 0.74-diopter shift in SE towards myopia with every 0.1 increase in AL/CRC ratio (P < 0.001, r2 = 0.33). CONCLUSION: The correlation between SE and AL/CRC is stronger than that between AL or CRC alone. This suggests that in a research setting, when cycloplegic refraction is difficult to perform on 3-year-old children, AL/CRC may be the next best reference for refractive error. TRANSLATIONAL RELEVANCE: In the research setting, AL/CRC may be the next best reference for refractive error over AL alone when cycloplegic refraction is unavailable in 3-year old children.

Current and predicted demographics of high myopia and an update of its associated pathological changes.

PURPOSE: Excessive axial elongation of the eye in high myopia can cause biomechanical stretching leading to various ocular complications. The purpose of this review is to provide an update on various pathologic changes, especially in the chorio-retina and sclera that have been reported recently using advanced ophthalmic bio-imaging modalities such as optical coherence tomography, magnetic resonance imaging and fundus photography. RECENT FINDINGS: The prevalence rates of pathologic myopia (myopic retinopathy and maculopathy) mirror the prevalence rates of high myopia as the risks of pathologic myopia increase with high myopia. Peripapillary and sub-foveal choroidal thinning, scleral thinning, and deformed/irregular eye shapes were found to be strongly associated with various pathologic myopic lesions, especially with posterior staphyloma and chorio-retinal atrophy. Considering the increasing prevalence rate of myopia and pathologic myopia, these degenerative changes are likely to increase dramatically over the next few decades due to the rapid growth in the number of individuals with high myopia and the ageing population. SUMMARY: The current prevalence rates of pathologic myopia in older adults might have significantly underestimated the future prevalence rates and warrants age of onset of myopia being considered a major risk factor for pathologic myopia. Using advanced technology, identification of novel quantifiable chorio-retinal and scleral parameters in pathologic myopia would help to identify people at risk of developing pathologic myopia and potentially may revolutionise the management of myopia especially in risk prognostication and monitoring of disease progression.