PURPOSE:To investigate the effect of peripheral scleral lens landing zone modifications upon short-term regional variations in corneal oedema. METHODS:Nine healthy participants wore different scleral lens designs ((1) spherical landing zone, (2) toric landing zone, (3) peripheral notches, and (4) peripheral channels) in a randomised order on four separate days for 100 min. Stromal oedema was quantified using high-resolution optical coherence tomography across the central, mid-peripheral, and peripheral cornea with the lens in situ. Eye Surface Profiler (ESP) images were also captured following the application of 10 μL of 2% sodium fluorescein, over a period of 100 min. Central and peripheral fluorescent intensity data were extracted from the ESP images and analysed using customised software to quantify tear exchange. RESULTS:The channel lens design displayed less central oedema compared to the toric design (1.57 ± 0.45% less oedema, p = 0.04). In the corneal periphery, the magnitude of oedema was less for both the toric lens (2.66 ± 0.66% less oedema, p = 0.02) and the channel design (3.39 ± 0.97% less oedema, p = 0.04) in comparison to the spherical lens design. A highly significant correlation was observed between the magnitude of peripheral tear exchange after 90 min of lens wear and the magnitude of peripheral oedema (r = -0.61, p < 0.001). CONCLUSIONS:Scleral lenses with either a toric landing zone or peripheral channels exhibited less peripheral corneal oedema than a spherical landing zone design, due to enhanced peripheral tear exchange.

To develop a Scheimpflug-based image analysis technique to quantify tear exchange during scleral lens wear and investigate fluid reservoir tear dynamics during fenestrated lens wear. Nine healthy participants wore a scleral lens (KATT™, Capricornia Contact Lenses) with a single 0.3 mm diameter limbal fenestration in one eye for 90 min. Central (0–2.5 mm from the corneal apex) and peripheral (−1.0 to 0 mm from the scleral spur) stromal cornea oedema was measured using optical coherence tomography. Scheimpflug images were obtained during lens wear at multiple time points following the application of sodium fluorescein to the bulbar conjunctiva. These images were exported and annotated manually to select the region of interest (the fluid reservoir) from which the intensity of each pixel was extracted to provide a measure of fluorescent intensity (in arbitrary units [AU] on a scale of 0–255) throughout lens wear across the central 10 mm. The coefficient of repeatability for central fluid reservoir intensity measurements was 7 AU (on a scale of 0–255 AU). Fluid reservoir fluorescent intensity varied with measurement location (p < 0.001), being greater towards the periphery (4 and 5 mm from the centre). On average, intensity differences between the peripheral and central fluid reservoir diminished within 10 min of sodium fluorescein application. Two patterns of tear dynamics were observed and were classified as low and high flow. Low flow participants (n = 6) exhibited greater central (3.72× more) and peripheral (2.25× more) corneal oedema, but the difference was not statistically significant. The ingress and mixing of sodium fluorescein within the fluid reservoir stabilised between central and peripheral locations after 10 min of fenestrated scleral lens wear. Two patterns of tear dynamics were observed (low and high flow), with low flow participants exhibiting greater corneal oedema. Future research utilising the developed technique may provide further insights into tear exchange during scleral lens wear with different fenestration sizes and configurations.

Purpose:To examine changes in retinal perfusion density (PD) following short-term exposure to optically induced myopic defocus, an ocular growth-inhibitory stimulus, and achromatic digitally simulated myopic blur, an ocular growth stimulus. Methods:The left eyes of 12 emmetropic and 12 myopic healthy young adults (mean ± SEM age: 24 ± 1 years) underwent optical coherence tomography angiography to assess retinal PD before and following 60 minutes of blur exposure. Optical myopic defocus was induced by viewing a video through +2 D lenses, digitally simulated myopic blur by viewing the same video filmed with a +2 D defocused camera, and the control (no-blur) condition by viewing the original video through optimal refractive correction. PD changes were examined using linear mixed models, with the control-condition changes as a covariate. Results:A significant blur by eccentricity interaction was observed (P < 0.001), with the overall retinal PD increasing with optical myopic defocus compared to simulated myopic blur in the fovea by 2.9% ± 1.0% (P = 0.003) but decreasing in the outermost 2- to 3-mm parafovea by -2.3% ± 0.5% (P < 0.001). Significant PD changes were also observed associated with the blur condition, perfusion layer, eccentricity, and refractive status (interaction, P = 0.04). The most pronounced effects were observed in the foveal deep capillary plexus, where emmetropes exhibited increased PD during optical myopic defocus and decreased PD during simulated myopic blur (3.8% ± 2.3% vs. -6.4 ± 2.2%; P < 0.001), but myopes exhibited significantly different responses compared with emmetropes to both the optical blur (-4.0% ± 2.3%; P = 0.035) and the simulated myopic blur (0.7% ± 2.3%; P = 0.046). Conclusions:Significant blur-driven changes were observed in the retinal PD of emmetropic eyes, increasing with optical myopic defocus but decreasing with simulated myopic blur of comparable magnitude, particularly in the foveal deep capillary plexus, with these responses not observed in myopic eyes. These bidirectional retinal perfusion responses are unlikely to be driven solely by blur magnitude or contrast modulations and are more plausibly related to vergence cues that were present with optical myopic defocus but absent in digitally simulated myopic blur.

Precise blink detection is essential for a range of applications, including eye-tracking. Although numerous methods for blink detection have been proposed, their performance may not be optimal under certain complex real-world scenarios. This study introduces a deep learning approach tailored for mobile eye-tracking devices to accurately classify blinks. The dual approach integrates a variational autoencoder (VAE) followed by a classifier that distinguishes between blinks and non-blinks based on the latent vector. To optimize the VAE’s performance, several experimental conditions are explored, including three different data input groupings. Subsequently, to identify the most suitable classifier for the blink detection task, four different classifiers were evaluated. The architecture was tested with two image sizes. The results illustrate that a more complex and diverse dataset requires a higher latent space dimensionality, while image size does not significantly impact performance, indicating that the VAE can capture adequate information even when reduced significantly from the original size. Regarding input data grouping, the additional information from using both eyes or multiple frames does not seem to improve decision-making significantly. Among the classifiers, the K-Nearest Neighbours (KNN) demonstrated the best overall performance. The proposed VAE-classifier method was optimized to achieve an accuracy of more than 99.5%, outperforming other approaches and demonstrating the effectiveness of VAE-based methods for blink detection. Test on clinical videos also demonstrated an excellent agreement with the ground truth. This method surpasses conventional blink detection techniques used in mobile eye trackers, further demonstrating this technique’s potential to support clinical and research eye-tracking applications.

PURPOSE:To quantify the effect of landing zone modifications on tear exchange during short-term scleral lens wear. METHODS:Nine healthy adults with normal corneas wore scleral lenses with three different landing zone modifications (toric landing zone (control condition), peripheral notches, or channels) in a randomised order. Following the application of 10 µl of 2 % sodium fluorescein, Eye Surface Profiler (ESP) images were captured over a period of 100 min. Sodium fluorescein was reapplied at 90 min to assess tear exchange following lens settling. Central and peripheral fluorescent intensity data (quantified in arbitrary units, AU) were extracted from the ESP and analysed using customised software in MATLAB. RESULTS:Fluorescent intensity varied significantly with lens design, time, and corneal location (p < 0.001). Averaged across all time points, the channel design displayed a higher level of fluorescent intensity (22 ± 2 AU) compared to the toric control (19 ± 1 AU) (p < 0.01) and notch designs (18 ± 1 AU) (p < 0.001). Following the reapplication of sodium fluorescein after 90 min of lens wear, the channel design also displayed a greater increase in fluorescent intensity ten minutes later (15 ± 3 AU increase) compared to the toric (10 ± 5 AU increase) and notch design (12 ± 5 AU increase) averaged across both central and peripheral locations (groove > toric and notch, both p < 0.05). CONCLUSIONS:Landing zone modifications influence tear dynamics during short-term scleral lens wear. The channel design provided a consistent increase in tear ingress, mainly in the periphery. These findings provide quantitative evidence that channel modifications can enhance tear exchange in the short-term and may inform future innovations in scleral lens customisation.

To compare the magnitude of central, mid-peripheral and peripheral stromal corneal oedema induced during short-term fenestrated and non-fenestrated scleral lens wear. Nine healthy participants wore a non-fenestrated and a fenestrated (0.3-mm diameter limbal fenestration) scleral lens (KATT™, Capricornia Contact Lenses), hexafocon B material (Dk 141 × 10−11 cm3 O2(cm)/[(s) (cm2) (mmHg)]) in one eye under open-eye conditions for 90 min on two separate days. Scleral lens thickness, fluid reservoir thickness and stromal corneal oedema were measured using high-resolution optical coherence tomography. Stromal oedema was quantified across the central (0–2.5 mm from the corneal apex), mid-peripheral (−3.0 to −1.0 mm from the scleral spur) and peripheral (−1.0 to 0 mm from the scleral spur) cornea with the lens in situ. The magnitude of oedema was corrected based on variations in fluid reservoir thickness between the lens conditions. There was a significant effect of lens type (p = 0.04) on stromal oedema, with less oedema observed with the fenestrated (0.36 ± 0.45

Tear exchange during contact lens wear is essential for ocular surface integrity, facilitating debris removal, and maintaining corneal metabolism. Fluorophotometry and fluorogram methods are typically used to measure tear exchange, which require hardware modifications to a slit lamp biomicroscope. This manuscript introduces an alternative method using a corneoscleral profilometer, the Eye Surface Profiler (ESP), to quantify tear exchange during corneal and scleral rigid lens wear by assessing fluorescence intensity changes over time. As a proof of concept, a healthy participant wore a corneal and a scleral rigid lens on separate days. After lens application, 2

PURPOSE:Low concentration atropine is an effective treatment to slow myopia progression and axial elongation and also reduces accommodation. On-axis ocular dimensions of the eye change during accommodation; hence, this study aimed to quantify the effect of 0.025% atropine eye drops on accommodation-induced changes in ocular biometry. METHODS:Twenty-eight myopic participants with a mean (SD) age of 17.0 (6.0) years (range: 8.0-25.5 years) and spherical equivalent refraction (SER) of -2.03 (1.05) D (range: -0.75 to -4.38 D) were enrolled. Baseline ocular biometry measurements of the left eye were captured using an optical biometer (Zeiss IOLMaster 700) for 0, 2, 4 and 6 D accommodation stimuli, presented via a Badal optometer. The accommodation response (AR) was determined using wavefront aberrometry (Imagine Eyes irx3) for the same accommodation stimuli and following cycloplegia using 1% tropicamide. Participants instilled 0.025% atropine eye drops nightly for 1 week in both eyes, and ocular biometry measurements were repeated on the day after the final atropine dose. RESULTS:Anterior chamber depth (ACD) and corrected vitreous chamber depth (cVCD) decreased, and crystalline lens thickness (LT), anterior segment length (ASL), crystalline lens centre position (LCP) and the AR increased significantly during accommodation (all p ≤ 0.009). Accommodation-induced changes in ACD and LT were reduced following 0.025% atropine use (both p ≤ 0.01), with significant pre- and post-atropine differences for the 4 and 6 D stimuli (all pairwise comparisons, p ≤ 0.004). On average, ACD, ASL and LCP increased, while cVCD, corrected axial length (cAL), and the AR decreased following 1 week of 0.025% atropine use (all p ≤ 0.002). CONCLUSIONS:The AR and on-axis ocular biometric changes during accommodation were reduced following 1 week of 0.025% atropine use. These findings may have implications for the association between near work and myopia, and atropine's mechanism of action in humans.

Optical coherence elastography (OCE) is a non-invasive imaging technique that measures the biomechanical properties of materials and tissues. This systematic review focuses on the applications of OCE in the anterior segment of the eye, including the cornea, iris, and crystalline lens, and its clinical relevance in diagnosing and managing ocular diseases. A systematic literature review was conducted using the PRISMA framework to identify studies published between 2014 and 2024. The review included studies that reported intrinsic biomechanical properties of anterior segment tissues measured using OCE. Databases searched included Scopus, Pub Med, and IEEE Xplore. Twenty-five studies met the inclusion criteria. The review found that OCE has been used to measure intrinsic biomechanical parameters such as Young’s modulus and shear modulus in ocular tissues. OCE has been utilised to assess corneal stiffness in keratoconus, lens elasticity in presbyopia and cataract formation, and iris biomechanical changes under different lighting conditions. The studies demonstrated that OCE could detect subtle biomechanical changes associated with ocular diseases and measure treatment efficacy, such as collagen crosslinking for keratoconus management. The findings highlight the potential of OCE to enhance clinical diagnostics and patient care by providing detailed insights into the biomechanical properties of ocular tissues. However, variability in measurement techniques, the complexity of the method and reliance on animal models limit the current clinical translation of OCE. Standardised measurement protocols and further development and in vivo validation are needed to overcome these barriers. OCE shows promise as a valuable non-invasive tool for high-resolution assessments of tissue biomechanics, which can subsequently support the diagnosis and management of ocular diseases. Future research should focus on standardising OCE methods and integrating them into clinical practice to fully realise their potential in improving patient outcomes.

Purpose:This retrospective cross-sectional study examined regional changes in choroidal vascularity index (CVI) with physiological aging in healthy emmetropes. Methods:Deep learning methods were used for segmentation and binarization of enhanced depth imaging optical coherence tomography images of the choroid collected from 280 healthy emmetropic subjects (mean spherical equivalent refraction: +0.39 ± 0.38 D), including 83 children (5-12 years), 77 adolescents (13-17 years), and 120 adults (18-41 years). The CVI, calculated as the ratio of luminal versus total choroidal area (in percent), and luminal and stromal choroidal thickness were measured across the 5-mm horizontal macular region centered on the fovea. Linear mixed models were used to examine age-related regional changes in the choroid while controlling for gender and imaging time of day. Results:The macular CVI reduced significantly from childhood (65% ± 0.5%) and adolescence (63% ± 0.5%) to adulthood (59% ± 0.4%) (P < 0.001). Significant regional variations were observed (P < 0.001) with the CVI increasing from the fovea (61% ± 0.3%) toward the perifovea (64% ± 0.3%) and from the temporal (61.4% ± 0.3%) toward the nasal hemiretina (63% ± 0.3%). The age-related decrease in the CVI was greater in the nasal (-7% ± 0.7%) than the temporal (-6% ± 0.7%) macula (P = 0.014) and was associated with a significant nasal stromal thickening (45 ± 5 µm; P < 0.001) and temporal luminal thinning (-16 ± 6 µm; P = 0.033) from childhood to adulthood. Conclusions:Physiological aging was associated with a significant region-dependent decline in the CVI driven, primarily by stromal thickening in the nasal and luminal thinning in the temporal macula. Translational Relevance:These age-related changes in the CVI provide new insights into the physiological morphology of the choroid during aging and may aid clinicians in understanding the spatial and age-associated predilections of certain chorioretinal diseases.

PURPOSE:Although it is well known that astigmatism correction with toric contact lenses improves clinical vision measures, their effects on real-world visual performance using digital devices such as smartphones are less well understood. This study aimed to examine how toric soft contact lenses impact functional near visual performance with a smartphone, in comparison to spherical equivalent contact lenses. METHODS:Fifteen healthy young adults (mean age 23.6 ± 2.8 years) with low to moderate astigmatism (-0.50 D to -1.50 D) participated in this prospective, repeated measures randomised crossover trial. Either toric or best sphere soft daily disposable contact lenses (lens material Verofilcon A) were worn during two separate study visits. At each visit, near visual acuity (VA) was assessed, and participants performed a reading task on a smartphone with both high and low contrast text displays. A mobile eye tracker was worn during the reading task to track objective measures of visual fatigue such as palpebral aperture height and near focusing demand. RESULTS:Both high and low contrast near VA were significantly better with the toric correction compared to the best sphere (p = 0.001). While reading on a smartphone, the average reading speed was not significantly different between the sphere and toric lenses (p = 0.18). Significantly fewer errors were made while reading with the toric lens compared to the best sphere lens for the low contrast (p = 0.04), but not for high contrast text (p = 0.4). For measures of palpebral aperture height, and focusing demand, a significant lens by time interaction was found (both p < 0.05), with a significantly greater focusing demand and a narrower palpebral aperture observed towards the end of the reading task with the best sphere lens. CONCLUSION:Significant visual and functional benefits were found for digital near visual tasks associated with toric contact lens correction.

PURPOSE:The accurate segmentation of corneal and contact lens boundaries in anterior segment optical coherence tomography (AS-OCT) images provides essential clinical information. The purpose of this study was to evaluate the performance of sixteen different deep learning (DL) models developed to segment AS-OCT images obtained during scleral lens wear. METHODS:AS-OCT images were obtained from 15 participants with normal corneas after 0 and 480 min of scleral lens wear. An experienced observer manually annotated the boundaries of interest in each image (considered the ground truth) including the anterior and posterior scleral lens surfaces, the anterior corneal epithelial surface, the anterior stromal interface, and the endothelium. Four different architectures were adapted for semantic segmentation (U-Net, U-Net++, FPN, and MA-Net) each of which was tested with five different encoders (EfficientNet-B4, DenseNet201, VGG19, ResNet34, and Xception). Following training, the segmentation performance of each model was evaluated using the Dice coefficient (measurement of the area overlap) and the mean absolute boundary error. RESULTS:All DL models displayed a high level of performance for classification and segmentation of the scleral contact lens and fluid reservoir (with Dice coefficients typically > 99 % and mean absolute error values of < 1 pixel). Misclassification issues arose for some models, likely linked to the lower reflectivity and homogeneity of the interface between Bowman's layer and the corneal stroma. Overall, only minor differences were observed between models, with the U-Net++/VGG19 combination displaying the best performance with an overall Dice score of 99.26 % and per class Dice scores ranging from 99.11 to 99.77 %. CONCLUSION:The U-Net++/VGG19 DL model displayed the best performance for AS-OCT image segmentation during scleral lens wear based on the overall Dice coefficient. Further assessment of DL models involving the segmentation of eyes with corneal disease and altered tissue morphology during scleral lens wear is warranted.

Many ocular conditions are linked to changes in the vasculature and circulatory system of the posterior eye. Over the past 25 years, optical coherence tomography (OCT) has revolutionized ocular imaging, providing highly detailed anatomical information on the retina and choroid. However, current clinical OCT devices are unable to quantify blood flow rate or velocity in ocular tissues. This limitation is significant, as such measurements could provide valuable insights for assessing eye health and managing ocular diseases. This research addresses this issue by developing methodologies using a phantom imaging model, feature extraction, and machine learning methods to quantify blood flow rate with clinical OCT imaging. Specifically, it demonstrates that using a range of image features and a linear discriminant model, the flow rate can be classified in OCT images with 90% accuracy by utilizing speckle statistical features. This study represents a novel attempt to automatically quantify flow rate using OCT images and speckle metrics, aiming to enhance the ability of OCT in assessing ocular vasculature.

Abstract Background Blue light activates melanopsin, a photopigment that is expressed in intrinsically photosensitive retinal ganglion cells (ipRGCs). The axons of ipRGCs converge on the optic disc, which corresponds to the physiological blind spot in the visual field. Thus, a blue light stimulus aligned with the blind spot captures the ipRGCs axons at the optic disc. This study examined the potential changes in choroidal thickness and axial length associated with blue light stimulation of melanopsin-expressing ipRGCs at the blind spot. It was hypothesized that blue light stimulation at the blind spot in adults increases choroidal thickness. Methods The blind spots of both eyes of 10 emmetropes and 10 myopes, with a mean age of 28 ± 6 years (SD), were stimulated locally for 1-minute with blue flickering light with a 460 nm peak wavelength. Measurements of choroidal thickness and axial length were collected from the left eye before stimulation and over a 60-minute poststimulation period. At a similar time of day, choroidal thickness and axial length were measured under sham control condition in all participants, while a subset of 3 emmetropes and 3 myopes were measured after 1-minute of red flickering light stimulation of the blind spot with a peak wavelength of 620 nm. Linear mixed model analyses were performed to examine the light-induced changes in choroidal thickness and axial length over time and between refractive groups. Results Compared with sham control (2 ± 1 μm, n = 20) and red light (−1 ± 2 μm, n = 6) stimulation, subfoveal choroidal thickness increased within 60 min after blue light stimulation of the blind spot (7 ± 1 μm, n = 20; main effect of light, p < 0.001). Significant choroidal thickening after blue light stimulation occurred in emmetropes (10 ± 2 μm, p < 0.001) but not in myopes (4 ± 2 μm, p > 0.05). Choroidal thickening after blue light stimulation was greater in the fovea, diminishing in the parafoveal and perifoveal regions. There was no significant main effect of light, or light by refractive error interaction on the axial length after blind spot stimulation. Conclusions These findings demonstrate that stimulating melanopsin-expressing axons of ipRGCs at the blind spot with blue light increases choroidal thickness in young adults. This has potential implications for regulating eye growth.

Oxygen delivery and tear exchange are considered essential to maintain corneal homoeostasis during contact lens wear. Since the 1940s, fenestrations and back surface channels have been utilised in scleral, corneal rigid, and soft contact lenses in an attempt to enhance corneal oxygen transmission, facilitate the removal of carbon dioxide from the post-lens tear layer, minimise corneal oedema and prevent post-lens tear stagnation. This review examines the use of contact lens fenestrations and channels in both clinical and laboratory settings, and the effect of these modifications upon tear exchange and corneal oedema. Despite almost a century of modifying contact lenses to alter tear dynamics and promote corneal health, the evidence regarding the efficacy of fenestrations and channels is mixed.

Significance: The biomechanical properties of the cornea are important for vision and ocular health. Optical coherence elastography (OCE) has the potential to improve our capacity to measure these properties. Aim: This study tested a static compression OCE method utilising a commercially available optical coherence tomography (OCT) device, to estimate the Young's modulus of ex-vivo porcine corneal tissue. Approach: OCT was used to image corneal tissue samples before and during loading by static compression. The compressive force was measured with a piezoresistive force sensor, and tissue deformation was quantified through automated image analysis. Ten ex-vivo porcine corneas were assessed and the corneal thickness was also measured to assess the impact of corneal swelling. Results: An average (standard deviation) Young's modulus of 0.271 (+/- +/- 0.091) MPa was determined across the 10 corneas assessed. There was a mean decrease of 1.78 % in corneal thickness at the end of the compression series. These results showed that there was a moderate association between corneal thickness and the Young's modulus recording (R2 2 = 0.274). Conclusions: Optical coherence elastography utilising clinical instrumentation, can reliably characterise the mechanical properties of the cornea. These results support the further investigation of the technique for in-vivo measurement of the mechanical properties of the human cornea.

To quantify the magnitude and recovery of central and limbal corneal oedema induced by short-term unilateral eyelid closure without contact lens wear. The left eye of 10 adults with healthy corneas was patched using a folded eye pad for 30 min. High-resolution optical coherence tomography images (which captured the limbal and central corneal regions simultaneously) were obtained before patching, immediately after eye opening and again at 1, 2, 5, 6, 9, 10, 14 and 15 mins after eyelid opening. Oedema was measured from the limbus (scleral spur) to the central cornea (thinnest corneal location) along the horizontal meridian. A greater amount of limbal oedema was noted (mean [SD] 3.84 [1.79]

AbstractThe protective effects of time spent outdoors emphasize the major role of daylight in myopia. Based on the pathophysiology of myopia, the impact of blue light stimulation on the signaling cascade, from melanopsin at the blind spot to clinically relevant biomarkers for myopia, was investigated. Parameters and site of light stimulation are mainly defined by the photopigment melanopsin, that is sensitive to blue light with a peak wavelength of 480 nm and localized on the intrinsically photosensitive retinal ganglion cells (ipRGC) whose axons converge to the optic disc, corresponding to the physiological blind spot. Blue light at the blind spot (BluSpot) stimulation provides the opportunity to activate the vast majority of ipRGC and avoids additional involvement of rods and cones which may exert incalculable effects on the signaling cascade.Experimental studies have applied anatomical, histochemical, electrophysiological, imaging, and psychophysical methods to unravel the mode of action of BluSpot stimulation. Results indicate activation of melanopsin, improvement of contrast sensitivity, gain in electrical retinal activity, and increase of choroidal thickness following BluSpot stimulation. Short-term changes of clinically relevant biomarkers lead to the hypothesis that BluSpot stimulation may exert antimyopic effects with long-term application.