Assessment of Schlemm's canal with swept-source optical coherence tomography in Graves' ophthalmopathy.

PURPOSE: To evaluate the Schlemm's canal (SC) parameters obtained by swept-source optical coherence tomography (OCT) different in Graves' ophthalmopathy (GO) eyes compared to healthy eyes. METHODS: This cross-sectional observational study evaluated 64 eyes of 32 GO cases and 56 eyes of 28 healthy controls. The study was conducted between October 2020 and June 2021. SC images were obtained from the temporal limbus of individuals using swept-source OCT. SC length (SCL) and SC area (SCA) were measured. The relationship between SC parameters in the patient group and intraocular pressure (IOP), retinal nerve fiber layer (RNFL) thickness, Graves' disease (GD) duration, and clinical activity score (CAS) was evaluated. RESULTS: In the GO group, 64 eyes of 32 patients were evaluated, and in the age and gender-matched healthy control group, 56 eyes of 28 individuals were assessed. SC images from 4 eyes of 4 patients in the patient group and 1 eye of 1 patient in the control group were not clear, preventing SCL and SCA measurements for these eyes. SCL and SCA measurements were found to be lower, and IOP and Hertel values were higher in the GO group compared to the healthy controls. However, no significant correlation was observed between SCL and SCA with IOP, RNFL thickness, GD duration, GO duration, or CAS in the GO group. In the GO group, the mean value of SCA was found to be higher in eyes with glaucoma or OHT compared to those without. CONCLUSION: These findings indicate that SC in GO-affected eyes is shorter and has a smaller area than in healthy individuals. Additionally, higher IOP and Hertel values were observed in the GO group compared to healthy controls. This study suggests that assessing SC using anterior segment OCT could provide valuable insights into the regulation of IOP and the development of glaucoma in GO-affected eyes.

Comparative evaluation of corneal and limbal epithelial thickness in brachycephalic dogs with and without corneal diseases using spectral domain optical coherence tomography.

OBJECTIVE: To evaluate alterations in epithelial thickness during corneal degeneration, corneal pigmentation, and additional features observed through spectral-domain optical coherence tomography (SD-OCT) in brachycephalic dogs. ANIMALS AND PROCEDURES: The study used 55 eyes from 49 brachycephalic dogs that underwent OCT-containing ophthalmic examinations. The examined eyes were classified into corneal degeneration, corneal pigmentation, and normal groups according to corneal lesions. For each eye, corneal epithelial thickness (CET) in the central cornea and maximum limbal epithelial thickness (maxLET) in 4 quadrants of limbus (superior, inferior, nasal, and temporal) were measured from OCT images. Additional abnormal findings on OCT images, including irregular epithelium, subepithelial hyperreflectivity, and conjunctivochalasis, were also recorded. RESULTS: The corneal degeneration group had significantly thinner nasal and temporal maxLETs than that of the normal group (p < .001). In the central corneal OCT image of the corneal degeneration group, an irregular epithelium was observed in 70.6% and subepithelial hyperreflectivity in 82.4%, both of which were significantly higher than the normal group (p < .001). In a comparative analysis, the nasal, temporal, and inferior maxLETs were significantly thinner in the corneal pigmentation group than those in the normal group (p < .001, p < .001, and p = .01, respectively). CONCLUSIONS: Morphological changes in the limbal epithelium were observed in dogs with corneal degeneration and corneal pigmentation. LET reduction could be associated with their pathogenesis and would be valuable as an additional parameter for corneal diseases.

Assessment of corneal and limbal epithelial thickness by spectral-domain optical coherence tomography in brachycephalic and non-brachycephalic dogs.

OBJECTIVE: To investigate the variance in corneal epithelial thickness (CET) and limbal epithelial thickness (LET) according to the age and skull type by using spectral-domain optical coherence tomography (SD-OCT) in normal dogs. ANIMALS AND PROCEDURES: This study used an eye each from 46 dogs (24 brachycephalic and 22 non-brachycephalic dogs) assessed to have clear corneas. Each dog was classified according to age into groups 1 (0-5 years), 2 (6-10 years), and 3 (>11 years). OCT imaging was performed on the central cornea for CET and perpendicular to the quadrant of the limbus for LET. The average of the maximum LET (maxLET) value was measured in four eye quadrants. RESULTS: Corneal epithelial thickness was not significantly different according to age in brachycephalic and non-brachycephalic dogs. Visualization of the limbal invagination was better when the maxLET was thick. Nasal and temporal maxLETs were significantly thicker than superior and inferior maxLETs in non-brachycephalic dogs. In brachycephalic dogs, there was a significant decrease in nasal maxLET with age (rs  = -0.489, p = .015). Significant differences between brachycephalic and non-brachycephalic dogs were observed in nasal maxLET (p = .024) and temporal maxLET (p = .011). CONCLUSIONS: Invagination was better visualized in the nasal and temporal limbal quadrants of non-brachycephalic dogs compared with brachycephalic dogs, and the maxLETs of the regions were thicker than those of the brachycephalic dogs. CET and LET measurements using SD-OCT can help in clinical assessment and research on ocular surface diseases in dogs.

In-vivo imaging of the conventional aqueous outflow system.

PURPOSE OF REVIEW: The aim of this study was to provide a comprehensive summary of in-vivo imaging techniques of the aqueous outflow system and discuss its role in improving our understanding of glaucoma pathogenesis and management. RECENT FINDINGS: Our understanding of the aqueous outflow system is largely derived from ex-vivo studies. Recent innovations in imaging technology and techniques enable in-vivo evaluation of the conventional outflow system in real-time. Optical coherence tomography allows for noninvasive, high-resolution, volumetric imaging of ocular tissues. Dynamic structural changes have been observed at the trabecular meshwork and Schlemm's canal. In parallel, aqueous angiography using injected tracers show a similar dynamism with variable and pulsatile flow signals. SUMMARY: In-vivo imaging enable real-time evaluation of the conventional aqueous outflow pathway. This emerging field shows great promise to expand our understanding of the pathogenesis and treatment of glaucoma.

Comparison of Subjective and Objective Methods of Corneoscleral Limbus Identification from Anterior Segment Optical Coherence Tomography Images.

SIGNIFICANCE: This study evaluates the reliability and validity of an automatic method of the external and internal limbal points identification from anterior segment optical coherence tomography (OCT) images in comparison with manual delineation. PURPOSE: The purpose of this work was to evaluate the repeatability and precision of a previously proposed automatic method of external and internal limbal points identification and to compare them with the manual delineation by experienced clinicians in terms of limbus diameter. METHODS: Optical coherence tomography tomograms obtained for 12 healthy volunteers without a history of eye diseases were analyzed. Fifteen OCT tomograms were captured for each patient. For all the images, the external and internal limbal points were determined using both the automatic and manual methods. The external and internal limbus diameters were used as the comparative parameter between the methods under consideration. The statistical analysis included mean, standard deviation, the Passing-Bablok regression, and the Pearson correlation coefficient. RESULTS: A strong linear dependence between the automatic and manual methods was identified. While compared with the subjective estimates from clinicians, the automatic technique overestimated the external limbus diameter (bias equals 0.21 mm for optometrist and 0.23 mm for ophthalmologist) and slightly underestimated the internal limbus diameter (bias equals 0.13 mm for optometrist and 0.04 mm for ophthalmologist). The automatic method showed significantly better repeatability than the manual method in the case of external limbal points identification and comparably high repeatability for internal limbal points recognition. CONCLUSIONS: Because of high precision and excellent repeatability, the automatic method of limbal points identification may be successfully used for estimation of the dynamic changes in the geometry of the anterior segment of the eye, where the large number of captured OCT images needs to be processed automatically with high precision.

Corneoscleral Topography Measured with Fourier-based Profilometry and Scheimpflug Imaging.

SIGNIFICANCE: Precise measurement of corneoscleral topography makes a valuable contribution to the understanding of anterior eye anatomy and supports the fitting process of contact lenses. Sagittal height data, determined by newer noninvasive techniques, are particularly useful for initial scleral lens selection. PURPOSE: The purpose of this study was to investigate the agreement and repeatability of Fourier-based profilometry and Scheimpflug imaging, in the measurement of sagittal height and toricity of the corneoscleral region. METHODS: Minimal (Minsag), maximal (Maxsag) sagittal height, toricity (Maxsag - Minsag), and the maximum possible measurement zone diameter of 38 subjects were compared using the Eye Surface Profiler (ESP; Eagle Eye, Houten, the Netherlands) and the corneoscleral profile module of the Pentacam (Oculus, Wetzlar, Germany) at two different sessions. Correlations between the instruments were analyzed using the Pearson coefficient. Differences between sessions and instruments were analyzed using Bland-Altman and paired t tests. RESULTS: For an equal chord length, the measurement with Pentacam was significantly greater for Minsag (344 µm; 95% confidence interval [CI], 322 to 364 µm; P < .001) and significantly greater for Maxsag (280 µm; 95% CI, 256 to 305 µm; P < .001), but significantly smaller for toricity (-63 µm; 95% CI, -95 to -31 µm; P < .001). Maximum possible measurement zone diameter with ESP (16.4 ± 1.3 mm) was significantly greater than with Pentacam (14.8 ± 1.1 mm) (P < .001). Repeated measurements from session 1 and session 2 were not significantly different for Pentacam and ESP (P = .74 and P = .64, respectively). The 95% CIs around differences indicate good repeatability for Pentacam (mean difference, -0.9 µm; 95% CI, -6.7 to 4.8 µm) and ESP (4.6 µm; -22.4 to 31.6). CONCLUSIONS: Although both instruments deliver useful data especially for the fitting of scleral and soft contact lenses, the sagittal height and the toricity measurements cannot be considered as interchangeable.

Intravital multiphoton microscopic imaging platform for ocular surface imaging.

The purpose of this study is to provide an intravital noninvasive multiphoton microscopic platform for long-term ocular imaging in transgenic fluorescent mice with subcellular resolution. A multiphoton microscopic system with tunable laser output was employed. We designed a mouse holder incorporated with stereotaxic motorized stage for in vivo three-dimensional imaging of ocular surface in 3 transgenic mouse line with fluorescent protein (FP) expression to visualize distinct structures. With our imaging platform and the expression of FPs, we obtained the three-dimensional images across the whole cornea from epithelium to endothelium and in conjunctiva with subcellular resolution in vivo. Specified EGFP expression in corneal epithelium of K5-H2B-EGFP mice helped to identify both corneal and limbal epithelial cells while ubiquitous nuclear FP expression in R26R-GR mice allowed us to visualized nuclei of all cell types. Universal membrane-localized FP in mT/mG mice outlined all cell boundaries, nerve fibers, and capillaries. The simultaneously collected second harmonic generation signals from collagenous stroma provided architectural contrast. Time-lapsed recording enabled monitoring the mitotic activity of corneal epithelial cells and limbal epithelial cells. We developed an intravital multiphoton microscopic stereotaxic imaging platform and showed that, by incorporating FP-expressing transgenic mice, this platform enables in vivo 4-dimensional ophthalmic study at subcellular resolution.

Salzmann's nodular degeneration of cornea associated with thyroid eye disease.

Salzmann's nodular degeneration (SND) typically occurs in patients who are female, 50-60 years old, and have a history of corneal inflammation and irritation. Multiple case reports have documented associations between SND and trachoma, viral infections, trauma, contact lens wear, corneal surgeries and corneal exposure. The authors describe a patient with bilateral SND confirmed by anterior segment optical coherence tomography (OCT) imaging in the context of thyroid eye disease (TED) and history of LASIK. Treatment involved propylthiouracil (PTU), artificial tear use, loteprednol etabonate ophthalmic gel, eyelid taping and selenium supplementation and prospective superficial keratectomy with diamond burr polish.

Characterizing Anterior Segment OCT Angle Landmarks of the Trabecular Meshwork Complex.

PURPOSE: To identify the presence or absence of 3 identifiable landmarks: trabecular meshwork (TM), Schlemm's canal (SC), and a novel landmark termed the band of extracanalicular limbal lamina (BELL), which is a landmark adjacent to SC visible on anterior segment (AS) OCT. These landmarks also were analyzed pathologically to identify all 3 landmarks. DESIGN: Retrospective review. PARTICIPANTS: One eye per participant from prior institutional review board-approved studies in which AS OCT imaging was performed. METHODS: Horizontal images from 2-dimensional angle analysis scans using a CASIA SS-1000 (Tomey, Nagoya, Japan) AS OCT were evaluated by masked readers. Logistic regression was used to analyze the potential factors of age, gender, race, intraocular pressure, gonioscopy grade, angle location, and history or presence of surgery on the visibility of these structures. Pathologic correlation on 5 previously enucleated eyes also was performed. MAIN OUTCOME MEASURES: Presence or absence of angle landmarks-TM, SC, and BELL-using Anterior Chamber Analysis and Interpretation software (ACAI, Houston, TX). RESULTS: Three hundred three angles of 153 horizontal images were included in this study. The mean age was 51.5±16.0 years, with 98 women (64%) and 100 white persons (66%). The outer border of the BELL was observed in 288 angles (95%), TM was found in 220 angles (73%), and SC was seen in 120 angles (40%). The outer border of the BELL was more visible in white persons (P = 0.02) than Asians and in eyes with a Spaeth gonioscopy grade of E than those with a grade of A (P = 0.02). Both TM (P = 0.001) and SC (P = 0.001) were more visible in temporal angles (81% for TM, 49% for SC) than in nasal angles (64% for TM, 30% for SC). Additionally, SC was more visible in open angles (43%) than in narrow angles (27%; P = 0.02). These 3 structures were verified in a pathologic study. CONCLUSIONS: We identified a novel AS OCT landmark adjacent to SC. This structure also was identified on pathologic samples from enucleated eyes. Further study is needed to determine the pathophysiologic relevance of these findings.

Toward in vivo two-photon analysis of mouse aqueous outflow structure and function.

The promise of revolutionary insights into intraocular pressure (IOP) and aqueous humor outflow homeostasis, IOP pathogenesis, and novel therapy offered by engineered mouse models has been hindered by a lack of appropriate tools for studying the aqueous drainage tissues in their original 3-dimensional (3D) environment. Advances in 2-photon excitation fluorescence imaging (TPEF) combined with availability of modalities such as transgenic reporter mice and intravital dyes have placed us on the cusp of unlocking the potential of the mouse model for unearthing insights into aqueous drainage structure and function. Multimodality 2-photon imaging permits high-resolution visualization not only of tissue structural organization but also cells and cellular function. It is possible to dig deeper into understanding the cellular basis of aqueous outflow regulation as the technique integrates analysis of tissue structure, cell biology and physiology in a way that could also lead to fresh insights into human glaucoma. We outline recent novel applications of two-photon imaging to analyze the mouse conventional drainage system in vivo or in whole tissues: (1) collagen second harmonic generation (SHG) identifies the locations of episcleral vessels, intrascleral plexuses, collector channels, and Schlemm's canal in the distal aqueous drainage tract; (2) the prospero homeobox protein 1-green fluorescent protein (GFP) reporter helps locate the inner wall of Schlemm's canal; (3) Calcein AM, siGLO™, the fluorescent reporters m-Tomato and GFP, and coherent anti-Stokes scattering (CARS), are adjuncts to TPEF to identify live cells by their membrane or cytosolic locations; (4) autofluorescence and sulforhodamine-B to identify elastic fibers in the living eye. These tools greatly expand our options for analyzing physiological and pathological processes in the aqueous drainage tissues of live mice as a model of the analogous human system.

Diagnosis of corneal limbal stem cell deficiency.

PURPOSE OF REVIEW: A state of limbal stem cell deficiency (LSCD) can be secondary to a number of etiologies, resulting in either a reduction in the total number of limbal stem cells or an abnormality in stem cell function. Initially, the epithelium becomes irregular and hazy; however, this condition may progress to persistent corneal epithelial defects, stromal scarring, ulceration, and even perforation. Since LSCD secondary to a variety of etiologies may be reversible, and various factors are prognostic of disease progression, timely diagnosis is important. This review will describe current knowledge of diagnostic techniques for LSCD and understanding of epithelial stem cell function. RECENT FINDINGS: Conjunctivalization, regarded as the most reliable clinical finding diagnostically, can be identified as late staining of epithelium with fluorescein. While identifying loss of the palisades of Vogt by slit-lamp examination, can provide a high suspicion of LSCD, but this is not diagnostic. Impression cytology is a simple, noninvasive technique that aids in the diagnosis of LSCD, but a negative result also cannot rule out the diagnosis. Recent findings have also shown that imaging techniques including in-vivo confocal microscope and optical coherent tomography can also aid in diagnosing LSCD; however, several challenges remain before these techniques become standard diagnostic methods in clinical practice. Meanwhile, determination of the absence of limbal epithelial crypts and focal stromal projections using image reconstruction techniques may assist in the diagnosis of LSCD. Furthermore, histologic markers may help not only to improve sensitivity and specificity of conventional techniques in diagnosis of LSCD, but also to identify human limbal stem cells and determine their number and function in LSCD. SUMMARY: Efforts to develop and improve techniques for diagnosing LSCD are ongoing. Increased knowledge of limbal stem cells and components of their niches may not only help in understanding the pathogenesis of LSCD but may improve its diagnosis, thereby ameliorating the prognosis of patients with this devastating disease.

ULTRASOUND MEASUREMENTS OF THE DISTANCE BETWEEN LIMBUS AND RETINAL BREAK IN EYES WITH MEDIA OPACITIES.

PURPOSE: To assess the reproducibility and accuracy of ultrasound (US) measurements in determining the distance between corneoscleral limbus and retinal break and its relation with the distance measured by indirect ophthalmoscopy, in patients undergoing a laser retinopexy procedure. METHODS: Forty-four patients with a single retinal break, scheduled for laser a retinopexy procedure (26 phakic patients and 18 pseudophakic patients), underwent 5 repeated measurements by high-resolution US and 3 measurements (at the time of the laser procedure, 1 and 3 months) by indirect ophthalmoscopy with scleral indentation of the corneoscleral limbus-retinal break distance with a caliper. RESULTS: In the phakic patients group, measurements ranged from 8.75 mm to 14.45 mm (12.56 ± 1.24, mean ± SD) and from 9.5 mm to 15 mm (12.35 ± 1.32) with US and indirect ophthalmoscopy, respectively. In the pseudophakic patients group, measurements ranged from 9.04 mm to 13.95 mm (11.88 ± 1.33) and from 8.5 mm to 13.2 mm (11.93 ± 0.99) with US and indirect ophthalmoscopy, respectively. The correlation coefficient was greater than 0.97. Measurement variability was very small. In phakic eyes, it was 0.13 ± 0.08 mm and 0.13 ± 0.07 mm with US and indirect ophthalmoscopy, respectively. In pseudophakic eyes, it was 0.12 ± 0.05 mm and 0.14 ± 0.05 mm with US and indirect ophthalmoscopy, respectively. US and indirect ophthalmoscopy measurements were not statistically different (Student's t-test, P = 1.71). The analysis of the variance among phakic and pseudophakic patients confirmed that measurements of the two groups do not differ significantly (Fisher's exact test, P = 0.16). The univariate analysis showed no significant difference in both US and indirect ophthalmoscopy measurements (ANOVA, P = 0.09) and between the two types of measurements and patient groups (ANOVA, P = 0.38). CONCLUSION: This study suggests relevant accuracy and reliability of US readings and provides the possibility of using this technique for localizing tears in eyes with media opacities by identifying the meridian and corneoscleral limbus-retinal break distance.

[Comparative analysis of the value of information provided by anterior segment optical coherence tomography and confocal laser scanning microscopy for identifying the palisades of Vogt in normal limbus]. / Sravnitel'nyi analiz informativnosti issledovaniya palisad fogta metodami opticheskoi kogerentnoi tomografii i lazernoi skaniruyushchei konfokal'noi mikroskopii v norme.

AIM: to conduct a comparative analysis of the value of information provided by anterior segment optical coherence tomography (AS-OCT) and in vivo confocal laser scanning microscopy (CLSM) for identifying the palisades of Vogt (POV) in normal limbus. MATERIAL AND METHODS: POV were studied in 15 healthy participants (30 eyes) without any anterior segment disease. Two examination methods were used: AS-OCT En Face imaging (RTVue XR Avanti, 3D Cornea protocol) and CLSM (HRT3). Concordance of the results was then analyzed. RESULTS: Structural features of POV were distinguishable by both methods. CLSM was able to visualize POV in both the superior and inferior limbi of all the 15 patients (30 eyes). Within the inferior corneal hemisphere, POV had the appearance of well-differentiated hyperreflective double-contoured structures organized in parallel lines at the level of basal epithelium. The structure of the superior limbus, as judged from CLSM data, varied significantly: «classic¼ palisades were seen in only 13 eyes (43%), while in the other 17 cases (57%) POV were atypical. On OCT, POV structure was seen in detail in 29 eyes. By comparing the abilities of CLSM and OCT to visualize POV, a strong positive correlation (rS=0.99, p<0.05) was revealed between the results obtained in both the superior and inferior limbi. CONCLUSION: OCT data provide a detailed understanding of POV structure and strongly correlate with CLSM results. Taking into consideration the noninvasiveness, demonstrativeness, and repeatability of AS-OCT En Face imaging as well as the high value of provided information, the method cay be recommended as an alternative in POV diagnostics.

Measurement of corneal and limbal epithelial thickness by anterior segment optical coherence tomography and in vivo confocal microscopy.

BACKGROUND: To compare corneal epithelial thickness (CET) and limbal epithelial thickness (LET) measured by anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscope (IVCM) in normal subjects, and evaluate the consistency between them. METHODS: Thirty-eight normal subjects (17 men and 21 women) were enrolled in this study. AS-OCT was performed at central cornea and the superior, inferior, nasal and temporal limbus. Then followed by IVCM examination performed at the same location. Agreement was analyzed by mean difference (AS-OCT minus IVCM), 95 % limits of agreement (LoA) (1.96 standard deviation of the difference), and Bland-Altman analysis. RESULTS: The average CET measured by AS-OCT and IVCM was 55.6 ± 4.0 µm and 51.9 ± 4.9 µm respectively. The value measured by IVCM was significantly lower than that measured by AS-OCT (P = 0.015). The average LET values tested by AS-OCT were 10.3 and 10.9 % less at nasal and temporal quadrant (nasal: P = 0.019, temporal: P = 0.003), and were similar as those measured by IVCM at superior and inferior quadrant. In subjects older than 40 years, CET and LET values measured by AS-OCT were significantly higher than those by IVCM. Such differences were not found in subjects ≤ 40 years old. CONCLUSIONS: CET values measured by IVCM are lower than those by AS-OCT, while LET values measured by two devices have good agreement. These two techniques have their own advantages in measuring epithelial thickness and are mutually complementary.

Correlation Between Anterior Chamber Angle Status and Limbal Stem Cell Deficiency in Primary Angle-Closure Glaucoma.

PURPOSE: To investigate the correlation between the opening and closing states of anterior chamber angle (ACA) and the density of limbal epithelial basal cells (LEBCs) in subjects with primary angle-closure glaucoma (PACG). DESIGN: Cross-sectional observational study. METHODS: A total of 54 eyes of 29 patients diagnosed with PACG were included in the study. Fifty-four eyes from normal subjects were included as control. Automatic evaluation system for ultrasound biomicroscopy images of anterior chamber angle was used to assist ophthalmologists in identifying the opening or closing state of ACA, and the in vivo confocal microscopy (IVCM) was used to evaluate the density of LEBCs in different directions. RESULTS: (1) The average density of LEBCs in the superior, inferior, nasal, and temporal limbus of the eyes in the PACG group was lower than that in the control group, and this pattern did not align with the density distribution observed in the control group. (2) In the early, moderate and advanced PACG, the density of LEBCs corresponding to the closed angle was lower than that in the control group (P < .05). Compared with the density of LEBCs corresponding to the closed angle and the open angle, the closed angle of PACG in the early, moderate and advanced stages was less than that in the open angle (P < .05 in the early and moderate stages; advanced stage P > .05). (3) The basal cell density was processed by dimensionless analysis. In the data calculated by averaging and minimizing, both closed angle dimensionless values were smaller than the open angle (P < .05). (4) Comparative analysis was conducted among the normal, open-angle, and closed-angle conditions in the superior, inferior, nasal, and temporal limbus. In the early stage of PACG, significant differences were observed in 4 limbal regions (P < .05), while in the moderate PACG stage, this difference was noted in 3 limbal regions (P < .05). In advanced PACG, 2 limbal regions exhibited significant differences (P < .05). These findings suggest that during the early PACG stage, angle closure is the predominant influencing factor on LEBCs density, while in the advanced stage, the decrease in density is attributed to a combination of angle closure and the natural progression of the disease. CONCLUSIONS: There is a significant correlation between anterior chamber angle status and LEBCs. Advanced PACG and angle closure should be highly suspected of the occurrence of limbal stem cell deficiency (LSCD).

Characterization of the external limbus on corneoscleral topography with ultrawide-field optical coherence tomography.

PURPOSE: To present a new method for 3-dimensional external limbal demarcation on corneoscleral topography derived from optical coherence tomography (OCT). Limbal shape is investigated and compared to other landmarks. METHODS: Images from the anterior segment were obtained with a ultrawide-field (20 mm) OCT. An automated algorithm was developed to demarcate the topographic limbus based on the transition from corneal to scleral curvature. The internal limbus was manually identified as the scleral spur on the OCT images. The external topographic limbus was fit with a circle on a plane. Ellipticity and ovality were defined by the lateral limbal deviation from the best-fit circle. Toricity was defined by the axial deviation from the best-fit plane. Repeatability was assessed by the within-subject standard deviation from two repeated measurements. For comparison, the white-to-white (WTW) diameter was obtained from Pentacam HR. RESULTS: 18 eyes from 11 subjects were analyzed. The topographic limbal diameter was 12.16 ± 0.68 mm (mean ± standard deviation) horizontally and 11.18 ± 0.65 mm vertically. The repeatability for the topographic limbal diameter was 0.054 mm. The internal and WTW horizontal limbal diameters were significantly smaller (linear mixed-effects model (GLMM), p <.017). The vertical internal limbal diameter was significantly larger (GLMM p <.05). The topographic limbus had significant ellipticity (0.25 ± 0.13 mm, wider horizontally, repeatability of 0.07 mm) and toricity (0.15 ± 0.08 mm, flatter horizontally, repeatability of 0.10 mm). Low coefficients of determination were found for the topographical limbus with the internal limbus (R2=0.021 and R2=0.039, for horizontal and vertical diameters respectively) and with the WTW (R2=0.146 for the horizontal diameter). CONCLUSION: The proposed method to demarcate the 3D external topographical limbus is repeatable. The topographic limbal shape and size cannot be accurately derived from WTW nor internal limbus measures. This new technology may improve the process of scleral lens fitting.

Evaluation of different OCT systems in quantitative imaging of human Schlemm's canal.

We examined the performance of human Schlemm's canal (SC) imaging using different OCT devices: CIRRUS 5000 (840 nm, spectral-domain (SD)-OCT), PLEX Elite 9000 (1060 nm, swept-source (SS)-OCT) and CASIA SS-1000 (1310 nm, SS-OCT), and analyzed potential impact factors on visualization and the quantitative assessment of SC morphology in a pilot study. Ten healthy subjects were imaged using three OCT devices by a single experienced operator on the same day. Each eye underwent two cubic scans by each device, one on nasal and the other on temporal quadrant. The B-scan showing the largest SC was manually selected for processing. Four quantitative metrics, including one morphological metric as cross-sectional area (CSA), and three performance metrics as contrast, continuity, and coverage, were derived from the datasets. Repeated-measures ANOVA was used to investigate the difference between these parameters from the three devices (P < 0.05). We found the CSA measured from CIRRUS was significantly larger than PLEX, followed by CASIA. The contrast was highest in CIRRUS, followed by PLEX and CASIA. The coverage was also higher in CIRRUS as compared to PLEX and CASIA. No significant difference was seen in the continuity from the three devices. In summary, we showed the measurements from the three devices were not interchangeable.

Rosai-Dorfman disease manifesting as an epibulbar ocular tumour.

The authors report a rare case of extranodal Rosai-Dorfman disease without systemic involvement. A 14-year-old girl presented with a slowly progressive, non-tender, well-circumscribed, perilimbal nodule in the right eye. Excisional biopsy was performed and histopathologic and immunohistochemical analysis established the diagnosis. Systemic evaluation revealed no other masses. After complete excision of the epibulbar lesion, the patient is asymptomatic and remains on regular follow up with no signs of recurrence. Rosai-Dorfman disease is an infrequent, benign histiocytic disorder that can rarely manifest as an exclusive extranodal mass. We report a case of solitary epibulbar Rosai-Dorfman disease, successfully treated with complete surgical excision of the lesion.

The utility of anterior segment optical coherence tomography angiography for the assessment of limbal stem cell deficiency.

PURPOSE: To determine the utility of anterior segment optical coherence tomography angiography (AS-OCTA) in assessing limbal stem cell deficiency (LSCD). METHODS: Twenty-six eyes of 24 LSCD patients, classified clinically into stage I, II and III, and 12 eyes of 12 healthy subjects were included. AS-OCTA images were analyzed by two masked observers, measuring the maximum corneal vascular extension (CoVE) from the limbus to the furthest vessel over the cornea, and corneal vascular thickness (CoVT) from the most superficial to the deepest corneal vessel. RESULTS: CoVE was 0.27 ± 0.10, 0.79 ± 0.21, 1.68 ± 0.89 and 2.53 ± 0.82 mm in controls, stage I, II and III LSCD, respectively (p < 0.001). The CoVT was 51.0 ± 19.4, 113.7 ± 36.6, 129.7 ± 39.3 and 336.0 ± 85.0 µm, respectively (p < 0.001). There was a significant difference in CoVE and CoVT between all stages compared to controls, and between stage I and III LSCD (p < 0.001). Further, CoVE showed a significant difference between stage I and II, whereas CoVT showed a significant difference between stage II and III LSCD (p < 0.001). BCVA showed strong correlation with CoVT (r = 0.765, p < 0.001) and moderate correlation with CoVE (r = 0.547, p = 0.001). AS-OCTA parameters showed excellent intra- and inter-class correlation coefficients (>0.900). CONCLUSION: LSCD demonstrates significant changes in CoVE and CoVT as early as stage I LSCD in comparison to controls. CoVE and CoVT strongly correlate to both disease severity and BCVA. AS-OCTA may provide novel quantitative and non-invasive parameters to assess LSCD.

The impact of limbus detection, arcus lipoides and limbal vessels on the primary patency of clear cornea incisions in femtosecond laser-assisted cataract surgery.

PURPOSE: To analyse the factors influencing the primary patency of clear corneal incisions in femtosecond laser-assisted cataract surgery (FLACS). METHODS: In this prospective single-centre study, the graphical user interfaces of 159 patients undergoing femtosecond laser-assisted cataract surgery were documented by video. Subsequently, the quality of limbus detection along with the incidence of vessels and an arcus lipoides were assessed by a grading system and analysed in relation to the primary patency of the incisions. In particular, the differences between a superior and a temporal main incision were analysed. RESULTS: The designed grading system could be applied in all cases without any problems. Limbus detection was highly inhomogeneous but had no influence on the patency of the incisions (46.3% poor, 18.4% moderate, 35.1% good). The characteristics of the arcus lipoides had little influence on the patency of the main incisions. Pronounced vascular ingrowth caused more tissue bridges but did not reduce the patency of the incisions. Temporal access was generally easier to open than a superior one (97.1% versus 88.9%). CONCLUSION: We showed a patency rate of superior FLACS incisions of over 97% with the Femto LDV Z8 in our study. Temporal main incision is preferable to superior main incision in more difficult situations. The new grading system is suitable for further studies to provide information on the quality of the incision.