Metrics of Anterior Sclera in Normal Chinese Adults: Anterior Segment Imaging Using the Swept-Source Optical Coherence Tomography.

PURPOSE: To measure the corneoscleral limbus and anterior sclera parameters of normal Chinese adults by swept-source optical coherence tomography (OCT). MATERIALS AND METHODS: In this cross-sectional study, a total of 56 Chinese subjects with ametropia were evaluated in the Eye Hospital of Wenzhou Medical University from September 2020 to December 2020, including 26 (46.4%) men, with an average age of 24.7±1.8 years old. The OCT SS-1000 (CASIA, Tomey, Tokyo, Japan) was used to measure the sagittal height, corneoscleral junction (CSJ) angle, and scleral angle. RESULTS: The chord was across the corneal center and the line connecting the center of the cornea and the center of the chord was perpendicular to the chord. The mean sagittal height at chord lengths of 10.0, 12.3, and 15.0 mm were 1,756±72, 2,658±110, and 3,676±155 µm, respectively. The absolute values of the differences between horizontal and vertical meridians at three chord lengths were 54±40, 70±67, and 117±95 µm, respectively. One-way analysis of variance showed that the differences of CSJ angles at 12.3-mm chord and scleral angles at 15.0-mm chord in the four segments were statistically significant ( F values were 32.01 and 13.37, respectively, both P <0.001). The CSJ angles from low to high were 176.53±2.14° (nasal), 178.66±1.84° (inferior), 179.13±1.20° (temporal), and 179.31±1.68° (superior), and 87.5% of the nasal angles were less than 179°. The scleral angles from high to low were 38.35±2.47° (temporal), 38.26±3.37° (superior), 35.37±3.10° (nasal), and 35.30±4.71° (inferior). CONCLUSIONS: The morphology of corneoscleral limbus and anterior sclera is asymmetrical in normal Chinese adults. The nasal side of the corneoscleral limbus has the largest angle, and the superior and temporal sides of the scleral angle are larger.

Five-year-old children show cooperative preferences for faces with white sclera.

The cooperative eye hypothesis posits that human eye morphology evolved to facilitate cooperation. Although it is known that young children prefer stimuli with eyes that contain white sclera, it is unknown whether white sclera influences children's perception of a partner's cooperativeness specifically. In the current studies, we used an online methodology to present 5-year-old children with moving three-dimensional face models in which facial morphology was manipulated. Children found "alien" faces with human eyes more cooperative than faces with dark sclera (Study 2) but not faces with enlarged irises (Study 1). For more human-like faces (Study 3), children found human eyes more cooperative than either enlarged irises or dark sclera and found faces with enlarged irises cuter (but not more cooperative) than eyes with dark sclera. Together, these results provide strong support for the cooperative eye hypothesis.

Evolution of the uniformly white sclera in humans: critical updates.

The human eye characteristically has exposed and uniformly white sclera, which is hypothesized to have evolved to enhance eye-gaze signaling for conspecific communication. Although recent studies have put this hypothesis into question, current morphological and experimental evidence supports its key premise, albeit with recommendations for critical updates.

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.

Multi-view convolutional neural networks for automated ocular structure and tumor segmentation in retinoblastoma.

In retinoblastoma, accurate segmentation of ocular structure and tumor tissue is important when working towards personalized treatment. This retrospective study serves to evaluate the performance of multi-view convolutional neural networks (MV-CNNs) for automated eye and tumor segmentation on MRI in retinoblastoma patients. Forty retinoblastoma and 20 healthy-eyes from 30 patients were included in a train/test (N = 29 retinoblastoma-, 17 healthy-eyes) and independent validation (N = 11 retinoblastoma-, 3 healthy-eyes) set. Imaging was done using 3.0 T Fast Imaging Employing Steady-state Acquisition (FIESTA), T2-weighted and contrast-enhanced T1-weighted sequences. Sclera, vitreous humour, lens, retinal detachment and tumor were manually delineated on FIESTA images to serve as a reference standard. Volumetric and spatial performance were assessed by calculating intra-class correlation (ICC) and dice similarity coefficient (DSC). Additionally, the effects of multi-scale, sequences and data augmentation were explored. Optimal performance was obtained by using a three-level pyramid MV-CNN with FIESTA, T2 and T1c sequences and data augmentation. Eye and tumor volumetric ICC were 0.997 and 0.996, respectively. Median [Interquartile range] DSC for eye, sclera, vitreous, lens, retinal detachment and tumor were 0.965 [0.950-0.975], 0.847 [0.782-0.893], 0.975 [0.930-0.986], 0.909 [0.847-0.951], 0.828 [0.458-0.962] and 0.914 [0.852-0.958], respectively. MV-CNN can be used to obtain accurate ocular structure and tumor segmentations in retinoblastoma.

MULTIPLE INTRAVITREAL INJECTIONS DO NOT CAUSE ANTERIOR SCLERAL THINNING: An Ultrasound Biomicroscopy Study.

PURPOSE: To evaluate possible changes in anterior scleral thickness and structure and changes in the anterior segment in eyes receiving multiple intravitreal injections using ultrasound biomicroscopy imaging. METHODS: Prospective, interventional, nonrandomized, cross-sectional study. Both eyes from 33 patients previously treated at least by 15 intravitreal injections in one eye only for retinal diseases were included. Intravitreal injections were performed by ophthalmologists using an aseptic standardized procedure. Ultrasound biomicroscopy examination was performed in all eyes, and scleral thickness was measured at the pars plana in four quadrants. Anterior chamber depth and ciliary body size were measured. Scleral thickness in the study eye was compared with the fellow eye. Secondary outcome measures were 1) anterior chamber depth; 2) ciliary body size; 3) scleral qualitative changes in the study eye compared with the fellow eye and 4) risk factors for scleral thinning. RESULTS: There was no statistically significant difference in scleral thickness between the study and fellow eyes when comparing each quadrant between the two eyes (P = 0.86 superotemporal; P = 0.76 superonasal; P = 0.72 inferonasal; P = 0.55 inferotemporal). Scleral thickness was neither related to the number of injections nor to the duration of treatment in the treated eye. CONCLUSION: Multiple intravitreal injections do not impact scleral thickness in a clinical practice using different injection sites.

Limbus misrepresentation in parametric eye models.

PURPOSE: To assess the axial, radial and tangential limbus position misrepresentation when parametric models are used to represent the cornea and the sclera. METHODS: This retrospective study included 135 subjects aged 22 to 65 years (36.5 mean ±9.8 STD), 71 females and 64 males. Topography measurements were taken using an Eye Surface Profiler topographer and processed by a custom-built MATLAB code. Eye surfaces were freed from edge-effect artefacts and fitted to spherical, conic and biconic models. RESULTS: When comparing the radial position of the limbus, average errors of -0.83±0.19mm, -0.76±0.20mm and -0.69±0.20mm were observed within the right eye population for the spherical, conic and biconic models fitted up to 5mm. For the same fitting radius, the average fitting errors were -0.86±0.23mm, -0.78±0.23mm and -0.73±0.23mm for the spherical, conic and biconic models respectively within the left eye population. For the whole cornea fit, the average errors were -0.27±0.12mm and -0.28±0.13mm for the spherical models, -0.02±0.29mm and -0.05±0.27mm for the conic models, and -0.22±0.16mm and 0.24±0.17mm for the biconic models in the right and left eye populations respectively. CONCLUSIONS: Through the use of spherical, conic and biconic parametric modelling methods, the eye's limbus is being mislocated. Additionally, it is evident that the magnitude of fitting error associated with the sclera may be propagating through the other components of the eye. This suggests that a corneal nonparametric model may be necessary to improve the representation of the limbus.

Finite element analysis of trans-lamina cribrosa pressure difference on optic nerve head biomechanics: the Beijing Intracranial and Intraocular Pressure Study.

The present study aims to assess the potential difference of biomechanical response of the optic nerve head to the same level of trans-lamina cribrosa pressure difference (TLCPD) induced by a reduced cerebrospinal fluid pressure (CSFP) or an elevated intraocular pressure (IOP). A finite element model of optic nerve head tissue (pre- and post-laminar neural tissue, lamina cribrosa, sclera, and pia mater) was constructed. Computed stresses, deformations, and strains were compared at each TLCPD step caused by reduced CSFP or elevated IOP. The results showed that elevating TLCPD increased the strain in optic nerve head, with the largest strains occurring in the neural tissue around the sclera ring. Relative to a baseline TLCPD of 10 mmHg, at a same TLCPD of 18 mmHg, the pre-laminar neural tissue experienced 11.10% first principal strain by reduced CSFP and 13.66% by elevated IOP, respectively. The corresponding values for lamina cribrosa were 6.09% and 6.91%. In conclusion, TLCPD has a significant biomechanical impact on optic nerve head tissue and, more prominently, within the pre-laminar neural tissue and lamina cribrosa. Comparatively, reducing CSFP showed smaller strain than elevating IOP even at a same level of TLCPD on ONH tissue, indicating a different potential role of low CSFP in the pathogenesis of glaucoma.

The lymphangiogenic and hemangiogenic privilege of the human sclera.

PURPOSE: Most organs of the human body are supplied with a dense network of blood and lymphatic vessels. However, some tissues are either hypovascular or completely devoid of vessels for proper function, such as the ocular tissues sclera and cornea, cartilage and tendons. Since many pathological conditions are affecting the human sclera, this review is focussing on the lymphangiogenic and hemangiogenic privilege in the human sclera. METHODS: This article gives an overview of the current literature based on a PubMed search as well as observations and experience from clinical practice. RESULTS: The healthy human sclera is the outer covering layer of the eye globe consisting mainly of collagenous extracellular matrix and fibroblasts. Physiologically, the sclera shows only a superficial network of blood vessels and a lack of lymphatic vessels. This vascular privilege is actively regulated by balancing anti- and proangiogenic factors expressed by cells within the sclera. In pathological situations, such as open globe injuries or ciliary body melanomas with extraocular extension, lymphatic vessels can secondarily invade the sclera and the inner eye. This mechanism most likely is important for tumor cell metastasis, wound healing, immunologic defense against intruding microorganism, and autoimmune reactions against intraocular antigens. CONCLUSIONS: The human sclera is characterized by a tightly regulated vascular network that can be compromised in pathological situations, such as injuries or intraocular tumors affecting healing outcomes Therefore, the molecular and cellular mechanisms underlying wound healing following surgical interventions deserve further attention, in order to devise more effective therapeutic strategies.

Anterior chamber lens sizing: Comparison of white-to-white and scleral spur-to-scleral spur methods.

PURPOSE: To determine the most accurate method of estimating scleral-spur-to-scleral-spur (STS) distance for ophthalmologists without access to an anterior chamber optical coherence tomography (AS-OCT) instrument when selecting an anterior chamber intraocular lens (AC IOL). SETTING: Robert Cizik Eye Clinic, Houston, TX. DESIGN: Prospective cohort study. METHODS: The eyes of 65 participants aged 18 years or older were imaged by the Lenstar LS 900 optical biometer and CASIA SS-1000 swept-source Fourier-domain AS-OCT. Eyes were excluded if the anterior segment anatomy was significantly altered and the angle could not be visualized. When both eyes were eligible, 1 eye was randomly selected. The white-to-white (WTW) distance, STS distance, and axial length were recorded and compared. The difference between STS and horizontal WTW was calculated for each meridian. The mean (±SD) differences, 95% limits of agreement, and Bland-Altman agreement were computed for each pair of STS and WTW measurements. RESULTS: The study comprised 65 eyes of 65 participants. In nearly every case, WTW + 0.5 and WTW + 1 overestimated STS. The horizontal WTW without adjustment was the best predictor of STS. The WTW best corresponded to the vertical STS meridian (6 to 12 o'clock) and not the horizontal meridian (3 to 9 o'clock), along which AC IOLs are traditionally placed. CONCLUSIONS: The horizontal WTW method without an adjustment factor most accurately estimated STS distance and should be used to select AC IOL size when AS-OCT is not available. If AS-OCT is available, it should be used instead. In addition, AC IOLs should be placed in a vertical orientation rather than the traditional horizontal orientation to minimize sizing errors.

Dual effect of the Valsalva maneuver on autonomic nervous system activity, intraocular pressure, Schlemm's canal, and iridocorneal angle morphology.

BACKGROUND: The Valsalva maneuver (VM) is widely used in daily life, and has been reported to cause high intraocular pressure (IOP). This study aimed to assess changes in IOP, the Schlemm's canal (SC), autonomic nervous system activity, and iridocorneal angle morphology in healthy individuals during different phases of the VM. METHODS: The high frequency (HF) of heart rate (HR) variability, the ratio of low frequency power (LF) and HF (LF/HF), heart rate (HR), IOP, systolic (SBP) and diastolic blood pressure (DBP), the area of SC (SCAR), pupil diameter (PD), and some iridocorneal angle parameters (AOD500, ARA750, TIA500 and TISA500) were measured in 29 young healthy individuals at baseline, phase 2, and phase 4 of the VM. SBP and DBP were measured to calculate mean arterial pressure (MAP) and mean ocular perfusion pressure (MOPP). HF and the LF/HF ratio were recorded using Kubios HR variability premium software to evaluate autonomic nervous system activity. The profiles of the anterior chamber were captured by a Spectralis optical coherence tomography device (anterior segment module). RESULTS: Compared with baseline values, in phase 2 of the VM, HR, LF/HF, IOP (15.1 ± 2.7 vs. 18.8 ± 3.5 mmHg, P < 0.001), SCAR (mean) (7712.112 ± 2992.14 vs. 8921.12 ± 4482.79 µm2, P = 0.039), and PD increased significantly, whereas MOPP, AOD500, TIA500, and TISA500 decreased significantly. In phase 4, DBP, MAP, AOD500, ARA750, TIA500and TISA500 were significantly lower than baseline value, while PD and HF were remarkably larger than baseline. The comparison between phase 2 and phase 4 showed that HR, IOP (18.8 ± 3.5 vs. 14.7 ± 2.9 mmHg, P < 0.001) and PD decreased significantly from phase 2 to phase 4, but there were no significant differences in other parameters. CONCLUSIONS: The expansion and collapse of the SC in different phases of the VM may arise from changes in autonomic nervous system activity. Further, the effects of the VM on IOP may be attributed to changes in blood flow and ocular anatomy. TRIAL REGISTRATION: This observational study was approved by the ethics committee of Tongji Hospital (Registration Number: ChiCTR-OON-16007850, Date: 01.28.2016).

Skeletons of the Eye: An Evolutionary and Developmental Perspective.

The ocular skeleton, composed of the scleral cartilage and scleral ossicles, is present in many vertebrates. The morphology of the scleral cartilage and ossicles varies within different extant reptiles (including birds) and also varies dramatically from the morphology in extant teleosts. This incredible range of diverse morphologies is the result of millions of years of evolution. Both the position of these elements within the eye and the timing of development vary amongst different vertebrates. While the development of both the scleral cartilage and scleral ossicles is somewhat understood in reptiles and in teleosts, the functional advantage of these elements is still debated. Most reptiles have a multi-component scleral ossicle ring composed of a series of flat bone plates and a scleral cartilage cup lining the retina, some sharks have calcified cartilage plates, and some teleosts have two bones while most others only have a ring of scleral cartilage. The data presented shows that different vertebrates have adapted to similar selective pressures in different ways. However, the reason why sarcopterygians have a series of overlapping bones in the sclera remains unclear. A better understanding of the ocular skeletal diversity in Reptilia as well as a better understanding of the mechanisms of vision within different environments (i.e., air vs. water) and that used by secondarily aquatic organisms is needed. This review discusses the observed variation in morphology and development of the ocular skeleton in the context of evolution and highlights our knowledge gaps in these areas. Anat Rec, 2018. © 2018 American Association for Anatomy.

Scleral pigmentation leads to conspicuous, not cryptic, eye morphology in chimpanzees.

Gaze following has been argued to be uniquely human, facilitated by our depigmented, white sclera [M. Tomasello, B. Hare, H. Lehmann, J. Call, J. Hum. Evol. 52, 314-320 (2007)]-the pale area around the colored iris-and to underpin human-specific behaviors such as language. Today, we know that great apes show diverse patterns of scleral coloration [J. A. Mayhew, J. C. Gómez, Am. J. Primatol. 77, 869-877 (2015); J. O. Perea García, T. Grenzner, G. Hesková, P. Mitkidis, Commun. Integr. Biol. 10, e1264545 (2016)]. We compare scleral coloration and its relative contrast with the iris in bonobos, chimpanzees, and humans. Like humans, bonobos' sclerae are lighter relative to the color of their irises; chimpanzee sclerae are darker than their irises. The relative contrast between the sclera and iris in all 3 species is comparable, suggesting a perceptual mechanism to explain recent evidence that nonhuman great apes also rely on gaze as a social cue.

Variation of Peripapillary Scleral Shape With Age.

Purpose: To define the shape of the anterior surface of the peripapillary sclera (PPS) and evaluate its relationship with age and ocular determinants in a population-based Chinese cohort. Methods: The optic nerve heads of 619 healthy Chinese subjects were imaged with spectral-domain optical coherence tomography. To assess the shape of the PPS/Bruch's membrane (BM), we measured the angle between a line parallel to the nasal anterior PPS/BM boundary and one parallel to the temporal side. A negative value indicated that the PPS/BM followed an inverted v-shaped configuration (peak pointing toward the vitreous), whereas a positive value indicated that it followed a v-shaped configuration (peak pointing toward the orbital tissues). A linear regression model was used to evaluate the relationship between the PPS angle and other ocular parameters. Results: The mean PPS angle was 3.68° ± 6.73° and the BM angle was 9.69° ± 5.05°. The PPS angle increased on average by 0.233 deg/y. A v-shaped PPS was significantly associated with age (ß = 0.087, P = 0.004), peripapillary choroidal thickness (ß = -0.479, P < 0.001), lamina cribrosa depth (ß = 0.307, P < 0.001), and BM angle (ß = 0.487, P < 0.001) after adjusting for best corrected visual acuity, central corneal thickness, and axial length. Conclusions: The anterior surface of PPS of an elderly adult population had a v-shaped configuration and was more pronounced with increasing age, thin peripapillary choroid, and a deep cup. Such a change in shape with age could have an impact on the biomechanical environment of the optic nerve head.

Artefact-free topography based scleral-asymmetry.

PURPOSE: To present a three-dimensional non-parametric method for detecting scleral asymmetry using corneoscleral topography data that are free of edge-effect artefacts. METHODS: The study included 88 participants aged 23 to 65 years (37.7±9.7), 47 women and 41 men. The eye topography data were exported from the Eye Surface Profiler software in MATLAB binary data container format then processed by custom built MATLAB codes entirely independent from the profiler software. Scleral asymmetry was determined initially from the unprocessed topography before being determined again after removing the edge-effect noise. Topography data were levelled around the limbus, then edge-effect was eliminated using a robust statistical moving median technique. In addition to comparing raw elevation data, scleral elevation was also compared through fitting a sphere to every single scleral surface and determining the relative elevation from the best-fit sphere reference surface. RESULTS: When considering the averaged raw topography elevation data in the scleral section of the eye at radius 8 mm, the average raw elevations of the right eyes' sclera were -1.5±1.77, -1.87±2.12, -1.36±1.82 and -1.57±1.87 mm. In the left eyes at the same radius the average raw elevations were -1.62±1.78, -1.82±2.07, -1.28±1.76 and -1.68±1.93 mm. While, when considering the average raw elevation of the sclera after removing the edge effect, the average raw elevations of the right eyes were -3.71±0.25, -4.06±0.23, -3.95±0.19 and -3.95±0.23 mm. In the left eyes at the same radius the average raw elevations were -3.71±0.19, -3.97±0.22, -3.96±0.19 and -3.96±0.18 mm in the nasal, temporal, superior and inferior sides respectively. Maximum raw elevation asymmetry in the averaged scleral raw elevation was 1.6647±0.9015 mm in right eyes and 1.0358±0.6842 mm in left eyes, both detected at -38° to the nasal side. Best-fit sphere-based relative elevation showed that sclera is more elevated in three main meridians at angles -40°, 76°, and 170° in right eyes and -40°, 76°, and 170° in left eyes, all measured from the nasal meridian. Maximum recorded relative elevation asymmetries were 0.0844±0.0355 mm and 0.068±0.0607 mm at angular positions 76° and 63.5° for right and left eyes in turn. CONCLUSIONS: It is not possible to use corneoscleral topography data to predict the scleral shape without considering a method of removing the edge-effect from the topography data. The nasal side of the sclera is higher than the temporal side, therefore, rotationally symmetric scleral contact lenses are more likely to be translated towards the temporal side. The scleral shape is best described by levelled raw elevation rather than relative elevation.

In vivo assessment of the anterior scleral contour assisted by automatic profilometry and changes in conjunctival shape after miniscleral contact lens fitting / Valoración in vivo del contorno de la esclera anterior asistida por perfilometría automática, y de los cambios en la forma conjuntival tras el uso de lentillas mini-esclerales

Purpose: To compare the shape of the anterior sclera of candidates to scleral lens (ScCL) fitting with regular and irregular corneas and analyze the changes induced in the shape of the sclero-conjunctiva after ScCL wear. Methods: Thirty-five eyes of 18 subjects (19 eyes with irregular corneas and 16 with regular corneas) were consecutively recruited. Three measures of sclero-conjunctival shape were taken with Eye Surface Profiler (ESP, Eaglet Eye, Houten, The Netherlands). Tangent angles and ocular sagittal heights (OC-SAG) were analyzed at different chords from 13 to 17 mm in the nasal, temporal, superior and inferior regions. The 19 eyes with irregular cornea were selected to wear ScCL and the changes in their sclero-conjunctival surface parameters were compared before and after 3 h of lens wear. Results: Irregular corneas showed higher OC-SAG values than regular corneas in all the chords analyzed, with statistical significant differences in the temporal region. Regarding tangent angles, regular corneas showed lower values (flatter surface), with statistical significant differences at 8 and 8.50 mm on the nasal and 8.50 mm on the temporal region. Some changes were seen in sclero-conjuctival shape after short-term ScCL wear. There was an augment in OC-SAG after 3h of scleral lens wear and a reduction on tangent angles, namely on the nasal region at 7.5 mm and 8.00 mm chord lengths, which is coincidental with the landing zone of ScCL. Conclusions: ESP shows mild differences in scleral shape between eyes with regular and irregular corneas. ESP might be valuable in quantifying the mechanical impact of the ScCL on the anterior eye surface

Objetivo: Comparar la forma de la esclerótica anterior de los candidatos a utilizar lentes de apoyo escleral (ScCL) con córneas regulares e irregulares, y analizar los cambios inducidos en la forma de la superfície esclero-conjuntival tras el uso de dichas lentes. Métodos: Se incluyeron consecutivamente treinta y cinco ojos de 18 sujetos (19 ojos con córneas irregulares y 16 con córneas regulares). Se realizaron tres mediciones de la forma esclero-conjuntival con el dispositivo Eye Surface Profiler (ESP, Eaglet Eye, Houten, The Netherlands). Se analizaron los ángulos tangenciales y las alturas sagitales oculares (OC-SAG) a diferentes cuerdas, de 13 a 17 mm en las regiones nasal, temporal, superior e inferior. Se seleccionó a los 19 ojos con córnea irregular para utilizar ScCL, comparándose los cambios de los parámetros de su superficie esclero-conjuntival antes y después del uso de lentillas durante 3 horas. Resultados: Las córneas regulares reflejaron valores OC-SAG superiores a las córneas regulares en todas las cuerdas analizadas, con diferencias estadísticamente significativas en la región temporal. En cuanto a los ángulos tangenciales, las córneas regulares reflejaron unos valores inferiores (superficie más plana), con diferencias estadísticamente significativas a 8 y 8,5 mm en la región nasal, y 8,5 mm en la región temporal. También se apreciaron algunos cambios en la forma esclero-conjutival tras el uso a corto plazo de ScCL. Se produjo un aumento de los valores OC-SAG tras 3 h de uso de lentillas esclerales, y una reducción de los ángulos tangenciales, es decir, en las distancais correspondientes a las cuerdas de la región nasal a 7,5 mm y 8 mm, lo cual es coincidente con la zona de apoyo de las ScCL. Conclusiones: El dispositivo ESP muestra leves diferencias en la forma escleral entre los ojos con córneas regulares e irregulares, y ha es capaz de por lo que podría resultar de utilidad para cuantificar el impacto mecánico de las lentes ScCL en la superficie anterior del ojo

OCT-Detected Optic Nerve Head Neural Canal Direction, Obliqueness, and Minimum Cross-Sectional Area in Healthy Eyes.

PURPOSE: To assess anterior scleral canal opening (ASCO) offset relative to Bruch's membrane opening (BMO) (ASCO/BMO offset) so as to determine neural canal direction, obliqueness, and minimum cross-sectional area (NCMCA) in 362 healthy eyes. DESIGN: Cross-sectional study. METHODS: After optical coherence tomography optic nerve head and retinal nerve fiber layer thickness (RNFLT) imaging, BMO and ASCO were manually segmented. Planes, centroids, size, and shape were calculated. Neural canal direction was defined by projecting the neural canal axis vector (connecting BMO and ASCO centroids) onto the BMO plane. Neural canal obliqueness was defined by the angle between the neural canal axis and the BMO plane perpendicular vector. NCMCA was defined by projecting BMO and ASCO points onto a neural canal axis perpendicular plane and measuring the area of overlap. The angular distance between superior and inferior peak RNFLT was measured, and correlations between RFNLT, BMO, ASCO, ASCO/BMO offset, and NCMCA were assessed. RESULTS: Mean (SD) NCMCA was significantly smaller than either the BMO or ASCO area (1.33 (0.42), 1.82 (0.38), 2.22 (0.43) mm2, respectively), and most closely correlated to RNFLT (P < .001, R2 = 0.158). Neural canal direction was most commonly superior-nasal (55%). Mean neural canal obliqueness was 39.4° (17.3°). The angular distance between superior and inferior peak RNFLT correlated to neural canal direction (P ≤ .008, R2 = 0.093). CONCLUSIONS: ASCO/BMO offset underlies neural canal direction, obliqueness, and NCMCA. RNFLT is more strongly correlated to NCMCA than to BMO or ASCO, and its peripapillary distribution is influenced by neural canal direction.

Geometrical characterization of the corneo-scleral transition in normal patients with Fourier domain optical coherence tomography.

PURPOSE: To characterize the geometry at the corneo-scleral transition for a normal population and its correlation with other anatomic parameters of the eyeball. METHODS: Transversal epidemiologic study on a sample of 100 individuals (right eye) in different ethnic groups (Africans and Caucasians). All of them were examined with Fourier domain optical coherence tomography, auto-refractometer, topographer, and biometer to obtain the corneo-scleral angle (CSA) and additional clinical parameters. The dataset was analyzed to determine correlations between different anatomical parameters and nasal (CSAn) and temporal CSA (CSAt) values. RESULTS: The CSAt presents a significant but low correlation with the anterior chamber depth-ACD (r = 0.25; p = 0.024), the white-to-white (W-W) distance (r = 0.27; p = 0.022), and the anterior chamber volume (r = 0.25; p = 0.016). CSAn did not correlate significantly with any clinical variable, with all values being lower than 179° (concave). Ethic groups presented significant differences for pachymetry (Pac) and corneal volume (p = 0.033 and p = 0.014), being greater for Caucasians, and temporal corneo-iridial angle (p = 0.006), being greater for Africans. CSA presented and inverse correlation with age. CONCLUSIONS: The CSAn presents a more concave profile for the normal population, whereas the CSAt presents a planar-convex profile with a great influence of age. In particular, the older the patient, the more convex the CSAt is. This age-related evolution of the CSAt and the concavity on the nasal direction must be considered when prescribing scleral contact lenses or when performing limbal incisions during refractive interventions.

Optical coherence tomography and scleral contact lenses: clinical and research applications.

Anterior segment optical coherence tomography (OCT) provides a wealth of opportunities for modern contact lens practice. OCT imaging has numerous clinical and research applications related to the tear film, cornea, conjunctiva, sclera and ocular adnexae, in addition to soft, rigid, and hybrid contact lenses. This review summarises the potential use of OCT imaging in modern scleral contact lens practice including initial lens selection, assessing the scleral contact lens fit with respect to the cornea and sclera, and accurately quantifying the ocular response to lens wear. Recent advances in the understanding of anterior segment metrics including scleral thickness, curvature, toricity, and the anatomy of the corneoscleral limbal junction are also discussed.