Correlations of Corneal Endothelial Morphology and Corneal Thickness With Anterior Segment Parameters in Healthy Individuals.

PURPOSE: The purpose of this study was to investigate the associations between central corneal endothelial cell density (ECD), endothelial morphology, and corneal thickness (central corneal thickness) with the anterior chamber depth, corneal volume (CV), white-to-white (WTW) distance, mean anterior chamber angle (CAmean), and gender in healthy individuals. METHODS: This observational study included 136 healthy volunteers. The ECD, coefficient of variation of cell area, and hexagonal cell appearance ratio (%Hex) were measured by means of specular microscopy. The central corneal thickness, anterior chamber depth, CV, WTW distance, and the angle width of 12 points were taken by the Pentacam HR Scheimpflug anterior segment imaging. The arithmetical mean of the 12 points was considered as the CAmean. We used mixed effect linear regression model for the statistical analysis of the data. RESULTS: ECD was positively correlated with CV ( P = 0.028), while after adjusting for age, it was negatively correlated with age ( P < 0.001). Coefficient of variation of cell area was positively correlated with CAmean ( P = 0.036), while after adjusting for age, it was positively correlated with age ( P < 0.001) and CAmean ( P = 0.005). Hex was negatively correlated with WTW ( P = 0.023) and CAmean ( P = 0.025), and after adjusting for age, this correlation remained the same ( P = 0.029 when correlated with WTW and P = 0.035 with CAmean). CONCLUSIONS: There were significant changes in the morphology of the corneal endothelial cells in eyes with wider anterior chamber angle. Greater pleomorphism and polymegethism of the corneal endothelium was observed in healthy patients with wider CAmean. Deepening of the anterior chamber as myopia progresses could render the corneal endothelium more fragile and susceptible to mechanical stress, which is an area worthy of further study.

Refractive Status and Biometric Characteristics of Children With Familial Exudative Vitreoretinopathy.

Purpose: To compare biometric characteristics between patients with early-stage familial exudative vitreoretinopathy (FEVR) and healthy controls. Methods: This case-control study included 50 FEVR eyes in stage 1-2 and 50 control eyes matched by age, gender and spherical equivalent (SE). Biometric parameters including axial length (AL), white-to-white diameter (WTW), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), pupil diameter, vitreous chamber depth, anterior and posterior corneal surface curvature radius (ACR and PCR), anterior lens surface curvature radius (ALR) and posterior lens surface curvature radius were measured using IOLMaster 700 and compared between cases and controls using paired t-test. Correlations between SE and biometric measures were assessed using Pearson correlation coefficient (r) in cases and controls. Results: Both FEVR cases and matched controls had a mean age of 7.6 years, 48% female and mean SE of -5.3 D (80% myopia). Compared to controls, FEVR eyes had smaller AL (P = 0.009), WTW (P = 0.001), ACD (P < 0.001), and ALR (P = 0.03), but larger CCT (P = 0.02) and LT (P = 0.01). In FEVR eyes, SE was negatively correlated with AL (r = -0.79, P < 0.001), positively correlated with ACR (r = 0.29, P = 0.04) and PCR (r = 0.33, P = 0.02), whereas in controls, SE was negatively correlated with AL (r = -0.82, P < 0.001) and LT (r = -0.34, P = 0.02), positively correlated with ALR (r = 0.29, P = 0.04). Conclusions: Patients at early stage of FEVR exhibited a unique eye morphology resembling ocular development arrest, which may help to develop screening and early detection tools for FEVR. In FEVR patients, myopia is very prevalent and significantly associated with corneal curvature increase.

3T high-resolution magnetic resonance imaging, conventional ultrasonography and ultrasound biomicroscopy of the normal canine eye.

BACKGROUND: Advances in MRI coil technology and increased availability of high-field MRI in veterinary medicine enable the acquisition of images of increasingly high spatial resolution while preserving signal-to-noise ratio.The purpose of the present study was to compare 3T high-resolution magnetic resonance imaging (HR-MRI) with ultrasound (US) and ultrasound biomicroscopy (UBM) in the normal canine eye, to assess its potential to depict normal ocular anatomy. RESULTS: HR-MRI was compared with US and UBM in 10 eyes from 10 healthy beagle dogs. Ocular structures (cornea, anterior chamber, iridocorneal angle, iris, lens, ciliary body, choroid, vitreous body, posterior wall of the eye, optic nerve and optic nerve sheath, extraocular muscles) were assessed subjectively and central corneal thickness (CCT), anterior chamber depth (ACD), aqueous depth (AQD), anteroposterior, mediolateral and dorsoventral lens diameter (APLD, MLLD, DVLD), anteroposterior diameter of the globe including and excluding the scleroretinal rim (APDSRR, APD), vitreous chamber depth (VCD) and optic nerve sheath diameter (ONSD) were measured in HR-MRI and in US. Optic nerve diameter (OND) was measured in HR-MRI. HR-MRI and UBM appearance of the anterior segment were subjectively compared. Detailed reference high-resolution MRI images of normal eyes of Beagle dogs are provided. CONCLUSIONS: HR-MRI allowed assessment of all structures identified with US and UBM. The MRI examinations were performed under general anesthesia with the addition of a neuromuscular blocking agent, while US and UBM examinations were performed in conscious animals. Visibility of the entire ocular wall, the lens, the structures caudal to the ciliary body and the optic nerve and its sheath was superior with HR-MRI. HR-MRI allowed the distinction of retina, choroid and sclera, and the delineation of structures not previously identified in canine eyes with MRI, including Tenon's capsule and the sub-Tenon's space.Plane selection was more accurate with HR-MRI compared to US. In general, the range of measurements was narrower for MRI than for US. CCT, AQD, APLD, MLLD, APD, APDSRR and ONSD differed significantly between HR-MRI and US, respectively (p = 0.005-0.027).Micro-MRI may be useful for the assessment of ocular pathologies in the future.

Anterior Segment Anatomy and Conventional Outflow Physiology of the Tree Shrew (Tupaia belangeri).

Purpose: Rodent and primate models are commonly used in glaucoma research; however, both have their limitations. The tree shrew (Tupaia belangeri) is an emerging animal model for glaucoma research owing in part to having a human-like optic nerve head anatomy, specifically a collagenous load-bearing lamina. However, the anterior segment anatomy and function have not been extensively studied in the tree shrew. Thus, the purpose of this study was to provide the first detailed examination of the anterior segment anatomy and aqueous outflow facility in the tree shrew. Methods: Aqueous outflow dynamics were measured in five ostensibly normal eyes from three tree shrews using the iPerfusion system over a range of pressures. Gross histological assessment and immunohistochemistry were performed to characterize anterior segment anatomy and to localize several key molecules related to aqueous outflow. Results: Anterior segment anatomy in tree shrews is similar to humans, demonstrating a scleral spur, a multilayered trabecular meshwork and a circular Schlemm's canal with a single lumen. Average outflow facility was 0.193 µL/min/mm Hg (95% confidence interval, 0.153-0.244), and was stable over time. Outflow facility was more similar between contralateral eyes (approximately 5% average difference) than between eyes of different animals. No significant dependence of outflow facility on time or pressure was detected (pressure-flow nonlinearity parameter of 0.01 (95% % confidence interval, -0.29 to 0.31 CI µL/min/mm Hg). Conclusions: These studies lend support to the usefulness of the tree shrew as a novel animal model in anterior segment glaucoma and pharmacology research. The tree shrew's cost, load-bearing collagenous lamina cribrosa, and lack of washout or anterior chamber deepening provides a distinct experimental and anatomic advantage over the current rodent and nonhuman primate models used for translational research.

Comparison of A-Scan ultrasonography and the Lenstar optical biometer in Guinea pig eyes.

OBJECTIVE: To compare the biometric parameters provided by A-scan ultrasonography and the Lenstar optical biometer in guinea pig eyes, including anterior segment depth (ASD), lens thickness (LT), vitreous chamber depth (VCD), and axial length (AL), and differences of them between treated form deprivation (FD) eyes and untreated fellow eyes after 4 weeks of FD. METHODS: Three-week-old guinea pigs (N = 41) were subjected to biometric measurements before monocular FD (baseline) and after a 4-week FD. Statistical analyses including within-subject standard deviation (SDwithin), coefficient of variation (CV), and intraclass correlation coefficient (ICC), used to evaluate repeatability for both the A-scan ultrasonography and the Lenstar individually, and correlation and Bland-Altman analyses were used to assess agreement between the two methods. The absolute values of ASD, LT, VCD and AL as measured by the two devices were compared, and the differences of them between treated (T) and untreated fellow (F) eyes (ΔASD, ΔLT, ΔVCD and ΔAL) (Δ = T-F) were compared between the two devices after 4 weeks of FD. RESULTS: Measurements by the Lenstar (ICC: 0.923-0.994) were more repeatable than A-scan ultrasonography (ICC: 0.825-0.870). There was a high correlation for AL (r = 0.851, P < 0.001), a moderate correlation for VCD (r = 0.571, P < 0.001) and LT (r = 0.423, P < 0.001), and a low correlation for ASD (r = 0.230, P < 0.01) between the two devices. The values for ASD, VCD and AL measured by A-scan ultrasonography were larger than those measured by the Lenstar (all, P < 0.001), while LT provided by A-scan ultrasonography was much smaller than that of the Lenstar (P < 0.001). Bland-Altman plots showed poor agreement of absolute values of the four parameters between the two devices. Moreover, there was a high correlation between both methods for ΔAL (r = 0.704, P < 0.001), a moderate correlation for ΔVCD (r = 0.534, P < 0.001) and ΔASD (r = 0.574, P < 0.001), and no correlation for ΔLT (r = 0.303, P = 0.054). The ΔASD, ΔLT, and ΔAL measurements obtained by A-scan ultrasonography were greater than those obtained by the Lenstar (all, P < 0.001), while ΔVCD was mildly smaller using A-scan ultrasonography (P < 0.05). Bland-Altman plots illustrated there is good agreement of ΔAL, ΔVCD, ΔASD, and ΔLT between the two devices. CONCLUSIONS: The Lenstar exhibited better repeatability and provided smaller measurements for AL, VCD and ASD than A-scan ultrasonography. Furthermore, a high correlation and a good agreement for the ΔAL was observed between the two devices after a period of FD. In summary, the two devices cannot replace each other directly to obtain absolute values of ASD, LT, VCD and AL, but the Lenstar still can serve as an option in measuring ΔAL between eyes in guinea pig myopia model.

Visualization of different anatomical parts of the enucleated human eye using X-ray micro-CT imaging.

Micro-CT visualization allows reconstruction of eye structures with the resolution of light microscopy and estimation of tissue densities. Moreover, this method excludes damaging procedures and allows further histological staining due to the similar steps in the beginning. We have shown the feasibility of the lab-based micro-CT machine usage for visualization of clinically important compartments of human eye such as trabecular outflow pathway, retina, iris and ciliary body after pre-treatment with iodine in ethanol. We also identified the challenges of applying this contrasting technique to lens, cornea, and retina and proposed alternative staining methods for these tissues. Thereby this work provides a starting point for other studies for imaging of human eyes in normal and pathological conditions using lab-based micro-CT systems.

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.

The 360° circumferential opening of Schlemm's canal in normal individuals detected by enhanced depth imaging optical coherence tomography.

We aimed to observe the opening status and morphological parameters of Schlemm's canal (SC) in normal eyes using enhanced depth imaging optical coherence tomography (EDI-OCT).Consecutive EDI-OCT scans were used to examine the right eye of 20 normal individuals. EDI-OCT was performed clockwise for 8 regions (at the 12:00, 1:30, 3:00, 4:30, 6:00, 7:30, 9:00 and 10:30 o'clock positions). Image processing and analysis in java software was used to measure the area, perimeter, and diameter of SC. Twenty-one serial scans of each region were evaluated and a total of 168 images were included in the analyses of each eye.The SC was detected in 100.0% of the sections. The distribution of individual measurements of SC was highly variable. The mean values of SC size significantly differed among the different clock-face positions. The mean values of the area, perimeter, and diameter of SC in the 9:00 o'clock position were the lowest, and those at the 7:30 o'clock position were the highest (P < .05). There was no obvious association between intraocular pressure and SC size at any clock position.Although SC tends to open circumferentially in normal individuals, the distribution of individual measurements is highly variable. Morphological manifestation of SC measured by EDI-OCT is a useful way to evaluate the circumferential opening status of SC.

Morphology and evolution of the snake cornea.

To investigate whether the thickness of the cornea in snakes correlates with overall anatomy, habitat or daily activity pattern, we measured corneal thickness using optical coherence tomography scanning in 44 species from 14 families (214 specimens) in the collection at the Natural History Museum (Denmark). Specifically, we analyzed whether the thickness of the cornea varies among species in absolute terms and relative to morphometrics, such as body length, spectacle diameter, and spectacle thickness. Furthermore, we examined whether corneal thickness reflects adaptation to different habitats and/or daily activity patterns. The snakes were defined as arboreal (n = 8), terrestrial (n = 22), fossorial (n = 7), and aquatic (n = 7); 14 species were classified as diurnal and 30 as nocturnal. We reveal that the interspecific variation in corneal thickness is largely explained by differences in body size, but find a tendency towards thicker corneas in diurnal (313 ± 227 µm) compared to nocturnal species (205 ± 169 µm). Furthermore, arboreal snakes had the thickest corneas and fossorial snakes the thinnest. Our study shows that body length, habitat, and daily activity pattern could explain the interspecific variation in corneal morphology among snakes. This study provides a quantitative analysis of the evolution of the corneal morphology in snakes, and it presents baseline values of corneal thickness of multiple snake species. We speculate that the cornea likely plays a role in snake vision, despite the fact that results from previous studies suggest that the cornea in snakes is not relevant for vision (Sivak, Vision Research, 1977, 17, 293-298).

Predictive value of intracrystalline interphase point measured by optical low-coherence reflectometry for the estimation of the anatomical position of an intraocular lens after cataract surgery.

PURPOSE: To investigate the predictive value of the intracrystalline interphase point (ICIP) measured with optical low-coherence reflectometry (OCLR) to estimate the final lens position (FLP) of an intraocular lens (IOL) after cataract surgery. SETTING: Alcañiz Hospital, Teruel, Spain. DESIGN: Single-center retrospective descriptive study. METHODS: Patients undergoing cataract surgery were enrolled. They were grouped according to the IOL implanted as follows: Group 1, Acrysof IQ aspheric SN60WF IOL (77 eyes); Group 2, enVista MX60 IOL (71 eyes); Group 3, CT Asphina 409 IOL (44 eyes). An OCLR-based biometer (Lenstar LS 900 system) was used for biometric measurements preoperatively and at 4 to 5 weeks postoperatively. RESULTS: The study comprised 192 eyes of 174 patients (mean age: 76.4 years). One hundred seventy eyes (88.5%) eyes showed an absolute refractive prediction error (ARPE) less than 0.50 diopters (D). The mean ARPE was 0.25 D ± 0.21 (SD). Significantly higher FLP values were found in Group 2 compared with the other two groups (P < .001). Significantly lower ICIP values were found in the eyes with an ARPE of 0.50 D or more compared with eyes that had an ARPE less than 0.50 D in Group 1 (P = .042) and Group 2 (P = .023). The correlation of the FLP with the ICIP was good in all three groups (r ≥ 0.74, P <.001). Three linear expressions were obtained to predict the FLP from the ICIP and other preoperative data (R2: 0.85, 0.69, and 0.49 in Groups 1, 2, and 3, respectively). CONCLUSIONS: The position of the ICIP measured with OCLR correlated with the FLP after cataract surgery, and it can be used to optimize IOL power calculations.

Changes in the anterior segment of the eye following uncomplicated pars plana vitrectomy. A review.

Pars plana vitrectomy is currently the most common technique used in retinal surgery. Although primarily involving the posterior segment of the eye it also affects the anterior segment. As this is a less published topic, the aim of this paper was to review the literature on changes in the anterior segment after uncomplicated pars plana vitrectomy using data based literature search. The conclusions are that even in otherwise ophthalmologically healthy patients, complications may occur in the anterior segment. Surgeons need to pay utmost attention in glaucoma patients and in those with endothelial insufficiency who are at highest risk of complications. He/she must also correctly plan a potential cataract surgery if not already done earlier. From the literature, most of the changes in the anterior segment after uncomplicated PPV are found to be temporary.

Anterior segment parameters measured in young healthy cats using a rotating Scheimpflug camera.

OBJECTIVE: The purpose of this study is to measure parameters of the anterior segment of normal feline eyes using a rotating Scheimpflug camera in young and adult cats. PROCEDURE: Sixteen domestic short-haired (DSH) healthy cats (seven castrated males and nine spayed females) with a mean age of 17 months (SD = 3.5) were anesthetized. Cats were considered immature and adults if they were < or ≥12 months of age, respectively. The keratometric values, the anterior chamber depth (ACD), and central corneal thickness (CCT) of the right eye of each animal were measured using a Pentacam Oculus topographer. The repeatability of the measures was assessed by calculating the coefficient of variation of the successive measures in cats (five repetitions per cat). We performed an ANOVA to test the effect of age on the parameters measures. RESULTS: The mean CCT and ACD were 601.97 ± 38 µm and 5.27 ± 0.04 mm, respectively. No significant differences were observed between adult and young cat's measures. The average keratometric value was 39.6 ± 0.3 D. The mean average cylindrical error was 2.48 ± 0.35 D (43.75% "against-the-rule" astigmatism and 43.75% "oblique" astigmatism). CONCLUSION: The Oculus Pentacam under clinical conditions give CCT and ACD values very similar to those reported in previous studies. Corneal astigmatism measures were markedly elevated (>2 D). Further studies with a larger population of cats of various breeds and ages are needed to confirm or refute these results, using a rotating Scheimpflug camera.

Effect of contact lenses on ocular biometric measurements based on swept-source optical coherence tomography / Efeito de lentes de contato em um biômetro ocular baseado na tomografia de coerência óptica de varredura

ABSTRACT Purpose: To determine the reliability of swept- source optical coherence tomography in cases in which soft contact lenses cannot be removed when acquiring biometric measurements. Methods: Eight subjects were included and only one eye per participant was analyzed. Each eye was measured six times by swept-source optical coherence tomography with the IOLMaster 700 instrument (Carl Zeiss Meditec, Jena, Germany). Axial length, central corneal thickness, anterior chamber depth, lens thickness, and keratometric measurements were evaluated for the naked eye and while wearing soft contact lenses of three different powers (-1.5, -3.0, and +2.0 D). Results: There were statistically significant changes in axial length, central corneal thickness, anterior chamber depth, and keratometric measurements with soft contact lenses as compared to the naked eye (p<0.001). However, there were no significant differences in lens thickness outcomes between the naked eye and while wearing the three soft contact lenses (p>0.5). The changes in axial length, central corneal thickness, and anterior chamber depth were lens-specific and dependent on the thickness of the lens used. Conclusions: Sept-source optical coherence tomography based lens thickness measurements while wearing soft contact lenses are comparable to those of the naked eye. However, the thickness and the optical design of the soft contact lens may lead to significant differences in the axial lengh, central corneal thickness, anterior chamber deph, and keratometric measurements.

RESUMO Objetivo: Determinar a confiabilidade da tomografia de coerência óptica de varredura em casos especiais em que lentes de contato gelatinosas não podem ser removidas ao realizar medições biométricas. Métodos: Oito indivíduos foram incluídos e apenas um olho por participante foi analisado. Cada olho foi medido seis vezes por tomografia de coerência óptica de varredura com o instrumento IOLMaster 700 (Carl Zeiss Meditec, Jena, Alemanha). O comprimento axial, a espessura central da córnea, a profundidade da câmara anterior, a espessura da lente e as medidas ceratométricas foram avaliados a olho nu e enquanto usavam lentes de contato gelatinosas de três diferentes potências (-1,5, -3,0 e +2,0 D). Resultados: Houve alterações significativas no comprimento axial, espessura central da córnea, profundidade da câmara anterior e medidas ceratométricas com as lentes de contato gelatinosas em comparação com as a olho nu (p<0,001). No entanto, não houve diferenças significativas nos resultados de espessura do cristalino entre o olho nu e enquanto usava as três lentes de contato gelatinosas (p>0,5). As alterações de comprimento axial, espessura central da córnea e profundidade da câmara anterior foram específicas da lente e dependentes da espessura da lente usada. Conclusões: As medições da espessura da lente baseadas na tomografia de coerência óptica da Sept-source, enquanto usam lentes de lentes de contato gelatinosas, são comparáveis às do olho nu. Entretanto, a es pessura e o desenho óptico da lente de contato gelatinosa podem levar a diferenças significativas no comprimento axial, na espessura central da córnea, na profundidade da câmara anterior e nas medidas ceratométricas.

Effect of contact lenses on ocular biometric measurements based on swept-source optical coherence tomography.

PURPOSE: To determine the reliability of swept- source optical coherence tomography in cases in which soft contact lenses cannot be removed when acquiring biometric measurements. METHODS: Eight subjects were included and only one eye per participant was analyzed. Each eye was measured six times by swept-source optical coherence tomography with the IOLMaster 700 instrument (Carl Zeiss Meditec, Jena, Germany). Axial length, central corneal thickness, anterior chamber depth, lens thickness, and keratometric measurements were evaluated for the naked eye and while wearing soft contact lenses of three different powers (-1.5, -3.0, and +2.0 D). RESULTS: There were statistically significant changes in axial length, central corneal thickness, anterior chamber depth, and keratometric measurements with soft contact lenses as compared to the naked eye (p<0.001). However, there were no significant differences in lens thickness outcomes between the naked eye and while wearing the three soft contact lenses (p>0.5). The changes in axial length, central corneal thickness, and anterior chamber depth were lens-specific and dependent on the thickness of the lens used. CONCLUSIONS: Sept-source optical coherence tomography based lens thickness measurements while wearing soft contact lenses are comparable to those of the naked eye. However, the thickness and the optical design of the soft contact lens may lead to significant differences in the axial lengh, central corneal thickness, anterior chamber deph, and keratometric measurements.

In vivo assessment of the anterior scleral contour assisted by automatic profilometry and changes in conjunctival shape after miniscleral contact lens fitting.

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 17mm 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 3h 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 8.50mm on the nasal and 8.50mm 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 7.5mm and 8.00mm 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.

[Differences in anterior segment structure between Chinese Han people and American Caucasians].

Objective: To compare the difference of anterior segment structure between Chinese Han people and American Caucasians, and to explore the confounding factors of anterior chamber angle. Methods: Cross-sectional study. The study was designed to include two healthy groups of Chinese Han people (enrolled from Department of Ophthalmology, Peking University Third Hospital) and American Caucasians (enrolled from Department of Ophthalmology, University of California, San Francisco) from May 2008 to December 2010, each with approximately 120 participants, including 15 persons of each gender in each decade between 40 and 80 years of age. The parameters of the anterior segment were measured by the automatic refractive test, A-ultrasound and ultrasound biomicroscopy. Differences between the two groups were compared with the independent-sample t test or Wilcoxon two-sample test for continuous variable data and the χ(2) test for classified variable data. Multiple linear regression models were performed to analyze the associated factors of anterior chamber angle. Results: There were 118 subjects (118 eyes) and 117 subjects (117 eyes) enrolled in the Chinese and American Caucasians groups, respectively. Compared to Caucasians, Chinese had smaller A-ultrasound measured anterior chamber depth [(3.03±0.34) mm vs. (3.38±0.36) mm, t=-5.791, P<0.001], smaller relative lens position [0.227 (0.198, 0.256) vs. 0.235 (0.191, 0.262), Z=-3.063, P=0.002], smaller axial length [23.3 (20.9,28.3) mm vs. 24.2 (20.8,28.5) mm, Z=-5.510, P<0.001], smaller iris root distance [0.111 (0.000, 0.401) mm vs. 0.142 (0.000, 0.451) mm, Z=-3.188, P=0.001], smaller ciliary body thickness at 1 mm posterior to the scleral spur [0.661 (0.424, 0.892) mm vs. 0.716 (0.467, 0.942) mm, Z=-3.456, P=0.001], smaller trabecular ciliary process distance [0.780 (0.410, 1.400) mm vs. 0.930 (0.420, 1.470) mm, Z=-3.191, P=0.001], smaller trabecular ciliary process angle [73.4° (36.3°, 115.3°) vs. 81.1° (47.9°, 147.9°), Z=-3.407, P=0.001], smaller angle opening distance at 500 µm (AOD500) [0.181 (0.000, 0.703) mm vs. 0.264 (0.000, 0.806) mm, Z=-3.444, P=0.001], smaller angle recess area (ARA) [0.118 (0.011, 0.457) mm(2) vs. 0.179 (0.000, 0.626) mm(2), Z=-3.814, P<0.001], larger spherical equivalent [0.40 (-5.80, 4.00) D vs. -0.70 (-8.00, 4.00) D, Z=-5.454, P<0.001], larger lens thickness [(4.62±0.40) mm vs. (4.52±0.40) mm, t=2.077, P=0.039] and larger iris thickness [0.430 (0.280, 0.600) mm vs. 0.410 (0.240, 0.580) mm, Z=-2.263, P=0.024]. On average, with each decade of the increased age, Chinese had a greater decrease in the AOD500 than Caucasians (0.040 mm in Chinese vs. 0.030 mm in Caucasians), while the angle recess area decreased at the same rate (0.020 mm(2) in both groups). After adjusted for age, gender, spherical equivalent, axial length and other parameters of the anterior segment, the trabecular ciliary process angle [for AOD500, standardized regression coefficient (SRC)=0.487, R(2)=0.549, P<0.001; for ARA, SRC=0.372, R(2)=0.502, P<0.001] and anterior chamber depth (for AOD500, SRC=0.413, R(2)=0.476, P<0.001; for ARA, SRC=0.331, R(2)=0.403, P<0.001) were the main factors of anterior chamber angle parameters for Chinese and Caucasians, respectively. Conclusions: Compared with age and gender matched American Caucasians, Chinese Han people have more crowded anterior chambers and narrower anterior chamber angles. The more anteriorly positioned ciliary processes and shallower anterior chambers are the main factors that contributed to more crowded anterior chambers in Chinese Han people and American Caucasians, respectively. (Chin J Ophthalmol, 2018, 54: 820-826).

Relationship between the biomechanical properties of the cornea and anterior segment measurements.

OBJECTIVE: To evaluate the relationship of biomechanical properties, corneal hysteresis and corneal resistance factor with age, sex and various corneal parameters measured with a Pentacam in normal subjects. METHODS: A total of 226 eyes from 113 patients were enrolled in this study. The subjects underwent Ocular Response Analyzer and Pentacam evaluations. A varying-intercept multilevel regression was implemented using Bayesian inference. The predictor variables were age, sex, central corneal thickness, corneal volume at a 7-mm diameter, anterior chamber angle and volume, anterior chamber depth, mean radius of the corneal curvature and corneal astigmatism. RESULTS: Corneal hysteresis ranged from 5.5 to 14.8 mmHg (mean 10.42±1.74 mmHg), and the corneal resistance factor ranged from 5.7 to 15.5 mmHg (mean 10.23±1.88 mmHg). No predictor variable other than gender and central corneal thickness had a significant correlation with either corneal hysteresis or corneal resistance factor. Corneal hysteresis was positively associated with female sex and with central corneal thickness, and corneal resistance factor was positively associated with central corneal thickness. CONCLUSION: Despite the associations found, only a small fraction of the variance in biomechanical measurements could be explained by the descriptors that were evaluated, indicating the influence of other corneal aspects on the biomechanical characteristics.

Ocular Biometric Diurnal Rhythms in Emmetropic and Myopic Adults.

Purpose: To investigate diurnal variations in anterior and posterior segment biometry and assess differences between emmetropic and myopic adults. Methods: Healthy subjects (n = 42, 23-41 years old) underwent biometry and spectral-domain optical coherence tomography imaging (SD-OCT) every 4 hours for 24 hours. Subjects were in darkness from 11:00 PM to 7:00 AM. Central corneal thickness, corneal power, anterior chamber depth, lens thickness, vitreous chamber depth, and axial length were measured. Thicknesses of the total retina, photoreceptor outer segments + RPE, photoreceptor inner segments, and choroid over a 6-mm annulus were determined. Results: All parameters except anterior chamber depth demonstrated significant diurnal variations, with no refractive error differences. Amplitude of choroid diurnal variation correlated with axial length (P = 0.05). Amplitude of axial length variation (35.71 ± 19.40 µm) was in antiphase to choroid variation (25.65 ± 2.01 µm, P < 0.001). The central 1-mm retina underwent variation of 5.03 ± 0.23 µm with a peak at 12 hours (P < 0.001), whereas photoreceptor outer segment + RPE thickness peaked at 4 hours and inner segment thickness peaked at 16 hours. Diurnal variations in retina and choroid were observed in the 3- and 6-mm annuli. Conclusions: Diurnal rhythms in anterior and posterior segment biometry were observed over 24 hours in adults. Differences in baseline parameters were found between refractive error groups, and choroid diurnal variation correlated with axial length. The retina and choroid exhibited diurnal thickness variations in foveal and parafoveal regions.