Corneal Parameters Research Articles

Effect of recombinant human nerve growth factor treatment on corneal nerve regeneration in patients with neurotrophic keratopathy.

Neurotrophic Keratopathy (NK) is a neurodegenerative corneal disease that results in diminished corneal sensation. Previous studies have found that Cenegermin 0.002%, a recombinant human nerve growth factor (rhNGF), improves corneal epithelial healing in stage 2 and 3 NK patients. However, rhNGF effect on corneal sensation and nerve regeneration has not been well established. Thus, this study aims to analyze the effect of rhNGF on corneal nerve regeneration using in vivo confocal microscopy (IVCM) and on corneal sensitivity in NK patients. This is a retrospective, longitudinal, case-control study that included patients with NK, treated with rhNGF for at least 4 weeks, with pre- and post-treatment IVCM images available for analysis. Chart reviews were conducted documenting prior medical and surgical history, clinical signs and symptoms, and corneal sensation using Cochet-Bonnet esthesiometry. Corneal nerve parameters were assessed by IVCM. Sex- and age-matched reference controls were selected from a database of healthy subjects for comparison. The study included 25 patients, with 22 (88%) stage 1, two (8%) stage 2, and 1 (4%) stage 3 NK patients, with a median age of 64 years (range: 30-93 years). Total, main, and branch nerve densities [median (range) in mm/mm2] were lower in the NK group pre-treatment [2.3 (0.0-21.1); 1.7 (0.0-13.0); 0.5 (0.0-10.2); respectively] vs. controls [22.3 (14.9-29.0); 10.1 (3.2-15.4); and 12.1 (6.2-18.4), (p < 0.0001 for all), respectively]. Post-treatment nerve densities increased compared to pre-treatment to 5.3 (0.0-19.4, p = 0.0083) for total, 3.5 (0.0-13.2, p = 0.0059) for main, and 2.0 (0.0-10.4, p = 0.0251) for branch nerves, but remained lower than controls (p < 0.0001 for all). Corneal sensation increased from 2.3 ± 1.1 cm pre-treatment to 4.1 ± 1.4 cm post-treatment (p = 0.001). Median best corrected visual acuity significantly increased following rhNGF treatment from 0.4 (0.0-1.6) to 0.12 (-0.1 to 1.6) (p = 0.007). Patients with NK treated with at least 4 weeks of rhNGF, showed a significant increase in corneal nerve densities after treatment. A significant increase in corneal sensation, as well as best corrected visual acuity, was observed following treatment.

Effect of central corneal curvature on corneal material stiffness parameter acquired by dynamic corneal responses.

The stress-strain index (SSI) is a measure of corneal material stiffness, which is obtained using the Corvis ST algorithm based on dynamic corneal response parameters. The reduced SSI corresponds to the longer axial length (AL). In a previous study, we found SSI increases as the corneal curvature flattens, whereas a flatter corneal curvature indicates a longer AL (emmetropia or myopia). Therefore, in this cross-sectional study, we aimed to address these contradictory findings. First, we characterized the features of SSI, curvature radius of the anterior corneal surface (CR), and AL and analyzed their correlation with advanced myopia. Next, we compared the relationship between AL and SSI after adjusting for the effect of CR. We found a significant positive correlation between SSI and CR, which contradicts the developmental law of axial myopia. Furthermore, after accounting for the effect of CR, we observed a stronger correlation between SSI and AL than that in the unadjusted model. In conclusion, CR is an independent influencing factor for SSI in addition to AL, which masked the decrease in SSI caused by prolonged AL in axial myopia.

Neuroinflammatory Findings of Corneal Confocal Microscopy in Long COVID-19 Patients, 2 Years after Acute SARS-CoV-2 Infection.

To describe corneal confocal microscopy findings in patients with long COVID-19 with persistent symptoms over 20 months after SARS-CoV-2 infection. A descriptive cross-sectional study that included a total of 88 patients; 60 patients with Long COVID-19 and 28 controls. Long COVID-19 diagnosis was established according to the World Health Organization criteria. Corneal confocal microscopy using a Heidelberg Retina Tomograph II (Heidelberg Engineering, Heidelberg, Germany) was performed to evaluate sub-basal nerve plexus morphology (corneal nerve fiber density, nerve fiber length, nerve branch density, nerve fiber total branch density, nerve fiber area, and nerve fiber width). Dendritic cell density and area, along with microneuromas and other morphological changes of the nerve fibers were recorded. Long COVID-19 patients presented with reduced corneal nerve density and branch density as well as shorter corneal nerves compared to the control group. Additionally, Long COVID-19 patients showed an increased density of dendritic cells also with a greater area than that found in the control group of patients without systemic diseases. Microneuromas were detected in 15% of Long COVID-19 patients. Long COVID-19 patients exhibited altered corneal nerve parameters and increased DC density over 20 months after acute SARS-CoV-2 infection. These findings are consistent with a neuroinflammatory condition hypothesized to be present in patients with Long COVID-19, highlighting the potential role of corneal confocal microscopy as a promising noninvasive technique for the study of patients with Long COVID-19.

Evaluation of corneal structural changes in post-COVID-19 patients using anterior segment optical coherence tomography and specular microscopy

Purpose To detect corneal structural changes in people who have recovered from COVID-19 infection by specular microscopy and anterior segment optical coherence tomography (AS-OCT). Moreover, the study compares corneal endothelial and structural parameters between those who have recovered from COVID-19 and individuals who have neither been infected nor vaccinated. Methods This is a prospective observational case–control comparative study involving 108 eyes from 54 individuals. The participants are divided into two groups: the case group (individuals recovered from COVID-19 infection) with 54 eyes (27 individuals) and the control group (individuals with no history of COVID-19 infection or vaccination) with 54 eyes (27 individuals). Both groups are matched for age and sex. The study involves architectural analysis of the cornea using anterior segment OCT and evaluation of the corneal endothelium using specular microscopy. Results The case group’s mean cell density (CD) was 2445.5±310.6 cells/mm, while the control group was 2689.6±398.7 cells/mm (P value 0.001). This indicates a statistically significant decrease in CD among individuals in the case group compared with the control group. The case group’s mean cell area (SD) standard deviation was 169.6±115.2. In contrast, in the control group, it was 135.87±39.29 (P value 0.004), signifying a statistically significant increase in the case group. There was also a statistically significant increase in the average cell area (AVE) in the case group compared with the control group (P value 0.024). However, there were no statistically significant differences in other specular parameters, such as coefficient of variation (CV) or 6A or in the pachymetry. Similarly, no statistically significant differences in AS-OCT parameters were observed between both groups. Conclusion The study reveals a decrease in corneal endothelial cell count and an increase in the average cell area among individuals who have recovered from COVID-19 during their recovery period. However, it is noteworthy that the specular microscopy parameters remained within the clinically normal range for both groups, and visual acuity was unaffected.

Evaluation of the effect of the corneal suture removal on corneal biomechanics with Corneal visualization Scheimpflug technology (Corvis ST) after penetrating keratoplasty (PKP)

Background The cornea is a part of the anterior segment of the eye, which plays an important role in the refraction of light rays on the retina. Cornea also maintains the shape of the eyeball and constitutes a mechanical barrier, protecting the eye against external environmental factors. For the determination of corneal biomechanics, it requires application of an air puff and simultaneous imaging of the response of the tissues to the stimulus. Available methods include ocular response analyzer (ORA) and corneal visualization Scheimpflug technology (CORVIS ST). Aim To evaluate the effect of the corneal suture removal on the corneal biomechanics with CORVIS ST after penetrating keratoplasty. Patients and methods In this prospective study, the corneal biomechanics of 30 patients who had penetrating keratoplasty were evaluated before removal of the corneal sutures at least 6 months and after 3 months of removal of sutures with CORVIS ST. Results In this study, the CORVIS ST parameters were evaluated with significant reduction of the central corneal thickness, peak distance, deformation amplitude, and Ambrosio’s relational thickness to the horizontal profile. There was significant increase in the radius of curvature and stiffness parameters at first applanation. Conclusion Good corneal biomechanics in the period after 3 months of removal of the corneal sutures and weak corneal biomechanics in the period before removal of the corneal sutures at least 6 months after penetrating keratoplasty and the measured corneal parameters have potential benefits for monitoring postoperative wound healing.

Impact of SGLT2 Inhibitors on Corneal Nerve Morphology and Dendritic Cell Density in Type 2 Diabetes

ABSTRACT Purpose This study aims to determine the effects of SGLT2 inhibitors on corneal dendritic cell density and corneal nerve measures in type 2 diabetes. Methods Corneal dendritic cell densities and nerve parameters were measured in people with type 2 diabetes treated with SGLT2 inhibitors (T2DM-SGLT2i) [n = 23] and those not treated with SGLT2 inhibitors (T2DM-no SGLT2i) [n = 23], along with 24 age and sex-matched healthy controls. Results There was a reduction in all corneal nerve parameters in type 2 diabetes groups compared to healthy controls (All parameters: p < 0.05). No significant differences in corneal nerve parameters were observed between T2DM-SGLT2i and T2DM-no SGLT2i groups (All parameters: p > 0.05). Central corneal dendritic cells were significantly reduced [mature (p = 0.03), immature (p = 0.06) and total (p = 0.002)] in the T2DM-SGLT2i group compared to the T2DM-no SGLT2i group. Significantly, higher mature (p = 0.04), immature (p = 0.004), total (p = 0.002) dendritic cell densities in the T2DM-no SGLT2i group were observed compared to the healthy controls. In the inferior whorl, no significant difference in immature (p = 0.27) and total dendritic cell densities (p = 0.16) between T2DM-SGLT2i and T2DM-no SGLT2i were observed except mature dendritic cell density (p = 0.018). No differences in total dendritic cell density were observed in the central (p > 0.09) and inferior whorl (p = 0.88) between T2DM-SGLT2i and healthy controls. Conclusion The present study showed a reduced dendritic cell density in people with type 2 diabetes taking SGLT2 inhibitors compared to those not taking these medications.

Scleral Shape and Its Correlation With Corneal Topographic Parameters: A Review

Purpose. This review paper aims to summarize the outcomes of the different studies investigating the correlation between corneal and scleral profiles, outline the relationship between corneal and scleral curvatures and asymmetry, and describe the correlation between corneal astigmatism and scleral toricity in regular and irregular corneas. Material and Methods. Literature was reviewed from PubMed. A total of 48 articles were specifically selected for the current study. Results. The scleral and corneal radii are directly correlated; the greater the corneal radius, the larger the scleral radius. The cornea and sclera become gradually flatter and asym- metric as the distance from the corneal optical line increases. Similar to the central cornea, the limbal area is more likely to be spherical. The horizontal asymmetry between the nasal and temporal areas is greater than the vertical asymmetry, with the nasal region of the ocular surface being the flattest. In eyes with keratoconus, the sclera is steeper, more asym- metric, and irregular. Cone decentration predicts asymmetric sclera. Corneal and scleral toricity are more likely correlated when corneal astigmatism is greater than 2.00 D. Conclusion. Some correlations were found between corneal and scleral topography; however, performing both corneal and scleral topography are necessary when fitting contact lenses. Further investigation is needed with larger groups matched in age, refractive error, and biometry and comparing smaller or steepest eyes (i.e., Asiatic population) with larger or flatter eyes. It would also be interesting to compare such correlations in primary and secondary ectasia, investigating whether the scleral shape changes in secondary ectasia. Keywords Corneal topography, scleral profile, ocular surface asymmetry, profilometry, ocular surface radii, contact lens fitting

A comparative study of corneal topographical and central corneal thickness changes in diabetics and non-diabetics before and after phacoemulsification: A study protocol

Diabetes is a chronic metabolic disorder and it has its effects in the eye causing various ocular complications. It is also found that diabetes causes changes in the corneal morphology. Corneal components such as epithelium, endothelium, nerves, and immune cells are affected by hyperglycemia. These changes cause a significant effect on vision in individuals with diabetes. Assessment of corneal parameters like central corneal thickness and corneal topography changes related to diabetes are essential in patients undergoing modern-day cataract surgery like phacoemulsification. Systemic condition like diabetes along with cataract surgery like phacoemulsification can influence corneal healing and fluid balance leading to changes in corneal thickness. Postoperative changes in the cornea are also important to assess the corneal health after the surgery. Comparison of preoperative and postoperative corneal measurements help in assessing the effect of phacoemulsification and health status of the cornea. Study of these changes help in preventing complications and effect on visual outcome and specialised management for individuals with diabetes undergoing cataract surgery. In diabetic patients the risk of intraoperative and postoperative complications in cataract surgery increases compared to non diabetic patients. The aim of the study is to compare corneal curvature and astigmatism by corneal topography and central corneal thickness in diabetic patients and controls before and after phacoemulsification. CTRI registration number: REF/2023/08/071341

Prediction of SMILE surgical cutting formula based on back propagation neural network.

To predict cutting formula of small incision lenticule extraction (SMILE) surgery and assist clinicians in identifying candidates by deep learning of back propagation (BP) neural network. A prediction program was developed by a BP neural network. There were 13 188 pieces of data selected as training validation. Another 840 eye samples from 425 patients were recruited for reverse verification of training results. Precision of prediction by BP neural network and lenticule thickness error between machine learning and the actual lenticule thickness in the patient data were measured. After training 2313 epochs, the predictive SMILE cutting formula BP neural network models performed best. The values of mean squared error and gradient are 0.248 and 4.23, respectively. The scatterplot with linear regression analysis showed that the regression coefficient in all samples is 0.99994. The final error accuracy of the BP neural network is -0.003791±0.4221102 µm. With the help of the BP neural network, the program can calculate the lenticule thickness and residual stromal thickness of SMILE surgery accurately. Combined with corneal parameters and refraction of patients, the program can intelligently and conveniently integrate medical information to identify candidates for SMILE surgery.

Impact of Age on the Characteristics of Corneal Nerves and Corneal Epithelial Cells in Healthy Adults.

The aim of this study was to investigate age-related changes in corneal nerves and corneal epithelial cell parameters and to establish age-adjusted reference values. A total of 7025 corneal nerve images and 4215 corneal epithelial images obtained using in vivo confocal microscopy from 281 eyes of 143 healthy participants were included. Seven corneal nerve parameters and 3 corneal epithelial cell parameters were quantified using 2 automatic analytic software and analyzed across 6 age groups ranging from 21 to 80 years. There was a declining trend in all 7 nerve parameters with advancing age. In particular, corneal nerve fiber length and corneal nerve fiber density demonstrated a significant decrease in subjects aged 65 years or older compared with subjects younger than 65 years (10.8 ± 2.6 mm/mm 2 vs. 9.9 ± 2.0 mm/mm 2 , P = 0.011 in corneal nerve fiber length; 15.8 ± 5.2 fibers/mm 2 vs. 14.4 ± 4.3 fibers/mm 2 , P = 0.046 in corneal nerve fiber density), whereas corneal nerve fractal dimension demonstrated a borderline significant decrease ( P = 0.057). Similarly, there was a general declining trend in all epithelial cell parameters with advancing age. Corneal epithelial cell circularity was significantly lower in subjects aged 65 years and older as compared to subjects younger than 65 years (0.722 ± 0.021 μm 2 vs. 0.714 ± 0.021 μm 2 ; P = 0.011). Advancing age results in reduced corneal nerve metrics and alteration of corneal cell morphology. Aging effects should be considered when evaluating patients with corneal neuropathy.

A Comparison of Optical Biometers Used in Children for Myopia Control.

Abstract Purpose To assess the reproducibility (i.e., inter-device reliability) of the biometers Topcon MYAH, Oculus Myopia Master, and Haag-Streit Lenstar LS900 with the Carl Zeiss IOLMaster 700 and the intra-subject repeatability in myopic children in order to reliably detect axial growth for myopia management. Methods Twenty-two myopic children (11.1 ± 2.4 yr) with a spherical equivalent of − 3.53 ± 2.35 D were examined with each of the biometers to assess axial length (AL) and corneal parameters (steepK, flatK, meanK, vectors J0, J45), and16 of these children agreed to a second round of measurements. Reproducibility of the first measurements between the IOLMaster and every other biometer was assessed employing a Bland-Altman approach and paired Studentʼs t-test. Repeatability was assessed as intra-subject standard deviation and was used to estimate the minimum time interval required between two AL measurements to reliably detect axial growth of an eye of at least 0.1 mm/year. Results Repeatability for AL measurements was as follows: IOLMaster: 0.05 mm, Myopia Master: 0.06 mm, Myah: 0.06 mm, Lenstar: 0.04 mm; the respective minimal time interval for axial growth assessment in myopia management was estimated as 5.6, 6.6, 6.7, and 5.0 months, respectively. Best reproducibility of the AL measurement was found between IOLMaster and Lenstar [95% Limits of Agreement (LoA) for reproducibility − 0.06 to 0.02]. As regards to the measured means, Lenstar gave measures of AL that were longer than with the IOLMaster by 0.02 mm (p &lt; 0.001). Myopia Master measures of meanK were significantly lower (by 0.21 D with p &lt; 0.001) than the values from the IOLMaster. As for J0, all biometers deviated significantly from IOLMaster measurements (p &lt; 0.05). Conclusion Generally good agreement was observed between all the biometers. When assessing myopia progression in children, a time frame of at least 6 months between the AL measurements is advisable in order to reliably determine any deviation from a normal growth pattern.

Corneal parameters, ocular biometers, and retinal and choroidal thickness in acromegaly patients

BackgroundTo compare ocular findings of acromegaly patients with healthy individuals and investigate the relation of serum levels of insulin-like growth factor (IGF-1) along with growth hormone (GH) and pituitary tumor (adenoma) dimensions (TD) with specific ocular parameters. MethodsThe ocular parameters of acromegaly patients (n = 38) were compared with those of healthy subjects (n = 36). These parameters were intraocular pressure, keratometric (K1–K2) values, central corneal thickness (CCT), total axial length along with anterior chamber-lens-vitreous length, retinal nerve fiber layer (RNFL) thickness, central foveal thickness (CFT), choroidal thickness (CT), ganglion cell layer thickness (GCLT), and inner plexiform layer thickness (IPLT). Also investigated was whether there was a correlation between disease duration, TD, GH, IGF-I, CCT, RNFL, CFT, GCLT, IPLT, and CT. ResultsThe lens length of the acromegaly group was increased (p = 0.014). GH and IGF-1 levels were positively correlated with CT and CCT, respectively (p = 0.041, r = 0.343) (p = 0.03, r = 0.347). Analysis of TD also found a highly negative correlation with the mean RNFL thickness of the acromegaly patients (p < 0.01, r = -0.603). The mean value of the inner parts of GCLT and IPLT was negatively correlated with TD (p = 0.041, r = -0.343 and p = 0.025, r = -0.379, respectively). ConclusionSerum IGF-1 and GH levels might be determinant factors in CCT and CT, respectively. The pituitary adenoma size increasing may be prone to lead RNFL, ganglion cell layer, inner plexiform layer thinning. Increased lens thickness was found in the acromegaly group.

Assessment of Corneal Endothelial Cell Parameters Using Specular Microscopy in Previously Infected SARS-CoV-2 Patients

Purpose To assess the effects of severe acute respiratory syndrome coronavirus 2 (SARS CoV 2) infection on the endothelium of the cornea. Methods A cross-sectional, comparative study with subjects previously infected by SARS CoV 2 infection for not less than six months (group 1) and a group of sex and age-matched controls without previous infection of SARS CoV 2 (group 2). Endothelial cell parameters were examined using specular microscopy. Following full ophthalmologic examination the groups were matched with controls of the same sex and age with no prior ocular surface pathologies. Results 64 and fifty-three right eyes were examined in both groups one and two, respectively. Between the 2 groups no differences in any of the examined specular parameters were detected that are statistically significant. Conclusion No delayed effects on the corneal endothelium appear to be caused by SARS CoV 2 infection. Further studies comparing the same subject before and after infection will be of significance.

Corneal Morphological and Biomechanical Changes in Thyroid-Associated Ophthalmopathy.

This study aimed to evaluate corneal morphological and biomechanical changes in patients with thyroid-associated ophthalmopathy (TAO) and their correlations with activity and severity. Patients diagnosed with TAO were recruited and divided into groups by activity and severity. All subjects underwent a complete ophthalmic examination, including magnetic resonance imaging. Corneal topography was measured using a Pentacam device, and biomechanical parameters were obtained using a CorVis ST tonometer. Correlations among the corneal parameters, clinical activity score, and NOSPECS score were analyzed. Areas under the receiver operating characteristic curves were calculated to evaluate the diagnostic accuracy of corneal changes for active and severe TAO. Fifty-three eyes with TAO and 16 healthy eyes were enrolled in our study. The back elevation, CorVis biomechanical index, tomographic and biomechanical index, stiffness parameter at the first applanation, deviation from normality in back elevation, relational thickness, and overall deviation from normality were significantly increased in patients with TAO (all P <0.05), whereas the smallest corneal thickness, maximum Ambrósio relational thickness, and deformation amplitude (DA) ratio were significantly decreased (all P <0.05). The clinical activity score was strongly positively correlated with back elevation (γ = 0.515, P <0.001). The NOSPECS score was strongly positively correlated with relational thickness and tomographic and biomechanical index (γ = 0.429 and 0.515, P <0.001) and negatively correlated with maximum Ambrósio relational thickness (γ = -0.53, P <0.001). Moreover, maximum Ambrósio relational thickness and the Ambrósio relational thickness through the horizontal meridian showed desirable diagnostic capacity in distinguishing mild TAO from moderate-severe TAO (areas under the receiver operating characteristic curve, 0.799 and 0.769). Corneal morphological and biomechanical changes were found in patients with TAO, which might be related to the presence of inflammation. Measurements of corneal morphological and biomechanical parameters could serve as references in evaluating TAO.

Is Keratoconus More Than Just a Corneal Disease?

The aims of this study were to compare the scleral thickness (ST), lamina cribrosa thickness (LCT), and lamina cribrosa curvature index between patients with keratoconus and healthy controls and to evaluate the relationship between these values and corneal parameters. This cross-sectional study included 41 eyes of 41 patients with keratoconus and 30 eyes of 30 age-matched, sex-matched, and axial length-matched controls. Nasal and temporal STs were measured vertically, 4 mm posterior to the scleral spur, using anterior segment optical coherence tomography. The LCT was measured on the radial scans of the optic nerve head. The lamina cribrosa curvature index (lamina cribrosa curvature depth/curvature width × 100) was calculated to determine the degree of posterior bowing of the lamina cribrosa. The nasal ST and temporal ST were significantly lower in the keratoconus group than in the control group ( P = 0.016 and P = 0.023, respectively). The LCT was significantly lower in the keratoconus group compared with the control group ( P < 0.001). There was no significant difference between the groups for the lamina cribrosa curvature index ( P = 0.375). Correlation analysis revealed a significant correlation between the nasal and temporal STs and the central corneal thickness (r = 0.376, P < 0.001 and r = 0.387, P < 0.001, respectively). There was also a significant correlation between the temporal ST and the minimum corneal thickness in the keratoconus group (r = 0.332, P = 0.015). The LCT was significantly correlated with the central corneal thickness (r = 0.445, P < 0.001). Structural features of the cornea, sclera, and lamina cribrosa with similar collagen content may be similarly affected in patients with keratoconus. Further histologic studies are needed to confirm our results.

Genetic Correlations Among Corneal Biophysical Parameters and Anthropometric Traits.

The genetic architecture of corneal dysfunction remains poorly understood. Epidemiological and clinical evidence suggests a relationship between corneal structural features and anthropometric measures. We used global and local genetic similarity analysis to identify genomic features that may underlie structural corneal dysfunction. We assembled genome-wide association study summary statistics for corneal features (central corneal thickness, corneal hysteresis [CH], corneal resistance factor [CRF], and the 3 mm index of keratometry) and anthropometric traits (body mass index, weight, and height) in Europeans. We calculated global genetic correlations (rg) between traits using linkage disequilibrium (LD) score regression and local genetic covariance using ρ-HESS, which partitions the genome and performs regression with LD regions. Finally, we identified genes located within regions of significant genetic covariance and analyzed patterns of tissue expression and pathway enrichment. Global LD score regression revealed significant negative correlations between height and both CH (rg = -0.12; P = 2.0 × 10-7) and CRF (rg = -0.11; P = 6.9 × 10-7). Local analysis revealed 68 genomic regions exhibiting significant local genetic covariance between CRF and height, containing 2874 unique genes. Pathway analysis of genes in regions with significant local rg revealed enrichment among signaling pathways with known keratoconus associations, including cadherin and Wnt signaling, as well as enrichment of genes modulated by copper and zinc ions. Corneal biophysical parameters and height share a common genomic architecture, which may facilitate identification of disease-associated genes and therapies for corneal ectasias. Local genetic covariance analysis enables the identification of associated genes and therapeutic targets for corneal ectatic disease.

Relationship between corneal tissue and shape in short-term soft contact lens wear.

To investigate which morphometric and ocular surface tissue parameters are affected by short-term soft contact lens (CL) wear and to assess whether they carry related or independent information. Twenty-two healthy participants wore silicone hydrogel (SiHy; MyDay, CooperVision) soft CLs for 8 h in their left eye. Corneal tomography and corneoscleral topography were captured before and immediately after CL wear. Central corneal thickness (CCT), corneoscleral parameters (limbus position and corneoscleral junction [CSJ] angle) and corneal tissue parameters (corneal transparency and homogeneity) were evaluated. Corneoscleral parameters (limbus position and CSJ angle) were independent of corneal tissue parameters (transparency and homogeneity) at baseline and after CL wear. CCT was independent of all the other parameters examined at baseline, but baseline values of corneal tissue parameters were moderately correlated with CCT change (transparency: r = -0.51; p = 0.007), homogeneity: r = -0.46; p = 0.02). A complete characterisation of ocular surface changes following CL wear should consider corneoscleral topography and corneal densitometry simultaneously, since they carry complementary information.

Clinical Performance and Patient Satisfaction of Hybrid Contact Lenses in Patients with Keratoconus.

The aim of the study was to evaluate the fitting process, clinical performance, and patient satisfaction of hybrid contact lenses (HCL) in patients with keratoconus (KC). Sixty-eight KC patients (35 female, 33 male) who were prescribed HCL were included in the study. Corneal topographic parameters, best corrected visual acuity (BCVA) with eyeglasses, the number of HCL trials, prescribed HCL base curve (BC), and visual acuity with HCL were recorded from hospital records. A contact lens satisfaction survey was sent to the patients via email or WhatsApp and the data was statistically analyzed using IBM SPSS Statistics version 22.0. The study included 110 eyes of 68 patients with a mean age of 27.34±8 years (range: 12-48 years). According to the Amsler-Krumeich classification, 35.5% of the eyes were stage 1, 50.9% were stage 2, and 13.5% were stage 3 or 4. Mean K1, K2, and Kmean values were 7.14±0.50 mm (range 5.72-8.30 mm), 6.63±0.49 mm (range 5.07-7.84 mm), and 6.89±0.48 mm (range 5.39-8.06 mm), respectively. The average number of lens trials was 1.59±0.82 (range 1-4). The mean BC of the prescribed HCL was 6.84±0.50 mm (range 5.60-8.00 mm). BCVA with glasses was 0.36±0.2 (range 0.05-0.8), and 0.80±0.14 (range 0.3-1.0) with HCL (p<0.0001). The overall survey score was 3.54 out of 5, the overall satisfaction score was 3.27, the average vision satisfaction score was 3.62, the average satisfaction score for lens insertion and removal was 3.01, and the average satisfaction score for lens comfort was 2.97. Prescribed HCL BC is usually close to the topographic Kmean value and in most of the patients, fitting was successful with the first or second CL trial. The overall satisfaction score was moderate to good and the disadvantages were low comfort compared to soft CL, difficulty with insertion and removal, short lens life, and high cost.

The relationship between scleral thickness, corneal parameters, and interstitial lung disease in patients with rheumatoid arthritis

The relationship between scleral thickness, corneal parameters, and interstitial lung disease in patients with rheumatoid arthritis

Corneal Stress Distribution Evolves from Thickness-Driven in Normal Corneas to Curvature-Driven with Progression in Keratoconus

To introduce the novel parameter of Corneal Contribution to Stress (CCS) and compare stress distribution patterns between keratoconus (KCN) and normal corneas. Prospective, observational, cross-sectional study. The study included 66 eyes of 40 subjects diagnosed with KCN and 155 left eyes from 155 normal control (NRL) subjects. Tomography was obtained to calculate the newly proposed CCS, defined according to the hoop stress formula without intraocular pressure, R/2t, where R is the radius of curvature and t is the thickness. CCS maps were calculated from pachymetry and tangential curvature maps. Custom software identified the 2-mm-diameter zones of greatest curvature (Cspot-max), thinnest pachymetry (Pach-min), greatest stress (CCSmax), and lowest stress (CCSmin). Stress difference (CCSdiff) was calculated as CCSmax - CCSmin. Distances between Cspot-max vs. Pach-min, vs. CCSmax, and vs. CCSmin, as well as between Pach-min vs. CCSmax and vs. CCSmin, were calculated. t tests were performed between cohorts, and paired t tests were performed within cohorts. Univariate linear regression analyses were performed between parameters and distances. The significance threshold was P < 0.05. Corneal stress parameters, corneal features of maximum curvature, minimum thickness, and distances between corneal stress parameters and corneal features. CCSmax was significantly closer to Pach-min (0.79 ± 0.92) and Cspot-max (2.04 ± 0.85) than CCSmin (3.17 ± 0.38, 2.73 ± 1.53, respectively) in NRL, P < 0.0001, whereas CCSmin was significantly closer to Cspot-max (1.35 ± 1.43) than CCSmax (2.52 ± 0.72) in KCN, P < 0.0001. Cspot-max (severity) was significantly related to CCSdiff in KCN (P < 0.0001; R2= 0.5882) with a weak relationship in NRL (P < 0.0080, R2= 0.0451). Cspot-max was significantly related to the distance from Pach-min to CCSmax (P < 0.0001; R2= 0.3737) without significance in NRL (P= 0.8011). Corneal stress is driven by thickness in NRL, with greatest stress at thinnest pachymetry and greatest curvature. However, maximum stress moves away from thinnest pachymetry with progression in KCN, and minimum stress is associated with maximum curvature. Severity in KCN is significantly related to greater difference between maximum and minimum stress, consistent with the biomechanical cycle of decompensation. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.