Keratoconic Eyes Research Articles

Impact of Keratoconus on Contrast Sensitivity

Objective: Keratoconus (KC) disrupts corneal shape, leading to irregular astigmatism and increased higher-order aberrations (HOA), ultimately affecting visual quality. While visual acuity (VA) remains the standard, its limitations in early KC diagnosis are recognized. This study aimed to evaluate the impact of KC on contrast sensitivity function (CSF), a potentially more sensitive measure of visual performance.Material and Methods: A case-control design compared CSF in KC patients (n=7) to healthy controls (n=16). All subjects achieved the best-corrected visual acuity (BCVA) of 6/9 or better (logMAR ≤0.10). Corneal topography was measured using Tomey TMS-5 to confirm KC diagnosis. CSF was assessed with the Functional Acuity Contrast Test (FACT).Results: KC eyes exhibited significantly reduced CSF across all spatial frequencies compared to controls (p-value<0.05). Row A of the FACT chart (representing the lowest spatial frequency, 1.5 cpd) demonstrated the most prominent difference (t (21)=-3.073, p-value=0.003).Conclusion: Our findings reveal that KC patients, despite achieving good BCVA, demonstrate measurable deficits in CSF. This suggests CSF measurement with FACT may be a valuable tool for the early diagnosis and monitoring of KC, potentially offering a more sensitive and comprehensive assessment of visual function compared to BCVA alone.

Comparison of the quantitative contrast sensitivity function between early keratoconus and normal eyes

PurposeTo compare the characteristics of the quantitative contrast sensitivity function (qCSF) in eyes with early keratoconus (Early-KC) and normal control (NC) eyes and investigate the associated factors.DesignA cross-sectional study.MethodsThis study included 43 eyes of 43 patients with Early-KC (including subclinical keratoconus [SKC] and forme fruste keratoconus [FFKC]) and 77 NC eyes of 77 participants with corrected distance visual acuity (CDVA) all ≥ 20/20. Contrast sensitivity (CS) was assessed using the qCSF tests. Subgroup analysis was performed according to keratoconus type(SKC and FFKC) and astigmatism(cylindrical refraction >-1.0D or ≤-1.0D).ResultsSex ratio, spherical refraction, and spherical equivalent (SE) varied significantly between the two groups (all P < 0.01). The area under log CSF (AULCSF), CSF Acuity, and CS at low (1.0 and 1.5 cycles per degree [cpd]) and high (12.0 and 18.0 cpd) spatial frequencies decreased significantly in the Early-KC group than that in the NC group (all P < 0.05). The subgroup analysis revealed a similar decrease in the SKC group (all P < 0.05). AULCSF, CSF Acuity, and CS at high spatial frequencies of patients with cylindrical refraction ≤-1.0D in the Early-KC group decreased significantly (all P < 0.05) than those in the NC group. The index of vertical asymmetry and index of height decentration correlated negatively with CS at 1.5 cpd (r= -0.321 and -0.306; both P < 0.05).ConclusionsCS decreased significantly at low and high spatial frequencies in Early-KC, though with normal CDVA. The qCSF test can sensitively reflect visual performance in early keratoconus.

The Role of Pentacam Random Forest Index in Detecting Subclinical Keratoconus in a Chinese Cohort.

Purpose: This study aimed to evaluate the diagnostic accuracy of a novel shape index, the Pentacam Random Forest Index (PRFI), in detecting keratoconus (KC), specifically subclinical keratoconus, in Chinese refractive surgery candidates. Methods: This prospective cohort study included 856 participants who were divided into four groups based on their tomographic outcomes: the KC group (n = 137), the very asymmetric ectasia (VAE) group (n = 73), the normal cornea group (n = 363) and the tomographically suspected KC (TSK) group (n = 283). The diagnostic performance of PRFI and other widely used indices, including the shape index BAD-D and the combined index TBI, was assessed using receiver operating characteristic (ROC) curve analysis and compared using DeLong's test. The area under the curve (AUC), best cutoff values, and Youden index for each parameter are reported. Additionally, the false-positive rates of BAD-D and PRFI were calculated and compared in "normal corneas". Results: All shape and biomechanical parameters collected in this study were found to be significantly different among the four groups (KC, VAE, TSK, and normal groups; p = 0.000). The AUC of PRFI was the highest in detecting any form of KC (including clinical KC eyes and VAE-NT eyes) in Chinese refractive surgery candidates, outperforming the widely used shape index BAD-D (0.919 vs. 0.890, p < 0.001). There was no significant difference in performance between the PRFI and the combined TBI index (0.919 vs. 0.916, p > 0.05). For detecting subclinical KC eyes (i.e., VAE-NT), the AUC of PRFI was 0.774, which was statistically comparable to TBI (0.774 vs. 0.776, p > 0.05), while outperforming BAD-D (0.774 vs. 0.684, p < 0.001). The best cutoff values of PRFI for detecting any KC and VAE-NT eyes were determined to be 0.37 and 0.27, respectively. Additionally, PRFI demonstrated a lower false-positive rate than BAD-D (13.8% vs. 43.8%, p < 0.001). Notably, the relatively high false-positive rate of BAD-D observed in this study might be attributed to the smaller horizontal corneal diameter in tomographically suspected eyes. Conclusions: The PRFI proved to be a superior shape index compared to BAD-D in detecting any form of keratoconus, including subclinical cases, in Chinese refractive surgery candidates. This finding may be attributed to the relatively small corneas commonly observed in Asians.

Agreement in anterior segment measurements between swept-source optical coherence and dual Scheimpflug tomography devices in keratoconus eyes

PurposeTo evaluate the agreement of ocular biometry measured using a swept-source optical coherence (Casia 2) and a dual Scheimpflug (Galilei G6) tomography in keratoconus.MethodsThis retrospective study included 102 eyes from 102 keratoconus patient examined using both devices. Parameters compared included flat (Kf) and steep (Ks) keratometry, astigmatism of anterior, posterior, and total keratometry, central (CCT) and thinnest (TCT) corneal thickness. To assess the agreement, intraclass coefficient (ICC) and Bland-Altman analysis with 95% limits of agreement (LoA) were used.ResultsAnterior and total Ks and Kf showed moderate or good agreement with 95% limits of agreement (LoA) range over 9.75 D. Posterior Ks and Kf were lower in the Galilei G6 (all p < 0.001). Astigmatism showed moderate, poor, and moderate agreement for anterior, posterior, and total keratometry, respectively. CCT and TCT showed excellent agreement; however, the 95% LoA range was over 60 μm.ConclusionThe agreement between the two devices was not excellent for most parameters used to diagnose keratoconus and assess disease progression, and the differences were clinically significant. Therefore, the measurements from these two devices are not interchangeable for patients with keratoconus.

Relationship between Choroidal Thickness and Anterior Scleral Thickness in Patients with Keratoconus.

To evaluate the relationship between choroidal thickness (CT) and anterior scleral thickness (AST) in patients with subclinical keratoconus (SKC) and established keratoconus (KC). This single-center prospective case-control study included 97 eyes of 97 patients: 44 KC eyes, 14 SKC eyes, and 39 age- and axial length (AL)-matched healthy eyes. Using swept-source optical coherence tomography, the AST was manually measured in four directions and the CT was obtained automatically from the Early Treatment Diabetic Retinopathy Study (ETDRS) grid. Principal component analysis (PCA) was used to linearly reduce the dimensionality of nine CT inputs to one significant component, CT1. A multivariate model was created to evaluate the association between CT1, AST, and several ocular parameters in SKC and KC patients. Partial correlation was then performed to adjust the confounding factors and to examine the effect of AST on CT1. The PCA showed that CT1 accounts for 86.54% of the total variance in the nine original CTs of the ETDRS grid. The CT1 model was associated with age, AL, and AST in the superior meridian in SKC eyes, whereas in KC eyes, it was correlated with gender, age, AL, and AST in the inferior meridian (p < 0.001). The partial correlation between CT1 and AST in the superior zone was found to be significant, positive, and strong in SKC eyes (r = 0.79, p = 0.019), whereas a significant, positive, and moderate correlation between CT1 and AST at the inferior zone (r = 0.41, p = 0.017) was observed in KC eyes. Choroidal tissue was significantly correlated with the anterior sclera across the vertical meridian. This relationship was observed over the superior sclera in SKC eyes, whereas in established KC, it was over the inferior sclera. These results reveal new insights regarding the interactions between the anterior and posterior structures of the KC eyes and confirm the enigma of the pathophysiology of KC.

Morphological Features Among Gaussian, Sagittal, and Tangential Curvature Maps in Normal and Keratoconus Eyes Using AS-OCT.

Morphological Features Among Gaussian, Sagittal, and Tangential Curvature Maps in Normal and Keratoconus Eyes Using AS-OCT.

The development of a machine learning model to train junior ophthalmologists in diagnosing the pre-clinical keratoconus.

This study aims to evaluate the diagnostic performance of a machine learning model (ML model) to train junior ophthalmologists in detecting preclinical keratoconus (PKC). A total of 1,334 corneal topography images (The Pentacam HR system) from 413 keratoconus eyes, 32 PKC eyes and 222 normal eyes were collected. Five junior ophthalmologists were trained and annotated the images with or without the suggestions proposed by the ML model. The diagnostic performance of PKC was evaluated among three groups: junior ophthalmologist group (control group), ML model group and ML model-training junior ophthalmologist group (test group). The accuracy of the ML model between the eyes of patients with KC and NEs in all three clinics (99% accuracy, area under the receiver operating characteristic (ROC) curve AUC of 1.00, 99% sensitivity, 99% specificity) was higher than that for Belin-Ambrósio enhanced ectasia display total deviation (BAD-D) (86% accuracy, AUC of 0.97, 97% sensitivity, 69% specificity). The accuracy of the ML model between eyes with PKC and NEs in all three clinics (98% accuracy, AUC of 0.96, 98% sensitivity, 98% specificity) was higher than that of BAD-D (69% accuracy, AUC of 0.73, 67% sensitivity, 69% specificity). The diagnostic accuracy of PKC was 47.5% (95%CI, 0.5-71.6%), 100% (95%CI, 100-100%) and 94.4% (95%CI, 14.7-94.7%) in the control group, ML model group and test group. With the assistance of the proposed ML model, the diagnostic accuracy of junior ophthalmologists improved with statistical significance (p < 0.05). According to the questionnaire of all the junior ophthalmologists, the average score was 4 (total 5) regarding to the comprehensiveness that the AI model has been in their keratoconus diagnosis learning; the average score was 4.4 (total 5) regarding to the convenience that the AI model has been in their keratoconus diagnosis learning. The proposed ML model provided a novel approach for the detection of PKC with high diagnostic accuracy and assisted to improve the performance of junior ophthalmologists, resulting especially in reducing the risk of missed diagnoses.

Application of Artificial Intelligence in Ophthalmology: An Updated Comprehensive Review.

Artificial intelligence (AI) holds immense promise for transforming ophthalmic care through automated screening, precision diagnostics, and optimized treatment planning. This paper reviews recent advances and challenges in applying AI techniques such as machine learning and deep learning to major eye diseases. In diabetic retinopathy, AI algorithms analyze retinal images to accurately identify lesions, which helps clinicians in ophthalmology practice. Systems like IDx-DR (IDx Technologies Inc, USA) are FDA-approved for autonomous detection of referable diabetic retinopathy. For glaucoma, deep learning models assess optic nerve head morphology in fundus photographs to detect damage. In age-related macular degeneration, AI can quantify drusen and diagnose disease severity from both color fundus and optical coherence tomography images. AI has also been used in screening for retinopathy of prematurity, keratoconus, and dry eye disease. Beyond screening, AI can aid treatment decisions by forecasting disease progression and anti-VEGF response. However, potential limitations such as the quality and diversity of training data, lack of rigorous clinical validation, and challenges in regulatory approval and clinician trust must be addressed for the widespread adoption of AI. Two other significant hurdles include the integration of AI into existing clinical workflows and ensuring transparency in AI decision-making processes. With continued research to address these limitations, AI promises to enable earlier diagnosis, optimized resource allocation, personalized treatment, and improved patient outcomes. Besides, synergistic human-AI systems could set a new standard for evidence-based, precise ophthalmic care.

Scleral lens surface crazing in an eye with giant papillary conjunctivitis and keratoconus: Outcome of lens surface polishing

We present a case of scleral lens surface crazing in a patient with keratoconus (KC) and chronic giant papillary conjunctivitis (GPC). A 45-year-old Asian male with known keratoconus (KC) and allergic eye disease in both eyes, who is an experienced scleral lens user, presented with a 3-month history of lens intolerance in the right eye. On examination, the right eye scleral lens showed extensive lens surface crazing with poor surface wettability. The upper tarsal conjunctiva showed conjunctival hypertrophy – active GPC. After allergy treatment and symptomatic improvement, the scleral lens was refitted after intensive cleaning and polishing with aluminum oxide. The lens surface showed significant improvement and good fitting characteristics, and the patient resumed lens wear. At 6 months of follow-up, the patient was asymptomatic, and the ocular condition was stable.

Pachychoroid pigment epitheliopathy in keratoconic eyes.

To report the association between keratoconus (KC) and pachychoroid pigment epitheliopathy (PPE). As secondary outcome, we explored the relation between subfoveal choroidal thickness (SFCT) and topometric indexes. Retrospective, observational, cross-sectional, case-control study. Multicentric study including patients with KC and healthy controls. Each subject underwent a complete ophthalmological visit, Placido-based corneal topography, Scheimpflug corneal tomography and spectral-domain OCT (SD-OCT) with the enhanced depth imaging (EDI) mode on. Linear mixed models (LMM) were employed for comparison between groups, and to examine the impact of different topometric factors on SFCT. KC stages were defined according to Belin grading. Overall, 56 eyes from 35 KC patients and 52 eyes from 27 healthy, age- and axial length-matched control subjects were included in the study. PPE was found in 10 (17.9%) eyes from 8 KC patients, whereas was absent in all healthy controls. SFCT was statistically significantly higher in keratoconic eyes (median: 390µm; interquartile range (IQR): 339 - 425µm) compared to healthy eyes (median: 240µm; IQR: 200 - 288µm) (p < 0.001). SFCT did not differ across different KC stages and between keratoconic eyes with and without PPE. PPE is a relatively frequent finding in eyes with KC, being present in about 1 out of 6 cases, regardless of disease stage. What is known: Keratoconus (KC) is a corneal disorder commonly associated with other chorioretinal abnormalities. It is well known that keratoconic eyes display increased choroidal thickness, and the rare association between KC and central serous chorioretinopathy (CSC) has already been reported in the literature. We identified an association between KC and pachychoroid pigment epitheliopathy (PPE), a precursor or forme fruste of pachychoroid diseases, such as CSC. PPE presence is independent from corneal parameters and is observed in about 1 out 6 KC eyes.

Assessment of OCT and Angio-OCT Parameters in Keratoconus Patients with and without Penetrating Keratoplasty.

Background/Objectives: Keratoconus (KC) is a bilateral eye disease characterized by corneal thinning and cone-like deformation, leading to visual impairment. This study evaluated the radial peripapillary capillaries (RPCs) in keratoconus patients with and without penetrating keratoplasty (PKP) using OCT and angio-OCT, comparing the results to a control group. Methods: This retrospective study included 149 eyes, 97 from patients who underwent PKP between January 2018 and February 2023 and 52 from patients who did not undergo PKP. The control group comprised 72 patients (144 eyes) who were healthy volunteers. Measurements included the best corrected visual acuity (BCVA), the intraocular pressure (IOP), slit-lamp biomicroscopy, a fundus examination, and corneal topography, as well as OCT and angio-OCT assessments of the RPCs, retinal nerve fiber layer (RNFL), ganglion cell complex (GCC), and central retinal thickness (CRT). Statistical analyses were performed using Student's t-test and Pearson's correlation coefficient. Results: The RNFL was significantly thinner in KC eyes after PKP compared to control eyes (p < 0.001), and the CRT was significantly thicker in KC eyes after PKP compared to control eyes (p = 0.003). However, the GCC was similar across the groups (p = 0.0885). Additionally, RPCs inside the disc were significantly reduced in KC eyes after PKP compared to control eyes (p < 0.0001). A significant positive correlation was found between RPC whole vessel density and RNFL thickness as measured via angio-OCT (r = 0.308, p < 0.0001). Conclusions: This study found that the RPC density inside the disc is significantly reduced in keratoconus patients after penetrating keratoplasty, highlighting RPCs inside the disc as a potential diagnostic tool for further assessment of keratoconus.

Topographic, pachymetric and epithelial thickness distribution patterns in clinically unaffected fellow eyes of patients with asymmetric keratoconus

PurposeTo compare topographic, pachymetric and epithelial distribution patterns of clinically unaffected fellow eyes of patients with asymmetric keratoconus (AKC) with those of normal controls and keratoconic fellow eyes. MethodsA prospective, observational study was conducted at a tertiary care center, in which twenty-five clinically unaffected fellow eyes in patients with AKC were compared to 25 keratoconic fellow eyes and 67 normal controls. Pachymetric and epithelial thicknesses in the central 2 mm and 8 octants in the 2–5 mm and 5–7 mm zones were compared using Spectral Domain Optical Coherence Tomography (SDOCT). Scheimpflug derived topography was also compared. ResultsMean simulated keratometry of fellow eyes (43.6D ± 1.34 D) was comparable to that of control eyes (43.85D ± 1.57 D) (p > 0.99) and less than that of keratoconic eyes (47.08D ± 4.62 D) (p = 0.004). Central corneal and epithelial thicknesses of fellow eyes (474.28 ± 40.27 μm, 52.76 ± 7.45 μm, respectively) were less than in control eyes (505.97 ± 30.12 μm, 60.48 ± 8.37 μm) (p < 0.001 and p = 0.006, respectively) but comparable to those of keratoconic eyes (470.48 ± 44.19 μm, 52.48 ± 8.00 μm) (p > 0.99). Pachymetric differences of radially opposite octants in the 2–5 mm zone demonstrated thinning in the inferior and inferotemporal octants of fellow eyes which was greater than that seen in control eyes (p = 0.017 and 0.04, respectively) ConclusionReduced central epithelial thickness and greater pachymetric differences in radially opposite octants of the mid-peripheral cornea may be suggestive of susceptibility to ectasia despite normal topography.

Repeatability and agreement of two ocular biometers with single and dual Scheimpflug cameras in keratoconus eyes.

To evaluate the repeatability and agreement of two different ocular biometers and Scheimpflug devices in keratoconus eyes. This prospective, comparative trial took place at the University hospital, Goethe University, Frankfurt am Main, Germany. We included eyes with keratoconus, one eye per patient, randomly selected. Measurements were taken with Galilei G6 (Ziemer, Switzerland) and Pentacam AXL (Oculus, Germany), three consecutive measurements each. Repeatability and agreement were evaluated for simulated keratometry (simK), astigmatism (simA), maximum keratometry (KMax) and its axis, total keratometry (TCP), axial length (AL), anterior chamber depth (ACD), and thinnest pachymetry (TCT). Both devices showed an excellent repeatability with intra class correlation (ICC) of > 0.97 for all parameters. The 95% limits of repeatability (LoR95%) and agreement (LoA95%) were narrow for all parameters. The Galilei G6 had a narrower LoAR95% for TCT (2.1μm vs. 4.6μm), but a wider LoR95% for KMax (0.52D vs. 1.18D). No relevant difference was found for the other parameters. Agreement between the devices was good to moderate, especially for simK and TCP. Both devices show excellent repeatability with narrow LoR95% and high ICC for all parameters. The only relevant difference was found for KMax and TCT in favor of Pentacam AXL and Galilei G6, respectively. Agreement was good to moderate, and most parameters should not be considered interchangeable.

Repeatability and agreement of total corneal astigmatism measured in keratoconic eyes using four current devices.

To evaluate repeatability and agreement in measurements of total corneal astigmatism (TCA) in keratoconic eyes, using four optical coherence tomography (OCT)-based devices: Anterion, Casia SS-1000, IOLMaster 700, and MS-39. Three consecutive measurements were taken with each device in 136 eyes. TCA values were converted into components J0 and J45. The Anterion and the IOLMaster 700 also provided axial length (AL) measurements. The repeatability was calculated using pooled within-subject standard deviation (Sw). The agreement among the four devices was assessed by pairwise comparisons and Bland-Altman plots. For all devices, the repeatability of TCA measurements showed Sw ≤0.23 D for TCA magnitude, ≤0.14 D for J0, and ≤0.12 D for J45. There were statistically significant differences in TCA magnitude for each pair, except for IOLMaster 700 with MS-39, and Anterion with MS-39. The repeatability (Sw) of axis measurements had a statistically significant negative correlation with the TCA magnitude (p < 0.001 for all devices). Both Anterion and IOLMaster 700 had high repeatability in AL measurements (Sw: 0.007 mm for Anterion and 0.009 mm for IOLMaster 700). The difference in AL between the two was 0.015 ± 0.033 mm (p < 0.001). All four devices showed good repeatability in TCA measurements in keratoconic eyes, the agreement for TCA measurements between the tested devices was generally low. Anterion and IOLMaster 700 showed good repeatability and agreement in AL measurements.

Visual outcome in Keratoconus with spherical rigid gas permeable contact lens

Introduction: Keratoconus is a bileteral asymetric progressive ecteria of cornea commonly associated with vernal keratoconjunctivitis and Atopic dermatitis. Rigid gas permeable (RGP) contact lens is the first choice for refractive correction in keratoconic eyes. The visual outcome in Keratoconus with spherical RGP contact lens along with the mean age of presentation, gender predominance, ethnicity, associated conditions, refractive error and corneal astigmatism was evaluated. Methods: The records of the Keratoconus patients attending cornea and contact lens clinic for last 6 years were reviewed and analyzed using SPSS-14 software. Data on laterality, race, age, gender, refractive error, visual acuity (VA), associated conditions and contact lens parameters were obtained. A total of 22 patients with 38 keratoconic eyes were included in the study. Results: The mean age of Keratoconus presentation was 18.11 ± 4.45 years. Sixteen cases (72.73 %) were bilateral; 6 (27.27 %) were unilateral. Mean uncorrected visual acuity (UCVA) was 0.86 ± 0.40 Log MAR. Mean spectacle visual acuity was 0.54 ± 0.38 Log MAR. Mean visual acuity with spherical RGP contact lenses was 0.08 ± 0.14 Log MAR. The difference between mean spectacle visual acuity and mean VA with spherical RGP contact lens was statistically significant (p &lt; 0.001). Conclusion: In all stages of Keratoconus, improvement in visual acuity with spherical RGP contact lens was highly significant.

Outcomes of Donor Corneas of Different Thicknesses From Endothelial Keratoplasty in Deep Anterior Lamellar Keratoplasty for Keratoconus.

To evaluate the outcomes of divided residual donor corneas obtained from endothelial keratoplasty in keratoconus with deep anterior lamellar keratoplasty (DALK). In this retrospective, comparative, clinical study, 103 keratoconic eyes that underwent DALK were enrolled; 67 eyes received thin grafts from Descemet stripping automated endothelial keratoplasty, and 36 received thick grafts from Descemet membrane endothelial keratoplasty. Baseline and postoperative central corneal thickness (CCT), inferior corneal thickness, uncorrected distance visual acuity, corrected distance visual acuity, corneal astigmatism, mean keratometry, biomechanical properties, and complication rates were measured. Six months after transplantation, the group receiving thin grafts had a CCT of only 455.1 ± 43.0 μm, whereas that of the group receiving thick grafts was 546.7 ± 44.2 μm. Both CCT and inferior corneal thickness in the thin group were significantly lower than those in the thick group (measured with Pentacam at 36 months, P < 0.001) and remained throughout the 5-year follow-up period. Both procedures had comparable postoperative logarithm of the minimum angle of resolution UDVAs, logarithm of the minimum angle of resolution corrected distance visual acuity, astigmatism, and mean keratometry values (36 months; P = 0.335, 0.286, 0.680, and 0.365, respectively). Corneal biomechanical analysis revealed that the thin group had a significantly higher stiffness parameter at the first applanation than the thick group at the 2-year follow-up (P = 0.036) while other parameters were equivalent. The outcomes of keratoplasty with donor tissue are comparable regardless of the thickness of the graft, which suggests that transplantation with either type of the split corneal procedure for DALK in patients with keratoconus is feasible.

Insights into atypical segmental layer thicknesses and phase retardation in thick corneas using ultrahigh-resolution polarization-sensitive optical coherence tomography

BackgroundAccurately assessing corneal structural status is challenging when thickness deviates from the average. Polarization-sensitive optical coherence tomography (PS-OCT) measures tissue-specific polarization changes, providing additional contrast for accurate segmentations and aids in phase retardation (PR) measurements. Previous studies have shown PR's effectiveness in identifying sub-clinical keratoconus (KC) in asymmetric cases. Thus, this study aims to assess PR distribution in thick corneas with and without KC.MethodsIn this retrospective and cross-sectional study, 45 thick corneas from 30 Asian-Indian subjects, categorized into healthy (n = 26) and KC (n = 19) groups were analyzed. All eyes underwent standard clinical evaluations, tomographic assessments, and corneal biomechanics measurements. PR and individual layer thicknesses were measured using custom-designed ultrahigh-resolution PS-OCT. PR en-face maps were generated. Individual layer thicknesses and PR analysis was conducted across multiple zones, extending up to 8–10 mm in diameter. All eyes in the study had not undergone interventions, received topical medications, or had previous corneal disease history.ResultsSignificant differences were found in spherical and cylindrical powers, keratometry, pachymetry, and biomechanical indices (all P < 0.01). Thickness profiles from PS-OCT showed significant differences in the 4–8 mm zones only. Bowman's layer thickness significantly differed only in the central 2 mm zone (P = 0.02). The median PR values showed marginal differences in the central 2 mm zone (P = 0.0565). Additionally, there were significant differences observed in the 2–4 mm and 4–6 mm zones (P = 0.0274 and P = 0.0456, respectively). KC eyes exhibited an atypical PR distribution and corneal thinning, while normal eyes maintained a uniform Bowman’s layer thickness and PR maps with larger areas of higher PR.ConclusionThe study revealed distinctive PR distribution in thick corneas among healthy and KC groups. Using an ultrahigh-resolution PS-OCT the significance of Bowman's layer thickness in these groups was also emphasized. The study offered potential improvements in clinical diagnostics by enhancing our understanding of corneal structure and its altered function.

The HUC progression score: A new method for determining KERATOCONUS progression.

To establish new criteria for the progression of keratoconus, taking into account a Pentacam HR (high resolution) tomographeŕs repeatability limit. This is a retrospective observational study, including 224 eyes in 154 patients diagnosed with keratoconus and patients treated with crosslinking, with a follow-up of at least one year, in which the new progression score of the Cruces University Hospital for keratoconus progression was analyzed. This score takes into account: maximum keratometry, thinnest corneal thickness, maximum posterior elevation, vertical coma and RMS of high order aberrations, all based on the tomographer repeatability limit. The effectiveness or not of crosslinking was determined. The Receiver Operating Characteristics (ROC) curves obtained in our validation met the criteria by being far from the reference diagonal. Moreover, young patients are more likely to have keratoconus that progresses, and the percentage of patients that showed progression was 14.3% of the eyes studied, with the most advanced keratoconus showing the least progression. Taking into account the new progression score of the Cruces Hospital, we would have indicated crosslinking in 2 eyes only and we observed that none progressed one year after treatment. The the new progression score of the Cruces University Hospital is a method based on the real repeatability limit for keratoconic eyes. Moreover, it is easy to interpret and can be implemented with Pentacam software. It provides a numerical value that evaluates both the anterior and posterior surfaces of the cornea and corneal aberrations in the evolution of keratoconus.

Biomechanical changes following corneal crosslinking in keratoconus patients.

To evaluate the biomechanical and tomographic outcomes of keratoconus patients up to four years after corneal crosslinking (CXL). In this longitudinal retrospective-prospective single-center case series, the preoperative tomographic and biomechanical results from 200 keratoconus eyes of 161 patients undergoing CXL were compared to follow-up examinations at three-months, six-months, one-year, two-years, three-years, and four-years after CXL. Primary outcomes included the Corvis Biomechanical Factor (CBiF) and five biomechanical response parameters obtained from the Corvis ST. Tomographically, the Belin-Ambrósio deviation index (BAD-D) and the maximal keratometry (Kmax) measured by the Pentacam were analyzed. Additionally, Corvis E-staging, the thinnest corneal thickness (TCT), and the best-corrected visual acuity (BCVA) were obtained. Primary outcomes were compared using a paired t-test. The CBiF decreased significantly at the six-month (p < 0.001) and one-year (p < 0.001) follow-ups when compared to preoperative values. E-staging behaved accordingly to the CBiF. Within the two- to four-year follow-ups, the biomechanical outcomes showed no significant differences when compared to preoperative. Tomographically, the BAD-D increased significantly during the first year after CXL with a maximum at six-months (p < 0.001), while Kmax decreased significantly (p < 0.001) and continuously up to four years after CXL. The TCT was lower at all postoperative follow-up visits compared to preoperative, and the BCVA improved. In the first year after CXL, there was a temporary progression in both the biomechanical CBiF and E-staging, as well as in the tomographic analysis. CXL contributes to the stabilization of both the tomographic and biomechanical properties of the cornea up to four years postoperatively.

No Evidence of Chronic Infection in a Metagenomic Sequencing Study of the Keratoconus Corneal Epithelium.

Objectives: This study aims to assess the presence of pathogenic microorganisms in the corneal epithelial layer of keratoconus patients. Methods: DNA was extracted from corneal epithelial samples procured from ten individual keratoconus eyes and three healthy controls. Metagenomic next-generation sequencing (mNGS) was performed to detect ocular microbiota using an agnostic approach. Results: Metagenomic sequencing revealed a low microbial read count in corneal epithelial samples derived from both keratoconus eyes (average: 530) and controls (average: 622) without a statistically significant difference (p = 0.29). Proteobacteria were the predominant phylum in both keratoconus and control samples (relative abundance: 72% versus 79%, respectively). Conclusions: The overall low microbial read count and the lack of difference in the relative abundance of different microbial species between keratoconus and control samples do not support the hypothesis that a chronic corneal infection is implicated in the pathogenesis of keratoconus. These findings do not rule out the possibility that an acute infection may be involved in the disease process as an initiating event.