Mechanisms of Rubbing-Related Corneal Trauma in Keratoconus

Advances in keratoconus animal models: From genetics to biomechanics

Keratoconus is a disorder characterized by thinning and protrusion of the cornea into a cone shape, potentially leading to decreased vision and blindness. Understanding the pathogenesis of keratoconus and developing treatment strategies is crucial. Currently, animal models of keratoconus created through gene knockout and collagenase digestion have made significant progress in studying the pathogenesis of the disease. However, these models have limitations, such as unverified long-term effects. Future research should focus on optimizing the construction methods of animal models and enhancing long-term observation and evaluation to more accurately simulate human keratoconus. This paper reviews research progress on animal models of keratoconus, examining models constructed using methods such as gene editing, drug induction, cutting of corneal stroma, and mechanical stimulation.

Mechanoreceptor Piezo1 channel-mediated interleukin expression in conjunctival epithelial cells: Linking mechanical stress to ocular inflammation

PURPOSE

Mechanical stress on the ocular surface, such as from eye-rubbing, has been reported to lead to inflammation and various ocular conditions. We hypothesized that the mechanosensitive Piezo1 channel in the conjunctival epithelium contributes to the inflammatory response at the ocular surface after receiving mechanical stimuli.

METHODS

Human conjunctival epithelial cells (HConjECs) were treated with Yoda1, a Piezo1-specific agonist, and various allergens to measure cytokine expression levels using qRT-PCR. Piezo1 activation-induced intracellular signaling pathways were also investigated by Western blot. Mechanical stretching experiments were conducted to simulate Piezo1 activation in HConjECs. Specificity of Piezo1 was confirmed by PIEZO1 knockdown and GsMTx4. In in vivo studies, using immunohistochemistry, rats were administered Yoda1 eye drops to examine the inflammatory response in the conjunctiva and Piezo1-induced signaling activation.

RESULTS

HConjECs expressed functional Piezo1 channel which was the dominant mechanoreceptor among putative channels and whose activation significantly increased IL-6 and IL-8 expression through the p38 MAPK-CREB pathway. Piezo1-induced [Ca2+]i elevation was crucial for the production of IL-6. The Yoda1-induced inflammatory responses were blocked by PIEZO1 knockdown. Mechanical stretching mimicked these effects, which were suppressed by GsMTx4. In vivo, Yoda1 administration led to increased phospho-p38 MAPK, phospho-CREB, and IL-6 in the rat conjunctival epithelium, with significant neutrophil infiltration.

CONCLUSION

Mechanical stress-induced Piezo1 channel activation in conjunctival epithelial cells can cause ocular inflammation by upregulating pro-inflammatory cytokines via the p38 MAPK-CREB pathway and promoting neutrophil infiltration. These findings suggest that mechanical stimuli on ocular surface tissues are significant risk factors for ocular inflammation.

Corneal stromal cells from patients with keratoconus exhibit alterations in the ESCRT-dependent machinery responsible for multivesicular body formation

Previous studies have reported that exosomes produced by corneal stromal cells from keratoconus patients exhibit a molecular content distinct from those produced by cells from healthy donors. This study investigates differences in the expression of ESCRT components, regarded as the most critical mechanism in exosome biogenesis. The study included analysis of transcription levels of system-encoding genes using qRT-PCR reactions, as well as semiquantitative protein determination through immunocytochemistry. Of the 34 molecules analyzed, mRNA downregulation was observed in 8 in pathological cells. In keratoconus, genes encoding STAM2 from the ESCRT-0 complex and VPS37A, VPS37C, VPS37D and UBAP1 from the ESCRT-I complex were found to be underexpressed, although VPS37D could not be confirmed at the protein level. Additionally, two other expression alterations affected the ESCRT-III complex, involving the core protein CHMP4C and the regulatory protein CHMP1B. Finally, deregulation of the ubiquitin-specific peptidase UBPY was observed. Most changes identified in this study affected specific isoforms, which could suggest functional diversification and differences in cargo recognition in the context of pathology. Altogether, these findings suggest that the previously reported alteration in the molecular content of exosomes produced by stromal cells in keratoconus may be, at least partially, due to disruptions in the exosome synthesis machinery.

Pediatric keratoconus

Keratoconus is a common pediatric corneal disease, leading to vision impairment and amblyopia. Compared to its adult counterpart, pediatric keratoconus has an advanced presentation, rapid progression, higher incidence of complications such as corneal hydrops, and greater potential impact on the quality of life. It typically manifests during puberty and can evolve rapidly to more severe stages if left untreated. This rapid progression underscores the importance of early diagnosis through regular screening in pediatric populations and vigilant monitoring of pediatric keratoconus suspects. Concomitant ocular allergies, ocular anomalies, systemic diseases (e.g. syndromes), and poor compliance with contact lenses might impede prompt intervention and frequently postpone rehabilitation. Corneal collagen crosslinking is a crucial intervention in the management of pediatric keratoconus because it strengthens the corneal microstructure and halts the disease progression. When conservative measures fail, keratoplasty remains a viable option with generally favorable outcomes, though with unique challenges in post-operative care, including concerns related to sutures, long-term graft survival and need for repeated examinations under anesthesia. A multidisciplinary approach involving ophthalmologists, optometrists, pediatricians, and other healthcare professionals, focusing on early diagnosis and timely intervention, is essential for the comprehensive management of pediatric keratoconus and to mitigate its impact on children's lives.

Atopic disease and astigmatism: a population-based study

OBJECTIVES

To assess the relationship between atopic disease and astigmatism in adolescence and young adulthood.

METHODS

In this population-based cross-sectional study 897,811 medical records of Israeli adolescents and young adults without keratoconus were reviewed. The prevalence of low-to-moderate (3.00 > D ≥ 0.75) and high ( ≥ 3.00 D) astigmatism were calculated in cases with and without atopic disease, including ocular atopic disease (OAD), asthma, allergic rhinitis, atopic dermatitis, angioedema/urticaria, and history of anaphylaxis. Relationships were analysed using multinominal logistic regression, with adjustments for relevant sociodemographic factors.

RESULTS

A total of 897,811 adolescents were included in the analysis (mean age 17.2 ± 0.8 years, 57.8% men). OAD was found in 4702 individuals, with a prevalence of 0.5%. Adolescents with OAD demonstrated a gradual increase in odds ratio (OR) for low-to-moderate and for high astigmatism (OR 1.16, 95% CI 1.07-1.27 and OR 2.10, 95% CI 1.63-2.70, respectively). This group also showed increased OR for with-the-rule astigmatism (OR 1.34, 95% CI 1.21-1.48). Other atopic diseases were associated with more modest ORs for low-to-moderate (OR 1.09, 95% CI 1.07-1.11) and for high astigmatism (OR 1.10, 95% CI 1.02-1.19), persisting across all axis orientations. Sensitivity analysis revealed a dose-response relationship between OAD severity and astigmatism, and consistent point estimates in a group of 1331 adolescents diagnosed with OAD during military service.

CONCLUSIONS

This study establishes an association between OAD and astigmatism, highlighting the importance of effective OAD management. Further research into tailored therapeutic interventions that address both conditions concurrently is needed.

Corneal Topographic Changes Due to Pediatric Epiblepharon Surgery

Purpose

This study aimed to investigate changes in corneal morphology following pediatric lower-lid epiblepharon surgery using a topographic modeling system 5 (TMS-5®).

Patients and Methods

A randomized controlled trial compared two surgical interventions for pediatric epiblepharon: incisional (modified Hotz procedure with lid margin splitting) and nonincisional. Corneal topography analysis using the TMS-5® served as an outcome measure. The study included 89 eyes from 50 children aged 3-12 years (mean age, 7.5 ± 2.4 years) diagnosed with moderate epiblepharon. Patients were randomly assigned to the incisional (45 eyes from 25 patients) or nonincisional (44 eyes from 25 patients) groups. Parameters including surface regularity index (SRI), Standard Deviation of Corneal Power (SDP), Irregular Astigmatism Index (IAI), and corneal astigmatism (CYL) were evaluated. The positive rate of Keratoconus Screening System (Keratoconus Index [KCI] and Keratoconus Severity Index [KSI]) was assessed.

Results

The 6-month postoperative mean changes in corneal astigmatism were -0.34 ± 0.96 D (p = 0.012) and -0.21 ± 0.67 D (p = 0.22) in the incisional and nonincisional groups, respectively. Corneal astigmatism parameters significantly improved following both surgical procedures (p < 0.01). Preoperatively, 14.6% and 28.1% of patients were suspected of keratoconus using KCI and KSI, respectively, with a significantly reduced postoperative suspicion positivity rate (p < 0.01).

Conclusion

Corneal astigmatism significantly improved in the incisional group. Both surgical methods improved the postoperative corneal surface smoothness, corneal refractive power variability, and irregular astigmatism. Patients with epiblepharon were occasionally suspected of keratoconus when assessed with TMS, with a higher frequency indicated by KSI.

Evaluation of Ocular Parameters in Newly Diagnosed Obsessive-Compulsive Disorder Children With Eye-Rubbing Compulsion

PURPOSE

To determine the ocular structural changes in obsessive-compulsive disorder (OCD) children with eye-rubbing compulsion.

METHODS

Participants recruited at the child and adolescent psychiatry clinic were evaluated for the OCD diagnosis. All patients underwent imaging with Scheimpflug corneal topography (Sirius, CSO, Italy), Tomey EM-4000 specular microscopy (Nagoya, Japan), and Lenstar LS 900 (Haag-Streit AG, Switzerland) optical biometry.

RESULTS

Both naive OCD and healthy control groups consisted of 40 patients. Mean cylindric diopter, coma, and trefoil values were significantly higher in the right eyes of OCD children. (P = .043, .024, and .028, respectively). Besides, lens thickness, total ocular aberrations, and high ocular aberrations (P = .014, .040; .027, .038; and.020, .013, in right and left eyes, respectively) were bilaterally higher in OCD children.

CONCLUSION

Eye rubbing and mechanical trauma were proposed as risk factors for ocular structural changes. Early evaluation of corneal topographic parameters such as CylD, coma, and trefoil aberrations in newly diagnosed OCD children might assist in preventing future corneal ectatic diseases.

Allergic Rhinitis and Keratoconus: A Systematic Review and Meta-Analysis

BACKGROUND

The relationship between keratoconus and various allergic diseases has been a subject of controversy.

OBJECTIVE

In the present study, a systematic review and meta-analysis was conducted to investigate the association between allergic rhinitis (AR) and keratoconus.

METHODS

Relevant and eligible studies from PubMed, Web of Science, and the Cochrane Library were systematically reviewed to evaluate the association between AR and keratoconus. Observational studies that reported the number of patients with and without keratoconus, as well as the number of patients with keratoconus diagnosed with or without AR, were included. Two reviewers independently screened eligible studies and extracted data. A bivariate meta-analysis was conducted to calculate the pooled odds ratio of keratoconus in patients with versus without AR. A sensitivity analysis was performed using the adjusted odds ratio reported in the included studies to validate the findings.

RESULTS

Seven studies involving 775,574 participants were included in the meta-analysis. Among them, 29,082 patients had keratoconus. The pooled odds ratio of keratoconus in patients with AR was 1.71 (95% confidence interval [CI]: 1.36-2.15; P < .001; I2 = 96%), and the pooled adjusted odds ratio was 1.72 (95% CI: 1.23-2.40; P = .001; I2 = 97%).

CONCLUSIONS

Patients with AR have significantly higher odds of keratoconus than those without AR. Future studies are warranted to investigate the causal relationship and evaluate the cost-effectiveness of early screening, using methods such as corneal topography, and referral for keratoconus in patients with AR.

The Effect of Eyelid Laxity on Corneal Mapping and Corneal Topography

PURPOSE

To evaluate the effect of eyelid laxity on the structure of the cornea.

METHODS

This was a retrospective study performed in one institution. Patients with and without upper and lower eyelid laxity, which were determined using the snap-back test (SBT) and the upper eyelid distraction test (LDT), were evaluated for corneal structural changes with Scheimpflug imaging corneal tomography for the keratometric readings, and cor-neal spectral domain optical coherence tomography for the epithelial thickness (ET) measurements. The ET values were obtained using the statistics report for the superior quadrant (SET), the inferior quadrant (IET) within the 2- to 7-mm region, and central thickness (CET) within the 2-mm region. The minimum corneal thickness values within the central 5-mm region (MinCT) were also included in the study. Keratometric readings (in diopters), horizontal white-to-white (HWTW) measurements, pachymetry, and ET measurements were assessed along with the presence or absence of eyelid laxity.

RESULTS

A total of 170 eyes from 85 patients were evaluated (50.6% with eyelid laxity, and 49.4% without eyelid laxity). There was no significant difference between the mean keratometric readings, HWTW, and the mean IET and CET values (P > .05); however, the difference was significant for the MinCT and SET (P < .05). A statistically significant negative correlation was found between the SET values and age, LDT, and SBT measurements (P < .05).

CONCLUSIONS

A strong association was found between decreased SET and MinCT values and eyelid laxity. The possible reason for these decreases may be inflammation, which plays a role in the pathophysiology of eyelid laxity. [J Refract Surg. 2024;40(11):e783-e791.].

Inflammatory and genomic interactions within keratoconus susceptible patients: a nationwide registered case-control study

PURPOSE

This study aimed to investigate the association between variants in the interleukin (IL)-1 gene cluster and susceptibility to keratoconus (KC) in an Iranian population.

METHODS

In the case group, there were 188 KC patients diagnosed by clinical findings and corneal tomography. The control group included all 205 healthy controls with no personal or family history of eye-related, metabolic, or immune system-related disease. Using the standard salting out extraction procedure, genomic DNA was isolated from peripheral blood leukocytes. The genotypes were determined by applying agarose gel electrophoresis for the IL-1RN 86 bp VNTR and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for rs16944 and rs1143634.

RESULTS

The results showed a significant association between the IL-1β rs1143634 (rs1143634 T allele, P = 0.008) and IL-1RN 86 bp VNTR polymorphisms (LL and LS genotype, P = 0.048 and 0.012 respectively) and susceptibility to KC in the Iranian population. The genotype distributions of rs1143634 (P = 0.004) and rs2234663 (P = 0.042) significantly differed between case and control groups, with certain genotypes demonstrating a protective effect against KC. Logistic regression analysis revealed a protective effect of the IL-1RN L allele [odds ratio (OR) = 0.367, 95% confidence interval (CI): 0.240-0.562; P = 0.000] and certain haplotypes (OR = 0.628, 95% CI: 0.447-0.884; P = 0.007) against KC. However, no significant association was found for the IL-1β rs16944 polymorphism.

CONCLUSION

This study provides evidence for an association between variants in the IL-1 gene cluster and susceptibility to KC in an Iranian population. Further research on larger and more diverse populations is warranted to validate these findings and explore the underlying mechanisms involved.

A pilot study on Langerhans cells in keratoconus patients by in vivo confocal microscopy before and after corneal cross-linking and correlation with eye rubbing

PURPOSE

The aim of this study was to investigate the corneal microstructure and Langerhans cells using in vivo confocal microscopy in keratoconus patients before and after cross-linking, and to correlate the morphologic findings with clinical and patient-reported outcomes, including eye rubbing (ER) behavior.

METHODS

Patients with progressive keratoconus undergoing iontophoresis-assisted epithelium-on cross-linking (I-CXL) were consecutively enrolled. In vivo confocal microscopy was performed before and 6 months after treatment. Patients were asked to quantify their ER behavior on a Visual Analogue Scale (VAS) and completed the Keratoconus Outcomes Research Questionnaire and the Ocular Surface Disease Index questionnaires at the same time points. Visual acuity, tear osmolarity, topography, aberrometry, and pachymetry of both eyes were assessed.

RESULTS

Thirteen patients were included in this pilot study. Preoperatively, the mean Langerhans cells density was 35,615 cells per mm2, and the median morphology was 3. The mean ER VAS before treatment was 7,077 out of 10. The ER VAS showed significant positive correlations with both Langerhans cells density and morphology of the study eye. After treatment, a statistically significant reduction in ER VAS and in Langerhans cells variables was observed. The mean sub-basal plexus nerve density was comparable to pre-operative values 6 months after I-CXL.

CONCLUSIONS

Based on this preliminary evidence, the presence of high density of mature Langerhans cells in the central cornea of keratoconus patients and its correlation with eye rubbing support the role of inflammation in keratoconus. The reduction in these markers after treatment may suggest a potential of CXL in moderating immune-related inflammation and eye rubbing in the medium term.

Immediate sequential changes in the tear film lipid layer following eyelid massage in dry eye syndrome: A comparative control study

Background/Purpose

Meibomian glands are sebaceous glands that release meibum onto the ocular surface; enhancing the quality and quantity of meibum secretions has been proven to improve signs and symptoms of evaporative dry eye (EDE) and meibomian gland dysfunction (MGD). This study aimed to evaluate and compare the efficacy of a heated eye mask (HEM) and eyelid massage device EyePeace (EP) in alleviating signs and symptoms of evaporative dry eye.

Methods

Forty dry eye participants were recruited in a prospective, contralateral-eye trial study. After undergoing 10 min of HEM therapy, eyelid massage therapy was applied to one eye by the device. The efficiency was assessed at four time points: baseline (0 min), 5 min (5 min), 15 min (15 min), and 30 min (30 min). Non-invasive breakup time (NITBUT), redness score (RS Score), tear meniscus height (TMH), tear-film lipid layer (TFLL), endothelial cell count (ECC), meibomian gland expressibility (MGEx), meibomian gland quality (MGQ), conjunctivocorneal staining (CS), ocular surface temperature (OST), best corrected visual acuity (BCVA), intraocular pressure (IOP), central corneal thickness (CCT) flat-axis keratometry value (K1), and steep-axis keratometry value (K2), were examined.

Results

Baseline clinical measurements did not have statistically significant differences between the groups (all p > 0.05). After 30 min, a comparison was made between the HEM group and EP + HEM group, revealing significant changes only in the primary outcomes, TFLL (2.18 ± 0.45 versus 2.40 ± 0.50; p < 0.05), and MGEx grades (0.68 ± 0.53 versus 0.98 ± 0.70; p < 0.05). Improvements in NITBUT and TMH were sustained until 5 min and 15 min after using EP + HEM. No significant changes were observed in RS Score, MGQ, OST, CFS, BCVA, IOP, ECC, K1, K2, and CCT (all p > 0.05) at all test time points.

Conclusion

The application of a heated eye mask followed by a gentle massage using EyePeace on the eyelids can have a sustained improvement in the tear film lipid layer and meibomian gland expressivity score but not clinically significant, and does not pose any significant immediate impact on the cornea.Trial registration number: NCT06158997.

Causal Association Between Atopic Dermatitis and Keratoconus: A Mendelian Randomization Study

Purpose

Although many studies have indicated that atopic dermatitis (AD) could contribute to the risk of keratoconus (KC), the causality between AD and KC remains controversial. This study aimed to explore the potential causal associations between AD and KC.

Methods

Instrumental variables for both exposures and outcomes were obtained from large-scale genome-wide association study summary statistics from previous meta-analyses. Mendelian randomization (MR) was applied to infer causal associations between AD and KC. Our main analyses were conducted by inverse-variance weighted (IVW) method multiplicative random effect model, complemented with additional five models and sensitivity analyses. Reverse MR analysis was applied to determine the direction of the causal association between AD and KC.

Results

Both IVW and weighted median methods revealed a causal effect of AD on KC (IVW odds ratio [OR], 1.475; P = 4.16 × 10-4; weighted median OR, 1.351; P = 7.65 × 10-3). The weighted mode, simple mode, and MR Egger methods demonstrated consistent direction of causality. Evidence from all sensitivity analyses further supported these associations. Reverse MR analyses did not suggest causal effects of KC on AD.

Conclusions

This study supported a significant causal effect of AD on KC, and reverse MR analysis proved that the causal association was unilateral.

Translational Relevance

This study provides valid evidence that regular ophthalmic examinations are recommended for patients with AD to detect and prevent KC at an early stage.

Crosslinking with UV-A and riboflavin in progressive keratoconus: From laboratory to clinical practice - Developments over 25 years

Changes in the biomechanical and biochemical properties of the human cornea play an important role in the pathogenesis of ectatic diseases. A number of conditions in primarily acquired (keratoconus or pellucid marginal degeneration) or secondarily induced (iatrogenic keratectasia after refractive laser surgeries) ectatic disorders lead to decreased biomechanical stability. Corneal collagen cross-linking (CXL) represents a technique to slow or even halt the progression of ectatic pathologies. In this procedure, riboflavin is applied in combination with ultraviolet A radiation. This interaction induces the production of reactive oxygen species, which leads to the formation of additional covalent bonds between collagen molecules and subsequent biomechanical corneal strengthening. This procedure is so far the only method that partially interferes etiopathogenetically in the treatment of ectatic diseases that slows or stops the process of corneal destabilization, otherwise leading to the need for corneal transplantation. Besides, CXL process increases markedly resistance of collagenous matrix against digesting enzymes supporting its use in the treatment of corneal ulcers. Since the discovery of this therapeutic procedure and the first laboratory experiments, which confirmed the validity of this method, and the first clinical studies that proved the effectiveness and safety of the technique, it has been spread and adopted worldwide, even with further modifications. Making use of the Bunsen-Roscoe photochemical law it was possible to shorten the duration of this procedure in accelerated CXL and thus improve the clinical workflow and patient compliance while maintaining the efficacy and safety of the procedure. The indication spectrum of CXL can be further expanded by combining it with other vision-enhancing procedures such as individualized topographically-guided excimer ablation. Complementing both techniques will allow a patient with a biomechanically stable cornea to regularize it and improve visual acuity without the need for tissue transplantation, leading to a long-term improvement in quality of life.

Systemic and Ocular Associations of Keratoconus

Introduction

Keratoconus (KC) is the most prevalent corneal ectasia in the world and its pathogenesis is influenced by both ocular and systemic factors. This review explores the multifaceted associations between keratoconus and systemic health conditions, ocular characteristics, and various other environmental/exogenous factors, aiming to illuminate how these relationships influence the pathophysiology of the disease.

Areas Covered

This review will summarize the fundamental attributes of KC, review and discuss the systemic and ocular association of KC including molecular biomarkers, and provide an organized overview of the parallel alterations occurring within various biological pathways in KC.

Expert Opinion

Despite the substantial volume of research on keratoconus, the precise etiology of the disease remains elusive. Further studies are necessary to deepen our understanding of this intricate disorder and improve its management.

What's the situation with ocular inflammation? A cross-seasonal investigation of proteomic changes in ocular allergy sufferers' tears in Victoria, Australia

Background

Ocular allergy (OA) is a localized subset of allergy characterized by ocular surface itchiness, redness and inflammation. Inflammation and eye-rubbing, due to allergy-associated itch, are common in OA sufferers and may trigger changes to the ocular surface biochemistry. The primary aim of this study is to assess the differences in the human tear proteome between OA sufferers and Healthy Controls (HCs) across peak allergy season and off-peak season in Victoria, Australia.

Methods

19 participants (14 OA sufferers, 5 HCs) aged 18-45 were recruited for this study. Participants were grouped based on allergy symptom assessment questionnaire scoring. Proteins were extracted from human tear samples and were run on an Orbitrap Mass Spectrometer. Peaks were matched to a DIA library. Data was analyzed using the software MaxQuant, Perseus and IBM SPSS.

Results

1267 proteins were identified in tear samples of OA sufferers and HCs. 23 proteins were differentially expressed between peak allergy season OA suffers vs HCs, and 21 were differentially expressed in off-peak season. Decreased proteins in OA sufferers related to cell structure regulation, inflammatory regulation and antimicrobial regulation. In both seasons, OA sufferers were shown to have increased expression of proteins relating to inflammation, immune responses and cellular development.

Conclusion

Tear protein identification showed dysregulation of proteins involved in inflammation, immunity and cellular structures. Proteins relating to cellular structure may suggest a possible link between OA-associated itch and the subsequent ocular surface damage via eye-rubbing, while inflammatory and immune protein changes highlight potential diagnostic and therapeutic biomarkers of OA.

Keratoconus Frequency and Associated Risk Factors Among Patients Younger Than 18 Years With Significant Refractive Errors

INTRODUCTION

Keratoconus is an ectatic corneal disorder that causes low vision secondary to high myopia, irregular astigmatism, and loss of corneal transparency. In children, the disease behaves aggressively, progresses rapidly, is diagnosed at advanced stages, and presents an increased risk for corneal transplantation; however, only few studies in children have been conducted.

PURPOSE

The aims of this study were to determine the frequency of keratoconus in patients younger than 18 years who underwent the Pentacam study because of high myopia or high astigmatism in the oblique axis, analyze topographic criteria and classify them into severity groups, and identify associated risk factors.

METHODS

This was a retrospective observational cross-sectional study in which Pentacam examinations were analyzed. Frequency of keratoconus was determined and patients were classified according to visual acuity and severity scales. Medical records were reviewed to identify associated risk factors.

RESULTS

Four hundred twenty-six patients younger than 18 years were included, 40 (9.4%) had keratoconus according to Pentacam criteria. The mean age at diagnosis was 14.9 years, with male predilection (75%). Atopy was the only statistically significant risk factor, present in 85%. Family history was present in 7.5%. There were no differences in the distribution in groups according to visual acuity or Amsler-Krumeich scale. Most frequent ABCD classification was A2 (35.6%), B4 (47.9%), and C0 (35.6%), posterior curvature radius being a significant severity criterion.

CONCLUSIONS

The study found that frequency of keratoconus in children is higher than previously reported. Atopy has a clear and possible causal association. Early detection should be sought to reduce the risk of progression. Pentacam is a fundamental tool for early diagnosis using simple criteria.

The Plight of the Metabolite: Oxidative Stress and Tear Film Destabilisation Evident in Ocular Allergy Sufferers across Seasons in Victoria, Australia

Ocular allergy (OA) is characterised by ocular surface itchiness, redness, and inflammation in response to allergen exposure. The primary aim of this study was to assess differences in the human tear metabolome and lipidome between OA and healthy controls (HCs) across peak allergy (spring-summer) and off-peak (autumn-winter) seasons in Victoria, Australia. A total of 19 participants (14 OA, 5 HCs) aged 18-45 were recruited and grouped by allergy questionnaire score. Metabolites and lipids from tear samples were analysed using mass spectrometry. Data were analysed using TraceFinder and Metaboanalyst. Metabolomics analysis showed 12 differentially expressed (DE) metabolites between those with OA and the HCs during the peak allergy season, and 24 DE metabolites were found in the off-peak season. The expression of niacinamide was upregulated in OA sufferers vs. HCs across both seasons (p ≤ 0.05). A total of 6 DE lipids were DE between those with OA and the HCs during the peak season, and 24 were DE in the off-peak season. Dysregulated metabolites affected oxidative stress, inflammation, and homeostasis across seasons, suggesting a link between OA-associated itch and ocular surface damage via eye rubbing. Tear lipidome changes were minimal between but suggested tear film destabilisation and thinning. Such metabolipodome findings may pave new and exciting ways for effective diagnostics and therapeutics for OA sufferers in the future.

Evaluation of Keratoconus Disease with Tear Cytokine and Chemokine Levels Before and After Corneal Cross-Linking Treatment

OBJECTIVES

To compare tear cytokine and chemokine levels of keratoconus (KC) patients with controls to perceive etiology distinctly and to clarify the molecular changes after cross-linking (CXL).

METHODS

Tear samples were gathered from 34 participants in this prospective study. Participants underwent anterior and posterior segment examinations with slit-lamp biomicroscopy. Patients were assessed by corneal topography before and 3 months after CXL. Flat (K1), steep (K2), and average keratometry (Kmean), cylinder (CYL), and central corneal thickness (CCT) values were evaluated. After 3 months from CXL, samples were re-collected, and comparisons were made with preoperative values.

RESULTS

Levels of IFN-gamma, IL-8, IL-12, IL-17, TNF-α, IL-4 and IL-13 were detected higher in KC patients (p= 0.008, p= 0.047, p= 0.001, p= 0.001, p= 0.001, p= 0.001, p= 0.027, respectively). After CXL IL-4, IL-5, IL-6, IL-7, IL-8, TNF-α levels showed significant decrease (p= 0.005, p= 0.045, p= 0.010, p= 0.022, p= 0.001, p=0.002, respectively). As for the topographic measurements, postoperative CCT values were increased whereas Kmean reduced after CXL (p < 0.001, p = 0.015, respectively). (p= 0.001, p= 0.027, respectively).

CONCLUSION

Our findings imply that inflammation plays a key role in the development of KC and that this link is influenced by CXL therapy.

Vision-Related Quality of Life in Patients With Keratoconus With Enantiomorphic Topography After Bilateral Intrastromal Corneal Ring Implantation

PURPOSE

The aim of this study was to evaluate the quality of life (QOL) after intrastromal ring implantation in patients with keratoconus.

METHODS

This was a prospective, randomized, interventional study. We analyzed 60 eyes of 30 patients aged 16 to 35 years who were treated at the Department of Ophthalmology and Visual Sciences, Federal University of São Paulo, Brazil. The Visual Function Questionnaire (VFQ-25) and Short-Form 36 Questionnaire (SF-36) were used before intracorneal ring segment (ICRS) implantation and at 3, 6, and 12 months after surgical intervention.

RESULTS

The mean corrected visual acuity improved from a mean of 0.32 ± 0.2 logMAR (20/40) preoperatively to 0.14 ± 0.11 logMAR (20/25) 1 year postoperatively ( P = 0.001). The mean spherical equivalent varied from -7.24 ± 3.47 preoperatively to -4.13 ± 2.41 postoperatively ( P = 0.001). The overall composite score for the VFQ-25 improved from 55.1 preoperatively to 80.4 1 postoperatively ( P = 0.001). SF-36 showed statistically significant improvement in all scores. When analyzing the correlation between visual acuity and VFQ composite score, a significant correlation was found between both variables (Pearson correlation coefficient of -0.40, P = 0.001).

CONCLUSIONS

Patients with keratoconus had increased psychological symptoms and lower QOL and improved psychosocial criteria associated with corneal remodeling and decreased visual dependence on others after surgery. Extrapolation of these data to the whole keratoconus population suggests that ICRS implantation could improve QOL in these patients.

Atopic Disease as a Risk Factor for Recurrent Herpetic Keratitis

Recurrent herpetic keratitis is a leading cause of blindness worldwide. In this population-based cross-sectional study, the medical records of Israeli adolescents and young adults who underwent systematic preconscription evaluation for mandatory military service were reviewed. The prevalence of atopic conjunctival disease was evaluated in cases with and without documented recurrent herpetic keratitis. The association was tested using uni- and multivariant analyses. Overall, 940,892 adolescents and young adults were included. The mean age was 17.57 ± 1.50 years (range 16-20 years), and 40.70% of participants were female. Recurrent herpetic keratitis was documented in 160 cases, with a prevalence of 0.017% in this age group. Compared to the general population, patients with recurrent herpetic keratitis were significantly more likely to be males (p = 0.003) with a concomitant diagnosis of atopic conjunctival disease (p < 0.0001). Patients with atopic conjunctival disease were 10.60-fold more likely to experience recurrent herpetic keratitis (95% confidence interval (CI): 6.76-16.64, p < 0.0001). Upon multivariate analysis, the results remained significant (p < 0.001). Cases of severe atopic conjunctival disease were more prone to recurrent HSV keratitis compared to mild cases (p < 0.001). These findings suggest that the timely appropriate treatment of atopic conjunctival disease may help reduce the frequency and severity of recurrent HSV keratitis and its complications.

Corneal topometric indices and proclivity toward corneal ectasia in vernal keratoconjunctivitis

PURPOSE

To investigate changes in topometric corneal indices and proclivity toward corneal ectasia, as well as keratometric indices and anterior chamber dimensions in palpebral vernal keratoconjunctivitis (VKC).

METHODS

This study included 80 patients with clinically established symptoms of grade 0 or grade 1 palpebral VKC (group 1) and 66 healthy participants (group 2). After a comprehensive ophthalmic examination including best-corrected visual acuity, intraocular pressure measurements and slit-lamp biomicroscopy, pachymetric indices and anterior chamber dimensions were measured using the Pentacam HR rotating Scheimpflug device. Topometric indices, which are particularly useful for determining proclivity toward corneal ectasia, were extracted from a topometric map.

RESULTS

In groups 1 and 2, the mean ages were 13.11±5.22 and 16.45±5.09 years, respectively. The mean age at disease onset in group 1 was 10.09±5.03 years, and the mean disease duration was 36.23±8.43 months. Group 1 had significantly higher mean topometric indices than group 2, particularly the index of surface variance (P=0.001), index of vertical asymmetry (P=0.007), center keratoconus index (P=0.050), and Belin/Ambrosio enhanced ectasia total deviation value (P=0.032). Mean posterior corneal astigmatism differed significantly between groups 1 and 2 (P=0.003).

CONCLUSIONS

Significantly higher mean topometric indices in VKC indicate a proclivity for corneal ectasia, which could be attributed to general changes in the corneal ultrastructure caused by persistent itching-induced eye rubbing.

Deep Learning-Based Automatic Diagnosis of Keratoconus with Corneal Endothelium Image

INTRODUCTION

The primary objective of this study was to develop an end-to-end model that can accurately identify corneal endothelial cells and diagnose keratoconus based on corneal endothelial images acquired from a non-contact specular microscope.

METHODS

This was a retrospective case-control study performed at the Refractive Surgery Center of West China Hospital. A total of 403 keratoconus eyes (221 patients) and 370 myopic eyes (185 normal controls) were consecutively recruited from January 2021 to September 2022. Specular microscopy was used to image and measure the morphometric parameters of the corneal endothelial cells. A Fully Convolutional Network model with a ResNet50 (FCN_ResNet50) was established to perform the endothelial segmentation. The images were then classified using an ensemble machine learning system consisting of four pre-trained deep learning networks: DenseNet121, ResNet50, Inception_v3, and MobileNet_v2. The performance of the models was evaluated based on different metrics, such as accuracy, intersection over union (IoU), and mean IoU.

RESULTS

We established a fully end-to-end deep-learning model for the segmentation of endothelial and diagnosis of keratoconus. For endothelial segmentation, the accuracy of the FCN_ResNet50 model achieved near 90% with mean IoU converging to about 80%. The ensemble machine learning system can achieve over 92% accuracy, and > 98% area under curve (AUC) values to diagnose keratoconus with endothelial cell images. In addition, we constructed a diagnostic model based on deep-learning features and developed an associated nomogram which manifested an excellent performance for diagnosis and monitoring the progression of keratoconus.

CONCLUSIONS

Our research developed an end-to-end model to automatically identify and assess corneal endothelial morphological changes in keratoconus eyes. Moreover, we also constructed a novel nomogram, which can provide valuable information for the diagnosis, monitoring, and management of the disease.

The cellular responses of corneal fibroblasts to cyclic stretching loads

Mechanical signaling plays a crucial role in maintaining extracellular matrix (ECM) homeostasis in various structures. In this study, we investigated the responses of corneal fibroblasts to cyclic stretching loads using an in vitro cell culture system. Bovine corneal fibroblasts were cultured and subjected to equibiaxial cyclic strain of 15% for 72 h at a frequency of 0.25 Hz, with bovine skin fibroblasts used as a comparison. We explored various cellular behaviors, including morphological changes, cell proliferation, and metabolism in response to mechanical stretching loads. The expression of genes, protein secretion, and enzymatic activity for several major metalloproteinases was also determined through Q-PCR, Western blot, and gel zymography. Additionally, we investigated the involvement of mitogen-activated protein kinases (MAPKs) signaling pathways in the corneal fibroblasts when subjected to mechanical stimuli. Our findings revealed that, compared to skin fibroblasts, corneal fibroblasts were reluctant to morphological changes in response to a prolonged (72 h) and high-amplitude (15% of strain) cyclic stretching load. However, cyclic stretching loads stimulated the upregulation of MMP-2 expression in corneal fibroblasts via the MAPK signaling pathways involving extracellular signal-regulated kinase and p38. Together with a lack of upregulation in type I collagen expression, our results indicate the induction of the ECM degradation process in corneal fibroblasts in response to cyclic stretching. These findings emphasize the mechanoresponsive nature of corneal fibroblasts and shed light on the potential impact of intense mechanical stress on the cornea in both normal and pathological conditions such as keratoconus, providing valuable insights for understanding corneal mechanobiology.

The pre-Descemet's layer (Dua's layer, also known as the Dua-Fine layer and the pre-posterior limiting lamina layer): Discovery, characterisation, clinical and surgical applications, and the controversy

The pre-Descemet's layer/Dua's layer, also termed the Dua-Fine layer and the pre-posterior limiting lamina layer, lies anterior to the Descemet's membrane in the cornea, is 10 μm (range 6-16) thick, made predominantly of type I and some type VI collagen with abundant elastin, more than any other layer of the cornea. It has high tensile strength (bursting pressure up to 700 mm of Hg), is impervious to air and almost acellular. At the periphery it demonstrates fenestrations and ramifies to become the core of the trabecular meshwork, with implications for intraocular pressure and glaucoma. It has been demonstrated in some species of animals. The layer has assumed considerable importance in anterior and posterior lamellar corneal transplant surgery by improving our understanding of the behaviour of corneal tissue during these procedures, improved techniques and made the surgery safer with better outcomes. It has led to the innovation of new surgical procedures namely, pre-Descemet's endothelial keratoplasty, suture management of acute hydrops, DALK-triple and Fogla's mini DALK. The discovery and knowledge of the layer has introduced paradigm shifts in our age old concepts of Descemet's membrane detachment, acute corneal hydrops in keratoconus and Descemetoceles, with impact on management approaches. It has been shown to contribute to the pathology and clinical signs observed in corneal infections and some corneal dystrophies. Early evidence suggests that it may have a role in the pathogenesis of keratoconus in relation to its elastin content. Its contribution to corneal biomechanics and glaucoma are subjects of current investigations.

A high body mass index strengthens the association between the time of eye rubbing and keratoconus in a Chinese population: a case control study

BACKGROUND

Although body mass index (BMI) and eye rubbing are linked to an increased risk of keratoconus (KC), the interactive effect of eye rubbing and BMI on KC is largely unknown. This study aimed to evaluate the independent and interactive effects of BMI and eye rubbing on KC and to further explore the role of environmental factors on the occurrence of KC.

METHODS

A total of 621 individuals (291 KC patients and 330 control individuals) were enrolled in this hospital‑based study on KC patients in Central China after individuals missing BMI data were excluded. BMI was calculated as weight in kilograms divided by the square of height in meters. Data on eye rubbing was recorded through face-to-face interviews. Generalized linear regression models were used to analyze associations among BMI, eye rubbing and KC. Interaction plots were used to describe the interactive effects of BMI and eye rubbing on KC.

RESULTS

The β and 95% confidence interval (CI) were 0.923 (0.112, 1.733) (p = 0.026) and 3.356 (1.953, 4.759) (p < 0.001), respectively, for the effect of each 10 kg/m2 increase in BMI and each 1 min increase in eye rubbing on KC. The interaction of BMI and eye rubbing were positively correlated with KC (p < 0.001).

CONCLUSION

These findings suggested that a high BMI aggravated the negative effect of eye rubbing on KC, implying that individuals with a high BMI may be more susceptible to exposure to eye rubbing, which is related to an increased risk of KC.

Keratoconus International Consortium (KIC)- advancing keratoconus research

CLINICAL RELEVANCE

The Keratoconus International Consortium (KIC) will allow better understanding of keratoconus.

BACKGROUND

Keratoconus is a disorder characterised by corneal elevation and thinning, leading to reduced vision. The current gaps in understanding of this disease will be discussed and the need for a multi-pronged and multi-centre engagement to enhance our understanding of keratoconus will be highlighted.

DESIGN

KIC has been established to address the gaps in our understanding of keratoconus with the aim of collecting baseline as well as longitudinal data on several fields.

PARTICIPANTS

Keratoconus and control (no corneal condition) subjects from different sites globally will be recruited in the study.

METHODS

KIC collects data using an online, secure database, which enables standardised data collection at member sites. Data fields collected include medical history, clinical features, quality of life and economic burden questionnaires and possible genetic sample collection from patients of different ethnicities across different geographical locations.

RESULTS

There are currently 40 Australian and international clinics or hospital departments who have joined the KIC. Baseline data has so far been collected on 1130 keratoconus patients and indicates a median age of 29.70 years with 61% being male. A total of 15.3% report a positive family history of keratoconus and 57.7% self-report a history of frequent eye rubbing.

CONCLUSION

The strength of this consortium is its international, collaborative design and use of a common data collection tool. Inclusion and analyses of cross-sectional and longitudinal data will help answer many questions that remain in keratoconus, including factors affecting progression and treatment outcomes.

Transforming growth factor beta receptor 2 (Tgfbr2) deficiency in keratocytes results in corneal ectasia

PURPOSE

We hypothesized that Transforming growth factor beta receptor 2 (Tgfbr2) deletion in keratocyte (Tgfbr2kera-cko), the corneal stroma cell, can result in corneal thinning and generate a potential model for Cornea Ectasia (CE).

METHODS

Corneal thickness of Tgfbr2kera-cko and Tgfbr2Ctrl was examined with Optical Coherence Tomography (OCT) at post-natal (P) days 42 and 70, respectively. Histological H&E staining, transmission electron micrograph (TEM), and immunofluorescence staining (IFS) were harnessed to examine corneal cell morphology, proliferation, differentiation, and collagen fibrils.

RESULTS

Slit-Lamp revealed that corneas were transparent in both Tgfbr2kera-cko and Tgfbr2Ctrl, however, Tgfbr2kera-cko cornea was 33.5% and 42.9% thinner as compared with those of Tgfbr2Ctrl at P42 and P70, respectively. H&E and semithin section staining with toluidine blue-O confirmed that Tgfbr2kera-cko cornea has a thinner stroma. In contrast, the epithelium in Tgfbr2kera-cko was substantially thicker. The cell proliferation marker Ki67 expression level increased ∼9% in Tgfbr2kera-cko corneal epithelium as compared with that in Tgfbr2Ctrl, however, the Krt14 and Krt12 expression pattern was not obviously changed in Tgfbr2kera-cko corneal epithelium. It was noticed that Col1a1 expression was substantially reduced in Tgfbr2kera-cko as compared with that in Tgfbr2Ctrl. TEM showed that keratocytes were unhealthy and stromal collagen fibril density was significantly reduced in Tgfbr2kera-cko as compared with that in Tgfbr2Ctrl cornea. Moreover, mechanical eye-rubbing on Tgfbr2kera-cko resulted in corneal hydrops and edema.

CONCLUSION

Tgfbr2 in keratocytes is indispensable for the corneal stroma at postnatal homeostasis. The cornea phenotype manifested in these Tgfbr2kera-cko mice resembles corneal ectasia disease in humans.

Effect of eye rubbing on corneal biomechanical properties in myopia and emmetropia

Purpose: To investigate short-term changes in corneal biomechanical properties caused by eye rubbing in myopia and emmetropia and compare the different responses between the two groups. Methods: This was a prospective observational study of 57 eyes of 57 healthy subjects aged 45 years and younger. The participants were divided into myopia and emmetropia groups. All the subjects underwent eye rubbing by the same investigator using the same technique. Biomechanical parameters were recorded using the Corvis ST device before and after 1 min of eye rubbing. One week later, all the participants underwent the test again. Statistical methods were employed to compare the differences between the data from before and after the 1 min of eye rubbing and demonstrate the different responses of the two groups. Results: After 1 min of eye rubbing, smaller SP-A1 (p < 0.001), higher deformation and deflection amplitudes (p < 0.001, p = 0.012), higher peak distances (p < 0.001), earlier A1 times (p < 0.001), faster velocities (p < 0.001), and lower maximum inverse radii (p = 0.004) were observed. According to the automatic linear modeling analysis, the refractive states (B = -5.236, p = 0.010) and biomechanically corrected intraocular pressure (bIOP) (B = 0.196, p = 0.016) had influenced a decrease in the stiffness parameter at the first applanation (SP-A1). The central corneal thickness (CCT) had decreased only in the myopia group (p = 0.039). The change of SP-A1 in amplitude was larger in the myopia group than in the emmetropia group (p < 0.001). All the parameters returned to the baseline level 1 week later. Conclusion: Eye rubbing appears to alter corneal biomechanical properties temporarily and make the cornea softer, especially for myopic young patients.

Iatrogenic Keratectasia after Refractive Surgery - Causes, Prophylaxis, Therapy

Iatrogenic keratectasia is induced thinning and protrusion of the cornea after laser refractive surgery. Known risk factors include an excessively thin postoperative residual stromal bed, a thicker flap, or preoperatively undetected evidence of preexisting subclinical keratoconus. The rate of post-refractive ectasia in eyes without identifiable preoperative risk factors is 20 per 100 000 eyes for photorefractive keratectomy, 90 per 100 000 eyes for laser in situ keratomileusis, and 11 per 100 000 eyes for small incision lenticule extraction. Traditional screening tools for preoperative risk include the ectasia risk score system and percentage of tissue alteration. More recent methods include corneal elastography and epithelial mapping, in addition to Artificial Intelligence methods for data analysis. Therapy includes contact lenses, cross-linking, implantation of intracorneal ring segments, penetrating or lamellar keratoplasty, and, in early studies, implantation of corneal lenticules.

Medium to long term follow up study of the efficacy of cessation of eye-rubbing to halt progression of keratoconus

Purpose

To study the progression of keratoconus after cessation of eye rubbing with a minimum follow up of three-years.

Design

Retrospective, monocentric, longitudinal cohort study of keratoconus patients with a minimum of 3 years follow-up.

Participants

One hundred fifty three eyes of seventy-seven consecutive patients with keratoconus were included.

Methods

Initial examination consisted of anterior and posterior segment evaluation using slit-lamp biomicroscopy. At the initial visit, patients were thoroughly informed of their pathology and instructed to stop rubbing their eyes. Eye rubbing cessation was assessed at all the follow-up visits at 6 months, 1 year, 2 years, 3 years, and yearly afterward. Corneal topography using the Pentacam® (Oculus®, Wetzlar, Germany) was used to obtain maximum and average anterior keratometry readings (Kmax and Kmean), as well as thinnest pachymetry (Pachymin, μm) in both eyes.

Main outcome measures

The main outcomes measured were maximum keratometry (Kmax), mean keratometry (Kmean), and thinnest pachymetry (Pachymin) values at various time points to assess for keratoconus progression. Keratoconus progression was defined as a significant augmentation of Kmax (>1D), Kmean (>1D), or significant diminution of Pachymin (>5%) throughout the total follow-up duration.

Results

One hundred fifty three eyes of seventy-seven patients (75.3% males) aged 26.4 years old, were followed for an average of 53 months. Over the course of the follow-up, there was no statistically significant variation of ∆Kmax (+0.04 ± 0.87; p = 0.34), ∆ Kmean (+0.30 ± 0.67; p = 0.27) nor ∆Pachymin (-4.36 ± 11.88; p = 0.64). Among the 26 of the 153 eyes which had at least one criterion of KC progression, 25 admitted continuing eye rubbing, or other at-risk behaviors.

Conclusion

This study suggests that a significant proportion of keratoconus patients are likely to remain stable if close monitoring and strict ARB cessation are achieved, without the need for further intervention.

Artificial intelligence-based stratification of demographic, ocular surface high-risk factors in progression of keratoconus

Purpose

The purpose of this study was to identify and analyze the clinical and ocular surface risk factors influencing the progression of keratoconus (KC) using an artificial intelligence (AI) model.

Methods

This was a prospective analysis in which 450 KC patients were included. We used the random forest (RF) classifier model from our previous study (which evaluated longitudinal changes in tomographic parameters to predict "progression" and "no progression") to classify these patients. Clinical and ocular surface risk factors were determined through a questionnaire, which included presence of eye rubbing, duration of indoor activity, usage of lubricants and immunomodulator topical medications, duration of computer use, hormonal disturbances, use of hand sanitizers, immunoglobulin E (IgE), and vitamins D and B12 from blood investigations. An AI model was then built to assess whether these risk factors were linked to the future progression versus no progression of KC. The area under the curve (AUC) and other metrics were evaluated.

Results

The tomographic AI model classified 322 eyes as progression and 128 eyes as no progression. Also, 76% of the cases that were classified as progression (from tomographic changes) were correctly predicted as progression and 67% of cases that were classified as no progression were predicted as no progression based on clinical risk factors at the first visit. IgE had the highest information gain, followed by presence of systemic allergies, vitamin D, and eye rubbing. The clinical risk factors AI model achieved an AUC of 0.812.

Conclusion

This study demonstrated the importance of using AI for risk stratification and profiling of patients based on clinical risk factors, which could impact the progression in KC eyes and help manage them better.

Unravelling the Impact of Cyclic Mechanical Stretch in Keratoconus-A Transcriptomic Profiling Study

Biomechanical and molecular stresses may contribute to the pathogenesis of keratoconus (KC). We aimed to profile the transcriptomic changes in healthy primary human corneal (HCF) and KC-derived cells (HKC) combined with TGFβ1 treatment and cyclic mechanical stretch (CMS), mimicking the pathophysiological condition in KC. HCFs (n = 4) and HKCs (n = 4) were cultured in flexible-bottom collagen-coated 6-well plates treated with 0, 5, and 10 ng/mL of TGFβ1 with or without 15% CMS (1 cycle/s, 24 h) using a computer-controlled Flexcell FX-6000T Tension system. We used stranded total RNA-Seq to profile expression changes in 48 HCF/HKC samples (100 bp PE, 70-90 million reads per sample), followed by bioinformatics analysis using an established pipeline with Partek Flow software. A multi-factor ANOVA model, including KC, TGFβ1 treatment, and CMS, was used to identify differentially expressed genes (DEGs, |fold change| ≥ 1.5, FDR ≤ 0.1, CPM ≥ 10 in ≥1 sample) in HKCs (n = 24) vs. HCFs (n = 24) and those responsive to TGFβ1 and/or CMS. PANTHER classification system and the DAVID bioinformatics resources were used to identify significantly enriched pathways (FDR ≤ 0.05). Using multi-factorial ANOVA analyses, 479 DEGs were identified in HKCs vs. HCFs including TGFβ1 treatment and CMS as cofactors. Among these DEGs, 199 KC-altered genes were responsive to TGFβ1, thirteen were responsive to CMS, and six were responsive to TGFβ1 and CMS. Pathway analyses using PANTHER and DAVID indicated the enrichment of genes involved in numerous KC-relevant functions, including but not limited to degradation of extracellular matrix, inflammatory response, apoptotic processes, WNT signaling, collagen fibril organization, and cytoskeletal structure organization. TGFβ1-responsive KC DEGs were also enriched in these. CMS-responsive KC-altered genes such as OBSCN, CLU, HDAC5, AK4, ITGA10, and F2RL1 were identified. Some KC-altered genes, such as CLU and F2RL1, were identified to be responsive to both TGFβ1 and CMS. For the first time, our multi-factorial RNA-Seq study has identified many KC-relevant genes and pathways in HKCs with TGFβ1 treatment under CMS, suggesting a potential role of TGFβ1 and biomechanical stretch in KC development.

Impact of corneal collagen cross-linking on vision-related quality of life measured with the keratoconus outcomes research questionnaire (KORQ) in patients with keratoconus

PURPOSE

To assess the impact of corneal collagen cross-linking on self-reported vision-related quality of life (VR-QoL) in keratoconus patients by means of the Keratoconus Outcomes Research Questionnaire (KORQ), a new disease-specific patient reported outcomes measures (PROMs) tool.

METHODS

Patients with progressive keratoconus undergoing corneal collagen cross-linking were consecutively enrolled. Patients completed the KORQ before and after the treatment, at 1, 3 and 6 months. Data were collected regarding the visual acuity and the topographic, aberrometric and pachymetric parameters of both eyes. Patients were also asked to quantify their eye rubbing behavior on a Visual Analogue Scale (VAS) from 0 to 10, before and 6 months after treatment. The KORQ scores were associated with the visual acuity, topographic, aberrometric and pachymetric data by means of the Spearman correlation coefficient.

RESULTS

The Activity Limitation (AL) subscale score was higher after surgery. Preoperatively, negative correlations were observed between the KORQ AL score and Best Corrected Visual Acuity (logMAR), maximum keratometry, flattest keratometry, steepest keratometry, symmetry index front and higher order aberrations (HOA) of the treatment eye. Postoperatively, we observed a shift toward the fellow eye, with stronger correlation of the KORQ scores with the fellow eye parameters. The Symptoms subscale score correlated with the aberrometric parameters of both eyes at various time points. Statistically significant correlations were observed between the change in KORQ scores and the change in aberrometric parameters. A statistically significant reduction in the eye rubbing behavior was detected (p < 0,0001).

CONCLUSIONS

These results suggest that the corneal cross-linking treatment is effective both in improving the subjective perception of the disease by the patient and in stabilizing the objective indicators of disease progression. Keratometric, aberrometric and visual acuity values showed a significant impact on self-reported VR-QoL. Corneal cross-linking, by halting the worsening of these parameters, may bear a beneficial effect on VR-QoL.

The association between keratoconus and allergic eye diseases: A systematic review and meta-analysis

BACKGROUND

To investigate the association between keratoconus (KC) and allergic eye diseases, eye rubbing, and atopy.

METHODS

PubMed, Web of Science, Scopus, and Cochrane databases were searched for studies investigating eye allergy, atopy, and eye rubbing as risk factors for KC up to April 2021. Two authors independently screened all titles and abstracts against the predefined inclusion and exclusion criteria. The study analysed the prevalence of KC and its risk factors, including eye rubbing, family history of KC, atopy, and allergic eye diseases. The National Institutes of Health Study Quality Assessment Tool was used. Pooled data are presented as odds ratios (OR) and 95% confidence intervals (CI). The analysis was conducted using RevMan version 5.4 software.

RESULTS

The initial search yielded 573 articles. After screening, 21 studies were identified for qualitative analysis and 15 for quantitative synthesis. A significant association was found between KC and eye rubbing (OR = 5.22, 95% CI [2.80, 9.75], p < 0.00001), family history of KC (OR = 6.67, 95% CI [4.77, 9.33], p < 0.00001), and allergies (OR = 2.21, 95% CI [1.57, 3.13], p < 0.00001). However, no significant association was found between KC and allergic eye disease (OR = 1.82, 95% CI [0.37, 8.97], p = 0.46), atopy (OR = 1.54, 95% CI [0.58, 4.09], p = 0.39), allergic rhinitis (OR = 0.85, 95% CI [0.54, 1.33], p = 0.47), smoking (OR = 0.96, 95% CI [0.76, 1.21], p = 0.73), and asthma (OR = 1.58, 95% CI [0.99, 2.53], p = 0.05).

CONCLUSION

Significant associations were observed between KC and eye rubbing, family history, and allergy, but not with allergic eye disease, atopy, asthma, and allergic rhinitis.

[From ocular itching to eye rubbing: a review of the literature]

Ocular itching and eye rubbing are frequent complaints in an ophthalmology practice. Numerous studies address the consequences of eye rubbing, such as keratoconus. However, there are few studies concerning the pathophysiology of itching, its transmission pathways, or its interactions with eye rubbing. Through this literature review, we will address the various clinical, physiological and therapeutic aspects of this pair of symptoms with a variety of ocular consequences. We will then describe the state of the art in itching and scratching in dermatology, in order to draw a parallel between these two vicious cycles. A better understanding of the pathophysiology of ocular itching and eye rubbing, as well as new studies based on dermatological data, might allow more appropriate clinical management of our patients and their symptoms.

Assessment of meibomian gland drop-out and visibility through a new quantitative method in scleral lens wearers: A one-year follow-up study

OBJECTIVES

To validate a previously developed algorithm based on the visibility of meibomian gland images obtained with Cobra fundus camera and to assess the changes in meibomian glands in scleral lens wearers over one year of lens wear.

METHODS

Infrared meibography was obtained from the upper eyelid using the Cobra fundus camera in forty-three volunteers (34.2 ± 10.1 years). Meibographies were classified into 3 groups: Group 1 = good subjective gland visibility and gland drop-out < 1/3 of the total area; Group 2 = low visibility and gland drop-out < 1/3; and Group 3 = low visibility and gland drop-out > 1/3. Meibomian gland visibility metrics were then calculated using the developed algorithm from the pixel intensity values of meibographies. Repeatability of new metrics and their correlations with gland drop-out were assessed. Meibographies and ocular symptoms were also assessed after 1 year of scleral lens wear in 29 subjects.

RESULTS

Gland drop-out percentage was not statistically different between groups 1 and 2 (p = 0.464). Nevertheless, group 1 showed higher grey pixel intensity values than the other groups. Statistically significant correlations were found between gland visibility metrics and gland drop-out percentage. Repeatability was acceptable for all metrics, coefficient of variation achieving values between 0.52 and 3.18. While ocular symptoms decreased with scleral lens wear (p < 0.001), no statistically significant differences were found in gland drop-out percentage (p = 0.157) and gland visibility metrics (p > 0.217).

CONCLUSIONS

The proposed method can assess meibomian gland visibility in an objective and repeatable way. Scleral lens wear appears to not adversely affect meibomian gland drop-out and visibility while might improve dry eye symptoms after one year of lens wear. These preliminary results should be confirmed with a control group.

Keratoconus: A Biomechanical Perspective

PURPOSE

The relevance of corneal biomechanics and the importance of including it in the clinical assessment of corneal ectasias are being increasingly recognized. The connection between corneal ultrastructure, biomechanical properties, and optical function is exemplified by a condition like keratoconus. Biomechanical instability is seen as the underlying basis for the secondary morphological changes in the cornea. Asymmetric biomechanical weakening is believed to drive progressive corneal steepening and thinning. Biomechanical strengthening is the principle of collagen crosslinking that has been shown to effectively arrest progression of the keratoconus. Corneal biomechanics has therefore ignited the interest of researchers and clinicians alike and has given us new insights into the cause and course of the disease. This article is an overview of the extensive work published, predominantly in the last two decades, on the biomechanical aspect of keratoconus.

METHODS

Published articles on corneal biomechanics in the specific context of keratoconus were reviewed, based on an electronic search using PubMed, Elsevier, and Science Direct. The search terms used included "Corneal Biomechanics," "Mechanical properties of the cornea," "Corneal ultrastructure," "Corneal Collagen," and "Keratoconus". Articles pertaining to refractive surgery, keratoplasty, collagen crosslinking, or intrastromal rings were excluded.

RESULTS

The electronic search revealed more than 500 articles, from which 80 were chosen for this article.

CONCLUSIONS

The structural and organizational pattern of the corneal stroma determines its mechanical properties and are responsible for the maintenance of the normal shape and function of the cornea. Changes in the ultrastructure are responsible for the biomechanical instability that leads to corneal ectasia. As non-invasive methods for evaluating corneal biomechanics in vivo evolve, our ability to diagnose subclinical keratoconus will improve, allowing identification of patients at risk to develop ectasia and to allow early treatment to arrest progression of the disease.

Unraveling the mechanobiology of cornea: From bench side to the clinic

The cornea is a transparent, dome-shaped structure on the front part of the eye that serves as a major optic element and a protector from the external environment. Recent evidence shows aberrant alterations of the corneal mechano-environment in development and progression of various corneal diseases. It is, thus, critical to understand how corneal cells sense and respond to mechanical signals in physiological and pathological conditions. In this review, we summarize the corneal mechano-environment and discuss the impact of these mechanical cues on cellular functions from the bench side (in a laboratory research setting). From a clinical perspective, we comprehensively review the mechanical changes of corneal tissue in several cornea-related diseases, including keratoconus, myopia, and keratectasia, following refractive surgery. The findings from the bench side and clinic underscore the involvement of mechanical cues in corneal disorders, which may open a new avenue for development of novel therapeutic strategies by targeting corneal mechanics.

Independent and interactive effects of eye rubbing and atopy on keratoconus

Purpose

To evaluate the independent and interactive effects of eye rubbing and atopy on keratoconus (KC) in central China.

Methods

A total of 330 KC patients and 330 controls were recruited in the case-control study. Eye rubbing and history of atopy were recorded through face-to-face interviews. The association between KC and eye rubbing, atopy, interactive effects of eye rubbing and atopy were analyzed by logistic regression, and the odds ratios (OR), relative excess risk due to interaction (RERI), attributable proportion (AP), synergy (S) index, and 95% confidence intervals (95% CI) were calculated.

Results

A total of 228 patients (69.09%) had an eye rubbing history, and 53 (16.06%) had an atopy history in the KC group, which were both higher than that in the control group (p<0.001). Eye rubbing and atopy were positively associated with KC in multivariate analysis, with ORs (95% CIs) of 15.11 (10.02, 22.80) and 5.30 (2.59, 10.84), respectively. Compared to non-eye rubbing and non-atopy eyes, the risk for eye rubbing coexisted with atopy was 52.31 (12.25, 223.35). No significant associations were found between KC and multiplicative interaction (p=0.608). The RERI, AP, and S values were 32.89 (-43.35, 109.14), 0.63 (0.05, 1.21), and 2.79 (0.56, 13.96), respectively, with no significant association between additive interaction and KC. No significant associations were found between eye rubbing, atopy and the severity of KC (p>0.05).

Conclusion

Eye rubbing and atopy were separately positively associated with KC, and there was a strong impact of coexistent eye rubbing and atopy on KC in China. Further multi-center and cohort study need to be conducted to explore the role of eye rubbing and atopy in the occurrence and development of KC.

Exosomes Released by Corneal Stromal Cells Show Molecular Alterations in Keratoconus Patients and Induce Different Cellular Behavior

Exosomes have been related to various disorders, but their study in relation to ocular pathologies has been limited. In this article, we analyze exosomes produced by corneal stromal cells from healthy individuals and from patients with keratoconus. The proteomic study allowed for the identification of 14 new proteins with altered expression, related to molecules previously associated with the pathology. miRNA analysis detected 16 altered species, including miR-184, responsible for familial severe keratoconus. The prediction of its potential biological targets identified 1121 genes, including some related to this pathology. Exosomes produced by keratoconic cells induced a marked increase in the migration of stromal cells and corneal epithelium, while those produced by healthy cells had no effect on stromal cells. Both types of nanovesicles reduced the proliferation of stromal and corneal cells, but those produced by healthy cells had less effect. Exosomes produced by healthy cells had concentration-dependent effects on the transcription of genes encoding proteoglycans by keratoconus cells, with a relative normalization observed at concentrations of 240 µg/mL. These results show the alteration of stromal exosomes in keratoconus and suggest an influence on the development of the pathology, although the use of healthy exosomes could also have therapeutic potential.

Effect of corneal collagen crosslinking on viscoelastic shear properties of the cornea

The cornea is responsible for most of the refractive power in the eye and acts as a protective layer for internal contents of the eye. The cornea requires mechanical strength for maintaining its precise shape and for withstanding external and internal forces. Corneal collagen crosslinking (CXL) is a treatment option to improve corneal mechanical properties. The primary objective of this study was to characterize CXL effects on viscoelastic shear properties of the porcine cornea as a function of compressive strain. For this purpose, corneal buttons were prepared and divided into three groups: control group (n = 5), pseudo-crosslinked group (n = 5), and crosslinked group (n = 5). A rheometer was used to perform dynamics torsional shear experiments on corneal disks at different levels of compressive strain (0%-40%). Specifically, strain sweep experiments and frequency sweep tests were done in order to determine the range of linear viscoelasticity and frequency dependent shear properties, respectively. It was found that the shear properties of all samples were dependent on the shear strain magnitude, loading frequency, and compressive strain. With increasing the applied shear strain, all samples showed a nonlinear viscoelastic response. Furthermore, the shear modulus of samples increased with increasing the frequency of the applied shear strain and/or increasing the compressive strain. Finally, the CXL treatment significantly increased the shear storage and loss moduli when the compressive strain was varied from 0% to 30% (p < 0.05); larger shear moduli were observed at compressive 40% strain but the difference was not significant (P = 0.12).

The Impact of Repetitive and Prolonged Eye Rubbing on Corneal Biomechanics

PURPOSE

To evaluate the effect of simulated repetitive eye rubbing on the corneal biomechanics of porcine eyes using an ex vivo model system.

METHODS

The average rubbing force that patients with keratoconus apply to their eyelids was previously determined. Fresh porcine eyes with eyelids were either exposed to 10,500 rub cycles from a custom-built eye rubbing machine that rubbed with a similar force to knuckle human eye rubbing (n = 33) or no rubbing at all (control; n = 37). A total of 10,500 rubs are equivalent to 1 year of rubbing six times daily, five movements per rub. The corneal biomechanical properties of these eyes were then tested by measuring the elastic modulus of 5-mm strips.

RESULTS

The elastic modulus at the range of 1% and 5% of strain was 1.219 ± 0.284 and 1.218 ± 0.304 N/mm² in the eye rubbing group and the no-rub control group, respectively. Corneal stiffness was similar in both groups (P = .984).

CONCLUSIONS

The threshold to induce biomechanical changes (purely by eye rubbing) must be higher than 10,500 rubbing movements, suggesting that occasional eye rubbing may not affect corneal biomechanics in normal eyes, and likely only triggers keratoconus progression in predisposed corneas. Further in vivo studies assessing the impact eye rubbing has on inflammatory activity and the biomechanical properties of weakened corneas is warranted. [J Refract Surg. 2022;38(9):610-616.].

Acute Hydrops with Total Corneal Edema in a Very Young Child with Keratoconus: The Youngest Age Reported Case

Purpose

To present the youngest age ever reported for acute corneal hydrops with total corneal edema in a child with advanced bilateral keratoconus.

Methods

Patient presentation in ophthalmic clinic. The patient underwent various clinical tests and examinations including anterior segment optical coherence tomography (AS-OCT) and Scheimpflug corneal tomography.

Results

A 5-year-old girl presented with uncorrected distance visual acuity (UDVA) of 0.4 in the right eye and nonmeasurable UDVA associated with severe photophobia in her left eye of a 3-day duration. Intraocular pressure using the iCare tonometer was 14 and 5 mmHg in the right and left eyes, respectively. An old corneal hydrops scar and posterior subcapsular cataract (PSC) in the right eye and a total limbus to limbus corneal hydrops in the left eye were observed on slit-lamp examinations. Scheimpflug corneal tomography was possible in the right eye but, due to excessive irregularity and scaring, was not possible in the left eye. Corneal thinning and scarring were evident in the anterior segment optical coherence tomography in the right eye and very edematous cornea associated with stromal cleft and epithelial bullae in the left eye. A management plan consisting of topical hypertonic solution and ointment was started to reduce her symptoms.

Conclusion

Acute corneal hydrops may be the presenting sign of keratoconus; however, extensive hydrops involving the total cornea area at a very young age is very rare and has not been previously reported in the literature.

Corneal Epithelium Asymmetry in Children With Atopy: The Effect of Hand Dominance

Purpose

To evaluate the effect of eye rubbing on the epithelial thickness profile in tomographically normal corneas by AS-OCT and to compare right and left eyes in right-handed children.

Methods

Thirty right-handed boys (mean age 11.2 years) with ocular allergy and history of eye rubbing were evaluated using Scheimpflug (Pentacam HR, Oculus Wetzlar, Germany) and anterior segment optical coherence tomography. Epithelial thickness (ET) and full corneal thickness (CT) parameters were compared between right and left eyes with a non-parametric Mann–Whitney test. A p-value lower than 0.05 was considered for statistical significance.

Results

No eyes had topometric nor tomographic criteria for keratoconus. The min-max ET was lower in right eyes (−2.8 µm vs −3.5; p = 0.02). The difference between inferior and superior (I-S) octants was lower in right eyes (1.1 µm vs 1.9 µm; p = 0.03) as a result of inferotemporal thinning. The highest ET difference was registered between nasal and temporal octants and was more pronounced in the right eyes (2 µm vs 3.1 µm; p < 0.001).

Conclusion

AS-OCT analyses reveal different epithelial thickness patterns between the eyes in young atopic patients, likely eye rubbers. Inferior and temporal epithelial thickness seem to be more affected by thinning in the eye on the side of the dominant hand.

Risk Factors for Glaucoma Drainage Device Revision or Removal Using the IRIS Registry

PURPOSE

To elucidate risk factors for revision or removal of glaucoma drainage devices (GDD) in glaucoma patients in the United States.

DESIGN

Retrospective cohort study.

METHODS

IRIS Registry (Intelligent Research in Sight) patients who underwent GDD insertion between January 1, 2013 and December 31, 2018 were included. Various demographic and clinical factors were collected. Kaplan-Meier survival plots, Cox proportional-hazard models utilizing Firth's Penalized Likelihood, and multivariate linear regression models were used. The main outcome measures were hazard ratios (HR) and beta coefficient (β) estimates.

RESULTS

A total of 44,330 distinct patients underwent at least 1 GDD implantation, and 3354 of these underwent subsequent GDD revision or removal surgery. With failure defined as GDD revision/removal, factors significantly associated with decreased failure included unknown race (HR = 0.83; P = .004) and unknown ethnicity (HR = 0.68; P < .001). Factors associated with increased risk of GDD revision/removal surgery included presence of chronic angle-closure glaucoma (HR = 1.32; P < .001) and dry eye disease (HR = 1.30; P = .007). Additionally, factors associated with a decreased average time (in days) to GDD revision/removal included male sex (β = -25.96; P = .044), unknown race (β = -55.28; P = .013), and right-eye laterality (β = -38.67; P = .026). Factors associated with an increased average time to GDD revision/removal included having a history of a past eye procedure (β = 104.83; P < .001) and being an active smoker (β = 38.15; P = .024).

CONCLUSIONS

The size and scope of the IRIS Registry allows for detection of subtle associations between risk factors and GDD revision or removal surgery. The aforementioned demographic and clinical factors may all have an impact on GDD longevity and can inform the treatment options available for glaucoma patients.

Progression of Pediatric Keratoconus After Corneal Cross-Linking: A Systematic Review and Pooled Analysis

PURPOSE

Corneal collagen cross-linking (CXL) is an effective treatment to slow down keratoconus (KC) progression in adults. Several studies have also shown efficacious outcomes in pediatric populations, yet no systematic analysis has been performed and no accepted definition for progression is available in children after CXL. This study aimed to establish the most commonly used criteria for progression and to conduct a systematic review of the literature with pooled analysis to assess children's keratoconus progression after CXL.

METHODS

A systemic literature review combined with pooled analysis was performed on full-length studies of KC after CXL treatment in a pediatric population and the methods used to report progression were analyzed.

RESULTS

Thirty-seven studies (2078 eyes) were identified on the rates of KC progression after CXL. The most common method to report progression was increased Kmax, Kmean, or Ksteep by ≥1.0 diopter (78.3% of studies). Using these criteria, the mean pooled progression rate after epithelium-off CXL was 9.9% (95% confidence interval: 6.1% -14.6%, total pooled sample size: 1508 eyes) with high heterogeneity between studies [I 2 = 86.48% (95% confidence interval: 80.98 - 90.39), P < 0.0001].

CONCLUSIONS

When considering KC progression after CXL in children, with an increase in Kmax, Kmean, or Ksteep ≥ 1.0 diopter, the progression risk was roughly 10%. We encourage clear quantitative reporting of KC progression in future studies evaluating CXL efficacy in pediatric populations.

Prevalence of keratoconus in refractive surgery practice population in North Macedonia

PURPOSE

To determine the prevalence of keratoconus (KC) in relation to ethnicity in a group of people who consulted an ophthalmological care institution seeking for refractive surgery in N. Macedonia.

METHODS

This was a cross-sectional, interventional retrospective study. Chart reviews were performed for all new patients attending between January 2016 and January 2020 at the Sistina Ophthalmology Hospital in Skopje. All patients were screened; KC diagnosis and classification were based on the corneal topography. Ethnicity and gender classifications were according to patients' self-opinions.

RESULTS

A total of 2812 patients charts reviewed. The mean age was 31.71 years (SD  ± 9.73), and 1209 (43%) were male. A total of 2050 (72.9%) declared themselves as Macedonians, 649 (23.1%) Albanians, 76 (2.7%) Turks and 37 (1.3%) in other ethnicities. Differences in age between the ethnic groups were statistically significant (x² = 90.225, p < 0.001). KC was diagnosed in 343 patients (12.2%), while 9 (0.7%) were KC suspects and 6(0.21%) presented pellucid marginal degeneration. KC was more frequent in males (n = 246, 71.7% of total) and skewed toward younger patients. Increasing patients' age decreased the odds of KC diagnosis by 3.7% (95% CI 1.8%-4.4%) per annum. Males were four times more likely to be diagnosed with KC (AOR = 4.01; 95% CI 3.12-5.16). In comparison with Macedonian patients, Turks were more likely to be diagnosed with KC (AOR = 4.09; 95% CI 2.47-6.78). There was no difference between Macedonians and Albanians (p = 0.08).

CONCLUSION

The prevalence of KC at a refractive surgery practice in N. Macedonia is much higher compared with general population (6.8/100,000) and similar to the prevalence in Middle East Asia. Nationwide screening programs are needed to diagnose the disease earlier.