Prevalence and risk factors for keratoconus in a university-based population in Turkey

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 potential impact on the child's 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 (eg. 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's 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.

Air Pollution and the Prevalence of Keratoconus: Is There a Connection?

PURPOSE

Keratoconus is a progressive, asymmetrical corneal ectasia with multifactorial origin. Three identified risk factors for keratoconus include exposure to ultraviolet (UV) rays, eye rubbing, and atopy. Other factors like pollution would play a role in the physiopathology of keratoconus. In this study we investigate the effects of particles matter (PM) of 2.5 and 10 μm, but also nitrogen dioxide (NO2) and the correlation with the prevalence in the scientific literature.

METHOD

A literature review was performed using four databases (PubMed, Research gate, Google scholar and International Journal of Keratoconus and Ectatic Corneal Diseases) according to strict selection criteria. Levels of fine particles and nitrogen dioxide were extracted from available World Health Organization (WHO) databases and correlated with prevalences from epidemiological studies.

RESULTS

The mean pollution rate in the selected studies was 26.88 ± 25.26 μg/m3 for PM2.5 , 58.23 ± 60.98 μg/m3 for PM10 and 24.79 ± 12.58 μg/m3 for NO2. Pearson correlation tests revealed a significant positive correlation between prevalence of keratoconus with particles rate of PM2.5 (R = 0.58; p < 0.001), PM10 (R = 0.67; p < 0.001) and NO2 (R = 0.64; p = 0.00016).

CONCLUSION

Fine particles appear to be a risk factor for keratoconus. These pollutants may act indirectly by exacerbating known risk factors such as atopy and eye rubbing. Atmospheric pollution may also have a direct effect on the cornea, by disturbing the structure of the epithelium and increasing cell apoptosis.

Experimental Models for Keratoconus: Insights and challenges

Keratoconus, a progressive corneal disorder characterized by the thinning and conical protrusion of the cornea because of collagen degradation, poses significant challenges to patients and clinicians. Most successful animal models in keratoconus are based on genetic mutations and knock-outs in mice and rats that hinder normal corneal stromal architecture, thickness, or strength. While mice and rat models are suitable to study the molecular mechanism and physiological changes to the cornea, they are not suitable for experimental research; especially for surgical interventions like: Deep anterior lamellar keratoplasty (DALK), Stromal lenticule addition keratoplasty etc. using advanced therapies. This review article comprehensively examines recent advancements in experimental models for keratoconus, focusing on their potential for translational research and the challenges ahead. It explores the historical context of experimental models, focusing on animal-based models, mainly rabbits in particular. These advancements enable researchers to mimic the biomechanical and biochemical alterations observed in keratoconic corneas. While these models offer valuable insights into disease mechanisms and treatment development, several challenges remain in transforming experimental findings into clinical applications.

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.

Ectasia Detection by Anterior Segment Optical Coherence Tomography in Scheimpflug Tomographically Normal Keratoconus Fellow Eyes

PURPOSE

The purpose of this study was to determine whether the Scheimpflug tomographically normal fellow eyes of keratoconus patients are also classified as normal using an ectasia screening algorithm based on anterior segment optical coherence tomography (AS-OCT).

METHODS

This monocentric cross-sectional study included 22 very asymmetric ectasia patients with tomographically significant keratoconus in 1 eye and normal Scheimpflug tomography in the fellow eye. Twenty-two eyes of 22 healthy subjects served as a control group. We performed corneal tomography using Pentacam AXL (Oculus, Wetzlar, Germany) and used Belin/Ambrósio Enhanced Ectasia total deviation index as well as Belin ABCD keratoconus classification to identify Scheimpflug tomographically normal eyes. We also performed AS-OCT using Anterion (Heidelberg Engineering, Heidelberg, Germany) and analyzed for the presence of ectasia using the Screening Corneal Objective Risk of Ectasia (SCORE) algorithm, with positive values indicating ectasia suspect tomography.

RESULTS

The SCORE value was positive in 9.1% (n = 2) of the healthy eyes, in 45.5% (n = 10) of the Scheimpflug tomographically normal eyes of keratoconus patients and in all eyes (n = 22) with tomographically significant keratoconus. The Scheimpflug tomographically normal eyes of keratoconus patients had higher SCORE values compared with healthy controls ( P < 0.001). The median (interquartile range) SCORE value was -1.7 (1.3) in healthy controls, -0.5 (2.2) in Scheimpflug tomographically normal eyes of keratoconus patients, and 11.1 (11.0) in tomographically significant keratoconus eyes.

CONCLUSIONS

The Scheimpflug tomographically normal fellow eyes of keratoconus patients had higher AS-OCT-based SCORE values than healthy controls, with positive SCORE values found in 46% of the eyes, indicating early tomographic ectatic changes.

Estimated prevalence of keratoconus in the largest metropolitan area of Italy

PURPOSE

To estimate the prevalence of keratoconus in a population of subjects undergoing first eye examination in an eye clinic in Italy.

METHODS

A single-center, cross-sectional, study was conducted involving patients who underwent first eye examination at an eye clinic in Rome between September 2021 and June 2022. The prevalence of keratoconus was determined by Placido-disk corneal topography using the maximum keratometry (Kmax) value and the Cone Magnitude and Location Index (CLMI) for keratoconus screening. Subjective analysis was performed by two experienced corneal specialists, who classified the outcome into two groups: normal and keratoconus. Risk factors, including family history of keratoconus, allergy or atopy, thyroid disease, eye rubbing habit and gender were also examined.

RESULTS

A total of 512 subjects between 7 and 81 years old were evaluated. The inter-observer agreement to classify subjects in normal or keratoconus group was excellent (k = 1.0); the estimated prevalence in the specific population was 2.1%. Presence of positive family history (9% of keratoconus vs 5% normal), concomitant allergy or atopy (27% vs 9%) and eye rubbing habit (18% vs 4%) were associated with a higher risk of disease.

CONCLUSION

This study reported a high estimated prevalence of keratoconus in a metropolitan area of Italy, as found in recent studies in the Mediterranean and Middle East countries. Screening for keratoconus is highly recommendable and easily feasible with corneal topography under expert supervision and may be indicated primarily in young population to improve early detection and prompt therapeutic management for halting disease progression.

Comparison of different corneal imaging modalities using artificial intelligence for diagnosis of keratoconus: a systematic review and meta-analysis

PURPOSE

This review was designed to compare different corneal imaging modalities using artificial intelligence (AI) for the diagnosis of keratoconus (KCN), subclinical KCN (SKCN), and forme fruste KCN (FFKCN).

METHODS

A comprehensive systematic search was conducted in scientific databases, including Web of Science, PubMed, Scopus, and Google Scholar based on the PRISMA statement. Two independent reviewers assessed all potential publications on AI and KCN up to March 2022. The Critical Appraisal Skills Program (CASP) 11-item checklist was used to evaluate the validity of the studies. Eligible articles were categorized into three groups (KCN, SKCN, and FFKCN) and included in the meta-analysis. The pooled estimate of accuracy (PEA) was calculated for all selected articles.

RESULTS

The initial search yielded 575 relevant publications, of which 36 met the CASP quality criteria and were included in the analysis. Qualitative assessment showed that Scheimpflug and Placido combined with biomechanical and wavefront evaluations improved KCN detection (PEA, 99.2, and 99.0, respectively). The Scheimpflug system (92.25 PEA, 95% CI, 94.76-97.51) and a combination of Scheimpflug and Placido (96.44 PEA, 95% CI, 93.13-98.19) had the highest diagnostic accuracy for the detection of SKCN and FFKCN, respectively. The meta-analysis outcomes showed no significant difference between the CASP score and accuracy of the publications (all P > 0.05).

CONCLUSIONS

Simultaneous Scheimpflug and Placido corneal imaging methods provide high diagnostic accuracy for early detection of keratoconus. The use of AI models improves the discrimination of keratoconic eyes from normal corneas.

Investigation of Potential Crucial Genes and Key Pathways in Keratoconus: An Analysis of Gene Expression Omnibus Data

Keratoconus is one of the most common causes leading to visual impairment in young adult population. The pathogenesis of keratoconus remains poorly understood. The aim of this study was to identify the potential key genes and pathways associated with keratoconus and to further analyze its molecular mechanism. Two RNA-sequencing datasets of keratoconus and paired normal corneal tissues from the Gene Expression Omnibus database were obtained. Differentially expressed genes (DEGs) were identified, and the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were conducted. The protein-protein interaction (PPI) network of the DEGs was established, and the hub genes and significant gene modules of PPI were further constructed. Lastly, the GO and KEGG analyses of the hub gene were performed. In total, 548 common DEGs were identified. GO enrichment analysis showed that the DEGs were primarily associated with regulation of cell adhesion, the response to molecule of bacterial origin, lipopolysaccharide and biotic stimulus, collagen-containing extracellular matrix, extracellular matrix, and structure organization. KEGG pathway analysis showed that these DEGs were mainly involved in the TNF signaling pathway, IL-17 signaling pathway, Rheumatoid arthritis, Cytokine-cytokine receptor interaction. The PPI network was constructed with 146 nodes and 276 edges, and 3 significant modules are selected. Finally, top 10 hub genes were identified from the PPI network. The results revealed that extracellular matrix remodeling and immune inflammatory response could be the key links of keratoconus, TNF, IL6, IL1A, IL1B, CCL3, MMP3, MMP9, MMP1, and TGFB1 may be potential crucial genes, and TNF signaling pathway and IL-17 signaling pathway were the potential pathways accounting for pathogenesis and development of keratoconus.

The prevalence of keratoconus in northern Poland: A cross-sectional study of patients from a primary healthcare practice

INTRODUCTION

Keratoconus is defined as central and/or paracentral corneal thinning and steepening with consequent irregular astigmatism. To date, no prospective study has reported its prevalence in Central Europe. This study aimed to evaluate the prevalence of keratoconus assessed with Scheimpflug imaging in a profile of general medicine practice in Poland.

METHODS

This cross-sectional study collected data by inviting all patients aged 10-80 years subscribed to a single general practitioner in the Elbląg area, Poland. Corneal measurements were performed using a rotating Scheimpflug corneal tomography system. Three masked examiners established the diagnosis of keratoconus in the right or left eye. Fleiss' kappa coefficient (κ) was used to qualitatively analyze the interexaminer agreement.

RESULTS

Of 1,705 patients invited to the study, 771 agreed to participate (45.2%). The mean age of the 728 patients (60.6% female and 39.4% male) with gradable images in at least one eye was 53.6 ± 16.5 years. All of the examiners classified the same four cases as keratoconus (0.549%, 549 per 100,000, 95% confidence interval 150 to 1,400 per 100,000), of which two were bilateral. Fleiss' kappa showed almost perfect agreement among the three examiners regarding the diagnostic decision (κ = 0.784, 95% confidence interval 0.750 to 0.817, p < 0.001). The keratoconus cases were all women (p = 0.106), aged 48, 69, 70, and 71 years old.

CONCLUSION

The prevalence of keratoconus in this area was higher than that previously demonstrated in many European countries. Underestimation of the prevalence has been postulated but never demonstrated.

Sequence variants contributing to dysregulated inflammatory responses across keratoconic cone surface in adolescent patients with keratoconus

Background

Keratoconus (KTCN) is the most common corneal ectasia resulting in a conical shape of the cornea. Here, genomic variation in the corneal epithelium (CE) across the keratoconic cone surface in patients with KTCN and its relevance in the functioning of the immune system were assessed.

Methods

Samples from four unrelated adolescent patients with KTCN and two control individuals were obtained during the CXL and PRK procedures, respectively. Three topographic regions, central, middle, and peripheral, were separated towards the whole-genome sequencing (WGS) study embracing a total of 18 experimental samples. The coding and non-coding sequence variation, including structural variation, was assessed and then evaluated together with the previously reported transcriptomic outcomes for the same CE samples and full-thickness corneas.

Results

First, pathway enrichment analysis of genes with identified coding variants pointed to "Antigen presentation" and "Interferon alpha/beta signaling" as the most overrepresented pathways, indicating the involvement of inflammatory responses in KTCN. Both coding and non-coding sequence variants were found in genes (or in their close proximity) linked to the previously revealed KTCN-specific cellular components, namely, "Actin cytoskeleton", "Extracellular matrix", "Collagen-containing extracellular matrix", "Focal adhesion", "Hippo signaling pathway", and "Wnt signaling" pathways. No genomic heterogeneity across the corneal surface was found comparing the assessed topographic regions. Thirty-five chromosomal regions enriched in both coding and non-coding KTCN-specific sequence variants were revealed, with a most representative 5q locus previously recognized as involved in KTCN.

Conclusion

The identified genomic features indicate the involvement of innate and adaptive immune system responses in KTCN pathogenesis.

Prevalence and risk factors of keratoconus (including oxidative stress biomarkers) in a cohort study of Shiraz university of medical science employees in Iran

BACKGROUND

To determine the prevalence of keratoconus in Shiraz University of Medical Sciences Employees and the related risk factors including oxidative stress biomarkers.

METHODS

2546 subjects' mean age ± SD, 40.35 ± 6.70 (46% male) were recruited. All participants underwent objective refraction using auto-refractometer and retinoscopy, followed by subjective refraction, and bio-microscopy. Pentacam imaging was performed for the detected keratoconus patients. The prevalence of keratoconus and frequency of the visual impairment among keratoconus cases were evaluated. Potential risk factors of sex, age, family history of keratoconus, body mass index ≥ 30 kg/m², serum levels of glucose ≥ 100 mg/d, low-density-lipoprotein-cholesterol (LDL) ≥ 110 mg/dL, high-density-lipoprotein-cholesterol ≤ 40 mg/d, and triglycerides ≥ 150 mg/dL in the blood were evaluated.

RESULTS

The prevalence of keratoconus at least in one eye was 0.98% (95% CI: 0.6- 1.4%). The best corrected visual acuity in the keratoconus group was 0.06 ± 0.1 and the rest of the population was 0.01 ± 0.07 logMAR (p < 0.001). The frequency of visual impairment in the keratoconus group was zero. Odds ratios of the family history of keratoconus (21.00, 95% CI: 9.00-48.00, p < 0.001) and LDL ≥ 110 mg/dL (3.00, 95% CI: 1.20-6.40, p = 0.01) were significant.

CONCLUSIONS

Keratoconus is rare and is not considered a risk factor for visual impairment. A family history of keratoconus and elevated serum LDL levels are contributing risk factors, suggesting an inflammatory background for the disease. Serum levels of LDL ≥ 110 mg/dL in the blood increased the risk of keratoconus three folds.

Colombian Ocular Diseases Epidemiology Study (CODES): incidence and sociodemographic characterisation of keratoconus between 2015 and 2020

OBJECTIVE

To estimate the incidence and describe the demographic characteristics of keratoconus (KC) in Colombia using national health registry data between January 1st 2015 and December 31th 2020.

METHODS AND ANALYSIS

We conducted a nationwide, population-based study using the Integrated Social Protection Information System from the Colombian Ministry of Health, the unique official database in the country. We used the International Classification of Diseases code for KC (H186) to identify the number of new cases of KC and estimate the incidence rates both overall and according to age and sex. We made a standard morbidity ratio map to graph Colombia's morbidity risk of KC onset.

RESULTS

Of 50 372 424 subjects, 21 710 had KC between 2015 and 2020. However, due to the COVID-19 pandemic, all the incidence rates of this study were based on the 18 419 reported until 2019. The incidence rate in the general population was 10.36 (95% CI 10.08 to 10.64) per 100 000 inhabitants. The incidence peak among males was in their early 20s and females in their late 20s. The overall male to female incidence rate ratio was 1.60. Regarding the distribution of the disease, most cases were reported in Bogotá (48.64%), Antioquia (14.04%) and Cundinamarca (10.38%).

CONCLUSION

We performed the first nationwide, population-based study of KC in Latin America, finding distribution patterns similar to those reported in the literature. This study provides valuable information on the epidemiology of KC in Colombia, which is helpful in the development of policies for the diagnosis, prevention and treatment of the disease.

A randomized clinical trial assessing theranostic-guided corneal cross-linking for treating keratoconus: the ARGO protocol

The Assessment of theranostic guided riboflavin/UV-A corneal cross-linking for treatment of keratoconus (ARGO; registration number NCT05457647) clinical trial tests the hypothesis that theranostic-guided riboflavin/UV-A corneal cross-linking (CXL) can provide predictable clinical efficacy for halting keratoconus progression, regardless of treatment protocol, i.e., either with or without epithelial removal. Theranostics is an emerging therapeutic paradigm of personalized and precision medicine that enables real-time monitoring of image-guided therapy. In this trial, the theranostic software module of a novel UV-A medical device will be validated in order to confirm its accuracy in estimating corneal cross-linking efficacy in real time. During CXL procedure, the theranostic UV-A medical device will provide the operator with an imaging biomarker, i.e., the theranostic score, which is calculated by non-invasive measurement of corneal riboflavin concentration and its UV-A light mediated photo-degradation. ARGO is a randomized multicenter clinical trial in patients aged between 18 and 40 years with progressive keratoconus aiming to validate the theranostic score by assessing the change of the maximum keratometry point value at 1-year postoperatively. A total of 50 participants will be stratified with allocation ratio 1:1 using a computer-generated stratification plan with blocks in two treatment protocols, such as epithelium-off or epithelium-on CXL. Following treatment, participants will be monitored for 12 months. Assessment of safety and performance of theranostic-guided corneal cross-linking treatment modality will be determined objectively by corneal tomography, corneal endothelial microscopy, visual acuity testing and slit-lamp eye examination.

Association of 2 Lysyl Oxidase Gene Single Nucleotide Polymorphisms with Keratoconus: A Nationwide Registration Study

Purpose

Keratoconus (KC) is the most common primary ectatic corneal disease, characterized by progressive thinning of the cornea, affecting its shape and structure and leading to visual loss. Lysyl oxidase is an important component of the extracellular matrix and contributes to the homeostasis of corneal stromal extracellular matrix via enzymatic reaction. This nationwide registration study aims to examine the association of KC with 2 known single nucleotide polymorphisms, rs2956540 and rs10519694, in a population of Iranian descent.

Design

Case-control.

Participants

One hundred seventy-eight subjects with KC and 180 clinically healthy subjects participated in the study.

Methods

Genomic DNA was extracted from peripheral blood samples, and their genotypes were determined using tetra-primer amplification refractory mutation system-polymerase chain reaction.

Main Outcome Measures

Allele frequency for rs2956540 and rs10519694.

Results

Genotype frequency was significantly different between cases and controls for rs2956540 (P value = 0.019). The rs2956540 C allele carriers were significantly more frequent among KC cases than healthy controls (P value_chi-square = 0.015, P value_{Fisher exact} = 0.017). There was a significant difference in genotype frequency between groups for rs10519694 (P value = 0.001). T allele carriers were significantly more frequent among KC patients (P value_chi-square = 0.002, P value_{Fisher exact} = 0.001). Sex stratification revealed no significant differences in genotype frequency between males and females in cases and controls. Fitting the general linear model showed that rs10519694 could be considered a predictor for the development of KC (P value = 0.001); however, this was not observed for rs2956540 (P value = 0.323).

Conclusions

rs2956540 and rs10519694 are associated with KC in a population of Iranian descent. rs10519694 could potentially be used for KC risk prediction.

New Keratoconus Risk Factors: A Cross-Sectional Case—Control Study

Purpose

To evaluate risk factors associated with keratoconus in a monocentric cross-sectional case-control study.

Methods

This observational study occurred from June 2019 to February 2021 in a university hospital (France). The case group consisted of 195 patients with keratoconus in at least one eye who were followed up by a corneal specialist. The control group consisted of 195 patients without any evidence of keratoconus on slit-lamp examination and corneal topography, who were matched 1 : 1 to controls by age and sex. Data were collected by a self-completed paper questionnaire before the consultation, and a multivariate logistic regression was performed.

Results

Multivariate analysis revealed significant associations of keratoconus with family history (odds ratio [OR] = 22.2, p < 0.001), rubbing eyes (OR = 10.9, p < 0.001), allergy (any kind) (OR = 3.80, p < 0.001), smoking exposure (OR = 2.08, p=0.017), and dry eyes (OR = 1.77, p=0.045f). The worst eye was associated with the more rubbed eye (p < 0.001) and the more pressed eye during the night according to sleeping position (p < 0.041).

Conclusion

This study confirmed the association between keratoconus and eye rubbing, family history, and allergy. It highlighted the role of pressure on the eyes during sleep. Other less known risk factors such as dry eyes and smoking exposure should be explored in future studies.

Evaluating the association between MPDZ-NF1B rs1324183 and keratoconus in an independent northwestern Chinese population

Background

Keratoconus (KC) is a complex, non-inflammatory corneal degenerative disease. Although numerous studies have analyzed the correlation of SNP rs1324183, which located in MPDZ-NF1B gene, and KC in different populations, only few findings were repeated. In this study, to evaluate the association between rs1324183 and KC in a new independent Chinese population, we performed a replication study of the significantly associated rs1324183.

Methods

In total of 114 unrelated KC patients and 88 unrelated controls were recruited from Ningxia, China. We detected the genotypes and alleles of rs1324183 using PCR technology and Sanger sequencing and also analyzed the association between this locus and KC, its clinical parameters by statistical methods.

Results

The frequency of genotype AA (11, 9.6%) and genotypes containing allele A (47, 41.2%) of rs1324183 in KC were both higher than those of the control group. And genotype AA of rs1324183 conferred a higher risk of KC (OR > 1). Moreover, corneal parameter Belin/Ambrósio enhanced ectasia display final D value (BAD-D) had significant correlation (p = 0.002) with AA genotype of rs1324183 in KC.

Conclusions

Our replication study indicates that the results of rs1324183 associated with KC in our population is robust and further better illustrates the significance of BAD-D as a diagnostic indicator for KC. rs1324183 should be considered as the first genetic mark of KC risk in its future diagnosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02359-1.

Keratoconus: An updated review

Keratoconus is a bilateral and asymmetric disease which results in progressive thinning and steeping of the cornea leading to irregular astigmatism and decreased visual acuity. Traditionally, the condition has been described as a noninflammatory disease; however, more recently it has been associated with ocular inflammation. Keratoconus normally develops in the second and third decades of life and progresses until the fourth decade. The condition affects all ethnicities and both sexes. The prevalence and incidence rates of keratoconus have been estimated to be between 0.2 and 4,790 per 100,000 persons and 1.5 and 25 cases per 100,000 persons/year, respectively, with highest rates typically occurring in 20- to 30-year-olds and Middle Eastern and Asian ethnicities. Progressive stromal thinning, rupture of the anterior limiting membrane, and subsequent ectasia of the central/paracentral cornea are the most commonly observed histopathological findings. A family history of keratoconus, eye rubbing, eczema, asthma, and allergy are risk factors for developing keratoconus. Detecting keratoconus in its earliest stages remains a challenge. Corneal topography is the primary diagnostic tool for keratoconus detection. In incipient cases, however, the use of a single parameter to diagnose keratoconus is insufficient, and in addition to corneal topography, corneal pachymetry and higher order aberration data are now commonly used. Keratoconus severity and progression may be classified based on morphological features and disease evolution, ocular signs, and index-based systems. Keratoconus treatment varies depending on disease severity and progression. Mild cases are typically treated with spectacles, moderate cases with contact lenses, while severe cases that cannot be managed with scleral contact lenses may require corneal surgery. Mild to moderate cases of progressive keratoconus may also be treated surgically, most commonly with corneal cross-linking. This article provides an updated review on the definition, epidemiology, histopathology, aetiology and pathogenesis, clinical features, detection, classification, and management and treatment strategies for keratoconus.

Screening of Keratoconus Using Autokeratometer and Keratometer Keratoconus Index

The keratometer keratoconus index (KKI) is a diagnostic index for the risk of keratoconus calculated from autokeratometer test values. We partially modified the KKI equation and assessed it without limiting the target age and severity of keratoconus. This retrospective study included 179 eyes of 99 patients with keratoconus and 468 eyes from 235 normal controls. In the modified KKI, oblique astigmatism or against-the-rule astigmatism was defined as ≥1D astigmatism. KKI diagnostic power was analyzed in subgroups of <50 and ≥50-year-old patients, and at different keratoconus stages. Although the sensitivity of modified KKI was comparable with that of original KKI (92.7% vs. 95.5%), modified KKI specificity was significantly higher (79.7% vs. 68.6%) (p = 0.0001). Using the modified KKI, sensitivity reached 100% (4/4) and specificity, 63.5% (33/52), in ≥50-year-old patients, while overall sensitivity in keratoconus ≥stage 2 was 100% (30/30). In conclusion, the modified KKI proved to be effective in keratoconus screening at all stages. However, it should be noted that false-positive frequency is higher in ≥50-year-old patients.