Is consanguinity a risk factor for keratoconus?

Pediatric keratoconus epidemiology: a systematic scoping review

BACKGROUND

Pediatric keratoconus (pediatric KC) causes progressive deformation of the cornea in children and adolescents, leading to a gradual loss of vision and a need for rehabilitation. However, new treatments may halt the disease and prevent worse outcomes that require penetrating keratoplasty and its associated morbidity and high cost, irreversible loss of vision, and amblyopia. Few systematic reviews focus on keratoconus-and even fewer, on pediatric KC.

METHODS

Here, we report a systematic scoping review of pediatric KC epidemiology and discuss the studies reporting data on pediatric KC. We used PRISMA-ScR methodology and checklists in the elaboration of the manuscript. The inclusion criteria were: English language; publication between August 7, 1998, and August 7, 2019 (20 years); theme of the study pediatric KC epidemiology. The search strategy: searches of the PubMed-MEDLINE database and Cochrane Database of Systematic Reviews, using eight combinations of the following MeSH terms: keratoconus; child; incidence; prevalence; pediatrics; adolescent; epidemiology.

RESULTS

We charted and reviewed the selected articles. Initial searches included 1802 records; after the exclusion of article duplicates, we screened 777 records, read 97 articles in full text, and included 76 articles in this review.

CONCLUSIONS

Recent epidemiological studies with better methodologies demonstrated increased prevalence rates in comparison to the older literature. This effect may be due to better diagnostic methods and better sample selection than those in historical studies. Diagnosis remains a major challenge as the early disease is usually asymptomatic. Economic and social aspects of pediatric KC remain understudied in the pediatric literature. Global, inclusive, and proactive screening studies in schools are imperative to better understand the great impact of this disease in the young.

The effects of green tea tablets and metformin on ovulation and menstrual cycle regularity in women with polycystic ovary syndrome

Polycystic ovary syndrome is the most common cause of oligo-ovulation and anovulation among women of reproductive age, contributing to infertility. This study aimed to compare the effects of green tea tablets and metformin on ovulation, menstrual cycle regularity, and antioxidant biomarkers in women with polycystic ovary syndrome (PCOS). In this clinical trial study, 94 women with PCOS were randomly assigned to three groups: green tea (n = 33), metformin (n = 29), and control (n = 32). Menstrual status and oxidative stress parameters, including total antioxidant capacity, thiol, and lipid peroxidation, were compared before and 3 months after the intervention among all three groups. Data analysis was conducted using SPSS software version 22 and employing the analysis of variance and paired t-tests. Following the intervention, the mean menstrual cycle duration in the green tea, metformin, and control groups was 32.22 ± 12.78, 48.72 ± 37.06, and 48.53 ± 31.04 days, respectively (P = 0.040). There was no statistically significant difference between the three groups in terms of biochemical, hormonal, and antioxidant indices before and after the intervention (P > 0.05). The intake of green tea tablets was associated with better outcomes in regulating the menstrual cycle in women with PCOS.

Ethnicity, Progressive Keratoconus, and Outcomes after Corneal Cross-Linking in Southern Israel

PURPOSE

To assess clinical outcomes of corneal cross-linking (CXL) intervention in a population diagnosed with progressive keratoconus.

METHODS

This single-center retrospective cohort study included consecutive patients who underwent standard CXL or accelerated CXL for progressive keratoconus at a major teaching hospital in southern Israel between January 2015 and December 2019. Patients' medical files were reviewed, and pre-operative and post-operative data regarding demographics and clinical and tomographic characteristics were extracted and analyzed.

RESULTS

This study included 166 patients (representing 198 eyes), out of which 98 patients (123 eyes) were ethnically Bedouin, and 68 patients (75 eyes) were ethnically Jewish. Overall, 126 patients (144 eyes) had a follow-up of at least 12 months (16.84 ± 5.76). The mean patient age was 20.62 ± 7.1 years old. There were significant baseline differences between the two ethnic groups in best-corrected visual acuity (BCVA; p < 0.001), uncorrected visual acuity (UCVA; p < 0.001), mean keratometry (p = 0.028), and corneal thickness (p < 0.001). Significant changes in BCVA, UCVA, and pachymetry parameters within each group were found after 12 months. Negative binomial regression analysis showed a maximal keratometry below 55D (RR = 1.247, p < 0.001), and a standard CXL procedure (RR = 1.147, p = 0.041) are significantly related to the stability of KC after 12 months. However, the effect size of the origin of patients is negligible (RR = 1.047, p = 0.47).

CONCLUSIONS

In this study, the Bedouin population suffered from more progressive keratoconus when compared to the Jewish population. CXL was significantly effective in improving BCVA and UCVA in both groups after 12 months of follow-up. The effect size of the origin of patients on the stability of KC was found to be negligible.

A Cross-Sectional Analysis to Assess the Role of Atopy in Keratoconus Among Saudi Population

Background

In cases of atopy, IgE antibodies are formed in reaction to certain environmental factors like house dust mites, pollen, or even food allergens. Some studies have shown an association between atopic diseases and keratoconus. This study aims to determine the prevalence of atopy and its associated factors among keratoconus patients.

Materials and Methods

A cross-sectional study was conducted among the Jazan population attending ophthalmology clinics regardless of their sex. Data collection started in August 2020 and finished in mid-June 2021. The sample was selected using the convenience sampling technique, and the total sample size was 83 participants. Data were collected via a questionnaire-based interview that contained 46 questions in the Arabic language. The data collected were analyzed using SPSS software.

Results

Family history is the leading predisposing factor for keratoconus (P < 0.001). Also, eye rubbing was a significant (P < 0.015) trigger for keratoconus. However, other factors, including demographic factors such as gender and atopic conditions, did not have any significant association.

Conclusion

A combination of genetic and environmental factors is the leading cause of the development of keratoconus; however, family history is the most influential factor, followed by eye rubbing.

Management of keratoconus: an updated review

Keratoconus is the most common corneal ectatic disorder. It is characterized by progressive corneal thinning with resultant irregular astigmatism and myopia. Its prevalence has been estimated at 1:375 to 1:2,000 people globally, with a considerably higher rate in the younger populations. Over the past two decades, there was a paradigm shift in the management of keratoconus. The treatment has expanded significantly from conservative management (e.g., spectacles and contact lenses wear) and penetrating keratoplasty to many other therapeutic and refractive modalities, including corneal cross-linking (with various protocols/techniques), combined CXL-keratorefractive surgeries, intracorneal ring segments, anterior lamellar keratoplasty, and more recently, Bowman's layer transplantation, stromal keratophakia, and stromal regeneration. Several recent large genome-wide association studies (GWAS) have identified important genetic mutations relevant to keratoconus, facilitating the development of potential gene therapy targeting keratoconus and halting the disease progression. In addition, attempts have been made to leverage the power of artificial intelligence-assisted algorithms in enabling earlier detection and progression prediction in keratoconus. In this review, we provide a comprehensive overview of the current and emerging treatment of keratoconus and propose a treatment algorithm for systematically guiding the management of this common clinical entity.

Revisiting the oil droplet sign in keratoconus: Utility for early keratoconus diagnosis and screening

PURPOSE

An annular dark shadow (ADS) reflex has been observed while performing direct ophthalmoscopy on subjects with keratoconus. This study describes a method that may serve as a diagnostic technique for early keratoconus and may be used as a quantitative measure of severity.

METHODS

Healthy keratoconic subjects and keratoconus suspects underwent corneal tomography and a full ocular examination. Keratoconus severity was graded based on Belin ABCD criteria. An iPhone camera was connected to a direct ophthalmoscope to take a picture of the eye. The height of the ASD was measured using the AutoCAD software. Differences between subject groups were evaluated by chi-squared and Mann-Whitney tests. Spearman correlation compared ocular parameters and the height of the ADS. A multiple stepwise linear regression was used to predict the height of the ADS based on clinical parameters.

RESULTS

Fifty-eight subjects participated in this study: 37 healthy controls (37 eyes) and 21 keratoconics or keratoconus suspects (37 eyes). The ADS was present in all keratoconic and keratoconus-suspect eyes but in none of the controls. The height of the ADS was significantly correlated with keratoconus severity. Front corneal surface root mean square of higher order aberrations, sphere and anterior radius of curvature from the front apex curve are significant predictors of the height of the ADS.

CONCLUSIONS AND RELEVANCE

The ADS may be a useful method to diagnose keratoconus and keratoconus-suspect cases and serve as a grading and follow-up method for tracking disease severity.

Non-allergic eye rubbing is a major behavioral risk factor for keratoconus

Since the environmental, behavioral, and socioeconomic factors in the etiology of keratoconus (KTCN) remain poorly understood, we characterized them as features influencing KTCN phenotype, and especially affecting the corneal epithelium (CE). In this case-control study, 118 KTCN patients and 73 controls were clinically examined and the Questionnaire covering the aforementioned aspects was completed and then statistically elaborated. Selected KTCN-specific findings were correlated with the outcomes of the RNA-seq assessment of the CE samples. Male sex, eye rubbing, time of using a computer after work, and dust in the working environment, were the substantial KTCN risk factors identified in multivariate analysis, with ORs of 8.66, 7.36, 2.35, and 5.25, respectively. Analyses for genes whose expression in the CE was correlated with the eye rubbing manner showed the enrichment in apoptosis (TP53, BCL2L1), chaperon-related (TLN1, CTDSP2, SRPRA), unfolded protein response (NFYA, TLN1, CTDSP2, SRPRA), cell adhesion (TGFBI, PTPN1, PDPK1), and cellular stress (TFDP1, SRPRA, CAPZB) pathways. Genes whose expression was extrapolated to the allergy status didn't contribute to IgE-related or other inflammatory pathways. Presented findings support the hypothesis of chronic mechanical corneal trauma in KTCN. Eye-rubbing causes CE damage and triggers cellular stress which through its influence on cell apoptosis, migration, and adhesion affects the KTCN phenotype.

Keratoconus in pre-teen children: Demographics and clinical profile

Purpose

To study the demographics and clinical profile of keratoconus (KC) presenting in pre-teen children in India.

Methods

This was a retrospective case series conducted as a single-institutional study at a tertiary eye center in India. A total of 586 eyes from 294 KC patients (aged 12 years or less) without any active comorbid conditions of the eye were included in the study. Slit-lamp biomicroscopy was used to document the clinical signs of KC. Information on age; gender; reason for consultation; family history; history of allergy, atopy, and eye rubbing; manifest refraction; uncorrected and best-corrected distance visual acuity (UCVA and BCVA, respectively); clinical presentation; and contact lens usage were also analyzed, along with data on types of medical and surgical treatments for KC and their outcomes.

Results

The mean age of this pediatric KC patient cohort was 9.3 ± 1.8 years, and there was a male (70%) preponderance. Baseline mean UCVA, BCVA, steep keratometry, and flat keratometry were 0.86 ± 0.58 logMAR, 0.44 ± 0.38 logMAR, 54.82 ± 8.4 D, and 48.21 ± 9.5 D, respectively. Progression, necessitating collagen crosslinking (CXL), was noted in 12.7% eyes. Post-CXL, visual and topographic parameters remained stable without any complications till 6 months posttreatment. However, in eyes that did not undergo CXL, significant progression over time (P < 0.001) was observed. A keratoplasty was required in 2.3% eyes.

Conclusion

KC was present at an advanced stage in 25% of the pre-teens in our series, and therefore, it is an important diagnostic entity when a refractive error is diagnosed, even in very young children.

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.

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.

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.

Non-genetic risk factors for keratoconus

Keratoconus is a complex and multifactorial disease and its exact aetiology remains unknown. This current study examined the important environmental risk factors and their association with keratoconus. This study was registered in the PROSPERO International Prospective Register of systematic reviews under registration number CRD42021256792 in 2021. Scopus, Web of Science, PubMed, and Cochrane CENTRAL databases were searched for all relevant articles published from 1 January 1900 to 31 July 2021. National Institutes of Health Quality Assessment Tool was used to assess the methodological quality of the studies. The assessment for statistical heterogeneity was assessed using the Z-statistics on RevMan v5.4. P-value of <0.05 was considered as statistically significant and I² < 25% as homogenous. Thirty studies were included in this meta-analysis. Pooled odds ratio was calculated with 95% CI. The pooled odds ratio (OR) of eye rubbing, atopy, asthma, and eczema was 3.64 (95% CI, 2.02, 6.57), 1.90 (95% CI, 1.22, 2.94), 1.36 (95% CI, 1.15, 1.61) and 1.90 (95% CI, 1.22, 2.94), respectively. The OR for diabetes was 0.86 (95% CI 0.73, 1.02), and use of sunglasses, contact lens, allergic conjunctivitis, side sleep position and prone sleep position was 0.40 (95% CI, 0.16, 0.99), 1.68 (0.70, 4.00), 2.24 (95% CI, 0.68, 7.36), 3.81 (95% CI, 0.31, 46.23), 12.76 (95% CI, 0.27, 598.58), respectively. Twenty studies were considered to be of high quality, nine to be moderate and one to be low. Environmental risk factors have been identified to play a role in the susceptibility of keratoconus. However, further large-scale longitudinal studies are needed to understand the mechanisms between environmental risk factors and keratoconus.

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.

Keratoconus epidemiology: A review

Keratoconus is an ectatic corneal disease that affects both men and women, usually at a young age. Risk factors such as eye rubbing, environmental and genetic factors contribute to its pathogenesis. Keratoconus presents a variable prevalence, being as high as 5% of the population in the Middle East. In this review, an English-language search for keratoconus epidemiology was undertaken using the PubMed database. We present and discuss the findings of the most relevant epidemiological studies on keratoconus and describe its characteristics and risk factors, correlating them with its pathogenesis.

Association of IL4 rs2070874, FoxP3 rs3761548 Polymorphisms with Keratoconus in Algeria

Purpose

The aim of this case–control study was to determine the impact of environmental factors on the predisposition to develop keratoconus in a sample of Western Algerian population. Subsequently, we were interested in the implication of two single nucleotide polymorphisms (SNPs) IL4 rs2070874 and FOXP3 rs3761548, previously described as contributing to the occurrence of allergy, in the development of keratoconus.

Methods

The study included 70 unrelated KC cases and 70 controls originating from Western Algeria. DNA genotyping was done using predesigned probe-based allelic discrimination TaqManⓇ assays. Allele and genotype frequencies were compared between the cases and controls by Chi-square test and odds ratios with 95% confidence intervals.

Results

A significant association between risk factors such as family history, atopy, eye rubbing, and the development of keratoconus was found in our sample. Smoking would provide a protective effect against the pathology. No statistically significant differences were found in the allele and genotype frequencies between cases and controls neither for IL4 rs2070874 nor for FOXP3 rs3761548.

Conclusion

Our study provides, for the first time, a clear demonstration of the absence of association of the allergy-associated IL4 and FOXP3 polymorphisms with KC in a sample from Western Algerian population.

Environmental Risk Factors Associated With the Need for Penetrating Keratoplasty in Patients With Keratoconus

Purpose To identify environmental risk factors associated with the need for penetrating keratoplasty (PKP) (full-thickness corneal transplantation) in patients with keratoconus in a Middle Eastern country. Methods This is a retrospective case-control study. This study included patients with keratoconus who underwent PKPor were waitlisted for PKP. Controls were patients diagnosed with keratoconus who did not reach a stage that necessitates PKP. Groups were matched by age and gender. Chi-square test was used to figure out the association between different risk factors including eye rubbing, vernal keratoconjunctivitis (VKC), smoking, paternal consanguinity, eye dryness, family history, asthma, eczema, and diabetes with the need for PKP. Results A total of 111 patients were included in this study, there were 48 (43.26%) men and 63 (56.75%) women. The case group included 42 subjects and the control group included 69 subjects. We found statistically significant differences between the two groups in relation to eye rubbing (p=0.0005), VKC (p=0.005), paternal consanguinity (p=0.02), and smoking rate (p=0.04), all being significant in the group in need of PKP. On the other hand, we did not find out a statistically significant difference between the two groups in relation to family history (p=0.31), dryness (p=0.58), asthma (p=0.15), eczema (p=0.28), or diabetes (p=0.29). Conclusion This study has identified several risk factors associated with the need for PKP in patients with keratoconus, part of which are modifiable. These findings can benefit clinicians in community counseling and give recommendations that can help in preventing or - at least - delaying the need for PKP surgery in keratoconus, such as smoking cessation, aggressive treatment of VKC disease, eye rubbing avoidance, as well as raising awareness regarding the potential risks of paternal consanguinity in this disease entity.

Risk Factors for Development of Keratoconus: A Matched Pair Case-Control Study

BACKGROUND

Keratoconus, a progressive ectatic corneal disorder, is believed to be multifactorial in etiology with interaction between genetic and environmental factors. To date, risk factors for the development of the disease are extensively debated and need to be identified since they play a critical role in disease prevention and management. This study aimed to analyze associations between several hereditary and environmental predictors and the development of keratoconus.

PATIENTS AND METHODS

This was a retrospective matched pair case-control study. The study was conducted in Ibn-Alhaitham eye teaching hospital between March 2016 and April 2017. Patients with keratoconus (cases) and their age- and gender-matched controls were asked about childhood and early teenage eye rubbing, ocular trauma, obesity, contact lens wear, smoking and sunlight exposure, family history of keratoconus, parental consanguinity and information related to socio-economic status. Univariable and multivariable conditional logistic regression analyses were used to test the significance of associations.

RESULTS

A total of 166 individuals (83 cases and 83 controls; 60.2% female) were included. On univariable analysis, eye rubbing, family history of keratoconus and parental consanguinity were significant risk factors for keratoconus, whereas all other factors were non-significant. On multivariable analysis, eye rubbing (odds ratio: 4.93; P < 0.01), family history of keratoconus (odds ratio: 25.52; P < 0.01) and parental consanguinity (odds ratio: 2.89; P = 0.02), again, emerged as significant risk factors for disease development.

CONCLUSION

Family history of keratoconus, eye rubbing, and parental consanguinity were significant risk factors for keratoconus development. These results support the evidence for multifactorial etiology, the most important factor being hereditary predisposition.

Risk factors for progression following corneal collagen crosslinking in keratoconus

PURPOSE

To assess risk factors for progression following corneal collagen crosslinking (CXL) in eyes with keratoconus.

METHODS

Charts of patients who developed progression following conventional CXL treatment (Dresden protocol) were retrospectively evaluated in two centers (Center 1 and Center 2). 871 eyes of a total of 676 patients were analyzed. Progression was defined as > 1 diopter (D) increase in maximum keratometry (Kmax) readings compared to baseline.

RESULTS

Progression was noted in 20 eyes of 20 patients (progression rate 3%). The mean age of the patients was 17.65 ± 5.76 (11-34)-years-old, and the mean follow-up following CXL was 36.70 ± 25.72 (12-84)-months-old. The gender distribution was 13 (65%) females and seven (35%) males. Four eyes (20%) had mild, 13 eyes (65%) had moderate, and three eyes (15%) had severe keratoconus at baseline. Fifteen eyes (75%) had allergic conjunctivitis, and 20 eyes (100%) reported eye-rubbing. Cone location was central in 17 (85%) eyes, and peripheral in 3 (15%) eyes. A mean of 2.21 ± 1.30 D (1.00-5.30 D) steepening was determined at Kmax 6 to 82 months following CXL treatment.

CONCLUSIONS

Progression rate was found to be higher in the patients under the age of 17 years, female gender, allergic conjunctivitis, high preoperative Kmax (> 57 D), thin corneas (< 430 µm). The majority of progressive patients were central cone and moderate keratoconus.

Keratoconus in Africa: A systematic review and meta-analysis

PURPOSE

The aim of this review is to evaluate the prevalence of and factors associated with keratoconus in Africa.

METHOD

A systematic online literature search was conducted for articles on keratoconus in Africa. Meta-analysis was performed to estimate the prevalence of keratoconus in Africa. The Freeman-Tukey double arcsine transformation was used to minimize the effects of studies with extremely high or low prevalence estimates on the overall pooled estimates. Leave-one-out sensitivity analysis was used to assess the robustness of the pooled effects and potential outliers. Meta-regression was performed to explore associations between keratoconus, gender and age.

RESULTS

Twelve studies were included in the review; 5 from Egypt, 2 from South Africa, 2 from Kenya, 1 from Sudan, 1 from Ghana and 1 from Nigeria. Two studies were conducted in allergic conjunctivitis patients, 4 in keratoconus patients, 1 in contact lens service seekers, 1 in pre-LASIK patients, 1 in refractive patients and 1 in a student population. Eight studies were included in the meta-analysis. The overall prevalence estimate of keratoconus in Africa was 7.9% (95% CI: 2.5%-16.0%). The prevalence of keratoconus among males and females in Africa was estimated to be 9.3% (95% CI: 2.5%-19.5%) and 5.8% (95% CI: 1.5%-12.7%) respectively. The estimated prevalence of unilateral and bilateral keratoconus was 2.6% (95% CI: 0.4%-6.5%) and 5.8% (95% CI: 1.6%-12.3%), respectively. The estimated prevalence of mild keratoconus was 2.2% (95% CI: 0.7%-4.7%), moderate keratoconus was 3.5% (95% CI: 0.0%-11.8%) and severe keratoconus was 4.0% (95% CI: 0.0%-19.6%). There was no significant association between gender and the prevalence of keratoconus in Africa (p = 0.63), and age and the prevalence of keratoconus in Africa (p = 0.78).

CONCLUSION

The estimated prevalence of keratoconus reported here is higher than prevalence values reported in other meta-analyses or different geographical locations. This is mainly because studies included in this meta-analysis were either conducted on a cohort at high risk of keratoconus or a population with high possibility of finding keratoconus patients. There is a dearth of well-designed population-based studies on keratoconus in Africa, resulting in a lack of epidemiological information. This highlights the urgent need for research on keratoconus in Africa.

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

PURPOSE

This study aimed to determine the prevalence of keratoconus (KC) in the students and faculty members (aged ≥18 and ≤30 years) studying/working at the Medical and Health Sciences faculties of Eskişehir Osmangazi University.

SETTING

Eskişehir Osmangazi University.

DESIGN

Prevalence study.

METHODS

Subjects were randomly selected to undergo KC screening using a proportional stratified sampling method. Out of the 648 invited subjects, 585 (90.3%) responded to the invitation. The demographic data, medical/family history and habits of the subjects were collected using a standardized questionnaire. Subjects were classified as KC, ectasia susceptibility, and normal based on the corneal tomography. The chi-square and Kruskal-Wallis tests were used for the analysis of categorical variables and parametric values, respectively. Risk factors for KC were determined using logistic regression analysis.

RESULTS

The prevalence of KC was 2,393/100,000 (2.4%, 95% CI: 1.3%-4%), whereas that of ectasia susceptibility was 1,538/100,000 (1.5%, 95% CI: 0.7%-2.9%). Although the prevalence was much higher in male (4%, 95% CI: 1.7%-7.7%) than in female (1.6%, 95% CI: 1.1%-4.4%) the difference was not statistically significant (p=0.09). The majority (78.6%, n=11) of KC patients were unaware of their disease. Eye rubbing (OR:3.53, p=0.024) and consanguineous marriage (OR:12.87, p=0.032) were independent risk factors for KC.

CONCLUSION

This is the first population-based KC prevalence study in a randomized sample conducted in Turkey. The prevalence of KC in Turkey was much higher than in European countries but similar to neighboring countries in the Middle East. Eye rubbing and history of consanguineous marriage were significant risk factors.

Pediatric Keratoconus in A Tertiary Eye Center in Alexandria: A Cross-sectional Study

PURPOSE: To describe the clinical presentation, risk factors, and treatment choices documented in a pediatric keratoconus population treated at a tertiary referral center in Alexandria, Egypt.METHODS: A cross-sectional study of 80 patients with keratoconus aged 18 years or younger referred to the cornea clinic at the Alexandria University Main Hospital between July 2018 and October 2019 was included. Patients' history, initial presentation, best spectacle corrected visual acuity (BSCVA), clinical signs, topographic data, and treatment were recorded.RESULTS: Thirty patients were younger than 14 years and 50 were 14 years or older. Elements of the initial presentation included decreased vision in 26 patients, itching in 20 patients, both visual impairment and itching in 16 patients, accidental discovery during vision screening at school in 15 patients, and hydrops in three patients. All patients had bilateral keratoconus, except for four patients who had previously been treated by keratoplasty (n = 156 eyes). The mean logMAR BSCVA was 0.79 ± 0.63. The mean of the average keratometry (AveK), maximum keratometry (Kmax), central corneal thickness (CCT) and thinnest pachymetry reading were 51.16 ± 7.31 D, 59.18 ± 10.38 D, 458.44 ± 55.87 µ 440.08 ± 60.18 µ, respectively. 57 eyes (36%) had stage 1 disease, 43 eyes (28%) had stage 2 disease, 17 eyes (11%) had stage 3 disease and 39 eyes (25%) had stage 4 disease, respectively. No statistically significant differences in the LogMAR BSCVA, keratometry values, CCT, thinnest pachymetry reading, and the Amsler-Krumeich (AK) staging existed between the two age groups or between boys and girls. Crosslinking was indicated in 69 eyes (44%), while keratoplasty was the only viable solution for 39 eyes (25%), with three patients requiring keratoplasty in both eyes.CONCLUSION: Keratoconus in children can result in severe loss of vision. Keratoconus screening programs in elementary schools should be considered in populations with a high incidence of keratoconus for early detection and adequate intervention.

Eye rubbing in the aetiology of keratoconus: a systematic review and meta-analysis

PURPOSE

Keratoconus is a potentially blinding condition that slowly deforms the cornea in young people. Despite the increasing prevalence of keratoconus, the exact aetiology of the condition is unknown. This first systematic review examines the evidence of eye rubbing and its association with keratoconus and presents the findings of the meta-analysis.

METHODS

Two independent reviewers searched the electronic databases for all potential articles published from 1st of January 1900 to 31st of July 2020 on eye rubbing and keratoconus. The researchers assessed the methodological quality of the studies using the Newcastle-Ottawa scale for observational studies. The assessment for statistical heterogeneity was estimated using chi-square and I-square (I²) tests. A p value of < 0.05 was considered as statistically significant and I² < 30% as homogenous. Begg funnel plot was used to interpret the asymmetry or small study effects.

RESULTS

Eight case-control studies were included in this systematic review. Two studies assessed eye rubbing without odds ratios and thus were excluded. The pooled odds ratios for the six remaining studies included in the meta-analysis was 6.46 (95% CI 4.12-10.1). The study results were heterogenous (I² = 71.69 [95% CI 35.14-87.88]). All the studies scored moderate quality methodology on the Newcastle-Ottawa scale. Begg funnel plot showed asymmetry supporting heterogeneity.

CONCLUSION

Eye rubbing showed consistent association with keratoconus. However, the current evidence is limited to only a small number of case-control studies which present as heterogeneous and of sub-optimal methodological quality. Additionally, the cause-effect temporal relationship cannot be determined. Further studies are needed to address this intricate relationship of eye rubbing and its induction, ongoing progression, and severity of keratoconus.

The Enigma of Environmental Factors in Keratoconus

Keratoconus is an ectatic disorder with highly complex and varied causes including genetic variations and environmental factors. Its prevalence varies widely between regions and countries. Many environmental factors have been proposed to be associated with keratoconus, but the interpretation of their individual contributions is difficult due to the presence of many confounding variables. The current literature was reviewed to evaluate the strength of the associations and the causative effects of environmental factors on keratoconus. Ethnicity and consanguinity have been revealed as important determinants for geographical variations in keratoconus prevalence. Eye rubbing, atopy, floppy eyelid syndrome, contact lens wear, pregnancy, and thyroid hormone disturbances are likely associated with keratoconus. The first 4 factors can induce ocular surface inflammation, matrix metalloproteinase release, and keratocyte apoptosis, consistent with the postulated etiology of keratoconus. The associations of keratoconus with UV exposure, cigarette smoking, personality, and sex were less convincing once confounding factors were considered. Future studies powered for multivariate analysis of factors discussed will hopefully shed light on what is truly important in the development and progression of keratoconus.

The Prevalence and Risk Factors for Keratoconus: A Systematic Review and Meta-Analysis

PURPOSE

This study was conducted to determine the prevalence and risk factors for keratoconus worldwide.

METHODS

In this meta-analysis, using a structured search strategy from 2 sources, 4 electronic databases (PubMed, Web of Science, Google Scholar, and Scopus) and the reference lists of the selected articles were searched from inception to June 2018 with no restrictions and filters. The outcome of the study was the prevalence of keratoconus and its risk factors, including eye rubbing, family history of keratoconus, atopy, allergy, asthma, eczema, diabetes type I and type II, and sex.

RESULTS

In this study, 3996 articles were retrieved, of which 29 were analyzed. These 29 articles included 7,158,241 participants from 15 countries. The prevalence of keratoconus in the whole population was 1.38 per 1000 population [95% confidence interval (CI): 1.14-1.62 per 1000]. The prevalence of keratoconus was 20.6 per 1000 (95% CI: 11.68-28.44 per 1000) in men and 18.33 per 1000 (95% CI: 8.66-28.00 per 1000) in women in studies reporting sex. The odds ratio of eye rubbing, family history of keratoconus, allergy, asthma, and eczema was 3.09 (95% CI: 2.17-4.00), 6.42 (95% CI: 2.59-10.24), 1.42 (95% CI: 1.06-1.79), 1.94 (95% CI: 1.30-2.58), and 2.95 (95% CI: 1.30-4.59), respectively.

CONCLUSIONS

The results of this study, as the most comprehensive meta-analysis of keratoconus prevalence and risk factors, showed that keratoconus had a low prevalence in the world and eye rubbing, family history of keratoconus, allergy, asthma, and eczema were the most important risk factors for keratoconus according to the available evidence.

Incorrect sleeping position and eye rubbing in patients with unilateral or highly asymmetric keratoconus: a case-control study

PURPOSE

To evaluate eye rubbing and sleeping position in patients with Unilateral or Highly Asymmetric Keratoconus (UHAKC).

METHODS

Case-control study of consecutive UHAKC patients diagnosed at the Rothschild Foundation. Controls were age- and sex-matched, randomly selected refractive surgery clinic patients. Patients self-administered questionnaires regarding their family history of keratoconus, eye rubbing, and sleeping habits. All the eyes underwent a comprehensive ocular examination. Logistic regression was used to analyze univariate and multivariate data to identify risk factors for keratoconus.

RESULTS

Thirty-three UHAKC patients and 64 controls were included. Univariate analyses showed that daytime eye rubbing [OR = 172.78], in the morning [OR = 24.3], or in eyes with the steepest keratometry [OR = 21.7] were significantly different between groups. Allergy [OR = 2.94], red eyes in the morning [OR = 6.36], and sleeping on stomach/sides [OR = 14.31] or on the same side as the steepest keratometry [OR = 94.72] were also significantly different. The multivariate model also showed statistical significance for most factors including daytime eye rubbing [OR = 134.96], in the morning [OR = 24.86], in the steepest eye [OR = 27.56], and sleeping on stomach/sides [OR = 65.02] or on the steepest side [OR = 144.02]. A univariate analysis in UHAKC group, comparing the worse and better eye, showed that eye rubbing [OR = 162.14] and sleeping position [OR = 99.74] were significantly (p < 0.001) associated with the worse eye.

CONCLUSION

Our data suggests that vigorous eye rubbing and incorrect sleeping position are associated with UHAKC. This is especially true in rubbing the most afflicted eye, and contributory sleep position, including positions placing pressure on the eye with the steepest keratometry.

Genetics vs chronic corneal mechanical trauma in the etiology of keratoconus

Both genetic and environmental factors have been considered to play a role in the etiology keratoconus. Eye rubbing, and more recently eye compression due to sleeping position, have been identified to be highly related to the condition, and are present in a high percentage of patients. Today, the predominant model is that these factors can provide the "second hit" necessary to generate the condition in a genetically susceptible individual. In addition, the extremely high prevalence in Arab populations, where endogamy could play a role, the high concordance rate in monozygotic twins, and the presence of family history of the condition between 5 and 23% of cases, support a genetic influence. Segregation analysis studies suggest that keratoconus is a complex non-Mendelian disease. Results from linkage analysis, next generation sequencing studies and genome-wide association studies also have suggested that genetic factors are involved in the condition. Recently, it has been proposed that mechanical trauma (i.e. eye rubbing or eye compression at night), is a sine quanon condition for the onset of keratoconus, and quite possibly its only cause. There are various arguments for and against this hypothesis. Indeed, it is possible, as initially suggested around 55 years ago, that the term "keratoconus" include diverse phenotypically similar conditions, which are actually of different etiology.

The prevalence of corneal abnormalities in first-degree relatives of patients with keratoconus: a prospective case-control study

PURPOSE

Although there is a high prevalence of keratoconus in the Middle East including Israel, limited data is available describing first-degree relatives of patients with sporadic keratoconus (KC) using Scheimpflug imaging. The purpose of this study is to accurately phenotype first-degree relatives of patients with sporadic KC in Israel using corneal tomography, which may help determine the genetic aetiology of KC.

METHODS

First-degree relatives (N = 56) of 16 KC probands participated in this prospective case-control study. Healthy controls (N = 96) were from a previous study. Autorefraction, visual acuity, slit lamp biomicroscopy, retinoscopy, subjective refraction and Scheimpflug imaging (CSO Sirius Topographer) of keratoconus patients and their first-degree relatives were evaluated. The worse eye was used for KC and KC suspects. The main outcome measure was prevalence of abnormal corneal topography and tomography parameters, which was compared between first-degree relatives vs controls. p values < 0.05 were considered significant.

RESULTS

KC (N = 2) or KC suspect (N = 8) was diagnosed in 18% (95% CI 8-28%) of the first-degree relatives. At least one abnormal corneal parameter was evident in 34% of first-degree relatives, while this was significantly lower for controls (14%, χ2(1,N = 152)  = 8.8, p = 0.01). Qualitative analysis showed KC first-degree relatives had significantly more abnormal anterior corneal topography patterns than controls (34% vs 17%, χ2(1,N = 152)  = 5.9, p = 0.02). For first-degree relatives, sex was not a factor influencing prevalence of corneal abnormalities (18% for both men and women, χ2(1,N = 56)  = 0.0, p = 1.0). A significant correlation was found for first-degree relatives between age and most corneal parameters, while this was not evident for the control group.

CONCLUSIONS AND RELEVANCE

Eye care practitioners should consider first-degree relatives of patients with KC at moderate risk for the disease and/or corneal abnormalities.

Genetic and Environmental Risk Factors for Keratoconus

Keratoconus, a progressive corneal ectasia, is a complex disease with both genetic and environmental risk factors. The exact etiology is not known and is likely variable between individuals. Conditions such as hay fever and allergy are associated with increased risk, while diabetes may be protective. Behaviors such as eye rubbing are also implicated, but direct causality has not been proven. Genetics plays a major role in risk for some individuals, with many large pedigrees showing autosomal inheritance patterns. Several genes have been implicated using linkage and follow-up sequencing in these families. Genome-wide association studies for keratoconus and for quantitative traits such as central corneal thickness have identified several genetic loci that contribute to a cumulative risk for keratoconus, even in people without a family history of the disease. Identification of risk genes for keratoconus is improving our understanding of the biology of this complex disease.

The keratoconus enigma: A review with emphasis on pathogenesis

PURPOSE

To review the literature on the etiopathogenesis of keratoconus (KC).

METHODS

A literature search was conducted using PUBMED and Google Scholar for keratoconus. The authors analyzed epidemiology studies, reviews, and case reports.

RESULTS

Atopy and ocular surface inflammation are a common features of KC and should lead to a reconsideration of the traditional definition of KC as a "non inflammatory" condition. Co-morbidities suggest that KC may be the ocular manifestation of a systemic disease. Finally, KC shows higher prevalence in certain ethnicities, which calls into question the status of KC as a rare disease, at least in these communities.

CONCLUSION

We believe that future studies should test whether selected, high prevalence populations exhibit specific genetic background and/or ethno-specific environmental risk factors.

Comorbidity of Keratoconus and Fuchs' Corneal Endothelial Dystrophy: A Review of the Literature

INTRODUCTION

Comorbidity of keratoconus (KC) and Fuchs' corneal endothelial dystrophy (FD) has been sporadically reported in the literature since the early nineties. This review summarizes findings from the related literature while examining the possibilities related to the concurrent development of these disorders and the clinical significance for the clinician.

METHODS

NLM/PubMed, Ovid, Google Scholar, Cornea, and Cochrane database were reviewed for research papers presenting cases of comorbid KC and FD published between January 1990 and July 2019.

RESULTS

Fifteen papers which presented 69 cases were included in the study. Most cases were women (56.5%), involvement was bilateral (59.4%), and the age range was wide (15-82 years) with a normal distribution. Incidence is expected to be approximately 1 per 100,000. FD is the most frequent comorbid corneal dystrophy diagnosed in KC patients. There are 4 distinct possibilities for the cooccurrence of KC and FD, the most likely being that of chance.

CONCLUSION

The overall incidence of these disorders found in combination is very low and, in absence of other conclusively proven hypotheses, most likely attributable to chance. The treatment plan should be tailored to the needs of the individual patient, since the diagnosis can be made in any stage of life and could be part of a more complex presentation that includes another pathology of the cornea or senile cataract. The inclusion of preoperative topography and specular microscopy as routine in cataract preoperative assessment would protect against any postoperative complications in these patients.

PPIP5K2 and PCSK1 are Candidate Genetic Contributors to Familial Keratoconus

Keratoconus (KC) is the most common corneal ectatic disorder affecting >300,000 people in the US. KC normally has its onset in adolescence, progressively worsening through the third to fourth decades of life. KC patients report significant impaired vision-related quality of life. Genetic factors play an important role in KC pathogenesis. To identify novel genes in familial KC patients, we performed whole exome and genome sequencing in a four-generation family. We identified potential variants in the PPIP5K2 and PCSK1 genes. Using in vitro cellular model and in vivo gene-trap mouse model, we found critical evidence to support the role of PPIP5K2 in normal corneal function and KC pathogenesis. The gene-trap mouse showed irregular corneal surfaces and pathological corneal thinning resembling KC. For the first time, we have integrated corneal tomography and pachymetry mapping into characterization of mouse corneal phenotypes which could be widely implemented in basic and translational research for KC diagnosis and therapy in the future.

The correlation between keratoconus and eye rubbing: a review

Keratoconus is a non-inflammatory disorder which is gradual in development; corneal thinning and ectatic protrusion characterizes it. Keratoconus prevalence varies between different regions depending on several factors that affecting its prevalence. There are risk factors for developing keratoconus such as demographic and environmental factors. It was suggested that eye rubbing was associated with the development of keratoconus. The main aim of this review was to summarize the literature data about keratoconus and to identify the role of eye-rubbing in the aetiology of the disease. A number of 24 articles was reviewed through the PubMed, Google Scholar and Research Gates. There are many keywords used such as keratoconus, aetiology of keratoconus, eye rubbing, keratoconus prevalence, keratoconus and eye rubbing correlation. We concluded that eye rubbing causes the thinning of keratocyte, and the degree of effect of eye rubbing depends on the period and force of performing eye rubbing. It is recommended to avoid eye rubbing to prevent keratoconus, this can be achieved by avoiding itching and treating dryness of the eye and avoiding wearing eye lenses.

A nationwide population-based study of social demographic factors, associated diseases and mortality of keratoconus patients in Denmark from 1977 to 2015

PURPOSE

To study sociodemographic factors, associated diseases and survival of Danish keratoconus patients.

METHODS

All patients diagnosed with keratoconus 1977-2015 (n = 2679) were matched to 10 persons who had not been diagnosed with keratoconus (n = 26 790). Conditional logistic regression assessed whether sociodemographic factors and specific systemic diseases were associated with the odds of keratoconus. Mortality was assessed with time-to-event analysis.

RESULTS

After adjustment, non-Europeans had more than threefold higher odds of keratoconus compared to Europeans (OR, 3.34; 96% CI 2.94-3.80). Single persons had 27% higher odds (OR, 1.27; 95% CI 1.13-1.43), and divorced persons had 18% lower odds (OR 0.82; 95% CI 0.68-0.97) of keratoconus compared with persons in a relationship. Persons living in cities with <500 and 500-4999 inhabitants had 40% (OR, 0.60; 95% CI 0.51-0.71) and 30% (OR, 0.70; 95% CI 0.61-0.81) lower odds of keratoconus, respectively, compared with those living in the capital (>1 000 000 inhabitants). Persons receiving government substitution had 68% higher odds of keratoconus (OR, 1.68; 95% CI 1.30-2.17) compared to self-employed. Keratoconus patients had more than twofold higher odds of asthma (OR, 2.21; 95% CI 1.91-2.55), more than threefold higher odds of allergic rhinitis (OR, 3.44; 95% CI 2.75-4.30), more than sevenfold higher odds of atopic dermatitis (OR, 7.97; 95% CI, 6.21-10.21) and 69% higher odds of depression (OR, 1.69; 95% CI 1.18-2.43). Mortality rates were similar among keratoconus patients and controls (HR, 1.02; 95% CI 0.90-1.16).

CONCLUSION

Danish keratoconus patients differ from controls on several sociodemographic factors and have higher risk of allergic rhinitis, asthma, atopic dermatitis and depression. They do not have excess mortality compared to controls.

Interplay between hereditary and environmental factors to establish an in vitro disease model of keratoconus

Keratoconus (KC) is a bilateral corneal dystrophy and a multifactorial, multigenic disorder with an etiology involving a strong environmental component and complex inheritance patterns. The underlying pathophysiology of KC is poorly understood because of potential crosstalk between genetic-epigenetic variants possibly triggered by the environmental factors. Here, we decode the etiopathological basis of KC using genomic, transcriptomic, proteomic and metabolic approaches. The lack of relevant models that accurately imitate this condition has been particularly limiting in terms of the effective management of KC. Tissue-engineered in vitro models of KC could address this need and generate valuable insights into its etiopathology for the establishment of disease models to accelerate drug discovery.

Prevalence of Keratoconus in a Refractive Surgery Population

Objective

This study examined the prevalence of keratoconus among patients who were interested in undergoing refractive surgery. Corneal tomography measurements were used to help detect keratoconus.

Methods

Adult subjects who presented to the private hospital Cataract and Refractive Surgery Unit (Abha, Saudi Arabia) for refractive surgery evaluation were considered for inclusion in this cross-sectional, retrospective study. All subjects were from the Aseer province, a southern, high-altitude region in Saudi Arabia, and presented between January and December 2017. The incidence of keratoconus and other refractive surgery contraindications were examined.

Results

A total of 2931 patients were considered for inclusion in analyses. Of these, 2280 patients (77.8%) were not candidates for refractive surgery. These 2280 patients had a mean age of 24.1 ± 6.6 years and 1231 patients (54.0%) were male. Of the subjects who did not undergo refractive surgery, 548 (24%) had keratoconus, 400 (17.5%) were keratoconus suspects, 344 (15.1%) had thin corneas, 321 (14.1%) had high myopia, and 52 (2.3%) had a high astigmatism. An additional 479 subjects (21%) were candidates for refractive surgery, but chose not to undergo a procedure.

Conclusion

The incidence of keratoconus in Saudi Arabian refractive surgery prospects was 18.7%. Keratoconus was the most common reason for not performing refractive surgery and accounted for 24.0% of cases in which surgery was not performed.

Analysis of VSX1 Variations in Brazilian Subjects with Keratoconus

PURPOSE

To screen visual system homeobox 1 (VSX1) gene in Brazilian subjects affected with keratoconus (KCN).

METHODS

Seventy-three patients with KCN and 106 healthy controls were enrolled in this study. Patients were diagnosed with KCN based on eye examination and corneal topographic features according to Rabinowitz's criteria (K > 47.2, I-S > 1.4 and KISA > 100%). DNA from blood samples was extracted from donors, and the exons and exon-intron boundaries of VSX1 were sequenced. The potential impact of the identified amino acid changes was assessed with Poly-Phen2, SIFT, and PMUT analysis tools. Genotyping was confirmed by RLFP technique, which was also applied to genotype non-affected individuals.

RESULTS

We found three non-synonymous substitutions (L68H, R131S, and D105E) in VSX1 exon 1, with L68H mutation as a novel variation in this gene. In silico analysis indicated that all variations found were predicted to be probably damaging to VSX1 structure and function. Examination of R131S and L68H variations segregating in one family suggested a strong effect of these variations in increasing disease severity in the proband, which presented bilateral KCN leading to corneal grafting before the age of sixteen. We found a novel synonymous substitution (P79P) and two previously described exonic polymorphisms, with unknown roles in VSX1 pathogenesis.

CONCLUSION

VSX1 polymorphisms found in the Brazilian population support a genetic component in KCN pathogenesis. L68H is a novel mutation, and the phenotypic data suggest that this mutation might enhance disease severity when combined with other polymorphisms. However, further investigations are needed.

Prevalence of keratoconus in paediatric patients in Riyadh, Saudi Arabia

Background/aim

Keratoconus (KC) is a ectatic corneal disorder with marked progression during childhood and puberty that may lead to severe visual loss. In addition to KC prevalence, estimate shows major geographical variations; recent studies using Scheimpflug technology are in contrast to the 1980s and 1990s literature. The present study aims to determine the prevalence of KC in paediatric patients in Riyadh, Saudi Arabia (KSA).

Methods

This prospective, cross-sectional, observational, multicentre study collected data from paediatric patients from 6 years and 21 years of age who were seen at multiple non-ophthalmic emergency departments within KSA. Bilateral corneal measurements were performed using a rotational Scheimpflug corneal tomography system. Two masked examiners established the diagnosis of KC using both objective and subjective screening criteria. Cohen’s kappa coefficient (κ) was used to qualitatively analyse the interexaminer agreement.

Results

There were 522 patients (1044 eyes) evaluated, with an average age of 16.8±4.2 years (range 6–21 years). KC prevalence was 5.56% for examiner 1 and 3.83% for examiner 2. The κ was 0.81 (almost perfect agreement), with discrepancy in nine cases, which were jointly evaluated and consensus obtained. Final KC prevalence was 4.79% (95% CI 2.96 to 6.62) or 1:21 patients.

Conclusions

The prevalence of KC among paediatric patients in the KSA is considerably higher than numbers reported from earlier studies and from similar studies in other countries. This increase might be due to geographical variations in disease prevalence or due to the ability of screening technology to detect undiagnosed KC with greater accuracy.

Updates on Managements for Keratoconus

Purpose

Keratoconus is a progressive disease of the cornea which can lead to blindness as irregular astigmatism increases. Currently, a variety of methods are available for the treatment of keratoconus, and in certain cases, it may be difficult to choose the most appropriate option. This article reviews available treatment modalities for keratoconus to provide the practitioner with practical and useful information for selecting the most suitable option for each individual patient.

Methods

To review treatment methods for different stages of keratoconus, PubMed (United States National Library of Medicine) and Scopus (Elsevier BV) databases were searched using the keywords “keratoconus”, “contact lens”, “cross-linking”, “Intacs”, “keratoplasty”, “gene therapy”, and “irregular astigmatism”, and related articles were reviewed based on disease assessment parameters and treatment methods.

Results

Various methods are available for the treatment of keratoconus: eyeglasses and contact lenses in the early stages, cross-linking for stabilizing disease progression, intrastromal corneal ring segments (ICRS) for reducing refractive errors or flattening the cornea, and penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK), conductive keratoplasty, gene therapy and more recently, bowman layer transplantation (BL transplantation) in advanced stages of the disease. To achieve optimum results, it is essential to choose the best option for each individual patient.

Conclusions

A commonality of the reviewed papers was the advancement of novel diagnostic and treatment methods in ophthalmology, which can delay the need for corneal grafting. A better understanding of keratoconus treatment options can help enhance visual rehabilitation and prevent blindness in keratoconus patients.

Genetics in Keratoconus - What is New?

Background:

Keratoconus is characterized as a bilateral, progressive, non-inflammatory thinning of the cornea resulting in blurred vision due to irregular astigmatism. Keratoconus has a multifactorial etiology, with multiple genetic and environmental components contributing to the disease pathophysiology. Several genomic loci and genes have been identified that highlight the complex molecular etiology of this disease.

Conclusion:

The review focuses on current knowledge of these genetic risk factors associated with keratoconus.

Characteristics of Keratoconic Patients Attending a Specialist Contact Lens Clinic in Kenya

PURPOSE:

To describe the characteristics of keratoconus (KC) patients seen in a contact lens clinic of a children's hospital in Kenya.

RESULTS:

A total of 254 patients’ records were analyzed. Mean age at presentation to the clinic was 20.97 ± 11.13 year (range, 6–84 years) with 75% between the ages of 6 and 25 years. There was a preponderance of males (59.8%). Most patients were referred by an ophthalmologist. All patients were Africans. The most common complaints were blurred vision (50%), poor visual acuity with spectacles (33.5%), contact lens intolerance (11.8%), and other (unspecified). Most cases were severe (71%) followed by moderate (22.9%) and mild (6.2%). Mean BCVA was 0.24 ± 0.23 (6/11). An optical correction was provided in 98% of cases; 34.6% with spectacles, 31.1% with gas permeable lenses and the remaining with both. Referral for keratoplasty was warranted in 16.5%.

CONCLUSION:

This is the first study of KC conducted in Kenya. KC presented at a very early age and tended to be severe. Ophthalmologists were the main source of referral. The main presenting symptom was reduced vision. Optical correction was the most common management and the percentage of patients referred for surgery concurred with other studies.

Association between Family History and Keratoconus Severity

PURPOSE

The high prevalence of positive family history of keratoconus (KC) in KC patients is well-known. However, the results regarding the association between family history of KC and disease severity are controversial. The aim of this study was to evaluate the possible association between family history and severity of KC.

METHOD

Clinical data of 1496 KC patients were evaluated. All participants were asked if they had had a family member with KC. Topographic and keratometric measurements of KC patients, including central corneal thickness (CCT), thinnest corneal thickness (TCT), mean, flat, and steep keratometry values (K) by the use of Pentacam, best-spectacle corrected visual acuity (BCVA), spherical equivalent (SE), and astigmatism were recorded and compared according to patients with and without a family history of KC, first- or second-degree family members, and the number of family members with KC. Severity of KC was classified according to the Amsler-Krumeich classification.

RESULTS

Family history of KC was present in 292 (19.5%) patients. Of those 292 patients who had a family history of KC, 159 (54.5%) had one family member with KC and 133 (45.5%) had two or more family members with KC. There was not a significant difference between corneal pachymetry and K values of the patients with and without a family history of KC (p > 0.05). However, those with a positive family history of KC had more severe disease, according to the Amsler-Krumeich classification (p < 0.05). KC patients who had more family members with KC had significantly lower TCT and significantly higher steep K and astigmatism (p < 0.05), and had more severe disease, according to the Amsler-Krumeich classification (p < 0.05).

CONCLUSION

We suggest that patients with more family members with KC should be subject to screening to identify early disease.

Effect of Allergic Diseases on Keratoconus Severity

PURPOSE

To investigate the association between keratoconus (KC) and allergic diseases.

METHODS

In a prospective age- and sex-matched case--control study clinical data of 885 KC patients and 1526 controls were evaluated regarding the presence of various allergic diseases. Severity of KC and ophthalmic parameters of KC patients were compared between KC patients with and without allergic diseases.

RESULTS

The prevalence of allergic diseases was significantly higher in KC patients. KC patients with vernal keratoconjunctivitis (VKC) or allergic conjunctivitis (AC) had significantly thinner and steeper corneas in comparison with non-allergic KC patients. Only VKC and AC were significantly associated with KC severity.

CONCLUSIONS

Patients with VKC or AC were at increased risk of KC. They had more severe KC and should be closely followed up and intensively treated.

Keratoconus: an inflammatory disorder?

Keratoconus has been classically defined as a progressive, non-inflammatory condition, which produces a thinning and steepening of the cornea. Its pathophysiological mechanisms have been investigated for a long time. Both genetic and environmental factors have been associated with the disease. Recent studies have shown a significant role of proteolytic enzymes, cytokines, and free radicals; therefore, although keratoconus does not meet all the classic criteria for an inflammatory disease, the lack of inflammation has been questioned. The majority of studies in the tears of patients with keratoconus have found increased levels of interleukin-6 (IL-6), tumor necrosis factor-α(TNF-α), and matrix metalloproteinase (MMP)-9. Eye rubbing, a proven risk factor for keratoconus, has been also shown recently to increase the tear levels of MMP-13, IL-6, and TNF-α. In the tear fluid of patients with ocular rosacea, IL-1α and MMP-9 have been reported to be significantly elevated, and cases of inferior corneal thinning, resembling keratoconus, have been reported. We performed a literature review of published biochemical changes in keratoconus that would support that this could be, at least in part, an inflammatory condition.