Cross-Linking Improves the Quality of Life of People With Keratoconus: A Cross-Sectional and Longitudinal Study From the Save Sight Keratoconus Registry

PURPOSE

The purpose of this study was to comprehensively evaluate the patient-reported quality-of-life (QoL) outcomes after corneal cross-linking for keratoconus.

METHODS

This Save Sight Keratoconus Registry study used cross-sectional and longitudinal designs. For the cross-sectional study, 532 patients with keratoconus (mean age 30.9 ± 11.9 years; 31.6% female) completed the Keratoconus Outcomes Research Questionnaire (KORQ) and 343 patients with keratoconus (mean age 28.3 ± 10.7 years; 32.7% female) completed the Impact of Vision Impairment (IVI) questionnaires. Similarly, for the longitudinal study, 39 patients (mean age 24.2 ± 8.4 years; 23.1% female) completed the KORQ and 16 patients (mean age 27.9 ± 17.1 years; 50.0% female) completed the IVI questionnaire before and after 6 months of cross-linking. The QoL data were analyzed using the Andrich Rating Scale Model of Rasch analysis.

RESULTS

For both cross-sectional and longitudinal studies, the KORQ and IVI scales demonstrated satisfactory psychometric properties [ordered and well-spaced categories, variance explained by the measure 52%-73%, person separation index 2.4-3.9, and fit statistics <1.3 (most cases)]. The patients who had not undergone corneal cross-linking had worse mean activity limitation than those with cross-linking ( P = 0.008). However, the differences in symptoms and emotional scores between the groups were not statistically significant (both P > 0.05). The longitudinal study showed that cross-linking was associated with improved activity limitation, symptoms, and emotional scores.

CONCLUSIONS

The KORQ and IVI are psychometrically robust tools to evaluate the QoL outcomes of corneal cross-linking. Cross-linking is associated with improved activity limitation, symptoms, and emotional status.

Keratoconus International Consortium (KIC)- advancing keratoconus research

CLINICAL RELEVANCE

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

BACKGROUND

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

DESIGN

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

PARTICIPANTS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Vision-Related Quality of Life and Ocular Parameters in End-Stage Renal Disease Patients Undergoing Hemodialysis

Purpose

To evaluate the vision-related quality of life (VRQoL) of patients receiving hemodialysis through the assessment of the impact of vision impairment (IVI) questionnaire and ocular parameters, including best-corrected visual acuity (BCVA), intraocular pressure (IOP), and refraction as calculated by spherical equivalent (SE) of each eye.

Methods

Fifty-one patients with end-stage renal disease undergoing hemodialysis at a single center were recruited, and a total of 77 eyes were evaluated. BCVA, IOP, and SE were evaluated before and after hemodialysis (within 30 min).

Results

Of the 51 patients recruited, 13 (25%) were female, 37 (73%) were male, and one (2%) chose not to specify gender. The mean age was 61.85 ± 32 years. The mobility IVI score was correlated significantly with the presence of hypertension (P = 0.01), eye drop usage (P = 0.04), and gender (P = 0.04). Emotional IVI scores were correlated significantly with diabetes (P = 0.03) and hypertension (P < 0.01). IOP significantly correlated with the IVI overall score (P = 0.02), including the reading IVI subscale and the emotional IVI subscale. Several factors were associated with posthemodialysis ocular parameters, including predialysis ocular parameters, age, and hypertension (P < 0.05 for all).

Conclusions

IOP significantly correlated with VRQoL in hemodialysis patients. Demographic variables such as diabetes status, hypertension, eye drop usage, and gender also significantly correlated with subsections of the IVI questionnaire. This study investigated the relationship between ocular parameters and VRQoL in hemodialysis patients, and future longitudinal research is needed to further elucidate the mechanisms.

Diagnosis and Management of Keratoconus-A Narrative Review of Clinicians' Perspectives

This review discusses the current practices, attitudes, and trends in diagnosing and managing keratoconus (KC) in adults and children by optometrists and ophthalmologists in order to highlight the differences on a global scale. Two independent reviewers searched the electronic databases and grey literature for all potential articles published from 1 January 2000 to 1 June 2022 on management of KC. Keywords used in searches included "keratoconus", "diagnosis", "management", "treatment", "attitude", "practices", "opinion", "optometrist", "ophthalmologist", "consensus", and "protocol". A total of 19 articles was included in this review-12 from the database search and seven from the grey literature. Although a common stepwise approach of non-surgical management was noted, there were differences in the rates of prescribing rigid gas permeable lenses. Furthermore, while clinicians agreed on the need for early diagnosis, the timeline and type of referral varied significantly. A similar discordance was found in the milestones for surgical intervention and preferred surgical techniques. Practice patterns in keratoconus diagnosis and management vary throughout the world. Multiple recommendations and suggestions to minimise the differences have been provided in the literature, with the main themes being improvement in education, interdisciplinary patient care, and further research to reach consensus.

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.

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.

Accuracy of Machine Learning Assisted Detection of Keratoconus: A Systematic Review and Meta-Analysis

(1) Background: The objective of this review was to synthesize available data on the use of machine learning to evaluate its accuracy (as determined by pooled sensitivity and specificity) in detecting keratoconus (KC), and measure reporting completeness of machine learning models in KC based on TRIPOD (the transparent reporting of multivariable prediction models for individual prognosis or diagnosis) statement. (2) Methods: Two independent reviewers searched the electronic databases for all potential articles on machine learning and KC published prior to 2021. The TRIPOD 29-item checklist was used to evaluate the adherence to reporting guidelines of the studies, and the adherence rate to each item was computed. We conducted a meta-analysis to determine the pooled sensitivity and specificity of machine learning models for detecting KC. (3) Results: Thirty-five studies were included in this review. Thirty studies evaluated machine learning models for detecting KC eyes from controls and 14 studies evaluated machine learning models for detecting early KC eyes from controls. The pooled sensitivity for detecting KC was 0.970 (95% CI 0.949–0.982), with a pooled specificity of 0.985 (95% CI 0.971–0.993), whereas the pooled sensitivity of detecting early KC was 0.882 (95% CI 0.822–0.923), with a pooled specificity of 0.947 (95% CI 0.914–0.967). Between 3% and 48% of TRIPOD items were adhered to in studies, and the average (median) adherence rate for a single TRIPOD item was 23% across all studies. (4) Conclusions: Application of machine learning model has the potential to make the diagnosis and monitoring of KC more efficient, resulting in reduced vision loss to the patients. This review provides current information on the machine learning models that have been developed for detecting KC and early KC. Presently, the machine learning models performed poorly in identifying early KC from control eyes and many of these research studies did not follow established reporting standards, thus resulting in the failure of these clinical translation of these machine learning models. We present possible approaches for future studies for improvement in studies related to both KC and early KC models to more efficiently and widely utilize machine learning models for diagnostic process.

Machine learning with a reduced dimensionality representation of comprehensive Pentacam tomography parameters to identify subclinical keratoconus

PURPOSE

To investigate the performance of a machine learning model based on a reduced dimensionality parameter space derived from complete Pentacam parameters to identify subclinical keratoconus (KC).

METHODS

All 1692 available parameters were obtained from the Pentacam imaging machine on 145 subclinical KC and 122 control eyes. We applied a principal component analysis (PCA) to the complete Pentacam dataset to reduce its parameter dimensionality. Subsequently, we investigated machine learning performance of the random forest algorithm with increasing numbers of components to identify their optimal number for detecting subclinical KC from control eyes.

RESULTS

The dimensionality of the complete set of 1692 Pentacam parameters was reduced to 267 principal components using PCA. Subsequent selection of 15 of these principal components explained over 85% of the variance of the original Pentacam-derived parameters and input to train a random forest machine learning model to achieve the best accuracy of 98% in detecting subclinical KC eyes. The model established also reached a high sensitivity of 97% in identification of subclinical KC and a specificity of 98% in recognizing control eyes.

CONCLUSIONS

A random forest-based model trained using a modest number of components derived from a reduced dimensionality representation of complete Pentacam system parameters allowed for high accuracy of subclinical KC identification.

A multi-ethnic genome-wide association study implicates collagen matrix integrity and cell differentiation pathways in keratoconus

Keratoconus is characterised by reduced rigidity of the cornea with distortion and focal thinning that causes blurred vision, however, the pathogenetic mechanisms are unknown. It can lead to severe visual morbidity in children and young adults and is a common indication for corneal transplantation worldwide. Here we report the first large scale genome-wide association study of keratoconus including 4,669 cases and 116,547 controls. We have identified significant association with 36 genomic loci that, for the first time, implicate both dysregulation of corneal collagen matrix integrity and cell differentiation pathways as primary disease-causing mechanisms. The results also suggest pleiotropy, with some disease mechanisms shared with other corneal diseases, such as Fuchs endothelial corneal dystrophy. The common variants associated with keratoconus explain 12.5% of the genetic variance, which shows potential for the future development of a diagnostic test to detect susceptibility to disease.

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.

Association of Genetic Variation With Keratoconus

Importance

Keratoconus is a condition in which the cornea progressively thins and protrudes in a conical shape, severely affecting refraction and vision. It is a major indication for corneal transplant. To discover new genetic loci associated with keratoconus and better understand the causative mechanism of this disease, we performed a genome-wide association study on patients with keratoconus.

Objective

To identify genetic susceptibility regions for keratoconus in the human genome.

Design, Setting, and Participants

This study was conducted with data from eye clinics in Australia, the United States, and Northern Ireland. The discovery cohort of individuals with keratoconus and control participants from Australia was genotyped using the Illumina HumanCoreExome single-nucleotide polymorphism array. After quality control and data cleaning, genotypes were imputed against the 1000 Genomes Project reference panel (phase III; version 5), and association analyses were completed using PLINK version 1.90. Single-nucleotide polymorphisms with P < 1.00 × 10-6 were assessed for replication in 3 additional cohorts. Control participants were drawn from the cohorts of the Blue Mountains Eye Study and a previous study of glaucoma. Replication cohorts were from a previous keratoconus genome-wide association study data set from the United States, a cohort of affected and control participants from Australia and Northern Ireland, and a case-control cohort from Victoria, Australia. Data were collected from January 2006 to March 2019.

Main Outcomes and Measures

Associations between keratoconus and 6 252 612 genetic variants were estimated using logistic regression after adjusting for ancestry using the first 3 principal components.

Results

The discovery cohort included 522 affected individuals and 655 control participants, while the replication cohorts included 818 affected individuals (222 from the United States, 331 from Australia and Northern Ireland, and 265 from Victoria, Australia) and 3858 control participants (2927 from the United States, 229 from Australia and Northern Ireland, and 702 from Victoria, Australia). Two novel loci reached genome-wide significance (defined as P < 5.00 × 10-8), with a P value of 7.46 × 10-9 at rs61876744 in patatin-like phospholipase domain-containing 2 gene (PNPLA2) on chromosome 11 and a P value of 6.35 × 10-12 at rs138380, 2.2 kb upstream of casein kinase I isoform epsilon gene (CSNK1E) on chromosome 22. One additional locus was identified with a P value less than 1.00 × 10-6 in mastermind-like transcriptional coactivator 2 (MAML2) on chromosome 11 (P = 3.91 × 10-7). The novel locus in PNPLA2 reached genome-wide significance in an analysis of all 4 cohorts (P = 2.45 × 10-8).

Conclusions and Relevance

In this relatively large keratoconus genome-wide association study, we identified a genome-wide significant locus for keratoconus in the region of PNPLA2 on chromosome 11.

Risk factors and association with severity of keratoconus: the Australian study of Keratoconus

SIGNIFICANCE

Our results show that asthmatic patients tend to have more severe KC and thus close monitoring for disease progression would be advised, and appropriate treatment strategies may be actioned stabilise the condition that may reduce the need for future corneal transplantation.

PURPOSE

To explore a wide range of risk factors associated with the severity of keratoconus (KC).

METHODS

A cross-sectional study of KC patients was undertaken in Melbourne, Australia. A questionnaire addressing age, gender, educational background, ocular and medical history, smoking and alcohol consumption, and physical examination comprising anthropometric measurements was collected; eye examination was undertaken. The associations between a range of risk factors and the severity of KC were determined using univariate and multivariable linear regression analyses.

RESULTS

A total of 260 KC subjects were included in this study. Mean age of subject was 35.5 (SD = 14.8) years and the majority of the subjects were European 171 (68.2%). Initial univariate regression analysis identified the following risk factors at the p < 0.1 level with KC: higher body mass index, smoking cigarettes, diabetes, rheumatoid arthritis and asthma were associated with increased severity of KC, whereas eczema was associated with less severe KC. Following multivariable regression analysis, only asthma remained as a significant risk factor associated with 2.2 diopters (D) steeper average mean keratometry compared to KC subjects having no asthma [p = 0.03; β = 2.18; 95% confidence intervals: 1.22, 4.14].

CONCLUSION

Our study describes the comprehensive assessment of all the known risk factors in a large KC cohort recruited in Australia. Our study has reported asthma as the only risk factor found to be significantly associated with the severity of KC. The results of this study allow us to better understand the aetiology of KC and such knowledge could be useful in instigate systemic management of patients to slow or prevent KC.

Evaluating the Performance of Various Machine Learning Algorithms to Detect Subclinical Keratoconus

Purpose

Keratoconus (KC) represents one of the leading causes of corneal transplantation worldwide. Detecting subclinical KC would lead to better management to avoid the need for corneal grafts, but the condition is clinically challenging to diagnose. We wished to compare eight commonly used machine learning algorithms using a range of parameter combinations by applying them to our KC dataset and build models to better differentiate subclinical KC from non-KC eyes.

Methods

Oculus Pentacam was used to obtain corneal parameters on 49 subclinical KC and 39 control eyes, along with clinical and demographic parameters. Eight machine learning methods were applied to build models to differentiate subclinical KC from control eyes. Dominant algorithms were trained with all combinations of the considered parameters to select important parameter combinations. The performance of each model was evaluated and compared.

Results

Using a total of eleven parameters, random forest, support vector machine and k-nearest neighbors had better performance in detecting subclinical KC. The highest area under the curve of 0.97 for detecting subclinical KC was achieved using five parameters by the random forest method. The highest sensitivity (0.94) and specificity (0.90) were obtained by the support vector machine and the k-nearest neighbor model, respectively.

Conclusions

This study showed machine learning algorithms can be applied to identify subclinical KC using a minimal parameter set that are routinely collected during clinical eye examination.

Translational Relevance

Machine learning algorithms can be built using routinely collected clinical parameters that will assist in the objective detection of subclinical KC.

Do age-related macular degeneration genes show association with keratoconus?

Background

Keratoconus (KC) is a common corneal condition with an unknown gender predominance. Although numerous studies have investigated the genetic component of KC, no specific genes have yet been attributed to the condition. We recently reported posterior segment changes occurring in the eyes of KC patients. However, it is not clear whether these changes are part of KC pathogenesis or reflect changes in anatomical features of the eye manifested by changes at the cornea. Given retinal changes represent the main characteristics observed in age-related macular degeneration (AMD) and that pleiotropy has been demonstrated between different eye diseases, we wished to assess if known AMD associated genes were also associated with KC.

Methods

A total of 248 KC subjects and 366 non-KC (control) subjects were recruited from public and private clinics in Melbourne for this analysis. Nineteen single nucleotide polymorphisms (SNPs) previously associated with AMD, including rs10490924 (ARMS2/HTRA1), rs10737680 (CFH), rs13278062 (TNFRSF10A), rs1864163 (CETP), rs2230199 (C3), rs3130783 (IER3/DDR1), rs334353 (TGFBR1), rs3812111 (COL10A1), rs429608 (C2/CFB), rs4420638 (APOE), rs4698775 (CFI), rs5749482 (TIMP3), rs6795735 (ADAMTS9), rs8017304 (RAD51B), rs8135665 (SLC16A8), rs920915 (LIPC), rs943080 (VEGFA), rs9542236 (B3GALTL) and rs13081855 (COL8A1/FILIP1L), were genotyped in this cohort. Logistic regression was applied to evaluate the association between these SNPs and KC on both genders together, as well as each gender separately. Linear regression was also applied to assess the association between SNPs and corneal curvature. Bonferroni correction was applied to adjust for multiple testing.

Results

Genotyping data were available for 18 SNPs. The SNP, rs6795735 (ADAMTS9) was significantly associated with KC (p = 3.5 × 10^- 4) when both genders were assessed, whereas rs5749482 (TIMP3) was only associated in males (p = 7.7 × 10^- 4) following Bonferroni multiple correction. However, when the covariates of age and gender were included, the associations became non-significant. In addition, none of the SNPs appeared significant for corneal curvature.

Conclusions

Our study suggested a potential association of rs6795735 in the ADAMTS9 gene and rs5749482 in the TIMP3 gene in KC and that different associations may be gender specific. Overall, SNPs initially identified as associated with AMD following multiple correction may be further impacted by other factors such as age or gender and further studies are needed to resolve this issue.

Pooled genome wide association detects association upstream of FCRL3 with Graves' disease

Background

Graves’ disease is an autoimmune thyroid disease of complex inheritance. Multiple genetic susceptibility loci are thought to be involved in Graves’ disease and it is therefore likely that these can be identified by genome wide association studies. This study aimed to determine if a genome wide association study, using a pooling methodology, could detect genomic loci associated with Graves’ disease.

Results

Nineteen of the top ranking single nucleotide polymorphisms including HLA-DQA1 and C6orf10, were clustered within the Major Histo-compatibility Complex region on chromosome 6p21, with rs1613056 reaching genome wide significance (p = 5 × 10⁻⁸). Technical validation of top ranking non-Major Histo-compatablity complex single nucleotide polymorphisms with individual genotyping in the discovery cohort revealed four single nucleotide polymorphisms with p ≤ 10⁻⁴. Rs17676303 on chromosome 1q23.1, located upstream of FCRL3, showed evidence of association with Graves’ disease across the discovery, replication and combined cohorts. A second single nucleotide polymorphism rs9644119 downstream of DPYSL2 showed some evidence of association supported by finding in the replication cohort that warrants further study.

Conclusions

Pooled genome wide association study identified a genetic variant upstream of FCRL3 as a susceptibility locus for Graves’ disease in addition to those identified in the Major Histo-compatibility Complex. A second locus downstream of DPYSL2 is potentially a novel genetic variant in Graves’ disease that requires further confirmation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3276-z) contains supplementary material, which is available to authorized users.

Impact of keratoconus in the better eye and the worse eye on vision-related quality of life

PURPOSE

We assessed the impact of keratoconus disease indicators in the better eye and worse eye on quality of life (QoL) using the Vision and Quality of Life Index (VisQoL) multi-attribute utility instrument (MAUI).

METHODS

?tlsb -.01w?>Patients with keratoconus completed the six-item VisQoL utility measure. Visual acuity was assessed using a logMAR chart, and corneal thickness and the keratometric values were measured by using Scheimpflug imaging (Pentacam). Four indicators of keratoconus disease status were considered in this study, namely best corrected visual acuity (BCVA), average front corneal curvature (Front Km), thinnest corneal location (TCL), and spherical equivalent refractive error (SE). As keratoconus is an asymmetric condition, we considered the disease parameters separately for the better eye and the worse eye. The association between the four keratoconus indicators and VisQoL utilities was assessed using multivariate linear regression.

RESULTS

A total of 170 patients with keratoconus completed the VisQoL. Patients' median age was 33 (IQR = 18) years (range, 14-75 years) and 58% (n = 99) were males. The median VisQoL utility value was 0.60 (IQR, 0.46; range, 0.02-0.99). The VisQoL utilities reduced with increasing age (ρ = -0.18, P = 0.02) and were higher for males (median = 0.65, IQR = 0.49) than females (median = 0.51, IQR = 0.40). In univariate analyses, BCVA in the better and worse eye, and Front Km and TCL in the worse eye were associated with lower VisQol utilities. However, after adjusting for relevant covariates, only BCVA in the better eye remained associated significantly with reduced VisQoL utilities (β = -0.20, P = 0.018).

CONCLUSIONS

Using a vision-specific MAUI, our study demonstrated substantial disutility relating to keratoconus. Worse vision in the better eye (but not the worse eye) was associated independently with a reduction in VisQoL utilities, suggesting that considering VisQoL utilities based on vision in the better eye is an important estimate of the impact of keratoconus from the patients' perspective. Treatment and rehabilitation interventions to retard the progression of vision impairment in the better eye resulting from keratoconus would be most efficacious at an early stage to improve QoL outcomes for patients with this disease.

Association of the hepatocyte growth factor gene with keratoconus in an Australian population

PURPOSE

A previous study has indicated suggestive association of the hepatocyte growth factor (HGF) gene with Keratoconus. We wished to assess this association in an independent Caucasian cohort as well as assess its association with corneal curvature.

PARTICIPANTS

Keratoconus patients were recruited from private and public clinics in Melbourne, Australia. Non-keratoconic individuals were identified from the Genes in Myopia (GEM) study from Australia. A total of 830 individuals were used for the analysis including 157 keratoconic and 673 non keratoconic subjects.

METHODS

Tag single nucleotide polymorphisms (tSNPs) were chosen to encompass the hepatocyte growth factor gene as well as 2 kb upstream of the start codon through to 2 kb downstream of the stop codon. Logistic and linear regression including age and gender as covariates were applied in statistical analysis with subsequent Bonferroni correction.

RESULTS

Ten tSNPs were genotyped. Following statistical analysis and multiple testing correction, a statistically significant association was found for the tSNP rs2286194 {p = 1.1×10-(3) Odds Ratio 0.52, 95% CI--0.35, 0.77} for keratoconus. No association was found between the 10 tSNPs and corneal curvature.

CONCLUSIONS

These findings provide additional evidence of significant association of the HGF gene with Keratoconus. This association does not appear to act through the corneal curvature route.

Evaluating the association between keratoconus and the corneal thickness genes in an independent Australian population

PURPOSE

A recent genome-wide association study (GWAS) identified six loci associated with central corneal thickness that also conferred associated risk of keratoconus (KC). We aimed to assess whether genetic associations existed for these loci with KC or corneal curvature in an independent cohort of European ancestry.

METHODS

In total, 157 patients with KC were recruited from public and private clinics in Melbourne, Australia, and 673 individuals without KC were identified through the Genes in Myopia study from Australia. The following six single-nucleotide polymorphisms (SNPs) that showed a statistically significant association with KC in a recent GWAS study were selected for genotyping in our cohort: rs4894535 (FNDC3B), rs1324183 (MPDZ-NF1B), rs1536482 (RXRA-COL5A1), rs7044529 (COL5A), rs2721051 (FOXO1), and rs9938149 (BANP-ZNF469). The SNPs were assessed for their association with KC or corneal curvature using logistic or linear regression methods, with age and sex included as covariates. Bonferroni corrections were applied to account for multiple testing.

RESULTS

Genotyping data were available for five of the SNPs. Statistically significant associations with KC were found for the SNPs rs1324183 (P = 0.001; odds ratio [OR], 1.68) and rs9938149 (P = 0.010; OR, 1.47). Meta-analysis of previous studies yielded genome-wide significant evidence of an association for rs1324183, firmly establishing it as a KC risk variant. None of the SNPs were significantly associated with corneal curvature.

CONCLUSIONS

The SNPs rs1324183 in the MPDZ-NF1B gene and rs9938149 (between BANP and ZNF4659) were associated with KC in this independent cohort, but their association was via a non-corneal curvature route.

Gene patents related to common diseases of the eye

Visual impairment and blindness impose substantial morbidity and premature mortality on the population. The direct costs for vision disorders have been shown to be more than the cost of coronary heart disease, stroke, arthritis or depression and were estimated to be $9.85 billion in 2004 in Australia. Hence it is important to identify the causes of common eye diseases and understand their aetiology which in turn would allow determination of better management strategies and treatment options. Age related Macular Degeneration, Cataract, Diabetic Retinopathy, Glaucoma and uncorrected refractive errors represent the majority of the visual impairment and blindness in Australia and various parts of the world. This article reviews the gene patents available for these eye conditions and highlights the important discoveries that have so far contributed to our understanding of these diseases and provides valuable information as to where research will be heading in the future.