Prevalence of diabetic retinopathy in India: Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular Genetics Study report 2.

OBJECTIVE: The aim of the study was to estimate the prevalence of diabetic retinopathy in an urban Indian population older than 40 years. DESIGN: A population-based cross-sectional study. PARTICIPANTS: Five thousand nine hundred ninety-nine subjects residing in Chennai, India, were enumerated. METHODS: A multistage random sampling, based on socioeconomic criteria, was followed. Identified subjects with diabetes mellitus (based on the World Health Organization criteria) underwent detailed examination at the base hospital. The fundi of all patients were photographed using 45 degrees , 4-field stereoscopic digital photography. The diagnosis of diabetic retinopathy was based on Klein's classification of the Early Treatment Diabetic Retinopathy Study scale. MAIN OUTCOME MEASURES: These included age- and gender-adjusted prevalence of diabetes and diabetic retinopathy, and correlation of prevalence with history-based risk factors. RESULTS: The age- and gender-adjusted prevalence rate of diabetes in an urban Chennai population was 28.2% (95% confidence interval [CI], 27.0-29.3), and the prevalence of diabetic retinopathy in general population was 3.5% (95% CI, 3.49-3.54). The prevalence of diabetic retinopathy in the population with diabetes mellitus was 18.0% (95% CI, 16.0-20.1). History-based variables that were significantly associated with increased risk of diabetic retinopathy included gender (men at greater risk; odds ratio [OR], 1.41; 95% CI, 1.04-1.91); use of insulin (OR, 3.52; 95% CI, 2.05-6.02); longer duration of diabetes (>15 years; OR, 6.43; 95% CI, 3.18-12.90); and subjects with known diabetes mellitus (OR, 2.98; 95% CI, 1.72-5.17). Differences in the socioeconomic status did not influence the occurrence of diabetic retinopathy. CONCLUSIONS: The prevalence of diabetic retinopathy was 18% in an urban population with diabetes mellitus in India. The duration of diabetes is the strongest predictor for diabetic retinopathy. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Intron 4 VNTR of endothelial nitric oxide synthase (eNOS) gene and diabetic retinopathy in type 2 patients in southern India.

A 27-bp variable number tandem repeat (VNTR) in intron 4 of endothelial nitric oxide synthase (eNOS) gene has been associated with the risk for developing diabetic retinopathy (DR) in various ethnic populations. Hundred and eighty seven patients with retinopathy (cases; DR+) and 188 patients without retinopathy (controls: DR-) from southern India who had type 2 diabetes mellitus (T2DM) for more than 10 years, were included in the study. We could neither find significant allelic association with clinical severity of DR nor with macular edema. Our results suggest lack of association of intron 4 VNTR of eNOS gene with DR in southern India.

Diabetic retinopathy and IGF-1 gene polymorphic cytosine-adenine repeats in a Southern Indian cohort.

BACKGROUND/AIMS: Growth factors have been implicated in the pathogenesis of diabetic retinopathy (DR). IGF-1 is known to trigger a critical cascade of molecular events that initiate retinal angiogenesis. Increased vitreous IGF-1 levels have been correlated with the severity of ischemia-associated diabetic retinal neovascularization. In the present study, a cytosine-adenine (CA)(n) repeat in the promoter of the IGF-1 gene is studied for association with DR. METHODS: A total of 127 patients with retinopathy (cases: DR+) and 81 patients without retinopathy (controls: DR-) who had type 2 diabetes were recruited for the study. Patients underwent detailed clinical examination and DR was graded based on stereoscopic digital fundus photographs. Frequencies of alleles and genotypes between the two groups were analyzed for significance using relevant statistical tests. (CA)(17) and (CA)(18) repeats were the more frequent alleles. RESULTS: The frequency of the 18-repeat genotype was significantly higher in DR+ patients when compared to DR- patients and found to confer a 2.4 times (95% CI: 1.2-5.0) and 2.8 times (95% CI: 1.1-7.5) higher risk for developing DR and proliferative DR, respectively, when compared to <18-repeat genotypes. CONCLUSIONS: Our study suggests that the 18-repeat genotype is a susceptibility genotype for DR and its clinical severity in a Southern Indian cohort.

Genotype-phenotype correlation analysis in retinoblastoma patients from India.

BACKGROUND: Genetic analysis has a beneficial impact on retinoblastoma management enabling definite risk assessment. However, information regarding genotype-phenotype correlation in retinoblastoma is limited. AIM: To analyze the retinoblastoma susceptibility gene for mutations in retinoblastoma patients and correlate the genotypes the phenotypes. METHODOLOGY: Eleven retinoblastoma patients, who underwent molecular genetic studies were classified into high, moderate or low disease severity groups based on phenotype. RESULTS: Seven patients had high disease severity and four moderate disease severity. Eleven truncating mutations were detected; six were in the N-terminus region of the retinoblastoma protein and two in the A/B pocket (p=0.03). CONCLUSIONS: No significant association between mutation type and disease severity could be established in the present study. However a positive correlation between location of the mutations in certain domains of the retinoblastoma protein and disease severity was observed. To the best of our knowledge this is the first genotype-phenotype correlation study in retinoblastoma patients from India.

Sankara Nethralaya-Diabetic Retinopathy Epidemiology and Molecular Genetic Study (SN-DREAMS 1): study design and research methodology.

PURPOSE: To describe the methodology of the Sankara Nethralaya-Diabetic Retinopathy Epidemiology and Molecular Genetic Study (SN-DREAMS 1), an ongoing population-based study to estimate the prevalence of diabetes and diabetic retinopathy in urban Chennai, Tamil Nadu, South India, and also to elucidate the clinical, anthropometric, biochemical and genetic risk factors associated with diabetic retinopathy. METHODS: In this ongoing study, we anticipate recruiting a total of 5830 participants. Eligible patients, over the age of 40 years, are enumerated using the multistage random sampling method. Demographic data, socioeconomic status, physical activity, risk of sleep apnea, dietary habits, and anthropometric measurements are collected. A detailed medical and ocular history and a comprehensive eye examination, including stereo fundus photographs, are taken at the base hospital. Biochemical investigations (total serum cholesterol, high-density lipoproteins, serum triglycerides, hemoglobin, glycosylated hemoglobin HbA1c) and genetic studies of eligible subjects are conducted. A computerized database is created for the records. CONCLUSION: The study is expected to result in an estimate of the prevalence of diabetes and diabetic retinopathy and a better understanding of biochemical and genetic risk factors associated with diabetic retinopathy in an urban South Indian population. Worldwide, the prevalence of diabetes mellitus, in particular type II diabetes, is rising at an alarming rate. The World Health Organization (WHO) and International Diabetes Federation (IDF) have predicted that the number of cases of adult-onset diabetes would more than double by 2030 from the present level of 171 million to 366 million-an increase of 214%.1 In developed countries, this increase in diabetic population would be around 42% and in developing countries, particularly in India, it is even higher; i.e. 150%.1 In India, the prevalence of diabetes mellitus in the urban population is around 12.1%, as reported by the national urban diabetes study2 conducted in six major cities. Studies have shown the prevalence of diabetes to be higher among the high-income groups (25.5%) as compared to low-income groups (12.6%).3,4,5 The assessment of socioeconomic status was based on income,6, 7 education,2, 7 occupation2 or caste6-which are not representative of the actual socioeconomic status. In the present study, however, the sample was stratified on socioeconomic scoring. This scoring was calculated on the basis of several parameters such as the residence being rented or owned, the number of rooms in the house, the highest educational status, the highest salary, the highest occupation, material possessions (cycle, TV, audio, car, etc.) and house/land value. To the best of our knowledge, this kind of comprehensive socioeconomic scoring has not been done before for prevalence studies on diabetic retinopathy in the general population.

Diabetic retinopathy screening model for rural population: awareness and screening methodology.

CONTEXT: Worldwide, the prevalence of diabetic retinopathy is increasing at an alarming rate. WHO has predicted that in India the number of adults with diabetes will be the highest in the world: from 19 million in 1995 to 80 million in 2030. Although originally thought to be a disease of an urban population, the prevalence of diabetes mellitus is increasing in rural areas as well. The socioeconomic burden resulting from visual impairment or blindness caused by diabetic retinopathy, particularly in the working age group, is a serious concern. ISSUE: In order to combat diabetic retinopathy related blindness, Sankara Nethralaya, the premier eye institute of India, in collaboration with the Lions Clubs International Foundation (LCIF) and the RD Tata Trust, Mumbai, India launched a major diabetic retinopathy screening program in the rural community of South India. The objectives were to create awareness among the rural population of diabetic retinopathy with emphasis on early detection, to conduct diabetes and diabetic retinopathy screening camps, and to bring to the base hospital patients who have sight-threatening diabetic retinopathy, for ancillary investigations such as fluorescein angiography, ultrasound and to perform laser photocoagulation or vitreous surgery, or both. Other objectives included training general ophthalmologists and general physicians in order to develop an integrated diabetic retinopathy model. To address the question as to why certain individuals run the risk of developing sight threatening diabetic retinopathy, biochemical and genetic factors were also studied. The program was launched in June 2003 and 3 rural districts have been screened. To the time of writing, 128 screening camps had been organized, 103 awareness meetings conducted, 23 ophthalmologists trained and 43 general physicians attended the continuing medical education program on diabetic retinopathy. LESSONS: The key elements in the successful implementation of this program have been a team approach, involvement of community leaders and voluntary organizations, and support of the district and state administrators.

RPE65 gene: multiplex PCR and mutation screening in patients from India with retinal degenerative diseases.

We used multiplex PCR follwed by sequencing to screen for mutations in the 14 exons of the RPE65 gene in early-childhood-onset autosomal recessive retinitis pigmentosa (arRP) and Leber's congenital amaurosis (LCA) patients. The RPE65 protein is believed to play an important role in the metabolism of vitamin A in the visual cycle and mutations identified in the gene could have implications for vitamin A-based therapeutic intervention. We were able to identify a homozygous mutation (AAT --> AAG) in exon 9 in an arRP patient and a heterozygous missense transversion (AAT --> AAG) also in exon 9 of an LCA patient. We also identified a polymorphism in exon 10 (GAG --> GAA) in an arRP as well as an LCA patient. Mutation screening would be greatly facilitated by multiplex PCR which could cut down costs, labour and time involved. The nucleotide changes observed in this study could be de novo. Though a larger study has been undertaken, from the preliminary results it appears that in India the RPE65 gene seems to be less involved in causation of LCA.

Aditya Jyot-Diabetic Retinopathy in Urban Mumbai Slums Study (AJ-DRUMSS): study design and methodology - report 1.

PURPOSE: To describe the methodology of Aditya Jyot-Diabetic Retinopathy in Urban Mumbai Slums Study (AJ-DRUMSS), which was designed (i) to estimate the prevalence of diabetic retinopathy (DR) in a general population, (ii) to study the risk factors associated with DR in those with type 2 diabetes mellitus (DM), and (iii) to create awareness for early detection and develop timely interventional management for DR. METHODS: AJ-DRUMSS is an ongoing population-based cross sectional study conducted in seven wards of slums in Mumbai, India, wherein eligible subjects from the general population were screened for DR and profiled for their demographic, social and biochemical parameters to study the associations of these factors. RESULTS: To date, nearly 54,000 households have been enumerated for both awareness and DR prevalence in five study areas (out of seven) during 17 awareness campaigns and 78 DR screening camps. Of these, 4295 households were included in AJ-DRUMSS. Nearly 15,000 camp subjects (including subjects from awareness-focused areas who also turned up for the screening camps) were screened from the total enumerated households, of which 16.1% were diagnosed with type 2 DM. A total of 14.5% of these had evidence of DR and 3.5% had sight-threatening DR. CONCLUSIONS: A detailed study design of AJ-DRUMSS is described. In the screening camps nearly 3.5% of the diabetic population had sight-threatening DR, which needed an active interventional strategy. This study will help in formulating efficient eye care policies, making optimum use of available resources, reorienting healthcare providers and the ignorant within the population regarding the need for periodic ophthalmic surveillance and timely intervention.

Diabetic retinopathy: Validation study of ALR2, RAGE, iNOS and TNFB gene variants in a south Indian cohort.

PURPOSE: We previously reported the association of the Z-2 allele of the promoter dinucleotide repeat in the Aldose reductase (ALR2) gene, the (CCTTT)15 allele in the promoter of inductible nitric oxide synthase (iNOS) gene, and the (GT)13 promoter polymorphism in the tumor necrosis factor ß (TNFB) gene with an increased risk for diabetic retinopathy (DR), and the Gly82Ser polymorphism in the receptor for advanced glycation end products (RAGE) gene and the (GT)9 allele of the TNFB gene with low-risk for DR in a hospital-based self-reported type 2 diabetes mellitus (T2DM) patients. We have repeated the study in a population-based south Indian cohort to validate the same variations in these genes. MATERIALS AND METHODS: Type 2 diabetic patients with and without retinopathy (DR+ and DR- respectively) were recruited. (CA)(n) repeat, Gly82Ser, (CCTTT)(n) repeat and (GT)(n) repeat in ALR2, RAGE, iNOS and TNFB genes respectively were genotyped and their frequencies were analyzed using the relevant statistical tests. RESULTS: Different allelic associations were observed in the present study as compared to our previous reports. Z+2 allele of ALR2, 13-repeat genotype of iNOS, 15-repeat genotype of TNF-ß, genes were associated with susceptibility to DR. Gly82Ser polymorphisms of the RAGE gene were not associated with DR in the present study. CONCLUSION: The present data show a difference in the association of variations in ALR2, iNOS and TNFB genes with DR, when compared to our previous reports; this could be attributed to differences between the study populations of the past and present report.

Protein kinase C beta (PRKCB1) and pigment epithelium derived factor (PEDF) gene polymorphisms and diabetic retinopathy in a south Indian cohort.

PURPOSE: Polymorphisms in protein kinase C beta (PRKCB1) and pigment epithelium derived factor (PEDF) genes have been associated with diabetic nephropathy and retinopathy respectively. Association of promoter polymorphisms-1504C/T and-1440G/T in PRKCB1 gene and sequence variations in exon 4 of PEDF gene are studied with diabetic retinopathy (DR) in a south Indian population based cohort. METHODS: Type 2 diabetic patients with and without retinopathy (DR+ and DR- respectively) were recruited. The promoter region of PRKCB1 gene and exon 4 of PEDF genes were sequenced by polymerase chain reaction based direct sequencing and their frequencies were analyzed using relevant statistical tests. RESULTS: The genotype and alleles of the two promoter polymorphisms of PRKCB1 gene were uniformly distributed among DR+ and DR- and hence were not associated with the disease. The haplotypes were also not significantly associated with DR. A T130T polymorphism observed in the PEDF gene showed modest association with absence of diabetic retinopathy. CONCLUSION: Our results suggest lack of association of PRKCB1 gene promoter polymorphisms and moderate protective association of PEDF gene polymorphism with DR in the south Indian population.

Gene therapy in ophthalmology.

It has been more than a year since ophthalmologists and scientists under Dr. Robin Ali's team at the Moorsfield Eye Hospital and the Institute of Ophthalmology, University College London, successfully treated patients with a severely blinding disease, Leber's congenital amaurosis (LCA) using gene therapy. This success does not look to be transient, and this achievement in gene replacement therapy clinical trial for LCA has instilled hope in numerous families with patients suffering from this and similar retinal degenerative diseases, for whom restoration of lost vision has remained a distant dream so far. The encouragement that this success has given is expected to also lead to start of clinical trials for other blinding ocular diseases for which gene therapy experiments at the laboratory and animal levels have been successful. This article reviews the various studies that have led to the understanding of gene therapy outcomes in human ocular diseases and attempts to provide a brief sketch of successful clinical trials.

Association of VEGF gene polymorphisms with diabetic retinopathy in a south Indian cohort.

BACKGROUND: Polymorphisms in vascular endothelial growth factor (VEGF) gene have been associated with diabetic retinopathy (DR) in various populations. A promoter polymorphism and a 3'UTR variation are studied for association with DR. MATERIALS AND METHODS: Type 2 diabetic patients with and without retinopathy were recruited. The -634C/G and 936C/T polymorphisms were genotyped by direct sequencing and their frequencies were analyzed using relevant statistical tests. RESULTS: No significant association was observed between genotypes, alleles and haplotypes of -634C/G and 936C/T polymorphisms and DR or its severity. However, C(-634)G genotype was found to increase the risk for DR in patients with microalbuminuria (OR: 8.9, 95% CI: 1.4, 58.3). CONCLUSION: Our study broadly suggests lack of association of VEGF gene polymorphisms with DR.

Genotype-phenotype correlation analysis in retinoblastoma patients from India.

BACKGROUND: Genetic analysis has a beneficial impact on retinoblastoma management enabling definite risk assessment. However, information regarding genotype-phenotype correlation in retinoblastoma is limited. AIM: To analyze the retinoblastoma susceptibility gene for mutations in retinoblastoma patients and correlate the genotypes the phenotypes. METHODOLOGY: Eleven retinoblastoma patients, who underwent molecular genetic studies were classified into high, moderate or low disease severity groups based on phenotype. RESULTS: Seven patients had high disease severity and four moderate disease severity. Eleven truncating mutations were detected; six were in the N-terminus region of the retinoblastoma protein and two in the A/B pocket (p=0.03). CONCLUSIONS: No significant association between mutation type and disease severity could be established in the present study. However a positive correlation between location of the mutations in certain domains of the retinoblastoma protein and disease severity was observed. To the best of our knowledge this is the first genotype-phenotype correlation study in retinoblastoma patients from India.

RPE65 gene: multiplex PCR and mutation screening in patients from India with retinal degenerative diseases.

We used multiplex PCR follwed by sequencing to screen for mutations in the 14 exons of the RPE65 gene in early-childhood-onset autosomal recessive retinitis pigmentosa (arRP) and Leber's congenital amaurosis (LCA) patients. The RPE65 protein is believed to play an important role in the metabolism of vitamin A in the visual cycle and mutations identified in the gene could have implications for vitamin A-based therapeutic intervention. We were able to identify a homozygous mutation (AAT --> AAG) in exon 9 in an arRP patient and a heterozygous missense transversion (AAT --> AAG) also in exon 9 of an LCA patient. We also identified a polymorphism in exon 10 (GAG --> GAA) in an arRP as well as an LCA patient. Mutation screening would be greatly facilitated by multiplex PCR which could cut down costs, labour and time involved. The nucleotide changes observed in this study could be de novo. Though a larger study has been undertaken, from the preliminary results it appears that in India the RPE65 gene seems to be less involved in causation of LCA.