Prevalence of Childhood Blindness and Ocular Morbidity in a Rural Pediatric Population in Southern India: The Pavagada Pediatric Eye Disease Study-1.

PURPOSE: To determine the prevalence of childhood blindness and ocular morbidity in a rural pediatric population in South India. METHODS: A population-based, cross-sectional survey of children was conducted in three phases in Pavagada and Madhugiri taluks (subdivisions) of Tumkur district in the state of Karnataka, India. In the first phase, trained fieldworkers screened 23,100 children. In the second phase, children with eye diseases were referred to the peripheral hospital to be examined by a general ophthalmologist. In the third phase, children with major eye diseases were examined by a pediatric ophthalmologist. RESULTS: The prevalence of ocular morbidity was 2.66% (95% confidence interval, CI, 2.46-2.87%). The most commonly observed ocular morbidity was Bitot spots (1%) followed by refractive error (0.6%). In total, 18 children were blind and the prevalence of childhood blindness (best-corrected visual acuity <3/60) was 0.08% (95% CI 0.04-0.11%); 8 (44.44%) had retinal blindness, 5 (27.76%) had lens-related blindness, 2 (11.11%) had bilateral microphthalmos, 1 (5.56%) was blind due to anterior staphyloma in the right eye and anophthalmos in the left eye, 1 (5.56%) had bilateral uveal coloboma and 1 (5.56%) had cortical visual impairment. CONCLUSIONS: Nearly half of the blindness in the population was due to unavoidable causes (retinal). In addition to providing eye care services, an appropriate service delivery model would include the provision of rehabilitative and low vision services and implementation of genetic studies to understand the causes and increase awareness of inherited eye diseases.

No evidence for a genetic blueprint: The case of the "complex" mammalian photoreceptor.

Despite the intensity of the search for genes causing inherited retinal degenerations over the past 3 decades, of the approximately 200 disease genes identified to date, all appear to be ordinary housekeeping genes specifying proteins playing basic structural and functional roles in the mature photoreceptor cells. No genes or genetic elements have been identified which can be construed as having a specific morphogenic role, directing the development of the cytoarchitecture of any particular retinal cell. The evidence suggests that the cytoarchitecture of the retinal photoreceptors, although enormously complex, arises from the self-organization of the cells constituents without any regulation or direction from an external genetic blueprint.

Mutation spectrum in BBS genes guided by homozygosity mapping in an Indian cohort.

Bardet-Biedl syndrome (BBS), a ciliopathy disorder with pleiotropic effect manifests primarily as retinal degeneration along with renal insufficiency, polydactyly and obesity. In this study, we have performed homozygosity mapping using NspI 250K affymetrix gene chip followed by mutation screening of the candidate genes located in the homozygous blocks. These regions are prioritized based on the block length and candidature of the genes in BBS and other ciliopathies. Gene alterations in known BBS (22) and other ciliopathy genes such as ALMS1 (2) were seen in 24 of 30 families (80%). Mutations in BBS3 gene, inclusive of a novel recurrent mutation (p.I91T) accounted for 18% of the identified variations. Disease associated polymorphisms p.S70N (BBS2), rs1545 and rs1547 (BBS6) were also observed. This is the first study in Indian BBS patients and homozygosity mapping has proved to be an effective tool in prioritizing the candidate genes in consanguineous pedigrees. The study reveals a different mutation profile in the ciliopathy genes in Indian population and implication of novel loci/genes in 20% of the study group.

The pavagada pediatric eye disease study: objectives, methodology and participant characteristics.

PURPOSE: To explain the objectives and methodology of a population-based survey of children ≤15 years in rural South India. METHODS: A population-based cross sectional survey was performed by trained field workers (1st phase). Children with eye disease were referred to the peripheral rural hospital (2nd phase) to be examined by a general ophthalmologist. If major eye disease (cataract, strabismus) was identified they were referred to a pediatric ophthalmologist (3rd phase). RESULTS: The sample size was 29,850. In the 1st phase, 23,100 children were screened (response rate 77.39%). There were about 33% of children in each of the three stratified age groups (0-5, 6-10 and 11-15 years), with a nearly equal sex distribution in each group (range 47% to 52%). Of the 23,100 screened, 1538 were referred to the peripheral rural hospital. The general ophthalmologist evaluated 647 patients (42%) who came to the peripheral rural hospital (2nd phase) and referred 59 children to the pediatric ophthalmologist (3rd phase). The pediatric ophthalmologist, in addition to evaluating the 59 children referred from the 2nd phase, also evaluated those who did not report (891/1538) to the peripheral rural hospital. This evaluation was done in the field itself. All the 1538 children referred by the field workers were thus seen by an ophthalmologist (647 by the general ophthalmologist, 891 by the pediatric ophthalmologist and 59 by both). CONCLUSION: The study is expected to provide information about the prevalence of pediatric ocular morbidity that could help plan intervention strategies in this area.

OPTN gene: profile of patients with glaucoma from India.

PURPOSE: Optineurin gene (OPTN) mutations are reported in primary open angle glaucoma patients (POAG) from different populations. The coding and noncoding regions of OPTN were screened for mutations in 100 Indian high tension glaucoma patients (HTG). The frequency of the OPTN M98K mutation in an additional 120 patients (70 HTG and 50 normal tension glaucoma [NTG]) was analyzed by restriction enzyme digestion. METHODS: The HTG patients (about 40 years of age) were characterized by open angles on gonioscopy, with raised intraocular pressure (IOP) more than 21 mmHg (<21 mmHg on office diurnal phasing for NTG), and typical glaucomatous disc changes with corresponding visual field defects in the absence of any secondary cause. One hundred HTG patients and controls were screened for OPTN mutations by direct sequencing using an ABI prism 310/3100 Avant genetic analyzer. The M98K status was analyzed by restriction enzyme digestion with StuI. A genotype/phenotype correlation was also attempted for OPTN sequence alterations with clinical parameters such as age at diagnosis, intraocular pressure, cup:disc ratio, etc. The putative change in the transcription factor binding site for the IVS7 +24G>A polymorphism was attempted with AliBaba software (version 2.1). RESULTS: Six sequence alterations were observed in the 100 POAG patients by direct sequencing. The M98K substitution was observed in a total of 10 patients (7/170 HTG and 3/50 NTG) contributing to 4.1% in HTG and 6% in the NTG group and not in the controls. The IVS7+24G>A nucleotide change showed a significant difference in the HTG group (7/100) when compared to the control group (0/100) and found to be associated with increased IOP at diagnosis (p=0.03). The IVS7+24G>A polymorphism resulted in the creation of binding sites for transcription factors NF-1 and CPE that were not present in the wild type. CONCLUSIONS: The current study suggests a possible role of SNPs rather than mutations in OPTN in POAG pathology in the Indian population.

Prevalence and causes of blindness in the rural population of the Chennai Glaucoma Study.

AIM: To study the prevalence and causes of blindness in a rural south Indian population. METHODS: 3924/4800 enumerated (81.75%) subjects, aged 40 years or more from rural Tamil Nadu, underwent comprehensive ophthalmic examination-visual acuity, refraction, intraocular pressure, gonioscopy, cataract grading (LOCS II), retinal examination, and SITA Standard where indicated. Blindness was defined using WHO criteria as best corrected visual acuity of less than 3/60 and/or visual field of less than 10 degrees in the better eye. The influence of age, sex, literacy, and occupation was assessed using multiple logistic regression. RESULTS: 753 subjects (19.2%; 321 males, 432 females) presented with a visual acuity of <3/60; 132 subjects (3.36%, 95% CI: 2.80 to 3.93) were diagnosed to be blind. Cataract was responsible in 74.62% of eyes; glaucoma, cystoid macular oedema, optic atrophy, and corneal scars accounted for 3.79% each. Bilateral causes of blindness were cataract (78.63%), glaucoma (4.29%), optic atrophy (3.42%), cystoid macular oedema, and corneal scars (2.56% each). In 19 eyes (7.2%) the blindness was probably related to cataract surgery. Blindness was positively associated with increasing age (p<0.0001). CONCLUSION: 3.36% of the studied rural population was bilaterally blind, with cataract being the single most important cause.

Low frequency of myocilin mutations in Indian primary open-angle glaucoma patients.

Glaucoma is one of the major causes of blindness in the Indian population. Mutations in the myocilin (MYOC) gene have been reported in different populations. However, reports on MYOC mutations in Indian primary open-angle glaucoma (POAG) patients and juvenile open-angle glaucoma (JOAG) patients are sparse. We therefore screened 100 unrelated POAG/JOAG patients for MYOC mutations. Patients with POAG/JOAG were clinically diagnosed. Genomic DNA from such patients was collected and studied for MYOC mutations by direct sequencing. Nucleotide variations were compared with unrelated healthy controls by restriction enzyme digestion. Secondary structure prediction for the sequence variants was performed by Chou-Fasman method. A novel mutation in exon 1 (144 G-->Alpha) resulting in Gln48His substitution was observed in 2% of the patients. Four other polymorphisms were also observed. The novel mutation was seen in four other affected family members of a JOAG patient. The novel mutation was found to alter the secondary structure in the glycosaminoglycan initiation site of the protein. MYOC mutations were found in 2% of the population studied. MYOC gene may not be playing a significant role in causing POAG in the Indian population.

Inducible nitric oxide synthase gene and diabetic retinopathy in Asian Indian patients.

Nitric oxide, a signal transduction molecule, when modulated causes various diseases including diabetic retinopathy. In diabetes, allelic polymorphism of the inducible nitric oxide synthase (iNOS) gene is associated with retinopathy in the Northern Irish population. In the present study we investigated the Asian Indian population. One hundred and ninety-nine unrelated Asian Indian patients with 15 or more years of type 2 diabetes were divided into two groups: (a) diabetic retinopathy (DR) and (b) diabetic nonretinopathy (DNR) subjects. In these groups the pentanucleotide microsatellite repeat located 2.5 kb upstream of the transcription start site of the iNOS gene was amplified by polymerase chain reaction and analyzed. Eleven alleles, 175-225 bp, were identified. Allele 210 bp was significantly associated with retinopathy (p = 0.044). Individuals carrying this allele had twice the risk of developing retinopathy compared with those who did not carry this allele [odds ratio (OR) - 2.03; 95% CI 0.96-4.35]. Alleles 200 and 220 bp were also significantly associated with no retinopathy and no serious retinopathy complications, respectively. In the Asian Indian population, allele 210 bp of the iNOS gene is a high-risk allele for developing retinopathy and alleles 200 and 220 bp protect an individual from developing retinopathy or its complications.

Consanguinity and ocular genetic diseases in South India: analysis of a five-year study.

OBJECTIVE: Consanguineous marriage is a widely practised social custom in Asia and northern Africa. In south India, Dravidian Hindus have contracted consanguineous marriages for over 2,000 years. In the present study, the influence of consanguinity on the prevalence of visual disorders was examined in patients attending a specialist genetic eye clinic. SUBJECTS AND METHODS: A total of 2,335 patients attending Sankara Nethralaya, Chennai, India, were screened for genetic eye disorders over a five-year period. The patients were drawn from all parts of India and from neighbouring countries in south Asia. RESULTS AND DISCUSSION: Six hundred and seventy-three (28.8%) of the patients tested for ophthalmic genetic disorders reported a family history of consanguinity. The majority (n = 574) of these families were from south India. In the patient group as a whole, the most common form of consanguineous union was between first cousins (n = 367), followed by uncle/niece marriage (n = 177), equivalent to a mean coefficient of inbreeding alpha = 0.0202. Among the consanguineous families, 430 of 673 (63.9%) had retinitis pigmentosa, 167 of these cases were autosomal recessive and 199 were isolated cases. The public in regions such as south India should be made aware of the merits and demerits of consanguineous marriages.

Tumor necrosis factor allelic polymorphism with diabetic retinopathy in India.

The association of tumor necrosis factor (TNF) with diabetic retinopathy (DR) has been described previously. A total of 207 Asian Indian patients of 15-year duration of type 2 diabetes were identified. This group included (i) 100 patients with DR and (ii) 107 patients without retinopathy (DNR). In this study, we correlated the length of the (GT)n microsatellite di-nucleotide repeat upstream to the promoter region of TNF gene with susceptibility for the development of retinopathy. The microsatellite was polymerase chain reaction amplified and electrophoresed on polyacrylamide gel and silver stained. In our study population, there were 18 alleles ranging from 97 to 131 base pairs (bp). Allele 4 (103 bp) had a higher prevalence (9.81%) in the DNR group compared to that (2.5%) in the DR group (P=0.002). Patients with retinopathy and allele 8 (111 bp) had a tendency to develop proliferative diabetic retinopathy (PDR). In this study of Indian subjects, it is suggested that allele 4 is a low risk allele for developing retinopathy and allele 8 (111 bp) shows an association with PDR.

Genetic profile of 81 retinoblastoma patients from a referral hospital in southern India.

PURPOSE: To determine chromosomal abnormalities and inheritance pattern in patients with retinoblastoma from a referral hospital in southern India. MATERIALS AND METHODS: Eighty-one retinoblastoma patients from 78 families were included in this study. Peripheral venous blood was taken for chromosomal analysis and pedigree was ascertained for segregation analysis. RESULTS: Male to female ratio was 1.7:1, 55.56% were bilateral retinoblastoma, the mean age of onset was 12.37 months in bilateral and 33.07 months in unilateral cases (p=0.048). Majority (90.12%) had sporadic inheritance and 6.17% had autosomal dominant inheritance. In chromosomal abnormalities, 8.33% had 13q14 deletion, three cases had de novo balanced translocations. CONCLUSION: The age of onset of the disease was much earlier in the bilateral cases compared to unilateral cases. Sporadic inheritance was predominant while only a small percentage of patients had autosomal dominant inheritance. The percentage of patients with 13q14 deletion was higher than reported in the literature and three novel chromosomal translocations were observed. This is one of the largest series of cases reported from India.

Retinitis pigmentosa patients with sickle cell disease and dextrocardia and situs inversus syndrome.

Two cases of retinitis pigmentosa (RP) with associated sickle cell disease in one patient, and situs inversus totalis in the other are reported. To our best knowledge, these associations have never been reported in RP.

A frameshift mutation in prominin (mouse)-like 1 causes human retinal degeneration.

The disks of vertebrate photoreceptors are produced by outgrowths of the plasma membrane. Hence genes that encode retinal proteins targeted to plasma membrane protrusions represent candidates for inherited retinal degenerations. One such candidate is the gene encoding human prominin (mouse)-like 1 (PROML1, previously known as AC133 antigen) which belongs to the prominin family of 5-transmembrane domain proteins. Murine prominin (prom) shows a strong preference for plasma membrane protrusions in a variety of epithelial cells whereas PROML1 is expressed in retinoblastoma cell lines and adult retina. In the present study, molecular genetic analyses of a pedigree segregating for autosomal recessive retinal degeneration indicated that the affected individuals were homozygous for a nucleotide 1878 deletion in PROML1. This alteration is predicted to result in a frameshift at codon 614 with premature termination of translation. Expression of a similar prom deletion mutant in CHO cells indicated that the truncated protein does not reach the cell surface. Immunocytochemistry revealed that prom is concentrated in the plasma membrane evaginations at the base of the outer segments of rod photoreceptors. These findings suggest that loss of prominin causes retinal degeneration, possibly because of impaired generation of the evaginations and/or impaired conversion of the evaginations to disks.

Autosomal recessive retinitis pigmentosa locus RP28 maps between D2S1337 and D2S286 on chromosome 2p11-p15 in an Indian family.

Retinitis pigmentosa (RP) is a group of clinically and genetically heterogeneous disorders characterised by night blindness, constriction of visual field, and dystrophic changes of the retina. Previous genetic studies have shown extensive allelic and non-allelic genetic heterogeneity of RP. Here we describe an Indian family with multiple consanguineous marriages and a total of four patients with autosomal recessive (AR) RP. The homozygosity mapping strategy was successfully used and indicated close linkage between the disease locus and D2S380, D2S441, D2S291, and D2S1394 with maximum lod scores between 1.51-3.07 at theta=0.00. The analysis of multiply informative meioses maps the locus (RP28) for ARRP in this family between D1S1337 and D2S286 on 2p11-p15. The involvement of visinin (VSNL1), a promising candidate gene assigned to chromosome 2p by previous studies, has been excluded by the absence of linkage.

Homozygosity mapping of autosomal recessive retinitis pigmentosa locus (RP22) on chromosome 16p12.1-p12.3.

Autosomal recessive retinitis pigmentosa (arRP) is a genetically and clinically heterogeneous and progressive degenerative disorder of the retina, leading usually to severe visual handicap in adulthood. To date, disease loci/genes have been mapped/identified only in a minority of cases. DNA samples were collected from 20 large consanguineous Indian families, in which arRP segregated and that were suitable for homozygosity mapping of the disease locus. After excluding linkage to all known arRP loci, a genome-wide scan was initiated. In two families, homozygosity mapping, haplotype analysis, and linkage data mapped the disease locus (RP22) in an approximately 16-cM region between D16S287 and D16S420 on the proximal short arm of chromosome 16. No mutation has been found by direct sequencing in the gene (CRYM) encoding micron crystallin, which maps in the critical region.