Kim Ramasamy

Association analysis of nine candidate gene polymorphisms in Indian patients with type 2 diabetic retinopathy

BackgroundDiabetic retinopathy (DR) is classically defined as a microvasculopathy that primarily affects the small blood vessels of the inner retina as a complication of diabetes mellitus (DM).It is a multifactorial disease with a strong genetic component. The aim of this study is to investigate the association of a set of nine candidate genes with the development of diabetic retinopathy in a South Indian cohort who have type 2 diabetes mellitus (T2DM).MethodsSeven candidate genes (RAGE, PEDF, AKR1B1, EPO, HTRA1, ICAM and HFE) were chosen based on reported association with DR in the literature. Two more, CFH and ARMS2, were chosen based on their roles in biological pathways previously implicated in DR. Fourteen single nucleotide polymorphisms (SNPs) and one dinucleotide repeat polymorphism, previously reported to show association with DR or other related diseases, were genotyped in 345 DR and 356 diabetic patients without retinopathy (DNR). The genes which showed positive association in this screening set were tested further in additional sets of 100 DR and 90 DNR additional patients from the Aravind Eye Hospital. Those which showed association in the secondary screen were subjected to a combined analysis with the 100 DR and 100 DNR subjects previously recruited and genotyped through the Sankara Nethralaya Hospital, India. Genotypes were evaluated using a combination of direct sequencing, TaqMan SNP genotyping, RFLP analysis, and SNaPshot PCR assays. Chi-square and Fisher exact tests were used to analyze the genotype and allele frequencies.ResultsAmong the nine loci (15 polymorphisms) screened, SNP rs2070600 (G82S) in the RAGE gene, showed significant association with DR (allelic P = 0.016, dominant model P = 0.012), compared to DNR. SNP rs2070600 further showed significant association with DR in the confirmation cohort (P = 0.035, dominant model P = 0.032). Combining the two cohorts gave an allelic P < 0.003 and dominant P = 0.0013). Combined analysis with the Sankara Nethralaya cohort gave an allelic P = 0.0003 and dominant P = 0.00011 with an OR = 0.49 (0.34 - 0.70) for the minor allele. In HTRA1, rs11200638 (G>A), showed marginal significance with DR (P = 0.055) while rs10490924 in LOC387715 gave a P = 0.07. No statistical significance was observed for SNPs in the other 7 genes studied.ConclusionsThis study confirms significant association of one polymorphism only (rs2070600 in RAGE) with DR in an Indian population which had T2DM.

A comparison of brilliant blue G, trypan blue, and indocyanine green dyes to assist internal limiting membrane peeling during macular hole surgery.

Purpose: To compare surgical outcomes with three dyes, brilliant blue G (BBG), trypan blue (TB) and indocyanine green (ICG), used to facilitate internal limiting membrane peeling during macular hole surgery. Methods: This comparative, interventional cases series consisted of 50 eyes of 50 patients with senile idiopathic macular holes, who underwent vitrectomy with internal limiting membrane peeling using BBG (n = 15), TB (n = 20), or ICG (n = 15). The cases involving use of BBG and TB were enrolled prospectively and concurrently, and the cases using ICG were selected through chart reviews. We compared the intraoperative surgical facilitation with the 3 dyes and the surgical outcomes in terms of macular hole closure and visual improvement at 6 months. Results: The 3 groups were similar in mean age, sex distribution, preoperative best-corrected visual acuity, and duration of follow-up (P = 0.957, 0.974, 0.939, and 0.5524, respectively). Of the 3 dyes, BBG appeared to provide greatest intraoperative facilitation: most convenient to use and remove, and similar to ICG in terms of internal limiting membrane staining. Six months postoperatively, macular hole closed in 100%, 95%, and 86% eyes (P = 0.48) and visual improvement occurred in 80%, 85%, and 33% eyes (P = 0.005) in BBG, TB, and ICG groups, respectively. The BBG and TB groups also had a better final best-corrected visual acuity than ICG group (P = 0.05) and smaller percentage of visual decline (5% and 6.7% vs. 40% respectively; P = 0.049). Conclusion: Brilliant blue G was comparable with TB in optimizing visual and functional outcomes, while it was similar to ICG in ease of internal limiting membrane peeling.

Diabetic retinopathy: An update

Diabetes mellitus is a major cause of avoidable blindness in both the developing and the developed countries. Significant technological advances have taken place to improve the diagnostic accuracy of diabetic retinopathy. In the last three decades, the treatment strategies have been revised to include, besides laser photocoagulation, early surgical interventions and pharmacotherapies.

Single session of Pascal versus multiple sessions of conventional laser for panretinal photocoagulation in proliferative diabetic retinopathy: a comparitive study.

Background: Panretinal photocoagulation remains the gold standard for treatment of proliferative diabetic retinopathy, which can be done in a single session or in multiple sessions. However, because of different reasons, single session is less frequently practiced. We describe the results of a single session of pattern scan laser versus multiple sessions of conventional laser in cases of proliferative diabetic retinopathy. Methods: A prospective study was performed on 50 patients (100 eyes), in whom proliferative diabetic retinopathy was diagnosed recently. Two eyes of an individual patient were randomly assigned, one for a single session of panretinal photocoagulation using pattern scan laser and the other for multiple sessions of conventional laser. Results: Our study confirms that single session is effective and even better than conventional laser in relation to the effect of treatment. Conclusion: Complications and the associated pain are less; thus, the patients acceptance of PASCAL was high, and a single session was well tolerated with topical anesthesia alone.

Clinico-microbiological profile and visual outcomes of post-traumatic endophthalmitis at a tertiary eye care center in South India

PURPOSE To analyze the clinical and microbiological characteristics of eyes with post-traumatic endophthalmitis and factors influencing the visual outcomes in these cases. METHODS We performed a retrospective chart analysis of the clinical and microbiological data of 97 consecutive patients with post-traumatic endophthalmitis presenting to a tertiary eye care hospital in South India. RESULTS Thirty-nine (40.2%) cases were culture-positive, gram-positive cocci (n=24/42, 57.1%) being the commonest isolates. Staphylococcus epidermidis and Pseudomonas aeuruginosa were the commonest single isolates (n=10; 23.8%). Majority of the organisms were sensitive to chloramphenicol (n=27) or ciprofloxacin (n=26). Susceptibility to vancomycin (n=3) and amikacin (n=4) was poor. Cases with negative cultures at presentation were more likely to have improvement in visual acuity compared with culture-positive cases (on multivariate analysis, OR: 3.2, 95% CI: 1.1, 9.0). CONCLUSIONS In this series of post-traumatic endophthalmitis, a high prevalence of resistance of the culture isolates to vancomycin and amikacin was observed.

Genome-wide association study for sight-threatening diabetic retinopathy reveals association with genetic variation near the GRB2 gene

Aims/hypothesisDiabetic retinopathy is a serious complication of diabetes mellitus and can lead to blindness. A genetic component, in addition to traditional risk factors, has been well described although strong genetic factors have not yet been identified. Here, we aimed to identify novel genetic risk factors for sight-threatening diabetic retinopathy using a genome-wide association study.MethodsRetinopathy was assessed in white Australians with type 2 diabetes mellitus. Genome-wide association analysis was conducted for comparison of cases of sight-threatening diabetic retinopathy (n = 336) with diabetic controls with no retinopathy (n = 508). Top ranking single nucleotide polymorphisms were typed in a type 2 diabetes replication cohort, a type 1 diabetes cohort and an Indian type 2 cohort. A mouse model of proliferative retinopathy was used to assess differential expression of the nearby candidate gene GRB2 by immunohistochemistry and quantitative western blot.ResultsThe top ranked variant was rs3805931 with p = 2.66 × 10−7, but no association was found in the replication cohort. Only rs9896052 (p = 6.55 × 10−5) was associated with sight-threatening diabetic retinopathy in both the type 2 (p = 0.035) and the type 1 (p = 0.041) replication cohorts, as well as in the Indian cohort (p = 0.016). The study-wide meta-analysis reached genome-wide significance (p = 4.15 × 10−8). The GRB2 gene is located downstream of this variant and a mouse model of retinopathy showed increased GRB2 expression in the retina.Conclusions/interpretationGenetic variation near GRB2 on chromosome 17q25.1 is associated with sight-threatening diabetic retinopathy. Several genes in this region are promising candidates and in particular GRB2 is upregulated during retinal stress and neovascularisation.

Real-time polymerase chain reaction in the diagnosis of acute postoperative endophthalmitis.

PURPOSE To evaluate the efficacy of quantitative real-time polymerase chain reaction (qPCR) in the diagnosis of postoperative bacterial endophthalmitis among patients who underwent cataract surgery at a tertiary care center. DESIGN Prospective experimental study. METHODS This was a single-center study of 64 eyes of 64 patients presenting with clinical signs and symptoms of endophthalmitis within 1 year of cataract surgery. Patients with glaucoma filtering or cornea surgery in the past year, postoperative trauma, fungal endophthalmitis, or preoperative inflammatory conditions were excluded. Vitreous samples were obtained during vitreous tap or vitrectomy and sent for both culture and qPCR with sequencing. Vitreous samples obtained from 50 patients undergoing vitrectomy for noninflammatory indications served as controls. The main outcome measures were the sensitivity of qPCR compared to culture and concordance of results of pathogen identification with sequencing vs phenotypic speciation. RESULTS qPCR detected 16s bacterial DNA in 37 patients (66%), compared to 19 (34%) with traditional culture. Only 1 patient had a positive result by culture (Nocardia species) but negative result by qPCR. For the 18 samples positive by both qPCR and culture, there was a 100% concordance in pathogen identification between sequencing and phenotypic speciation. CONCLUSION In cases of suspected bacterial endophthalmitis, qPCR offers an improved diagnostic yield and may be a useful adjunct to traditional culture. Further large-scale clinical studies are needed to elucidate the full clinical utility of qPCR.

Atypical manifestations of acute posterior multifocal placoid pigment epitheliopathy

We report four patients with acute posterior multifocal placoid pigment epitheliopathy (APMPPE) with atypical features which were unilaterality, serous detachment of the neurosensory retina, retinal vasculitis and papillitis. All patients responded well to oral corticosteroids. We suggest that systemic corticosteroids could be useful in selected cases of APMPPE with atypical clinical features.

Software for reading and grading diabetic retinopathy: Aravind Diabetic Retinopathy Screening 3.0.

OBJECTIVE—To evaluate the validity and reproducibility of software for reading digital images and grading diabetic retinopathy. RESEARCH DESIGN AND METHODS—A prospective, comparative observational study was conducted on a series of patients with type 2 diabetes who presented at the retina clinic of a tertiary care center in India. A total of 210 eyes of 105 patients were allocated to one of three ophthalmologists, who performed dilated indirect and direct ophthalmoscopy and subsequently assessed the digital images of the same group of patients who were masked to the patients identity. The interobserver and intertest agreement between clinical assessments and grading of diabetic retinopathy using the software was estimated. RESULTS—Moderate nonproliferative diabetic retinopathy (NPDR) was most frequently diagnosed, both clinically and on evaluating digital images. The overall agreement between the clinical grading of diabetic retinopathy and the grading of images was 81.3% (κ = 0.69, SE 0.04, P < 0.0001); there was good agreement (81.3%) for NPDR (κ = 0.61, SE 0.05, P < 0.0001), but agreement was not as good (54.6%) for proliferative diabetic retinopathy (κ = 0.29, SE 0.11, P = 0.005). Clinically significant macular edema was diagnosed in 33.3% (70 of 210) of eyes clinically and in 40.2% (84 of 209) of eyes by grading images, and there was good agreement (89.5%) between the two (κ = 0.77, SE 0.07, P < 0.0001). CONCLUSIONS—Aravind Diabetic Retinopathy Screening 3.0 is a simple and valid tool to assist in the detection of sight-threatening retinopathy and could supplement dilated fundus examinations by ophthalmologists on patients to detect diabetic retinopathy.

Current State of Care for Diabetic Retinopathy in India

In this article we review the current state of care of diabetic retinopathy in India. We discuss the magnitude of the problem; diabetes, and diabetic retinopathy in India. We highlight the causes of vision loss in diabetic retinopathy. The current level of awareness among general population and physicians is a concern. Current screening strategies practiced in India and the situational analysis of ophthalmologists in India are also reviewed. We review the current management of diabetic macular edema and proliferative diabetic retinopathy. To know the current practice pattern among retinal surgeons in India, a survey was done and the results of the survey are presented. There are few studies in the Indian population which have found some genetic risk and protective factors and a summary of these studies are also presented in this article.