Sangeetha Srinivasan

Color vision abnormalities in type II diabetes: Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular Genetics Study II report no 2

Purpose: The purpose of this study is to assess color vision abnormalities in a cohort of subjects with type II diabetes and elucidate associated risk factors. Methods: Subjects were recruited from follow-up cohort of Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular Genetics Study I. Six hundred and seventy-three eyes of 343 subjects were included from this population-based study. All subjects underwent detailed ophthalmic evaluation, including the Farnsworth-Munsell 100 hue test. Results: The prevalence of impaired color vision (ICV) was 43% (CI: 39.2–46.7). Risk factors for ICV were higher heart rate (odds ratio [OR]: 1.043, [1.023–1.064]) and a higher intraocular pressure (IOP) (OR: 1.086, [1.012–1.165]). Subjects with clinically significant macular edema (CSME) had three times higher chance of having ICV. C1, C2, and C3 are the commonly found Early Treatment Diabetic Retinopathy Study (ETDRS) patterns. The moment of inertia method showed that the angle did not reveal any specific pattern of color vision defect. Although the major and minor radii were high in those with ICV, we did not observe polarity. Confusion index was high in subjects with ICV, indicating a severe color vision defect. Conclusions: The prevalence of ICV was 43% among subjects with type II diabetes. The most commonly observed patterns were increasing severities of the blue–yellow defect on ETDRS patterns, but no specific pattern was observed at the moment of inertia analysis. The presence of CSME, a higher heart rate, and IOP was significant risk factors for ICV. This functional impairment in color vision could significantly contribute to morbidity among subjects with diabetes.

The association of smokeless tobacco use and pack-years of smokeless tobacco with age-related macular degeneration in Indian population

Abstract Aim: To explore the association of use versus no use and the influence of pack-year use of smokeless tobacco with that of early and late age-related macular degeneration (AMD) in rural and urban south Indian population. We hypothesized that the use and pack-years of use would be significantly associated with both early and late AMD. We therefore sought to examine subjects who gave a history of using smokeless tobacco and we quantified the usage as pack-years, to examine the association with that of early and late AMD. Materials and methods: This was part of Sankara Nethralaya: Rural–Urban Age-related Macular degeneration study (SN-RAM study), which was conducted between 2007 and 2010. Subjects aged 60 years or older or those turning 60 in the present calendar year, with a history of using smokeless tobacco were noted along with duration and number of packs used per day. Smokeless tobacco was defined as chewed-tobacco (loose leaves) and/or snuff (finely chopped tobacco). Subjects underwent detailed ophthalmic evaluation including cataract grading using the Lens Opacities Classification System (LOCS III), 45° 4-field stereoscopic fundus photography and AMD evaluation. Pack-years of smokeless tobacco use was stratified as <15, 15–34 and ≥35 years; the association of tobacco use and pack-years of use with that of early and late AMD was examined. A p value of < 0.05 was considered statistically significant. Results: The number of smokeless tobacco users was significantly higher in rural (n = 767) than in urban groups (n = 281), p < 0.001. Of the 1048 users, 238 subjects (23%) provided details regarding quantification of use. There were no significant differences in the pack-years between rural and urban areas, p = 0.756 or that between AMD and no AMD, p = 0.562. Use of smokeless tobacco compared with no use was significantly associated with late AMD, OR= 3.178, 95%CI: 1.095, 9.227, p = 0.033, when adjusted for age, gender, rural-urban differences, presence of diabetes, socioeconomic status, systolic and diastolic blood pressure, total cholesterol, low-density and high-density lipoprotein levels. The association was not significant for early AMD, p = 0.582. The pack-years of use did not show a statistically significant association with early or late AMD. Furthermore, out of the 1048 subjects, 547 reported as using areca nut. Of which, 415 (75.8%) subjects had no AMD, 119 (21.7%) showed evidence of early AMD and 13 (2.4%) had late AMD. There was no significant association between the use of areca nut and early AMD, (X2 (1, N = 930) = 2.345, p = 0.126) or with that of late AMD (X2 (1, N = 761) = 0.075, p = 0.785). Conclusions: Smokeless tobacco use compared with no use, is associated with late AMD, regardless of the pack-years of use. Tobacco use is a modifiable risk factor. Efforts to reduce or stop the use of smokeless tobacco is indicated in an effort to prevent vision loss with respect to late AMD.

Development and Validation of a Diabetic Retinopathy Referral Algorithm Based on Single-Field Fundus Photography

Purpose To develop a simplified algorithm to identify and refer diabetic retinopathy (DR) from single-field retinal images specifically for sight-threatening diabetic retinopathy for appropriate care (ii) to determine the agreement and diagnostic accuracy of the algorithm as a pilot study among optometrists versus “gold standard” (retinal specialist grading). Methods The severity of DR was scored based on colour photo using a colour coded algorithm, which included the lesions of DR and number of quadrants involved. A total of 99 participants underwent training followed by evaluation. Data of the 99 participants were analyzed. Fifty posterior pole 45 degree retinal images with all stages of DR were presented. Kappa scores (κ), areas under the receiver operating characteristic curves (AUCs), sensitivity and specificity were determined, with further comparison between working optometrists and optometry students. Results Mean age of the participants was 22 years (range: 19–43 years), 87% being women. Participants correctly identified 91.5% images that required immediate referral (κ) = 0.696), 62.5% of images as requiring review after 6 months (κ = 0.462), and 51.2% of those requiring review after 1 year (κ = 0.532). The sensitivity and specificity of the optometrists were 91% and 78% for immediate referral, 62% and 84% for review after 6 months, and 51% and 95% for review after 1 year, respectively. The AUC was the highest (0.855) for immediate referral, second highest (0.824) for review after 1 year, and 0.727 for review after 6 months criteria. Optometry students performed better than the working optometrists for all grades of referral. Conclusions The diabetic retinopathy algorithm assessed in this work is a simple and a fairly accurate method for appropriate referral based on single-field 45 degree posterior pole retinal images.

Four-year incidence and progression of visual impairment in a South Indian population with diabetes

Purpose: The aim of this study is to investigate the 4-year incidence and progression of visual impairment (VI) and the associated risk factors for incident VI in a South Indian population with type 2 diabetes. Methods: A total of 634 participants with type 2 diabetes were found eligible after 4 years. Visual acuity (VA) was estimated using the modified Early Treatment Diabetic Retinopathy Study protocol. VA in the better eye was considered for the assessment of VI based on the World Health Organization criteria. Mild VI was defined as VA <20/40 but up to 20/60, moderate VI as VA <20/60 but up to 20/200, severe VI as VA <20/200 but up to 10/200, and blindness as VA worse than 10/200. Results: The 4-year incidence of any VI, mild VI, moderate VI, severe VI, and blindness was 21.7%, 18.3%, 3.4%, 0.0%, and 0.0%, respectively; of the 13 participants with VI at baseline, 12 (92%) showed worsening/progression of VI on follow-up. Multiple logistic regression showed that nuclear cataract of grades >4.0 (odds ratio [OR]: 2.612 [1.148–5.942], P = 0.022) and lower socioeconomic score (OR: 0.965 [95% confidence interval, (0.933-0.998)], P = 0.040) were associated with the risk of future incident VI. Refractive error (47%) and cataract (30%) were identified as the leading causes of incident VI at follow-up. Conclusions: VI seems to be a significant problem among diabetic participants in the South Indian population. Refractive error and cataract are the leading but treatable causes of incident VI in this population and would benefit from intervention.

Influence of serum lipids on the incidence and progression of diabetic retinopathy and macular oedema: Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular Genetics Study (SN-DREAMS II)

The importance of lipids on incidence and progression of diabetic retinopathy has not been studied in the Indian population.

Prevention of Age-Related Macular Degeneration

Abstract: Age‐related macular degeneration (AMD) compromises quality of life. However, the available therapeutic options are limited. This has led to the identification of modifiable risk factors to prevent the development or alter the natural course and prognosis of AMD. The identification and modification of risk factors has the potential for greater public health impact on reducing morbidity from AMD. Likewise, identifying the imaging clues and genetic clues could serve as a guide to recognizing the propensity for progression to severe and end stages of the disease. Several attempts, both successful and unsuccessful, have been made for interventions that could delay the progression of AMD. Of these, pharmacological interventions have shown promising results. The Age‐Related Eye Disease Study 1 and 2 have shown the beneficial role of antioxidants in a selected group of patients.

Structural and functional retinal abnormalities in type 2 diabetes with obstructive sleep apnea.

Dear Editor, We read with great interest the article titled “Choroidal thickness changes in obstructive sleep apnea syndrome: a systematic review and meta-analysis” by He et al. [1]. The authors observed evidence for reduced choroidal thickness (CT) in obstructive sleep apnea syndrome. Obstructive sleep apnea (OSA) is a sleep-related breathing disorder characterized by blockage of the upper airway, leading to partial reductions (hypopneas) and complete pauses (apneas) in breathing. This occurs when the muscles in the back of the throat relax, followed by collapse of the soft tissue. The episode usually lasts 10 to 30 s, but may persist for 1 min or longer, [2] leading to sudden reductions in blood oxygen saturation. We investigated the retinal thickness assessed as center point thickness (CPT), central subfoveal thickness (CSFT), retinal nerve fibre layer (RNFL) thickness, choroidal thickness (CT), dynamic contour tonometry for intraocular pressure (IOP) and ocular pulse amplitudes (OPA), color vision total error scores, body mass index (BMI), waistto-hip ratio (WHR), and 4-channel polysomnography in 16 people with type 2 diabetes mellitus (Type 2 DM) in an Indian population who were previously diagnosed to have OSA and were advised to use continuous positive airway pressure treatment at the sleep center. We defined sleep apnea as apnea-hypopnea index (AHI) ≥ 5 [2]. The study has been approved by the Institutional Review Board of Vision Research Foundation and has been performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study. All continuous variables assessed in our study were normally distributed. Table 1 provides a summary of the demographic, sleep study, and ophthalmic variables. Of the 16 individuals, only two patients (12.5 %) had diabetic retinopathy (mild non-proliferative diabetic retinopathy (NPDR)) one with unilateral and the other with bilateral diabetic retinopathy (DR) (both men, with a mean age of 46 years). Fourteen individuals (87.5 %) had no DR. Based on the AHI, both individuals with DR were identified as having severe OSA. In the group without DR, one person (7.2 %) had mild OSA, five individuals (35.7 %) with moderate OSA, and eight (57.1 %) with severe OSA. DR did not show significant association with the AHI in right eyes (RE) or in left eyes (LE) (r = 0.277, p = 0.999 in RE and r = 0.234, p = 0.421 in LE). Pearson’s correlations were performed between AHI (on a continuous scale) and a range of demographic, sleep study, and ophthalmic variables. Table 2 provides a summary of the correlations. Male gender was significantly associated with AHI (r = 0.655, p = 0.006). Age, blood pressure, duration of diabetes, BMI, and WHR did not show statistically significant correlations with the AHI. The average and lowest oxygen saturation showed a negative trend but was not statistically significant. For the reason that DR can present itself unilaterally or bilaterally, we collected data from both eyes of participants. * Rajiv Raman rajivpgraman@gmail.com

Failure to initiate early insulin therapy - A risk factor for diabetic retinopathy in insulin users with Type 2 diabetes mellitus: Sankara Nethralaya-Diabetic Retinopathy Epidemiology and Molecular Genetics Study (SN-DREAMS, Report number 35).

Context: Insulin users have been reported to have a higher incidence of diabetic retinopathy (DR). Aim: The aim was to elucidate the factors associated with DR among insulin users, especially association between duration, prior to initiating insulin for Type 2 diabetes mellitus (DM) and developing DR. Materials and Methods: Retrospective cross-sectional observational study included 1414 subjects having Type 2 DM. Insulin users were defined as subjects using insulin for glycemic control, and insulin nonusers as those either not using any antidiabetic treatment or using diet control or oral medications. The duration before initiating insulin after diagnosis was calculated by subtracting the duration of insulin usage from the duration of DM. DR was clinically graded using Klein′s classification. SPSS (version 9.0) was used for statistical analysis. Results: Insulin users had more incidence of DR (52.9% vs. 16.3%, P < 0.0001) and sight threatening DR (19.1% vs. 2.4%, P < 0.0001) in comparison to insulin nonusers. Among insulin users, longer duration of DM (odds ratio [OR] 1.12, 95% confidence interval [CI] 1.00-1.25, P = 0.044) and abdominal obesity (OR 1.15, 95% CI 1.02-1.29, P = 0.021) was associated with DR. The presence of DR was significantly associated with longer duration (≥5 years) prior to initiating insulin therapy, overall (38.0% vs. 62.0%, P = 0.013), and in subjects with suboptimal glycemic control (32.5% vs. 67.5%, P = 0.022). Conclusions: The presence of DR is significantly associated with longer duration of diabetes (>5 years) and sub-optimal glycemic control (glycosylated hemoglobin <7.0%). Among insulin users, abdominal obesity was found to be a significant predictor of DR; DR is associated with longer duration prior to initiating insulin therapy in Type 2 DM subjects with suboptimal glycemic control.

Screening practices for diabetic retinopathy

Diabetic retinopathy (DR) is a major cause of acquired blindness but is asymptomatic in its early stages. Therefore, there is an urgent need to establish a nation-wide efficient screening strategy for early detection, accurate diagnosis and timely treatment of vision threatening DR.