Rashima Asokan

Central corneal thickness in adult South Indians: the Chennai Glaucoma Study.

OBJECTIVE To evaluate the characteristics of central corneal thickness (CCT) and its association with age, gender, and intraocular pressure in rural and urban South Indian populations. DESIGN Population-based cross-sectional study. PARTICIPANTS Seven thousand seven hundred seventy-four subjects (rural-to-urban ratio, 3924:3850) aged 40 years and older were examined at a dedicated facility in the base hospital. INTERVENTION All subjects underwent a complete ophthalmic examination that included CCT measurements with an ultrasonic pachymeter and applanation tonometry. MAIN OUTCOME MEASURES Central corneal thickness. RESULTS Of the 7774 subjects examined, 974 had undergone cataract surgery and were excluded. The remaining 6800 were bilaterally phakic, of which 46 were excluded (17 glaucoma subjects receiving treatment, 12 with corneal pathologic features and 17 with incomplete data) and 6754 subjects data were analyzed. The mean CCT for the population was 511.4+/-33.5 microm, and CCT in males (515.6+/-33.8 microm) was significantly (P = 0.0001) greater than females (508.0+/-32.8 microm). The CCT was significantly greater (by 18 microm) in the urban population and decreased with age in both genders (P<0.0001). The decrease per decade was 4.34 microm (95% confidence interval [CI], 3.24-5.44) in the rural population and 2.41 microm (95% CI, 1.25-3.53) in the urban population. A 100-microm increase in CCT was associated with a 1.96-mmHg increase in intraocular pressure in the rural population, versus 2.45 mmHg for every 100 microm in the urban population. CONCLUSIONS In this population-based study, females and subjects living in a rural area had thinner corneas. A negative association with age and a positive association with intraocular pressure were seen. These findings will have implications in the diagnosis and management of glaucoma in this population. FINANCIAL DISCLOSURE(S) Proprietary or commercial disclosure may be found after the references.

Prevalence and associated factors for pterygium and pinguecula in a South Indian population

Citation information: Rashima A, Ramesh S Ve, Lokapavani V, Vijaya L & George R. Prevalence and associated factors for pterygium and pinguecula in a South Indian population. Ophthalmic Physiol Opt 2011. doi: 10.1111/j.1475‐1313.2011.00882.x

Prevalence and causes of vision loss in Central and South Asia: 1990–2010

Background To examine the prevalence, patterns and trends of vision impairment and its causes from 1990 to 2010 in Central and South Asia. Methods Based on the Global Burden of Diseases Study 2010 and ongoing literature searches, we examined prevalence and causes of moderate and severe vision impairment (MSVI; presenting visual acuity <6/18, ≥3/60) and blindness (presenting visual acuity <3/60). Results In Central Asia, the estimated age-standardised prevalence of blindness decreased from 0.4% (95% CI 0.3% to 0.6%) to 0.2% (95% CI 0.2% to 0.3%) and of MSVI from 3.0% (95% CI 1.9% to 4.7%) to 1.9% (95% CI 1.2% to 3.2%), and in South Asia blindness decreased from 1.7% (95% CI 1.4% to 2.1%) to 1.1% (95% CI 0.9% to 1.3%) and MSVI from 8.9% (95% CI 6.9% to 10.9%) to 6.4% (95% CI 5.2% to 8.2%). In 2010, 135 000 (95% CI 99 000 to 194 000) people were blind in Central Asia and 10 600 000 (95% CI 8 397 000 to 12 500 000) people in South Asia. MSVI was present in 1 178 000 (95% CI 772 000 to 2 243 000) people in the Central Asia, and in 71 600 000 (95% CI 57 600 000 to 92 600 000) people in South Asia. Women were generally more often affected than men. The leading causes of blindness (cataract) and MSVI (undercorrected refractive error) did not change from 1990 to 2010. Conclusions The prevalence of blindness and MSVI in South Asia is still three times higher than in Central Asia and globally, with women generally more often affected than women. In both regions, cataract and undercorrected refractive error were major causes of blindness and MSVI.

Genetic Association of SNPs near ATOH7, CARD10, CDKN2B, CDC7 and SIX1/SIX6 with the Endophenotypes of Primary Open Angle Glaucoma in Indian Population

Primary open angle glaucoma (POAG) belonging to a group of optic neuropathies, result from interaction between genetic and environmental factors. Study of associations with quantitative traits (QTs) is one of the successful strategies to understand the complex genetics of POAG. The current study attempts to explore the association of variations near/in genes like ATOH7, SIX1/SIX6 complex, CDKN2B, CARD10, and CDC7 with POAG and its QTs including vertical cup to disc ratio (VCDR), central corneal thickness (CCT), intra ocular pressure (IOP), and axial length (AL). Case-control study design was carried out in a sample size of 97 POAG cases and 371 controls from South India. Model-based (additive, recessive, dominant) association of the genotypes and their interaction was carried out between cases and controls using chi-square, linear and logistic regression methods. Nominal significance (P<0.05) was observed for QTs like i) VCDR with SNPs rs1900004 (ATOH7); rs1192415 (CDC7); rs10483727 (SIX1/SIX6), rs9607469 (CARD10); ii) CCT with rs1192415; iii) IOP with rs1900004 and iv) AL with rs1900004 and rs1063192 (CDKN2B). We were able to replicate previously known interactions between ATOH7-SIX6 and SIX6-CDKN2B along with few novel interactions between ATOH7—CDC7 and SIX6 with genes including CARD10 and CDC7. In summary, our results suggest that a probable interaction among the candidate genes for QTs, play a major role in determining the individual’s susceptibility to POAG.

Six-year incidence of angle-closure disease in a South Indian population: the Chennai Eye Disease Incidence Study.

PURPOSE To estimate the 6-year incidence of primary angle-closure (PAC) disease among adult population aged 40 years and older from rural and urban south India. DESIGN Population-based longitudinal study. METHODS A complete ophthalmologic examination, including applanation tonometry, gonioscopy, biometry, stereoscopic fundus examination, and automated perimetry was performed at both baseline and at the 6-year follow up at base hospital. Incident PAC disease was defined as the development of PAC disease during the 6-year follow-up in phakic subjects without PAC disease at baseline. Diagnosis was made using the International Society Geographical and Epidemiological Ophthalmology classification. RESULTS The data were analyzed for 3350 subjects (mean age, 56.4 ± 8.9 years; 1547 males, 1803 females) for a diagnosis of PAC disease at baseline and at follow-up examinations. The incidence of PAC disease was identified in 134 subjects (6-year incidence rate, 4.0%; 95% confidence interval (CI), 3.3-4.7). Among the 134 subjects, 88 subjects (2.6%, 95% CI, 2.1-3.2) were primary angle-closure suspects; 37 subjects (1.1%, 95% CI, 0.7-1.5) had primary angle closure, and 9 subjects (0.3%, 95% CI, 0.1-0.4) had primary angle-closure glaucoma. There was an inverse relationship between the incidence of PAC disease and the cataract surgery rates. Significant risk factors for PAC disease on logistic regressions were higher intraocular pressure, increased lens thickness, shorter axial length, shallow anterior chamber depth, anteriorly positioned lens, and hyperopia. CONCLUSIONS The average incidence of PAC disease per year was 0.7%. All biometric parameters were found to be strong predictors for the incidence of PAC disease.

Prevalence and causes of low vision and blindness in an urban population: The Chennai Glaucoma Study

Aim: To evaluate the prevalence and causes of low vision and blindness in an urban south Indian population. Settings and Design: Population-based cross-sectional study. Exactly 3850 subjects aged 40 years and above from Chennai city were examined at a dedicated facility in the base hospital. Materials and Methods: All subjects had a complete ophthalmic examination that included best-corrected visual acuity. Low vision and blindness were defined using World Health Organization (WHO) criteria. The influence of age, gender, literacy, and occupation was assessed using multiple logistic regression. Statistical Analysis: Chi-square test, t-test, and multivariate analysis were used. Results: Of the 4800 enumerated subjects, 3850 subjects (1710 males, 2140 females) were examined (response rate, 80.2%). The prevalence of blindness was 0.85% (95% CI 0.6–1.1%) and was positively associated with age and illiteracy. Cataract was the leading cause (57.6%) and glaucoma was the second cause (16.7%) for blindness. The prevalence of low vision was 2.9% (95% CI 2.4–3.4%) and visual impairment (blindness + low vision) was 3.8% (95% CI 3.2–4.4%). The primary causes for low vision were refractive errors (68%) and cataract (22%). Conclusions: In this urban population based study, cataract was the leading cause for blindness and refractive error was the main reason for low vision.

Is prophylactic laser peripheral iridotomy for primary angle closure suspects a risk factor for cataract progression? The Chennai Eye Disease Incidence Study

Background To report the risk of cataract progression among primary angle closure suspects (PACS) 6 years after they underwent laser peripheral iridotomy (LPI). Methods In the Chennai Eye Disease Incidence Study, 6 years after their baseline evaluation, 4421 subjects were examined again. As part of a detailed evaluation cataract was graded using the Lens Opacities Classification System II; progression was defined as change of cataract by two or more grades or history of cataract surgery in the 6-year period. Only bilaterally phakic subjects with less than N2 or C2 or P2 cataract at baseline with no history of any form of glaucoma, primary angle closure and pseudoexfoliation were included. Results There were 3205 eligible subjects. Of these, 190 had undergone LPI for PACS. In comparison to the study population, they were significantly older (p<0.001), female (p=0.008), urban residents (p=0.001) and patients with hypertension (p<0.001). During the intervening period, 53 subjects had undergone cataract surgery. The cataract progression rate was significantly greater (OR 1.7, 95% CI 1.3 to 2.4, p<0.001) in those who had undergone LPI. For the study population the baseline risk factors for progression of cataract were age (p<0.001), female gender (p=0.01), diabetes (p<0.001) and LPI (p<0.001). Diabetes and female gender were significant risk factors for nuclear and cortical cataract progression; LPI was a risk factor only for cortical cataract (OR 1.6, 95% CI 1.1 to 2.3, p=0.007). Conclusions There was significant cataract progression in 6 years following LPI for PACS.

Baseline Risk Factors for Incidence of Blindness in a South Indian Population: The Chennai Eye Disease Incidence Study

PURPOSE To report the baseline risk factors and causes for incident blindness. METHODS Six years after the baseline study, 4419 subjects from the cohort underwent a detailed examination at the base hospital. Incident blindness was defined by World Health Organization criteria as visual acuity of less than 6/120 (3/60) and/or a visual field of less than 10° in the better-seeing eye at the 6-year follow-up, provided that the eye had a visual acuity of better than or equal to 6/120 (3/60) and visual field greater than 10° at baseline. For incident monocular blindness, both eyes should have visual acuity of more than 6/120 (3/60) at baseline and developed visual acuity of less than 6/120 (3/60) in one eye at 6-year follow-up. RESULTS For incident blindness, 21 participants (0.48%, 95% confidence interval [CI], 0.3-0.7) became blind; significant baseline risk factors were increasing age (P = 0.001), smokeless tobacco use (P < 0.001), and no history of cataract surgery (P = 0.02). Incident monocular blindness was found in 132 participants (3.8%, 95% CI, 3.7-3.8); it was significantly more (P < 0.001) in the rural population (5.4%, 95% CI, 5.4-5.5) than in the urban population (1.9%, 95% CI, 1.8-1.9). Baseline risk factors (P < 0.001) were increasing age and rural residence, and no history of cataract surgery was a protective factor (P = 0.03). CONCLUSIONS Increasing age was a significant risk factor for blindness and monocular blindness. No history of cataract surgery was a risk factor for blindness and a protective factor for monocular blindness.

Comparison of saccadic reaction time between normal and glaucoma using an eye movement perimeter

Aim: To compare the saccadic reaction time (SRT) in both the central and peripheral visual field in normal and glaucomatous eyes using eye movement perimetery (EMP). Materials and Methods: Fifty-four normal and 25 glaucoma subjects underwent EMP and visual field testing on the Humphrey Field Analyser (HFA) 24-2 program. The EMP is based on infrared tracking of the corneal reflex. Fifty-four test locations corresponding to the locations on the 24-2 HFA program were tested. SRTs at different eccentricities and for different severities of glaucoma were compared between normal and glaucoma subjects. Results: Mean SRT was calculated for both normal and glaucoma subjects. Mann-Whitney U test showed statistically significant (P < 0.001) differences in SRTs between normal and glaucoma subjects in all zones. Conclusion: SRT was prolonged in eyes with glaucoma across different eccentricities.

Six-year incidence of visually significant age-related cataract: the Chennai eye disease incidence study.

The aim of this study is to report the 6‐year incidence of age‐related cataract in a population‐based study.