Prema Raju

Ocular biometry in occludable angles and angle closure glaucoma: a population based survey

Aim: To compare ocular biometric values in a population based sample of eyes with occludable angles, angle closure glaucoma, and normal subjects. Method: 2850 subjects from a population based glaucoma prevalence study underwent complete ocular examination including indentation gonioscopy. Ocular biometry was performed in all subjects classified to have occludable angles (n = 143); angle closure glaucoma (n = 22), and a random subgroup of 419 normal subjects. Ocular biometry readings between the groups were compared and statistically analysed using “t,” “z,” and Mann-Whitney U tests. Results: The mean age among subjects with occludable angles (54.43 (SD 9.53) years) and angle closure glaucoma (57.45 (8.5) years) was significantly higher (p<0.001) than normal subjects (49.95 (9.95) years). Axial length was shorter (p<0.001) in the occludable angle group (22.07 (0.69) mm) compared to the normal group (22.76 (0.78) mm). Anterior chamber depth (ACD) was shallower (p<0.001) among subjects with occludable angles (2.53 (0.26) mm) than normal subjects (3.00 (0.30) mm). Lens thickness (LT) was greater (p<0.001) in people with occludable angles (4.40 (0.53) mm) compared to normal subjects (4.31 (0.31) mm). No significant difference was noted in axial length, ACD (p = 0.451), and LT (p = 0.302) between angle closure glaucoma and occludable eyes. Conclusion: South Indian eyes with angle closure glaucoma and occludable angles seem to have significantly shorter axial lengths, shallower anterior chambers and greater lens thickness compared to the normal group.

Pseudoexfoliation in south India

Aim: To study the profile of pseudoexfoliation in a population based study. Method: 2850 consecutive subjects aged 40 years or older from a population based survey in a rural area of southern India underwent complete ophthalmic evaluation including history, visual acuity testing, refraction, slit lamp examination, applanation tonometry, gonioscopy, and dilated examination of the lens (including LOCS II grading of cataract), fundus, and optic disc. Patients with pseudoexfoliation syndrome were identified and their data were analysed with respect to age, sex, intraocular pressure, gonioscopic grading, cataract, and optic neuropathy. Results: 108 subjects had pseudoexfoliation syndrome (3.8 %). There was a significant increase in prevalence with age but no sex predilection. The condition was unilateral in 53 cases (49.1%) and bilateral in 55 cases (50.9%). 18 cases with pseudoexfoliation (16.7%) had high intraocular pressure (>21 mm Hg), 16 cases (14.8%) had occludable angles, and 14 cases (13%) had pseudoexfoliation glaucoma. There was a significantly higher prevalence of cataract among people with pseudoexfoliation compared to those without pseudoexfoliation (p = 0.014). Conclusion: The prevalence of pseudoexfoliation syndrome in the rural population of south India was 3.8%. Raised intraocular pressure was seen in 16.7% of people with pseudoexfoliation and glaucoma was present in 13%.

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.

Methods and design of the Chennai Glaucoma Study.

PURPOSE To describe the methodology of a population-based study to estimate the prevalence of glaucoma in a rural and urban South Indian population and to study the genetics of glaucoma in this population. METHODS A sample size of 4758 each for rural and urban populations in the Indian state of Tamil Nadu was calculated. Eligible subjects aged 40 years and above from the rural study area covering 32 contiguous villages and the urban area comprising five random clusters in Chennai city are enumerated. Demographic data are collected in the field. A detailed clinical examination, including glaucoma diagnostic procedures, is conducted at the examination centre. Pedigree ascertainment and genetic studies are performed for subjects with occludable angles or glaucoma. Data are recorded in a computerised database. CONCLUSIONS This study is expected to result in an estimation of the prevalence and a better understanding of the genetics of glaucoma in this region.

Influence of tobacco use on cataract development

Aim: To study the influence of tobacco use on cataract formation in a rural South Indian population. Methods: 3924 subjects from the Chennai Glaucoma Study conducted in rural south India underwent a comprehensive eye examination, including Lens Opacities Classification System II grading. Information on tobacco use, type of tobacco (smoking and smokeless), duration and quantity of use was collected. Results: 1705 (male:female (M:F) 1106:599) people used tobacco and were significantly older (mean (standard deviation (SD)) age 55.80 (10.64) years) than non-users (52.23 (10.51); p<0.001). 731 (M:F 730:1) people smoked, 900 (M:F 302:598) used smokeless tobacco, and 74 (M:F, 74:0) used tobacco in both forms. The unadjusted and adjusted (age and sex) odds ratio (OR) for a positive history of tobacco use and cataract was 1.72 (95% confidence interval (CI) 1.51 to 1.96) and 1.39 (95% CI 1.15 to 1.68), respectively. The unadjusted OR for smokers and smokeless tobacco users was 1.04 (95% CI 0.88 to 1.23) and 2.74 (95% CI 2.31 to 3.26), respectively. The adjusted OR was 1.19 (95% CI 0.89 to 1.59) and 1.54 (95% CI 1.22 to 1.95), respectively. No significant association was noted between smoking and any particular type of cataract. Smokeless tobacco use was found to be significantly associated with nuclear cataract even after adjusting for age and sex (OR 1.67, p = 0.067, 95% CI 1.16 to 2.39). Conclusion: Tobacco use was significantly associated with cataract. Smoking was not found to be significantly associated with cataract formation; however, smokeless tobacco use was more strongly associated with cataract.

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.

Neural rim characteristics of healthy South Indians: the Chennai Glaucoma Study.

PURPOSE To report neural rim dimensions for South Indians and examine rim shape with relevance to clinical evaluation. METHODS Healthy phakic participants (n = 623) of the Chennai Glaucoma Study with normal frequency-doubling perimetry underwent complete eye examinations including optic disc digital stereophotography. Planimetry was performed under stereoviewing conditions using custom software. Rim area, shape, and associations were examined. Rim area asymmetry was studied in a subgroup of 565 subjects. RESULTS Mean neuroretinal rim area was 2.29 +/- 0.39 mm(2). Disc area (P < 0.001) and type of cupping (P < 0.001) were associated with rim area. Mean rim area asymmetry was 0.18 +/- 0.15 mm(2); 95% of subjects had asymmetry < 0.5 mm(2). Disc area asymmetry (0.359, P < 0.0001) and intraocular pressure (IOP) asymmetry (P = 0.004) were related to rim area asymmetry. On average, the inferior rim was thickest and the temporal was thinnest. Mean inferior by superior rim width was 1.18 +/- 0.17; 2.5 percentile, 0.9. Thirty-eight (7.1%) subjects had the superior rim thicker than the inferior rim, the occurrence of which was associated with disc torsion (P = 0.002) and male sex (P = 0.04). Of the clinically relevant rim width measures in glaucoma (i.e., inferior, superior, and temporal) the temporal rim was thinnest in 469 (87.8%) eyes. Horizontally oval disc shape (P < 0.0001), type of cupping (P = 0.006), and astigmatism (P = 0.001) were associated with the presence of thicker temporal than superior/inferior rims. CONCLUSIONS The report provides hitherto unreported neural rim measurements among healthy South Indians. The ISNT rule (inferior rim thicker than superior rim, thicker than nasal rim, thicker than temporal rim) was violated in a significant minority. Physiological associations with such violations are described.

Outcomes of cataract surgery in a rural and urban south Indian population.

Purpose: To assess the visual outcome after cataract surgery in a south Indian population. Materials and Methods: Population-based cross-sectional study of subjects aged 40 years or more. Three thousand nine hundred and twenty-four rural subjects from 27 contiguous villages and 3850 urban subjects from five randomly selected divisions were studied. All subjects underwent a comprehensive ophthalmic examination that included visual acuity, refraction, slit-lamp biomicroscopy, applanation tonometry, gonioscopy, and dilated retinal examination. Statistical Analysis: Chi square test, t test and multivariate analysis were used. Results: Five hundred and twenty-eight (216 males, 312 females, 781 eyes) rural subjects (13.5%, 95% confidence interval (CI) 12.4% to 14.6%) and 406 (197 males, 209 females, 604 eyes) urban subjects (10.5%, 95% CI 9.6-11.5%) had undergone cataract surgery. Outcome of cataract surgery was defined based on visual acuity. Using best-corrected visual acuity for classification, the single most important cause for visual impairment was cystoid macular edema in the aphakic group and posterior capsule opacification in the pseudophakic group. Aphakia (visual acuity of <20/60 to ≤20/400 - odds ratio (OR) 1.8; 95% CI 1.3 to 2.6%, visual acuity of <20/400 - OR 6.2; 95% 4.0 to 9.8%), rural residence (visual acuity of <20/60 to ≤20/400 - OR 3.2; 95% CI 2.2 to 4.5% and visual acuity of <20/400 - OR OR 3.5; 95% CI 2.3 to 5.5%) were associated with visual impairment. The urban cataract-operated population had significantly more pseudophakics (P < 0.001), men (P = 0.02) and literates (P < 0.001). In the rural group the prevalence of cataract surgery (13.5% vs. 10.5%, P < 0.001) and number of people that had undergone cataract surgery within three years prior to examination (P < 0.001) were significantly greater. In 30% of rural and 16% of urban subjects uncorrected refraction was the cause of visual impairment. Conclusions: Surgery-related complications were major causes for visual acuity of <20/60.

The Chennai glaucoma study: prevalence and risk factors for glaucoma in cataract operated eyes in urban Chennai.

We report the prevalence and risk factors for glaucoma among aphakes and pseudophakes in 3850 subjects who participated in a population-based study in urban south India. The subjects underwent an ophthalmic examination including applanation tonometry, gonioscopy, optic disc evaluation and frequency doubling perimetry. Glaucoma was diagnosed using the International Society of Geographical and Epidemiological Ophthalmology (ISGEO) criteria. Thirty eight, 15 aphakes and 23 pseudophakes (0.99% of 3850 subjects) of the 406 persons who had undergone cataract surgery were diagnosed with glaucoma. Aphakes/pseudophakes were at higher risk of glaucoma as compared to the phakic population (Odds Ratio: 2.71, 95% CI: 1. 94, 3.38, p=0.001). On multivariate analysis, older age and higher intra ocular pressure were risk factors for glaucoma. Blindness attributable to glaucoma was detected in 20% of aphakic and 4.3% of pseudophakic eyes. Glaucoma was a significant cause of morbidity in those who had undergone cataract surgery in this urban population.

Glaucoma in aphakia and pseudophakia in the Chennai Glaucoma Study.

Aim: To determine the prevalence of glaucoma among aphakes and pseudophakes in a rural population of southern India. Methods: 3924 subjects aged 40 years or above underwent complete ophthalmic examination. Glaucoma in aphakia/pseudophakia was diagnosed using International Society of Geographical and Epidemiological Ophthalmology criteria in aphakic/pseudophakic people. Results: 54 subjects (37 aphakes, 17 pseudophakes) (1.38% of 3924 subjects, 11.2% of 482 aphakes/pseudophakes) had glaucoma in aphakia/pseudophakia. Aphakia, age, intraocular pressure (IOP), pseudoexfoliation, and peripheral anterior synechiae greater than or equal to 180 degrees of the angle were risk factors for glaucoma on univariate analysis. On multivariate analysis, IOP and aphakia were independent risk factors for glaucoma. 39 people (72.22%) with glaucoma had normal IOP at presentation. None of the people with glaucoma were aware of the disease. Blindness in one or both eyes was seen in 12 subjects (10 unilateral and two bilateral)—that is, 22.22% of people with glaucoma in aphakia/pseudophakia. Conclusions: Glaucoma is an important cause of ocular morbidity among aphakes and pseudophakes in this rural population of south India. This glaucoma, responsible for unilateral or bilateral blindness in 22.2% of those affected, was entirely undetected in this study population.