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

BACKGROUND: The aim of this study is to report the 6-year incidence of age-related cataract in a population-based study. DESIGN: The design used is a population-based cohort study. PARTICIPANTS: A cohort of 2484 phakic subjects, aged 40 years and above at baseline, from a south Indian population was included in the study. METHODS: Bilateral phakics with visual acuity of 6/12 or better and cataract less than N2, C2 and P2 on the Lens Opacities Classification System II at baseline were included. Subjects with glaucoma and corneal or retinal diseases were excluded. Incident visually significant cataract was defined as visual acuity of less than 6/18 with a corresponding one grade or greater change in Lens Opacities Classification System II or history of having undergone cataract surgery with evidence of pseudophakia or aphakia at the 6-year follow-up. MAIN OUTCOME MEASURES: Six-year incidence of visually significant cataract and associated risk factors data were collected. RESULTS: Incident visually significant cataract at 6 years was seen in 158 subjects (6.36%, 95% CI: 5.40-7.32, phakics:pseudophakics/aphakics 70:88). Incidence was higher in the rural cohort as compared with the urban cohort (P < 0.001). Incidence increased with age and was highest in the ≥70 years age group (odds ratio (OR):31.23, 95% CI: 15.20-64.16, P < 0.001). Other associated risk factors included illiteracy (OR 1.75, 95% CI: 1.17-2.61, P = 0.007) and smoking (OR 1.77, 95% CI: 1.08-2.88, P = 0.02). CONCLUSIONS: A significant proportion of the population developed visually significant age-related cataract at 6 years. Incident visually significant cataract was significantly greater for the rural cohort between 50 and 69 years old.

The Prevalence of Pseudoexfoliation and the Long-term Changes in Eyes With Pseudoexfoliation in a South Indian Population.

PURPOSE: To report the prevalence, long-term changes and associated factors for pseudoexfoliation (PEX) in a population aged 40 years and above from rural and urban south India. MATERIALS AND METHODS: At baseline (the Chennai Glaucoma Study), 7774 subjects were examined. After 6 years, as a part of the incidence study, 133 of the 290 subjects diagnosed with PEX at baseline were reexamined for long-term changes. Participants had detailed examination at base hospital. RESULTS: At baseline PEX was noted in 290 [3.73%, 95% confidence interval (CI), 3.3-4.2] subjects. It was associated with glaucoma in 24 (8.3%), ocular hypertension (OHT) in 21 (7.2%), and occludable angles in 24 (8.3%) subjects. The age-adjusted and sex-adjusted prevalence was 3.41% (95% CI, 3.39-3.43). Increasing age was a significant associated factor. Using the 40- to 49-year age group as a reference, the odds ratio increased from 8.4 (95% CI, 4.1-17.1) for the 50- to 59-year age group to 51.2 (95% CI, 25.8-101.6) for the 70 years and above age group. Other associated factors were rural residence (P<0.001), higher intraocular pressure (P<0.001), cataract (P<0.001), being underweight (P=0.01), manual labor (P=0.03), and aphakia (P<0.001). Of the 133 subjects reexamined, 8 (6.0%) subjects developed glaucoma and all had OHT at baseline. Rates of cataract surgery were (P<0.001) higher in subjects with PEX. CONCLUSION: Prevalence of PEX was higher in rural population and baseline OHT was a significant factor for conversion to glaucoma.

Six-Year Incidence and Baseline Risk Factors for Pseudoexfoliation in a South Indian Population: The Chennai Eye Disease Incidence Study.

OBJECTIVE: To estimate the 6-year incidence of pseudoexfoliation and its risk factors in a South Indian population. DESIGN: Longitudinal population-based study. PARTICIPANTS: Subjects 40 years of age or older without pseudoexfoliation at baseline. METHODS: Participants were examined at baseline and after a 6-year interval. The presence of pseudoexfoliation was looked for after pupillary dilation in either or both eyes at 1 or more locations. Glaucoma was defined using the International Society of Geographical and Epidemiological Ophthalmology Classification. Logistic regression was performed to identify the baseline risk factors that could predict the incident pseudoexfoliation. MAIN OUTCOME MEASURES: Six-year incidence, associated risk factors, and rural-versus-urban differences. RESULTS: From the study cohort of 4228 subjects, 87 subjects (male-to-female ratio, 48:39; rural-to-urban ratio, 69:18) demonstrated incident pseudoexfoliation (2.03%; 95% confidence interval [CI], 1.6-2.5; rural: -2.86%; 95% CI, 1.6-2.5; urban: 0.96%; 95% CI, 0.5-1.4). Pseudoexfoliation was associated with glaucoma in 1 subject (1.1%), with primary angle-closure suspicion in 10 subjects (11.5%), and with ocular hypertension in 2 subjects (2.2%). Significant predictive baseline risk factors were older age (P < 0.001), rural residence (P < 0.001), illiteracy (P = 0.02), pseudophakia (P = 0.04), and nuclear cataract (P = 0.05). With reference to the 40-to-49-year age group, the risk of incidence increased from 4.7 (95% CI, 2.4-9.4) for the 50-to-59-year age group to 12.9 (95% CI, 6.1-27.2) for 70 years of age and older group. CONCLUSIONS: In 6 years, pseudoexfoliation developed in 2.03% of the population. Rural and urban incidence was significantly different.

Six-year incidence of ocular hypertension in a South Indian population: the Chennai eye disease incidence study.

AIMS: To report the 6-year incidence and risk factors for ocular hypertension (OHT) in a population-based study in southern India. METHODS: 6 years after baseline evaluation, 56.9% subjects (participants:non-participants, 4421:3353) were re-examined at the base hospital. Incident OHT was defined as an intraocular pressure above the 97.5th centile for the population with no evidence of glaucoma in the 2852 phakic subjects, 40 years or older. Subjects with trauma, laser or incisional surgery at baseline or follow-up were excluded (total exclusions: 1569). RESULTS: Incidence of OHT at 6 years was 62/2852 subjects (2.17% (95% CI 1.64% to 2.71%, men:women, 36:26)). Incidence was higher in the rural cohort as compared with the urban cohort (80.6% vs 19.4%, p<0.001). A higher baseline intraocular pressure (with increasing OR: 16-18 mm Hg (OR 4.0, 95% CI 2.1 to 7.9), 19-21 mm Hg (OR 11.4, 95% CI 5.7 to 22.9), 22-24 mm Hg (OR 42.6, 95% CI 11.0 to 164.8, in the urban cohort)) and increasing age (50-59 years (OR 1.9, 95% CI 1.1 to 3.3), 70 years and above (OR 3.6, 95% CI 1.2 to 10.6)) were significantly associated risk factors for incident OHT. CONCLUSIONS: A significant proportion of this normal population converted to OHT. A higher incidence of conversion was seen in the rural population.

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.

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.

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.

Long-term change in central corneal thickness from a glaucoma perspective.

AIM: To investigate the longitudinal change in central corneal thickness (CCT) over 3 years in patients with glaucoma. MATERIALS AND METHODS: The Chennai Glaucoma Follow-up Study, an offshoot of the Chennai Glaucoma Study, was designed to evaluate the progression of glaucoma. A cohort of participants in the Chennai Glaucoma Study that were suffering from glaucoma or were at a higher risk for glaucoma underwent comprehensive ophthalmic evaluation at the base hospital at 6-month intervals during the years 2004 to 2007. The CCT (average of 10 readings) was measured between 11 am and 1 pm on any given day using an ultrasonic pachymeter. Patients with a history of ocular surgery, corneal disease and usage of topical carbonic anhydrase inhibitor were excluded. No patient was a contact lens wearer. RESULTS: One hundred and ninety-six patients (84 male, 112 female) met the inclusion criteria. We analyzed data from the right eye. The mean age of the patients was 59.97 ± 9.06 years. Fifty-nine (30.1%) of the patients were diabetic. The mean change in CCT (CCT at first patient visit--CCT at last patient visit) was 3.46 ± 7.63 µm. The mean change in CCT was 0.75 µm per year (R² = 0.00). Age, gender, intraocular pressure at the first patient visit and diabetic status had no significant influence on the magnitude of change in CCT. CONCLUSION: A carefully obtained CCT reading by a trained examiner need not be repeated for at least 3 years as long as the ocular and systemic factors known to affect the measurement of CCT are constant.

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

PURPOSE: To describe the prevalence and factors associated with pterygium and pinguecula in a south Indian population. METHODS: The Chennai Glaucoma Study examined 7774 (Urban 3850, Rural 3924) subjects aged above 40 years. All subjects underwent a comprehensive ophthalmic evaluation. Personal history, occupation and lifetime ultraviolet exposure were documented. The presence of pterygium and pinguecula on slit-lamp examination was recorded. The prevalence of pterygium and pinguecula, differences in the rural and urban populations and their association with age, gender, residence, nature of occupation, lifetime ultraviolet radiation exposure, tobacco use (smoking/smokeless), alcohol use, diabetes mellitus and hypertension were analyzed. RESULTS: The mean age of the subjects was 54.6 (SD: 10.6) years. Pterygium was present in either eye of 740 subjects (9.5%, 95% CI: 8.6-10.4%), of which 329 subjects were male and 411 subjects were female. The prevalence of pterygium differed significantly (OR: 4.60 95% CI: 3.82-5.56, p < 0.0001) between the urban (144, 3.7%, 95% CI: 3.1-4.3%) and the rural population (596, 15.2%, 95% CI: 14.1-16.3%). Pinguecula was present in either eye of 875 subjects (11.3%, 95% CI: 10.5-12.0%), of which 368 subjects were male and 507 subjects were female. The prevalence of pinguecula differed significantly (OR: 2.94, 95% CI: 2.51-3.43, p < 0.0001) between the urban (238, 6.2%, 95% CI: 5.4-6.9%) and the rural population (637, 16.2%, 95% CI: 15.1-17.4%). Pinguecula and pterygium were significantly associated with rural residence (p < 0.0001). We found rural residence and exposure to higher lifetime UV exposure to be significantly associated with the presence of pterygium (p < 0.0001). Non-use of spectacles was found to be associated with both pterygium (OR: 1.41, 95% CI: 1.12-1.79) and pinguecula (OR: 1.69, 95% CI: 1.38-2.08). The presence of pterygium and pinguecula was not associated with smoking, use of alcohol, nature of work, diabetes and hypertension. CONCLUSION: The prevalence of pterygium and pinguecula a South Indian population were 9.5% and 11.3% respectively. Rural residence were associated with presence of both pterygium and pinguecula. Higher lifetime UV exposure was associated with the presence of pterygia.

Importance of population-based studies in clinical practice.

In the last decade, there have been reports on the prevalence of glaucoma from the Vellore Eye Survey, Andhra Pradesh Eye Diseases Survey, Aravind Comprehensive Eye Survey, Chennai Glaucoma Study and West Bengal Glaucoma Study. Population-based studies provide important information regarding the prevalence and risk factors for glaucoma. They also highlight regional differences in the prevalence of various types of glaucoma. It is possible to gather important insights regarding the number of persons affected with glaucoma and the proportion with undiagnosed disease. We reviewed the different population-based studies from India and compare their findings. The lacunae in ophthalmic care that can be inferred from these studies are identified and possible reasons and solutions are discussed. We also discuss the clinical relevance of the various findings, and how it reflects on clinical practice in the country. Since India has a significantly high disease burden, we examine the possibility of population-based screening for disease in the Indian context.

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.