EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/78719
February 2012 Chief medical editor's corner of the world Could vitamin C reduce the cataract burden in India? T he Aravind Eye Hospital system is widely recognized as a leading model for delivering high volume medical and surgical care in the developing world. Using lower cost manual small incision cataract surgery for the poor, they are able to achieve quality outcomes in a very efficient, cost-effective manner that is scalable to high volumes. Theirs is one of the leading ophthalmic residency programs in India, and they have trained hundreds of other international visitors, the majority of whom practice in the developing world. However, many are not aware of the level and quality of original scientific research conducted at Aravind. As with many coun- tries, the projected increase in India's eld- erly population means that the burden of cataract will far outstrip the country's surgi- cal capacity within the next two decades. Therefore, strategies to delay or decrease cataract formation are a critical need and a particular focus of scientists at Aravind. The chair of the Aravind Eye Hospital system is my good friend, Dr. R.D. Ravindran. Besides being an accomplished administrator, Ravi is a brilliant surgeon— in fact he was able to master phaco chop faster than any other surgeon that I have ever taught or observed. He also oversees the impressive clinical and scientific re- search program at Aravind and was the lead author of an important study on vitamin C levels and cataract that was published in Ophthalmology last October. For this month's column, I asked Ravi to discuss his paper and its implications as a potential strategy for reducing the abnormally high incidence of cataract in India. Western pop- ulation studies have failed to show any de- finitive cataract-preventing benefit of antioxidants. However, an interesting point is that these conclusions may not account for the unique genetic, nutritional, and so- cioeconomic features of the sizable poor population in India. Because of the alarming projected increase in cataract disability in India, population specific research efforts such as Aravind's are of major importance. David F. Chang, M.D., chief medical editor D r. Chang:What gave you the idea to look at vita- min C deficiency as a possible factor in cataract development in India? How did you study this, and what were the findings? Dr. Ravindran: It is well known that vitamin C is a powerful reducing agent and protects the lens from ox- idative stress. Vitamin C is found at higher concentrations in the lens, aqueous, and vitreous. These levels are approximately 20 to 30 fold higher than plasma vitamin C lev- els.1,2 Vitamin C acts synergistically with vitamin E to maintain the an- tioxidant activity of glutathione.3 Early studies in India were among the first to report that vitamin C concen- trations measured in the aqueous of patients undergoing cataract extrac- tion were lower with mature cataracts compared to mild cataracts.4 In addi- tion, studies have reported that aque- ous vitamin C levels are considerably lower in Indian patients compared to those reported from western popula- tions.4 Finally, a pilot study done prior to the current study showed in- verse relationships between cataract and the plasma levels of vitamin C and other antioxidants.5 The current India Age-Related Eye Disease Study looked at the asso- ciation between cataract and various environmental, socioeconomical, and nutritional factors. This was a population-based study of 5,871 subjects conducted at two centers in India—the All India Institute of Medical sciences, New Delhi, in north India and the Pondicherry Aravind Eye Hospital in south India. The key strengths of the study were the large sample size and response rates, inclusion of two geographi- cally different areas of India, data on a wide range of potential confounders including plasma an- tioxidant levels, photographic as- sessment of cataract, and quality assurance in grading. Vitamin C levels were either de- ficient or substandard (<28 µmol/L) in 90% of the north Indian popula- tion and 74% of the south Indian population. In this vitamin C defi- cient population we found a strong association with lower vitamin C levels and cataract. This was simi- larly true for nuclear, cortical, and posterior subcapsular cataracts. Inverse association of vitamin C with cataract in older people in India Ravindran RD, Vashist P, Gupta SK, Young IS, Maraini G, Camparini M, Jayanthi R, John N, Fitzpatrick KE, Chakravarthy U, Ravilla TD, Fletcher AE Ophthalmology. 2011 Oct;118(10):1958-1965.e2. Epub 2011 Jun 25. Objective: To examine the association between vitamin C and cataract in the Indian setting. Design: Population-based cross-sectional analytic study. Participants: A total of 5,638 people aged ≥60 years. Methods: Enumeration of randomly sampled villages in 2 areas of north and south India to identify people aged ≥60 years. Participants were interviewed for socioeconomic and lifestyle factors (tobacco, alcohol, household cooking fuel, work, and diet); attended a clinical examination, including lens photography; and provided a blood sample for an- tioxidant analysis. Plasma vitamin C was measured using an enzyme-based assay in plasma stabilized with metaphosphoric acid, and other antioxidants were measured by reverse-phase high-pressure liquid chromatography. Main outcome measures: Cataract and type of cataract were graded from digital lens images using the Lens Opacity Classification System III (LOCS III), and cataract was classified from the grade in the worse eye of ≥4 for nuclear cataract, ≥3 for cortical cataract, and ≥2 for posterior subcapsular cataract (PSC). Any cataract was defined as any unoperated or operated cataract. Results: Of 7,518 enumerated people, 5,638 (75%) provided data on vitamin C, antioxi- dants, and potential confounders. Vitamin C was inversely associated with cataract (ad- justed odds ratio [OR] for highest to lowest quartile=0.61; 95% confidence interval (CI), 0.51-0.74; P=1.1×10(-6)). Inclusion of other antioxidants in the model (lutein, zeaxan- thin, retinol, β-carotene, and α-tocopherol) made only a small attenuation to the result (OR 0.68; 95% CI, 0.57-0.82; P < 0.0001). Similar results were seen with vitamin C by type of cataract: nuclear cataract (adjusted OR 0.66; CI, 0.54-0.80; P < 0.0001), cortical cataract (adjusted OR 0.70; CI, 0.54-0.90; P < 0.002), and PSC (adjusted OR 0.58; CI, 0.45-0.74; P < 0.00003). Lutein, zeaxanthin, and retinol were significantly inversely as- sociated with cataract, but the associations were weaker and not consistently observed by type of cataract. Inverse associations were also observed for dietary vitamin C and cataract. Conclusions:We found a strong association with vitamin C and cataract in a vitamin C- depleted population. Financial disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. EW NEWS & OPINION 23 Drs. Chang and Ravindran in Beijing, 2010 Dr. Chang: Is there good evidence that cataracts are more prevalent in India? What are the leading hy- potheses, in your opinion, as to why this is? Dr. Ravindran: India accounts for approximately 20% of the global burden of blindness, with cataracts being the principal cause.6 Com- pared to western countries, popula- tion-based studies have reported higher prevalence rates of cataract in India even after differing rates of cataract surgery are taken into ac- count.7-9 There are also differences in the types of cataract seen in elderly Indians, with the prevalence of pos- terior subcapsular cataracts being about 20% compared to less than 5% in elderly western populations.9 Other studies have shown that Indi- ans living abroad in Singapore and the U.K. have higher rates of continued on page 24