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Clinical and Epidemiologic Research: Heidi Bowie, Nathan G. Congdon, Hong Lai, and Sheila K. West Validity of a Personal and Family History of Cataract and Cataract Surgery in Genetic Studies Invest. Ophthalmol. Vis. Sci. 2003; 44: 2905-2908 [Abstract] [Full text] [PDF]

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Genetic Studies in Age-Related Cataract: Problems Encountered

Govindasamy Kumaramanickavel, Vedam Lakshmi Ramprasad, Srinivasa Kamalakar Rao, Krishnamoorthy Ravishankar   (9 October 2003)

Genetic Studies in Age-Related Cataract: Problems Encountered 9 October 2003
Govindasamy Kumaramanickavel , Vedam Lakshmi Ramprasad, Srinivasa Kamalakar Rao, Krishnamoorthy Ravishankar Send letter to journal: Re: Genetic Studies in Age-Related Cataract: Problems Encountered geneticsstaff{at}yahoo.co.in Govindasamy Kumaramanickavel, et al.	This is a letter responding to the manuscript of Bowie et al.1 that was recently published in IOVS. Currently we are not aware whether a single gene or multiple genes is/are responsible for the different phenotypes of age-related cataract. Although it is resource intensive, we believe that detailed evaluations involving appropriate equipment and highly trained personnel are necessary to conduct accurate studies of age-related cataracts and their possible genetic basis. The variable phenotypes of age-related cataracts give vital information that can be analyzed in several different ways, using parametric or non-parametric linkage programs in gene mapping studies involving either nuclear or extended families. Our experience with age-related cataract families is that no family has a uniform lens phenotype. The alternative methods of analysis we use include taking only posterior subcapsular, or cortical, or nuclear cataract as the principal phenotype for a family, or we combine all of them and categorize a family as "affected," as opposed to "unaffected." However, a major problem in categorizing an individual as belonging to a single phenotype is when the individual has a posterior subcapsular opacity in one eye and a nuclear opacity in the other. In such a situation we consider the individual only for combined analysis. In our ongoing study on the genetics of age-related cataract we use slit-lamp examination, but we also document LOCS II grading.2,3 We agree with the fact that neither oral history nor self-reporting shows good validity compared to phenotypic lens grading. Bowie et al. did not mention their various exclusion criteria or risk factors that such a study should consider when recruiting cases for genetic studies. What we do in our study is to take history of smoking,3 hypertension,4 alcoholism (Taylor A, et al. IOVS 2003;44:ARVO E-Abstract 4463), myopia,5 and long-duration administration oral/topical steroids,6 as these can influence the development and progression of age-related cataracts. Bowie et al. did mention diabetes as a risk factor. Vedam Lakshmi Ramprasad1 Srinivasa Kamalakar Rao2 Krishnamoorthy Ravishankar2 Govindasamy Kumaramanickavel1 1Department of Genetics and Molecular Biology 2Cataract & IOL Implantation Division Medical & Vision Research Foundations, Sankara Nethralaya, 18 College Road, Chennai, India References 1. Bowie H, Congdon NG, Lai H, West SK. Validity of a personal and family history of cataract and cataract surgery in genetic studies. Invest Ophthalmol Vis Sci. 2003;44:2905-2908. 2. Vijaya R, Gupta R, Panda G, Ravishankar K, Kumaramanickavel G. Genetic analysis of adult-onset cataract in a city-based ophthalmic hospital. Clin Genet. 1997;52:427-443. 3. Chylack LT, Jr, Leske MC, McCarthy D, Khu P, Kashiwagi T, Sperduto R. Lens opacities classification system II (LOCS II). Arch Ophthalmol. 1989;107:99. 4. Congdon NG. Prevention strategies for age related cataract: present limitations and future possibilities. Br J Ophthalmol. 2001;85:516-520. 5. Younan C, Mitchell P, Cumming RG, Rochtchina E, Wang JJ. Myopia and incident cataract and cataract surgery: The Blue Mountains Eye Study. Invest Ophthalmol Vis Sci. 2002;43:3625-3632. 6. Garbe E, Suissa S, LeLorier J. Association of inhaled corticosteroid use with cataract extraction in elderly patients. JAMA. 1998;280:539-543.