May 2011
Volume 52, Issue 6
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Letters to the Editor  |   May 2011
Author Response: Role of Higher Dietary Carbohydrate Intake in Cataract Development
Author Affiliations & Notes
  • Chung-Jung Chiu
    Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts.
  • Allen Taylor
    Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts.
Investigative Ophthalmology & Visual Science May 2011, Vol.52, 3594. doi:10.1167/iovs.11-7614
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      Chung-Jung Chiu, Allen Taylor; Author Response: Role of Higher Dietary Carbohydrate Intake in Cataract Development. Invest. Ophthalmol. Vis. Sci. 2011;52(6):3594. doi: 10.1167/iovs.11-7614.

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The authors thank Drs. Costagliola, Lobefalo, and Gallenga for their interest and comments regarding our paper, “Dietary carbohydrate in relation to cortical and nuclear lens opacities in the Melbourne Visual Impairment project.” 1  
They add important and interesting observations to the data contained in our paper, and it is possible that much of their rationale is reasonable. There are a few areas of discrepancy. They contest our proposal that there is a relationship between carbohydrate intake and risk for development of nuclear or cortical cataract. Part of their concern is that blood antioxidant levels may be related to these risks. Associations between blood antioxidant levels and cataract risk have been published. 2,3 Because blood levels represent only a single time point, we prefer to consider long-term intake of antioxidants and other food items. The data in our paper accounted for such long-term intake. The inconsistency between results of blood survey studies appears to have little to do with the level of industrialization, but is mainly due to the cross-sectional feature of most of these studies, in which only one blood sample was measured and related to cataract. Actually, data from diverse epidemiologic studies, including blood survey studies, suggest that proper nutrition, started early in life and maintained through maturity, may address some of the age-related compromises and provide for extended youthful function during older age and that proper nutrition, along with a healthy life style, may provide the least costly and most practical means of delaying cataract. 4  
We agree that some long-term damage to the body, especially the heart and circulatory system, may already be occurring at the prediabetes stage. However, even if the phenomenon also applies to nuclear and cortical cataract, the analysis below shows that the potential confounding effect from prediabetes is unlikely to explain our findings. Since the prevalence of cataract in people with diabetes is approximately 30% in the Visual Impairment Project cohort, 5 theoretically the cataract prevalence in people with prediabetes should be less than 30%. Even if 16.4% of our Australian subjects were in the prediabetic state, they could only account for <5% (30% × 16.4%) of the prevalent cataract cases in our study cohort. Furthermore, from an incidence point of view, diabetic cataracts can only account for a low percentage of overall incident cataracts in developed countries. Another example is derived from a British cohort in which it has been shown that the 5-year incidence of cataract was 10.4 (95% CI, 9.0–11.9) per 1000 person-years based on 18,089 person-years of follow-up among the 3606 diabetic patients with a mean (SD) age of 49.2 (17.8) years and a mean (SD) duration of diabetes of 7.6 (9.8) years at baseline. That is to say, less than 6% of diabetes patients developed cataract after more than 12 years of diabetes. 6 The incidence of cataract in people with prediabetes could be even lower than that in people with diabetes. Even if 16.4% of our Australian subjects were in the prediabetic state, they could only account for approximately 1% of incident cataract cases in our study cohort in a 5-year follow-up period. Therefore, it is unlikely that the proposed confounding effect from prediabetes could totally explain the association in our study. 1  
We, however, appreciate that Costagliola et al. raised the issue of prediabetes and suggest that it should be addressed in future studies. 
Footnotes
 Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views or policies of the U.S. Department of Agriculture, nor does mention of trade names, commercial products, or organizations imply endorsement by the US Government.
References
Chiu CJ Robman L McCarty CA . Dietary carbohydrate in relation to cortical and nuclear lens opacities in the Melbourne Visual Impairment Project. Invest Ophthalmol Vis Sci. 2010;51:2897–2905. [CrossRef] [PubMed]
Valero MP Fletcher AE De Stavola BL Vioque J Alepuz VC . Vitamin C is associated with reduced risk of cataract in a Mediterranean population. J Nutr. 2002;132(6):1299–1306. [PubMed]
Ferrigno L Aldigeri R Rosmini F Sperduto RD Maraini G . The Italian-American Cataract Study Group. Associations between plasma levels of vitamins and cataract in the Italian-American Clinical Trial of Nutritional Supplements and Age-Related Cataract (CTNS): CTNS Report 2. Ophthalmic Epidemiol. 2005;12:71–80. [CrossRef] [PubMed]
Chiu CJ Taylor A . Nutritional antioxidants and age-related cataract and maculopathy. Exp Eye Res. 2007;84:229–245. [CrossRef] [PubMed]
McCarty CA Mukesh BN Fu CL Taylor HR . The epidemiology of cataract in Australia. Am J Ophthalmol. 1999;128:446–465. [CrossRef] [PubMed]
Janghorbani MB Jones RB Allison SP . Incidence of and risk factors for cataract among diabetes clinic attenders. Ophthalmic Epidemiol. 2000;7:13–25. [CrossRef] [PubMed]
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