Cataract 28

Description

Age-related cataracts are one of the leading causes of visual impairment and blindness among the elderly worldwide. Among age-related cataracts, cortical opacities rank as the second most common type (Iyengar et al., 2004).

The preferred title/symbol of this entry was formerly 'Cataract, Age-Related Cortical, 1; ARCC1.'

Mapping

To identify susceptibility loci for cortical cataracts, Iyengar et al. (2004) genotyped a subset of families from the Beaver Dam Eye Study (performed in the population of Beaver Dam, Wisconsin) and did a model-free genomewide linkage analysis for markers linked to a quantitative measure of cortical opacity. They obtained evidence for linkage at marker D1S1622 on chromosome 1p35 (P less than 0.0002) and at marker D6S1053 on chromosome 6q12 (p less than 0.00008) in the initial scan. Five additional regions ( on chromosomes 1q31, 2p24, 2q11, 4q28, and 15q13) had suggestive linkage (p equal to or less than 0.01 or lod equal to or more than 1.18). The region on 6p12-q12 was selected for fine mapping, which showed that significant evidence of linkage remained for marker D6S1053 in this region (p less than 0.00005). Few regions identified in this scan had previously been implicated in congenital or age-related cataracts.

Inheritance

Congdon et al. (2005) quantified the risk for age-related cortical cataract and posterior subcapsular cataract (PSC) associated with having an affected sib after adjusting for known environmental and personal risk factors. Multivariate analysis revealed the magnitude of heritability for ARCC to be 24%, whereas that for PSC was not statistically significant (4%). The model revealed that increasing age, female gender, a history of diabetes, and black race increased the odds of ARCC, whereas higher levels of provitamin A were protective. A history of diabetes and steroid use increased the odds for PSC. Congdon et al. (2005) concluded that there is a significant genetic effect for ARCC but not for PSC.

Pathogenesis

Tan et al. (2007) studied the association of statin use with long-term incident cataract in the Blue Mountains Eye Study cohort. After controlling for age, gender, and other factors, statin use was found to reduce by 50% the risk of cataract development, principally nuclear or cortical cataract subtypes.