by Vanessa Caceres EyeWorld Contributing Writer
Meta-analysis leaves room for further research
A recently published study reported that postmenopausal hormone use might have a protective role in the formation of cataracts.1
However, ophthalmologists who reviewed the analysis cautioned that it is not the definitive word on the topic. The meta-analysis was led by Kairan Lai of the Eye Center, Second Affiliated Hospital, Hangzhou, China. The investigators analyzed four cohort and five case-control or cross-sectional studies, all related to postmenopausal hormone replacement therapy (HRT) use and cataract development. All of the studies analyzed were published prior to March 2013. Although the investigators found 96 citations in PubMed and EMBASE, they excluded those that did not meet their specific criteria, which led to the final nine studies analyzed. The studies were set in the United States, Europe, and Asia. Sample sizes in the studies ranged from 242 women to 20,000 women, the latter in a U.K. population-based case-control study. Some of the well-known studies included in their analysis were the Salisbury Eye Evaluation, the Framingham study, the Blue Mountains Eye Study, and the Beaver Dam Eye Study.
Overall, the studies indicated a decreased risk of cataract associated with postmenopausal hormone use, regardless of cataract type. The investigators also found an association between current HRT use and nuclear cataract in the case-control and cross-sectional studies, but they did not find an association between cortical cataract risk and posterior subcapsular cataract in women who had used HRT at any point.
“The current HRT users had a decreased risk of developing any type of cataract, nuclear cataract, and cortical cataract, but neither any type of cataract nor subtypes were correlated with the past HRT,” the investigators wrote. They added that these results should be interpreted with caution because of the limited number of studies in the subgroup analysis.
Investigators also found the women currently using HRT had a slightly lower risk for cataracts compared with past users. “Each article, which evaluated current and past HRT use separately, reported the same tendency,” they wrote. “One possible reason is that the exposure time and concentrations of estrogen in current users may be higher than those in past users.”
Investigators wrote that they are not entirely sure why the results indicate a protective effect between HRT and cataracts, but they said that previous research suggests that estrogen has antioxidant properties and preserves mitochondrial function and cell viability. This may help protect the lens from oxidative damage. The research also noted the possible involvement of several other biological mechanisms.
Limitations of the study as cited by the investigators include the use of self-report questionnaires in most of the studies, varying definitions of HRT use in each study, and different study designs. For these reasons, they recommend follow-up studies.
Analyzing the results
This research should provide some reassurance to patients and ophthalmologists regarding the use of HRT, said David R. Hardten, MD, Minneapolis. “This gives us advice on our patients who may be concerned about the eye effects; they can make the decision about HRT with their gynecologist without fearing, and maybe benefiting from, the effects on the eye,” Dr. Hardten said.
Evan Lewis Waxman, MD, University of Pittsburgh Medical Center, Pittsburgh, was surprised that the results seemed to contradict a popular 2010 report that showed women in Sweden on HRT were more likely to have cataract surgery than women who had not been on HRT.2 That study, which involved more than 30,000 women from the Swedish Mammography Cohort, concluded that long-time HRT use put women more at risk for cataracts, especially if they had more than one alcoholic drink daily.
However—”As I looked further into both papers, I started to see that the effect of HRT in each paper was small and that factors leading to uncertainty were so many that it was hard to come to any conclusion other than that women should not make a decision about HRT based on whether or not it will have any effect on cataracts,” Dr. Waxman said.
Nancy A. Tanchel, MD, Liberty Laser Eye Center, Vienna, Va., was somewhat surprised by the protective effect of HRT as found in the analysis, but noted that hormones seem to help skin and other tissues, so that finding is not completely new. She noted that HRT in its current form can have questionable safety but that cataracts are a relatively easy problem to treat. “So the protective effect of HRT for cataract development must be weighed against the serious negative effects,” Dr. Tanchel said. Dr. Waxman also supports considering the big-picture effects of HRT. “We would expect women to work with their doctors to make the decision about HRT based on the benefits versus risks of heart disease, stroke, blood clots, and breast cancer,” he said.
“Further research needs to be carried out to determine whether those getting HRT in the studies collated have avoided other risk factors for cataracts throughout life versus those not getting HRT,” Dr. Tanchel said.
Dr. Tanchel said if HRT were found to be truly protective, it would be useful to develop related drugs that have less systemic effects.
1. Lai K, Cui J, Ni S, Zhang Y, He J, Yao K. The effects of postmenopausal hormone use on cataract: A meta-analysis. PLOS One. 2013;8:e78647.
2. Lindblad BE, Håkansson N, Philipson B, Wolk A. Hormone replacement therapy in relation to risk of cataract extraction: A prospective study of women. Ophthalmology. 2010;117:424-430.
Editors’ note: The physicians interviewed have no financial interests related to their comments.