Timely cataract surgery resulting in enhanced vision was associated with a 40% reduction in mortality risk compared with no surgery, according to a new study published in the September issue of Ophthalmology.
The association, which was independent of variables such as number of medications and comorbid conditions, suggests that correcting visual impairment (VI) caused by cataracts has health benefits beyond merely improving eyesight, noted coauthor Jie Jin Wang, MMed, PhD, from the Centre for Vision Research, Department of Ophthalmology, and Westmead Millennium Institute, University of Sydney, and the Centre for Eye Research Australia, University of Melbourne, Australia, in a press release. The findings also support previous research showing a link between VI and increased mortality risk.
The investigators, lead by Calvin Sze-un Fong, MBBS, also from the Centre for Vision Research, Department of Ophthalmology, and Westmead Millennium Institute, used data from the Blue Mountains Eye Study (BMES) cohort, a prospective population-based study of vision and common eye diseases among older Australians. Study participants were aged 49 years or older at baseline and were living in a suburb of Sydney. They were identified in a door-to-door census and invited to have detailed baseline eye examinations between 1992 and 1994 (BMES I), with follow-up examinations in 1997-1999 (BMES II) and 2002-2004 (BMES III).
The current analysis included people with cataracts and VI at baseline, as well as people who had undergone cataract surgery before the baseline examination or during the follow-up period, with subsequent correction of vision. The main study outcome was death between the baseline period and December 31, 2007.
The investigators identified 354 participants affected by cataracts. Of those, 191 people had been treated with surgery and had good visual outcomes (170 before baseline and 21 between BMES I and BMES III, ending in 2004) and 163 people had VI resulting from untreated cataracts.
At the 5-year follow-up (BMES II), 154 participants (43.5%) remained alive, including 105 patients who had undergone cataract surgery (61.7% of the original 170) and 49 people who still had cataracts and VI (26.6% of the original 184). By the 10-year follow-up (BMES III), 87 participants remained alive, including 67 (36.4%) who had undergone cataract surgery and 20 (10.9%) with cataracts and VI. In a Cox model adjusted for age and sex and including the patients who underwent cataract surgery after the baseline examination, treatment was associated with a mortality hazard ratio (HR) of 0.60 (95% confidence interval [CI], 0.46 - 0.77), with presenting VI included as a time-dependent variable. Similarly, surgery was associated with an HR of 0.57 (95% CI, 0.39 - 0.83) compared with the nontreatment group when best-corrected VI was included as a time-dependent variable. The decreased mortality risk persisted even after adjusting for age, sex, smoking, self-reported health and mobility, diabetes, history of stroke, and number of medications. In that analysis, surgically treated presenting and best-corrected VI both were associated with an HR of 0.55 compared with the nontreatment group (95% CI, 0.41 - 0.73 and 0.35 - 0.86, respectively).
"These findings confirmed what we suspected," Dr. Wang, Senior Research Fellow at the Centre for Vision Research, Westmead Millennium Institute, told Medscape Medical News. "Given the consistent evidence from population-based observational studies showing that visual impairment is associated with increased mortality in older people, we aimed in this study to find evidence to support the reverse association that correcting visual impairment would be associated with better survival in older persons."
Nuclear cataracts are considered a biomarker of aging, so "one would expect that persons with a more severe level of nuclear cataract could have had more advanced stage of biological aging," and perhaps a higher mortality risk, Dr. Wang said. However, she pointed out that they also would have been more likely to undergo surgery than people with milder cataracts, so cataract severity per se probably does not account for the differences in survival.
The link between cataract surgery and survival is a surprise, said Ronald Klein, MD, MPH, professor of ophthalmology and visual sciences, University of Wisconsin School of Medicine and Public Health, Madison. "While I was aware of the strong relation of both cataract and [VI] to survival, I would not have hypothesized that the removal of cataract would also be associated with better survival."
Both Dr. Klein and the authors noted that patients with particularly severe comorbidities would have been poor surgical candidates and at higher risk of death, or there may have been additional, unaccounted-for contributors to mortality. Factors that may have enhanced survival "include physical and emotional well-being, optimism, and improved confidence associated with independent living after correcting cataract-related VI," the investigators write.
Other possible study limitations include the small sample size and reliance on patient self-reports for some of the data.
Dr. Fong has received a travel fellowship grant from the Centre for Eye Research Australia. Dr. Wang is funded by a National Health and Medical Research Council Senior Fellowship. Another author serves on the advisory boards for Novartis and Bayer and receives consulting fees and payments for lectures from these companies. The other authors and Dr. Klein have disclosed no relevant financial relationships.
Ophthalmology. 2013;120:1720-1727. Abstract
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Cite this: Cataract Surgery May Promote Longer Overall Survival - Medscape - Sep 17, 2013.