Multivitamin supplements and cataract prevention.

Age-related cataract is the leading cause of visual loss worldwide, with developing nations carrying most of this burden. The prevalence of cataract doubles with each decade of age after 40 years, such that most people in their 80s and 90s will be affected. Although cataract removal and intraocular lens implantation effectively treats this condition and restores good vision, cataract surgery is not without complications, particularly in an elderly patient. Additionally, the provision of cataract surgery requires trained ophthalmologists, appropriate postoperative follow-up management and refractive correction, and use of expensive operating facilities and microsurgical equipment. As many of these services are not readily available in developing countries, identifying methods to prevent or slow cataract development in the general population will be a major public health achievement. Prevention would lead to significant cost savings and avoidance of surgical complications in wealthy countries as well. Over the last 2 decades, there has already been a 3to 4-fold increase in cataract surgeries performed in the United States, with the threshold for cataract surgery in many countries now at 20/30 or better. Projections from the Centers for Medicare and Medicaid Services suggest an annual health care bill of $4 trillion by 2015 in the U.S. alone, with cataract surgery accounting for more than 10% of the annual Medicare budget. Cataract surgery is the most performed surgical procedure covered by Medicare. It has been suggested that a delay of 10 years in cataract onset would halve the number needing surgery and reduce the significant economic burden. For these reasons, there has been considerable interest in finding modifiable dietary risk factors for cataract, with 8 randomized control trials (RCTs) in the last decade alone. Unfortunately, results have not been encouraging so far. One major problem is that these trials have mainly concentrated on evaluating vitamins C, E, and -carotene, either alone or in some combinations, but no clear benefits on slowing cataract progression or reducing the need for cataract surgery have been found. Although it is possible that multivitamin supplements may be more effective in preventing cataract, to date there has been only one RCT that has evaluated multivitamin supplementation. This study, in rural Linxian, China, found a 36% reduction in the risk of nuclear cataract with multivitamin supplementation in adults between 65 and 74. Data from the Age-Related Eye Disease Study (AREDS) have also provided important insights. The AREDS did not find an association between high-dose vitamin C, E, and -carotene and a delay in progression of cataract in their primary report, but analysis of the observational aspects of the study suggested that multivitamin