Around the world and here in the United States, visual impairment appears to be on the rise, despite improved treatment. But, as always, the devil is in the details.

• Worldwide. The long-awaited results of the largest review on global vision impairment and blindness ever undertaken appeared in the December 13 issue of The Lancet.¹ Rupert Bourne, FRCOphth, MD, of Anglia Ruskin University’s Vision and Eye Research Unit collaborated with 79 ophthalmologists and optometrists to complete the systematic review of all published—and several unpublished—sources of global data on vision impairment and blindness, from 1980 to January 2012.

The bottom line: Treatment for cataracts and other forms of blindness and infectious disease, such as trachoma, has been successful in curtailing vision loss and blindness.

However, the report’s statistics indicate that blindness and vision loss has actually increased globally. Why? “The overall increase in the number of people suffering from blindness and vision loss is due to the huge population explosion that has occurred during the last couple of decades,” Dr. Bourne says. “However, the Global Burden of Disease findings actually show that this increase is not as large as one would expect given the increasing life expectancy in the world’s population over this time.”

When age is taken into account, blindness and visual impairment decreased on a worldwide level. “This points to the successful intervention in treating cataracts and other forms of blindness and infectious diseases, such as trachoma,” Dr. Bourne says.

The largest global cause of vision impairment, at 29.5% of the total, is “other vision loss,” which is due primarily to trauma as well as occupational and idiopathic conditions. Second is uncorrected refractive error, which accounts for 26.5% of vision impairment. Cataracts are the third largest contributor at 22.4%. Glaucoma and macular degeneration together account for 10.7%.

• United States. Findings from another large-scale study looking at visual impairment came out around the same time—however, this one looked at non-refractive visual impairment in the US. The prevalence of non-refractive visual impairment increased 21% overall among US adults ages 20-plus, and 40% among non-Hispanic whites ages 20-39. During that same time period, the prevalence of diabetes with 10 or more years since diagnosis also grew, according to the study, published in the December 12 issue of the Journal of the American Medical Association.²

Researchers at Johns Hopkins University School of Medicine analyzed these changes in prevalence and their relationship to demographic and systemic risks factors in a sample of 10,480 subjects, with data collected through the NHANES study from 1999 to 2002 and from 2005 to 2008. The participants also answered questionnaires and participated in laboratory tests and physical examinations.

The authors suggest that the rise in serious eye conditions—such as cataracts and glaucoma—in the US may be linked, to some degree, with the higher prevalence of diabetes. “If the current finding becomes a persisting trend, it could result in increasing rates of disability in the US population, including greater numbers of patients with end-organ diabetic damage who would require ophthalmic care,” the authors wrote. “Continued monitoring of visual disability and diabetes, as well as additional research addressing causes, prevention and treatment, is warranted.”

1. Global Burden of Disease Study 2010. Lancet. 2013 Dec 15;380(9859). Available at: www.thelancet.com/themed/global-burden-of-disease. Accessed January 6, 2013.
2. Ko F, Vitale S, Chou CF, et al. Prevalence of nonrefractive visual impairment in US adults and associated risk factors, 1999-2002 and 2005-2008. JAMA. 2012 Dec 12;308(22):2361-8.