Age-related macular degeneration (AMD) remained the most common cause of severe visual impairment over a 20-year period, researchers found.
In a study of nearly 5,000 people, of the 184 eyes with severe visual impairment at the patient's first visit and the 256 eyes in which severe visual impairment developed between visits, late age-related macular degeneration was the primary cause in 44% of eyes, followed by branch or central retinal vein occlusion in 8% and cataract in 10%, according to Ronald Klein, MD, of the University of Wisconsin School of Medicine and Public Health in Madison, and colleagues.
Rates of the condition "changed little over the 20 years of the study," they wrote online in the journal Ophthalmology.
However, the overall odds of incidence of visual impairment decreased from the first 5-year period studied to the last by 47% (OR 0.53, 95% CI 0.32 to 0.87, P=0.01), the authors noted.
Little research has been done to track trends in incidence of visual impairment over long periods of time and these details may be important because of an aging U.S. population, "who are most vulnerable to loss of vision resulting from age-related diseases," the investigators wrote in their introduction.
They analyzed 20-year trends in visual impairment and associations with age-related eye diseases and socioeconomic factors as found in the Beaver Dam Eye Study, a population-based cohort study.
The study included a baseline population of 4,926 participants ages 43 to 86 who were followed from 1988 to 1990, 3,721 participants who were followed up from 1993 to 1995, 2,962 participants followed up from 1998 to 2000, 2,375 participants followed up from 2003 to 2005, and 1,913 participants followed up from 2008 to 2010. The main reason for nonparticipation in the follow-up visits was death.
Outcomes included incidence of visual impairment and severe visual impairment. Visual impairment was defined as best-corrected visual acuity of poorer than 20/40 in the better eye among participants whose eyes both measured 20/40 or better at the beginning of a 5-year interval. Severe visual impairment was similarly defined using a measure of 20/200.
Mean participant age from the beginning to the end of the study increased from 62 years at baseline to 75.4. The study population included a great increase in the proportion of participants ages 85 and older, from 1% at baseline to 15% at the end of the fifth 5-year interval.
Of 9,548 person-visits, visual impairment developed in 1.4% (95% CI 1.1% to 1.6%) and severe visual impairment developed in 0.4% (95% CI 0.2% to 0.5%) of person-visits. Incidence was associated with age and ranged from 01.% among patients ages 50 to 54 to 14.6% among patients age 85 and older.
There were no statistically significant interactions between time period and age, nor was there a statistically significant difference in visual impairment between time periods, except with a comparison of periods 1 and 2 with periods 4 and 5, when incidence dropped by nearly half.
Additionally, a significant interaction between age, income, and age-related macular degeneration with incident visual impairment, cataract status, and cataract-age interaction was observed, though data on this interaction were not reported.
Overall incidence of severe visual impairment was associated with age, with no patients ages 50 to 54 and 60 to 64 reporting severe visual impairment, compared with 0.2% of patients ages 70 to 74, 1.6% of patients ages 80 to 84, and 6.9% of patients ages 85 and older. Age and age-related macular degeneration were associated with severe visual impairment incidence.
"Although the decline in incidence of impairment is not statistically significant after adjustment for age-related macular degeneration, the suggestions of a period effect may have public health implications," they concluded. "Age-related macular degeneration remained the leading cause of severe visual impairment in the [study], affecting a similar proportion of eyes throughout the 20 years."
The authors suggested that continued surveillance of visual impairment is needed to monitor changes in incidence and prevalence of impairment and the diseases associated with it in order to derive a cost-benefit analysis of new interventions.
They added that the study was limited by selective survival and visual acuity measures tainted by cognitive decline and comorbidities.
The study was funded by the National Institutes of Health, Research to Prevent Blindness, and the National Eye Institute.
The authors declared no conflicts of interest.
- Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner