Please use this identifier to cite or link to this item: http://hdl.handle.net/1946/15085
Iceland enjoys one of the highest life expectancies in the world and the population of middle-aged and elderly Icelanders is growing. Frequency of visual loss and retinopathy rises with increasing age and increases the need for assistance and rehabilitation. Cause-specific data may help identify preventable and treatable causes of visual loss and provide insight into which problems should be taken into consideration when planning future eye health care services.
Aims: To describe the prevalence and 5-year incidence of visual loss among middle-aged and older Icelanders, to provide information on the major causes of visual loss, and to update data on the prevalence of retinopathy and risk factors associated with retinopathy in older persons with and without diabetes mellitus (DM).
Methods: Papers I and II:
A random sample of 1,045 persons aged 50 years or more participated in the population-based Reykjavik Eye Study. All participants underwent a detailed eye examination in 1996, and 846 of the survivors participated in a follow-up examination in 2001. Visual impairment was defined according to WHO definitions as a best-corrected visual acuity of <6/18 but no worse than 3/60, or a visual field of ≥5° and <10° around a fixation point in the better eye. Best-corrected visual acuity of <3/60 in the better eye was defined as blindness. We also used United States criteria, which define visual impairment as best-corrected visual acuity of <6/12 and >6/60 in the better eye and blindness as best-corrected visual acuity ≤6/60. Causes of visual loss were determined for all eyes. Deterioration or improvement in vision were defined as a loss or gain of 2 or more Snellen lines.
A study population of 4,994 persons aged 67 years or more participated in the Age/Gene/Environment Susceptibility-Reykjavik Study (AGES-R). DM was defined as HbA1c ≥6.5% (≥48 mmol/mol), a self-reported history of DM, or use of diabetes medication. Retinopathy was assessed by grading fundus photographs using the modified Airlie House adaptation of the Early Treatment Diabetic Retinopathy Study protocol. Associations between retinopathy and risk factors were estimated for persons with and without diabetes by using odds ratios from logistic multivariate analyses.
Results: Papers I and II:
Using WHO criteria, the prevalence of bilateral visual impairment and blindness was 1.0% (95% CI 0.4-1.6) and 0.6% (95% CI 0.1-1.0), respectively. The 5-year incidence was 1.1% (95% CI 0.4-1.8) for visual impairment and 0.4% (95% CI 0.0-0.8) for blindness. The prevalence of unilateral visual impairment and blindness according to WHO criteria was 4.4% (95% CI 3.2-5.7) and 1.7% (95% CI 0.9-2.5), respectively, and the 5-year incidence was 3.5% (95% CI 2.3-4.8) and 1.2% (95% CI 0.5-2.0). The United States criteria are more inclusive and gave slightly higher figures.
Using WHO criteria, the major cause of bilateral visual impairment and blindness both at baseline and follow-up was age-related macular degeneration. According to United States criteria, we detected milder forms of visual loss and found that unoperated cataract was the major cause of less severe bilateral visual impairment at both baseline and 5-year follow-up. Regardless of the criteria used, the two most common causes of unilateral visual impairment at baseline were amblyopia and cataract, and at 5-year follow-up, cataract was the main cause of unilateral visual impairment.
Among the 516 persons (10.3%) with DM in the AGES-R study, gradable fundus photos were available for 512. The prevalence of retinopathy among persons with diabetes was 27.0% (95% CI 23.2-31.0). Five persons (1.0%; 95% CI 0.3-2.3) had proliferative retinopathy and another five had clinically significant macular edema (1.0%; 95% CI 0.3-2.3). Retinopathy was present in 476 persons (10.7%; 95% CI 9.8-11.6) without DM and three had clinically significant macular edema. Independent risk factors for retinopathy in persons with DM in a multivariate model were increased HbA1c, insulin use, use of oral hypoglycemic agents and higher systolic blood pressure. In persons without DM, increasing age and microalbuminuria were independent risk factors for retinopathy.
Conclusions: Prevalence and 5-year incidence of both uni- and bilateral visual impairment and blindness increased with age in the Reykjavik Eye Study. Age-related macular degeneration was the leading cause of severe visual loss in this population of middle-aged and older Icelanders, and unoperated cataract caused less severe visual loss.
The overall prevalence of retinopathy in our large, population-based Age/Gene/Environment Susceptibility-Reykjavik Study sample was 12.4%. Persons with diabetes mellitus were 2.5 times more likely to have retinopathy than persons without diabetes. However, the total number of people with retinopathy was threefold higher in the non-diabetic group, accounting for 75% of retinopathy cases.
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