Prevalence and causes of visual impairment and blindness in Icelanders aged 50 years and older: the Reykjavik Eye Study

Purpose: This study aimed to study the prevalences and causes of visual impairment and blindness in an Icelandic adult population. Methods: The Reykjavik Eye Study includes a random sample of citizens of Reykjavik aged >= 50 years, with an equal proportion (6.4%) for each year of birth and each sex. A total of 1045 persons were examined, representing a response rate of 75.8%. All participants underwent an extensive ophthalmological examination using a standard protocol. We used World Health Organization (WHO) definitions for bilateral visual impairment (best corrected visual acuity [VA] < 6/18 or visual field of >= 5 degrees and < 10 degrees around the fixation point in the better eye) and blindness (VA < 3/60 or visual field < 5 degrees in the better eye). We also used US criteria, which define bilateral visual impairment as present if VA is < 6/12 and blindness as present if VA is <= 6/60 (both in the better eye). The causes of visual loss were determined for all participants found to be visually impaired in one or both eyes. Results: The prevalences of bilateral visual impairment and blindness were 0.96% (95% confidence interval [CI] 0.37-1.55) and 0.57% (95% CI 0.12-1.03), respectively, using the WHO criteria, and 2.01% (95% CI 1.16-2.86) and 0.77% (95% CI 0.24-1.29), respectively, using the US criteria. The prevalence rates were 4.40% and 5.45% for unilateral visual impairment and 1.72% and 3.06% for unilateral blindness, using the WHO and US criteria, respectively. Age-related macular degeneration (AMD) was the major cause of bilateral visual loss, whereas the most common causes of unilateral visual loss were, in this order, amblyopia, cataract and glaucoma. Conclusions: Prevalence of visual loss increases with age. The leading cause of bilateral visual impairment and blindness was AMD, accounting for more than half of all cases, and cases of geographic atrophy outnumbered those of exudative AMD by two to one.