At the time of the prevalence (baseline) examination, nuclear cataract was found in 17%, cortical cataract in 16%, and posterior subcapsular cataract in 5% of the population
(Table 1) .
47 Late stages of age-related macular degeneration (AMD) were found in 2% and early stages in approximately 16% of the population.
48 Definite glaucoma was found in 2% and probable glaucoma in an additional 2%.
49 No age group was spared, and there were consistent increases in prevalence with increasing age for all these conditions. Best corrected visual acuity was obtained at the baseline examination to estimate visual function of the population.
46 Approximately 5% of the population had any visual impairment (vision 20/40 or poorer in the better eye), and 0.5% had severe impairment (20/200 or worse in the better eye). However, as anticipated, the frequency of these functional endpoints was uncommon in the youngest age group and increased with increasing age
(Table 1) . Even when persons with advanced cataract or late stages of AMD were not included, there was a change in visual function with age.
50 We found other ocular conditions to be relatively common, such as diabetic retinopathy (10.4% of those with diabetes),
51 retinopathy in nondiabetic persons (8% of those without diabetes; those with diabetes had on average more severe retinopathy),
52 and refractive errors (myopia: 28% in women, 24% in men; hyperopia: 49% in women and men).
53 In addition to specific ocular conditions, we have collected data on important ocular traits. In particular, we have quantitative measures of intraocular pressure, optic disc and cup diameters, retinal arteriole and venule diameters, and lens thickness. More recently, we have measured axial length, anterior chamber depth, and corneal curvature. These measurements have permitted the description of population distributions of these characteristics and have facilitated further investigations of the relationship of these characteristics to ocular and systemic diseases.