Cataract Prevalence and Distribution of Subtypes
While the adverse impact of cataract on vision worldwide is undeniable, the lack of a widely accepted, standardized classification for lens opacities makes it difficult to precisely determine the incidence and prevalence of cataract. Most estimates of the frequency of age-related cataract are based on data from select groups rather than from the general population. These population-based studies had differences in methodology, disease definition, and study participants.
According to data published by the National Institute of Health (NIH) in 2010, the risk of developing cataract in the United States increases with each decade of life starting around age 40. By age 75, half of white individuals in the United States have cataract. By age 80, 70% of white individuals have cataract, compared with 53% of black individuals and 61% of Hispanic American individuals. Among all people with cataracts in the United States, the vast majority (80%) were white, 8% were black, and 7% were Hispanic; 61% were women and 39% were men.
The Beaver Dam Eye Study conducted in the late 1980s reported that 38.8% of men and 45.9% of women older than 74 years had visually significant cataracts. For this study, “visual significance” was determined by photographic grading of lens opacities and a specified best-corrected visual acuity of 20/32 (logarithm of the minimum angle of resolution [logMAR] equivalent closest to the 20/30 Snellen fraction), excluding individuals with severe age-related maculopathy.
A follow-up to the Beaver Dam Eye Study in the early 1990s found incident nuclear cataract occurred in 13.1%, cortical cataract in 8.0%, and posterior subcapsular cataract (PSC) in 3.4% in the study cohort. The incidence of all types of lens opacities rose with increasing age.
The 1998 Salisbury Eye Evaluation project was a prospective population-based cohort study designed to identify racial differences in the prevalence of cataracts in a group of Americans older than 65 years. Nuclear cataract was noted in 50.7% of white participants versus 33.5% of black participants. Conversely, cortical cataract was more than 4 times more likely to be identified in black individuals than in white individuals. PSC was found at roughly the same rate in both groups, between 5% and 10%.
The Barbados Eye Study provided prevalence data on lens opacities in a predominantly black population. Cortical opacities were the most frequent type of cataract, and women had a higher frequency of opacification than did men.
Studies of Asian populations evaluating the incidence of different cataract subtypes include the Singapore Malay Eye Study and the Handan Eye Study. These studies suggest a higher rate of cortical cataract in Asian individuals than in white individuals. In 1994, the Italian-American Cataract Study Group conducted a study based in Parma, Italy. In this study’s subgroup of participants aged 65–74, the cataract incidence was 18% cortical, 6% nuclear, and 6% PSC.
The prevalence of congenital cataract varies from country to country. Retrospective studies have shown a rate of 3 to 4 visually significant cataracts per 10,000 live births in the United States. Infantile cataracts can be unilateral or bilateral and can vary in size, morphology, and opacification. Affected vision, as well as the course of treatment and prognosis, is widely variable and is described in more detail in BCSC Section 6, Pediatric Ophthalmology and Strabismus.
The Italian-American Cataract Study Group. Incidence and progression of cortical, nuclear, and posterior subcapsular cataracts. Am J Ophthalmol. 1994;118(5):623–631.
Kahn HA, Leibowitz HM, Ganley JP, et al. The Framingham Eye Study. I. Outline and major prevalence findings. Am J Epidemiol. 1977;106(1):17–32.
Klein BE, Klein R, Lee KE. Incidence of age-related cataract: The Beaver Dam Eye Study. Arch Ophthalmol. 1998;116(2):216–225.
Livingston PM, Carson CA, Stanislavzky YL, Lee SE, Guest CS, Taylor HR. Methods for a population-based study of eye disease: The Melbourne Visual Impairment Project. Ophthalmic Epidemiol. 1994;1(3):139–148.
Leske MC, Connell AM, Wu SY, Hyman L, Schachat A. Prevalence of lens opacities in the Barbados Eye Study. Arch Ophthalmol. 1997;115(1):105–111.
Varma R, Richter GM, Torres M, et al; Los Angeles Eye Study Group. Four-year incidence and progression of lens opacities: the Los Angeles Latino Eye Study. Am J Ophthalmol. 2010;149(5):728–734.
West SK, Duncan DD, Muñoz B, et al. Sunlight exposure and risk of lens opacities in a population-based study: The Salisbury Eye Evaluation project. JAMA. 1998;280(8):714–718.
Wu R, Wang JJ, Mitchell P, et al. Smoking, socioeconomic factors, and age-related cataract: The Singapore Malay Eye Study. Arch Ophthalmol. 2010;128(8):1029–1035.
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.