Clinical and Epidemiologic Research Meta-Analysis of Sex Differences in Presbyopia

PURPOSE. Uncorrected presbyopia is a significant cause of visual disability globally. Greater comprehension of the etiology of presbyopia and its contributing factors among medical and vision care providers could lead to changes in correction methods and account for sex differences in near-vision requirements. METHODS. A meta-analysis was performed using nine crosssectional studies that provided sufficient data to compare the prevalence and magnitude of presbyopia among men and women. This analysis was further subdivided into measurement methods to determine what differences in presbyopia might exist between men and women. RESULTS. Studies of presbyopia including sex as a contributing factor were highly heterogenic (P ¼ 0.01) but overall found female sex to be statistically significant in predicting earlier onset for presbyopia with an adjusted confidence interval (CI) using the Shore method of 95% CI [1.02, 1.45]. When limited to studies only measuring accommodative amplitude, female sex was not associated with presbyopia in a fixed effects model with a 95% CI [0.49, 1.07]. CONCLUSIONS. While an association between female sex and presbyopia for subjective measurements (near spectacle prescriptions and add powers) was indicated, measurements of accommodative amplitude show a weak tendency toward the opposite conclusion. This suggests that increased association of presbyopia for women is not due to a physiologic difference in accommodation but rather due to other sex differences, such as tasks performed and viewing distances. Age-based correction nomograms for presbyopia should therefore consider these sex differences when prescribing add powers for near tasks. (Invest Ophthalmol Vis Sci. 2012; 53:3215-3220) DOI:10.1167/iovs.12-9791 I t has been estimated that worldwide more than a billion adults are now affected by presbyopia, the age-related loss of accommodation that blurs near vision due to decreased focusing ability. According to worldwide census data, one third of the population is older than 40, an age when the effects of presbyopia become symptomatic enough that individuals begin using near-vision spectacles. As the global population ages, the prevalence of presbyopia will increase. By 2030, the global population older than 40 is expected to rise to 41%. 1 Although estimates show uncorrected presbyopia as one of the leading causes of disability and worthy of attention as a significant contributor to the global burden of disease, 2 it is commonly overlooked as a major source of disability due to the ease of acquiring spectacle readers in wealthy countries. With age, presbyopia eventually affects everyone but is generally measured and diagnosed only when an individual becomes symptomatic and presents to an eye care provider with need for near-vision correction. Due to the need for trained vision care providers, the burden of presbyopia is greatest among vulnerable populations, with sex, race, ethnicity, climate, rurality, and geographic locations considered to be contributing factors. 2-5 While presbyopia often manifests as a difficulty in reading small text, an inability to see near objects clearly can have a substantial impact on the quality of life regardless of literacy or profession. 3 In 1623, Benito Daza de Valdes noted that ''women with blurred vision [presbyopia] cannot follow the same guidelines as men-they require eyeglasses possessing more degrees because they do more delicate work and because they have weaker vision. '' 6 Recent studies confirm that women are indeed still being prescribed with higher near corrections than men of the same age. 7-12 The reason for this sex disparity is not immediately clear. Daza de Valdes made two different claims: women perform ''more delicate work'' and women have naturally ''weaker vision.'' These claims would imply that there are biological, societal, and environmental components to the need for higher-powered near prescriptions in women. Despite findings supporting the conclusion that women are given higher reading prescriptions than men of equal age, there is often no differentiation made among the biological, social, psychological, and cultural factors that could explain this difference. As illustrated in Loss of focusing ability, an underlying cause of presbyopia, occurs due to a loss of elasticity of the crystalline lens, which makes it less effective at increasing optical power with attempts at accommodation. As the ciliary muscle contracts during accommodation, tension on the zonules decreases, but a larger, stiffer presbyopic lens fails to increase in optical power to the same magnitude as a younger, more pliable crystalline lens