In every study conducted on presbyopia, described as the loss of near vision due to age, scientists have found that women are hit with the condition earlier, requiring bifocals and reading glasses at a ypunger age than their male counterparts.

In a recent study published in Investigative Ophthalmology and Visual Science, scientists have concluded that the discrepancy comes not from focusing ability, as had been previously thought, but possibly from preferred reading distance and arm length.

While presbyopia may seem like a surprising focus for a study, according to the paper’s authors, “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.”

The researchers examined nine previously conducted cross-sectional studies of men and women to compare frequency and severity of presbyopia. From there, researchers analyzed the comparable groups to determine the differences that may exist between men and women with the condition. They found, like their predecessors, that women tended to need bifocals and reading glasses earlier than men, and that women’s reading prescriptions tended to be higher than men of the same age.

The study authors found no difference in focusing ability between men and women, when looking at near objects. They did find, however, that women – who are, on average, shorter – tend to bring reading materials closer to their face, due to their shorter arms. Researchers hypothesize that act and bodily difference accounts for the difference in the condition.

Study authors are convinced that their findings reinforce the need for presbyopia correction for women, an unmet need in developing countries. They also state that their findings underscore the fact that presbyopia may have many factors.

The scientists contend that further studies will need to be undertaken, particularly ones that are more careful to control for outside factors that may contribute to the condition’s development. In particular, the paper suggests the need for longitudinal studies that would take into account preferred reading distance and the other, perhaps correctable changes that would occur over the years.