Increased astigmatism decreases near visual acuity

This prospective study found that increasing astigmatic power significantly decreases patients’ near visual acuity and reading performance.

Investigators compared the effects of various types of induced astigmatism on near visual acuity and reading performance in 23 healthy subjects. All subjects had spherical equivalent from −5 D to + 5 D, refractive astigmatism less than or equal to 0.75 D and age ≥ 18 years. All underwent cycloplegic and distance correction.

Both reading and near visual acuity significantly decreased with increased astigmatism. Reading acuity decreased significantly at both levels of induced astigmatism – -0.75 D and -1.5D – and near vision decreased significantly only at -1.5D. There was no significant decrease in reading speed at either level.

With-the-rule astigmatism decreased near visual and reading acuity whereas, in the tested range (-0.75 D and -1.5 D), against-the-rule astigmatism did not decrease visual or reading performance significantly.

They conclude that these findings are important for the direction of further research on the astigmatic influence on reading performance, especially considering that reading performance is, for most patients, crucial for handling everyday life and for determining satisfaction with surgical outcomes.