PRK-induced aberrations may enhance near vision

Eyes that have undergone PRK for the correction of myopia may have a delayed onset of symptoms associated with presbyopia and improved uncorrected near acuity, according to a study.

The authors said they attribute the findings to an additional 1 D pseudoaccommodative effect resulting from an increase in corneal spherical aberration and depth of field after surgery.

Jorge L. Alió, MD, PhD, and colleagues retrospectively analyzed the charts of 20 eyes that had undergone PRK with first-generation technology at least 10 years earlier and compared visual acuity with 20 eyes of age- and gender-matched control subjects. All patients were more than 40 years old; the mean age of the PRK group was 46.3 years old. Mean age of the control group was 47.6 years old.

Near acuity was J1 or better in 12 of the 20 PRK eyes; near acuity was J1 or better in four of the control eyes. Mean accommodations were 3.2 D in the right eye of the PRK group and 3.4 D in the left eye of the PRK group, compared with 2.1 D in the right eye of the control group and 2.3 D in the left eye of the control group, authors said.

The post-PRK patients did not report any near vision problems, the researchers said. They had better uncorrected near visual acuity than the control group, but slightly reduced distance vision. Although not statistically significant, the quality of distance vision was lower in the post-PRK group than in the control group, they said.

“Underlying intracorneal optical interactions, coupled with the changes in corneal front surface multifocality, are the most likely factors responsible for the PRK group having an amplitude of accommodation higher than that of controls,” the authors said.

The study is published in the May issue of Ophthalmology.