WTA reduces reading parameters and NVA

With-the-rule astigmatism (WTA) reduces reading parameters and near visual acuity (NVA) compared with against-the-rule astigmatism (ATR) and no astigmatism, according to a recent paper.

Professor Thomas Kohnen et al., Department of Ophthalmology, Johann Wolfgang Goethe-University, Germany, conducted a consecutive case series on 23 eyes of 23 participants. All subjects were fogged with 0 D, −0.75 D and −1.5 D of ATR astigmatism via lenses with spherical compensation.

Every participant was cyclopleged and distance corrected The outcome measures included reading acuity (RAc), reading speed (RS) and NVA. Data was compared using the outcomes of Wilcoxon-matched-pairs test, regression analysis and Bland–Altman analysis.

Increasing the amount of astigmatism caused a decreased NVA and RAc, whereas WTR astigmatism caused a reduced NVA, RAc and RS compared to the results of ATR astigmatism.

Outcomes revealed that that NVA was better than RAc with no astigmatism, −0.75 D WTR and −1.5 D WTR. The study group did not observe any differences between NVA and RAc for −0.75 D ATR and −1.5 D ATR.

For more information on the study please visit the British Journal of Ophthalmology.