Influence of additional astigmatism on distance-corrected near visual acuity and reading performance

Aim To investigate the effect of astigmatism on near vision performance. Methods In a consecutive case series 23 eyes of 23 participants were fogged with 0 D, -0.75 D and -1.5 D of with-the-rule (WTR) and against-the-rule (ATR) astigmatism (cylindrical lenses without spherical compensation). All subjects were cyclopleged and distance corrected. Reading acuity (RAc) and speed (RS) were measured with standardised sentences, near visual acuity (NVA) was assessed using single optotypes (Snellen E), all presented on a thin film transistor display using the Salzburg Reading Desk (SRD). Data were analysed using Wilcoxon-matched-pairs test, regression analysis and Bland-Altman analysis. Results An increasing amount of astigmatism resulted in a decreased NVA (p=0.16 for -0.75 D, p=0.005 for -1.5 D) and RAc (p=0.002 for -0.75 D, p=0.014 for -1.5 D). WTR astigmatism caused a reduced NVA, RAc and lower RS compared with ATR astigmatism (p<0.001). NVA was better than RAc with no astigmatism, -0.75 D WTR and -1.5 D WTR (p=0.03 for 0 D, p<0.001 for -0.75 D, p=0.03 for -1.5 D). There was no difference between NVA and RAc for -0.75 D ATR and -1.5 D ATR (p=0.06 for -0.75 D, p=0.5 for -1.5 D). Conclusions WTR astigmatism results in reduced reading parameters and NVA for -0.75 D and -1.5 D astigmatism compared with corresponding ATR astigmatism and no astigmatism added. No beneficial effect of astigmatism was detected.