The Effects of Axis-flip of the Refractive Cylinder on vision and patient reported outcome measures following Toric Intraocular Lens implantation

Purpose: To investigate the effects of cylinder axis-flip following toric intraocular lens (TIOL) implantation on vision and patient reported outcome measures (PROMs). Setting: Teaching hospital in the United Kingdom. Design: Post-hoc analysis of data from patients who participated in a prospective randomised study of TIOLs. Methods: Axis-flip was defined as a change in post-operative refractive cylinder axis of 90 0 +/- 22.5 0 from the pre-operative biometric axis. Uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (BDVA), residual refractive cylinder (RC), and CATPROM-5 and EQ5D3L quality of life (QOL) scores were analysed. Results: At 6 months, axis flip occurred in 29 (34.5%) of 84 eyes, of which 28 had with-the-rule astigmatism (WTR) pre-operatively. Mean (+/-standard deviation) UDVA (logMAR) was 0.13 (0.16) in flipped cases (FC) and 0.10 (0.14) in un-flipped cases (UF) (p=0.88). BDVA was 0.01 (0.11) in FC and was 0.00 (0.09) in UF (p=0.68). Mean RC was 0.74 dioptres (D) (0.41) in FC and 0.93D (0.47) in UF (p=0.08). Mean CATPROM-5 score was -6.22.98 (2.56) in FC and -5.52 (3.03) in UF (p=0.29). Mean EQ5D3L calibrated score was 0.89 (0.19) in FC and 0.85 (0.19) in UF (p=0.35). Retrospectively applying coefficients of adjustment to account for posterior corneal astigmatism (PCA), suggested that 6 eyes (21%) of FC with WTR might have avoided axis-flip. Conclusions: Axis flipping following TIOL implantation did not adversely influence visual acuity or PROMs scores. Most FC had WTR pre-operatively. Adjusting for PCA might have reduced axis flip in some of these eyes.