Distribution of preoperative and postoperative astigmatism in a large population of patients undergoing cataract surgery in the UK

Purpose To assess the prevalence and severity of preoperative and postoperative astigmatism in patients with cataract in the UK. Setting Data from 8 UK National Health Service ophthalmology clinics using MediSoft electronic medical records (EMRs). Design Retrospective cohort study. Methods Eyes from patients aged >= 65 years undergoing cataract surgery were analysed. For all eyes, preoperative (corneal) astigmatism was evaluated using the most recent keratometry measure within 2 years prior to surgery. For eyes receiving standard monofocal intraocular lens (IOLs), postoperative refractive astigmatism was evaluated using the most recent refraction measure within 2-12 months postsurgery. A power vector analysis compared changes in the astigmatic 2-dimensional vector (J(0), J(45)) before and after surgery, for the subgroup of eyes with both preoperative and postoperative astigmatism measurements. Visual acuity was also assessed preoperatively and postoperatively. Results Eligible eyes included in the analysis were 110 468. Of these, 78% (n=85 650) had preoperative (corneal) astigmatism >= 0.5 dioptres (D), 42% (n=46 003) >= 1.0 D, 21% (n=22 899) >= 1.5 D and 11% (n=11 651) >= 2.0 D. After surgery, the refraction cylinder was available for 39 744 (36%) eyes receiving standard monofocal IOLs, of which 90% (n=35 907) had postoperative astigmatism >= 0.5 D and 58% (n=22 886) >= 1.0 D. Visual acuity tended to worsen postoperatively with increased astigmatism (rho=-0.44, P<0.01). Conclusions There is a significant burden of preoperative astigmatism in the UK cataract population. The available refraction data indicate that this burden is not reduced after surgery with implantation of standard monofocal IOLs. Measures should be taken to improve visual outcomes of patients with astigmatic cataract by simultaneously correcting astigmatism during cataract surgery.