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

Abstract

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 (J₀, J₄₅) 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 (ρ=-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.

Keywords: angle; epidemiology; treatment other; vision.

Figure 1

Population selection and attrition for eyes included in the study population. IOL, intraocular lens; UDVA, uncorrected distance visual acuity.

Figure 2

Distribution of preoperative (corneal) (solid line) and postoperative (refractive) astigmatism (dashed line). The preoperative population includes all eligible eyes (N=110 468), while the postoperative population contains all eyes with monofocal intraocular lens (IOLs) and an eligible refractive measurement (N=39 744).

Figure 3

Distribution of preoperative (corneal) astigmatism according to type (A) and the distribution of postoperative (refractive) astigmatism according to co-pathology (B). The preoperative population includes all eligible eyes (N=1 10 468), while the postoperative population contains all eyes with monofocal intraocular lens (IOLs) and an eligible refractive cylinder value (N=39 744). Proportions reflect cases exceeding a certain level of preoperative and postoperative astigmatism.

Figure 4

Power vectors for all eyes implanted with monofocal intraocular lens (IOL) with both refractive cylinder and steepest meridian recorded 2–12 months postsurgery and preoperative astigmatism ≥0.5 D (n=28 845) for (A) all eyes, (B) eyes with and without co-pathologies and (C) eyes operated with and off the steepest meridian. Each point indicates the mean vector value. The arrow indicates the direction of change between presurgery and postsurgery (and not the magnitude). The P values represent the result of Hotelling’s T² test (A) and the multivariate linear regression adjusted for presence of co-pathologies (B) and steepest meridian of surgery (C).

figure 5

Box plot of UDVA (A) and BDVA (B) scores according to surgery axis and presence of co-pathologies. Note that eyes with preoperative corneal astigmatism <0.5 D were excluded.

figure 6

Uncorrected distance visual acuity (UDVA) levels at different categories of astigmatism severity for eyes with refraction and UDVA measured after surgery (N=19 095). Mild astigmatism:<1.5 D, moderate: 1.5 -<2.5 D and severe: 2.5 -<5.5 D. Eyes with ≥5.5 D were considered as potentially pathological corneas.