Purpose:
It is often assumed that patients with low corneal astigmatism are unlikely to need distance spectacles following routine phacoemulsification surgery. We assessed how often such patients actually use distance spectacles.
Methods:
We assessed 169 patients in a prospective randomised controlled trial of visual outcomes after bilateral sequential implantation with either the Tecnis Z9000 or the Acrysof MA60AC monofocal intraocular lenses. Patients had no comorbidity and 1.5D or less of pre-op corneal astigmatism. Surgeons targetted 0 to -0.5 D as their postoperative spherical equivalent. Wherever cataract density permitted biometry was performed using the IOLmaster otherwise A-scan biometry was performed. Manufacturers A constants were used. Four months after the second eye was operated on patients were interviewed about spectacle use and refracted. All refractions were in minus cylinder format.
Results:
The mean age of the patients was 70.7 years, 63 were male and 106 female. Average mean refractive spherical equivalent was -0.02D (range +2.5 to -1.875 D) and the mean cylinder = -0.67D (range 0 to -3.25 D). Since the surgery, 103 patients had obtained new spectacles. 38 (22%) wore glasses with a distance prescription either some or all of the time (Distance glasses-Yes). 131 never used distance glasses (Distance glasses-No).Table 1 shows the number (%) who wore distance glasses according to the presence or absence of residual cylinder ≥ 0.5 D. Logistic regression analysis was used to test whether refractive error predicted spectacle use.The odds of using distance glasses is 85% greater for those with 0.5 D residual cylinder compared to no cylinder (OR= 1.85; 95% CI = 1.37 - 2.50; p < .0001). There is no statistically significant effect for residual sphere (OR = 1.27; 95% CI=0.90 - 1.80; p> .1). The results were very similar for left eyes.
Conclusions:
In patients with no co-morbidity and low corneal astigmatism who need cataract surgery, 22% will use distance glasses after surgery. The odds of using distance glasses increases by 85% for every 0.5 D of residual cylinder. Post-operative spherical equivalent has no predictive effect on use of distance spectacles.
Clinical Trial:
UK national research register ID=N0141120818
Keywords: small incision cataract surgery • astigmatism • refractive surgery: optical quality