Irregular astigmatism and contrast visual acuity after small incision cataract surgery

Purpose. Small incision cataract surgery resulted in early postoperative recovery of visual function because of less intraocular inflammation and irregular astigmatism. Using the Variable Contrast Visual Acuity Charts (VCVAC), we reported that improved visual acuities (VAs) with intermediate- and low-contrast charts correlated negatively with the postoperative level of intraocular inflammation (ARVO 1995). In the present study we observed changes in contrast VA and irregular astigmatism at several time points postoperatively. Methods. Sixteen patients (22 eyes) aged 41-89 years (mean, 65.5) with no ocular pathologies except for cataract were selected as study patients. Phacoemulsification and intraocular lens implantation were performed through a 3-5 mm self-sealing incision. The irregular corneal astigmatism was quantified from the difference between the actual refractive power and the sine curve that approximates the refractive power of the regular cornea. The contrast VA was measured using the VCVAC, which consists of low- (2.5%), intermediate- (15%), and high- (90%) contrast charts. Those measurements were performed preoperatively and at 3 and 5 days, 2 weeks, and 1 month postoperatively. Results. The degree of regular astigmatism was not statistically different at any time postoperatively. However, the degree of irregular astigmatism within the central 2 mm of the cornea was 0.59D at 3 days and 0.51D at 5 days, and improved to 0.38D at 2 weeks postoperatively. The irregular astigmatism at 3 and 5 days postoperatively, which was statistically higher than that preoperatively (0.31D), was negatively correlated with the recovery of VAs with intermediate and low contrast. Conclusions. The irregular astigmatism may also influence the early postoperative VA with intermediate- and low-contrast charts as well as intraocular inflammation.