Background: To evaluate the torsional and flattening effect of steep meridian incisions and influence of posterior\ncorneal astigmatism (PCA) on total corneal astigmatism (TCA) after cataract surgery.\nMethods: One hundred thirty-two eyes underwent cataract surgery with steep meridian 2.2 mm microcoaxial and\n2.85 mm conventional clear corneal incisions. Eyes were divided into with-the-rule (WTR) astigmatism and againstthe-\nrule (ATR) astigmatism groups depending on the steeper meridian and measured with autokeratorefractor and\nPentacam�® before surgery, at 1 day, 1 week, 1 and 2 months postoperatively. Polar vector analysis was used to\nevaluate torsional effect of steep meridian incisions.\nResults: A decrease in astigmatic polar value (AKP) (+0) was observed in both keratometric and total astigmatism\n(TA) after 1 and 2 months, although the decrease was only statistically significant in TA (p < 0.05). The AKP(+45) was\nmore significant in the conventional group than the microcoaxial group at 2 months postoperatively (p < 0.05,\nrespectively). There was a significant correlation between corneal thickness of the superior quadrant and PCA in the\nWTR group (p = 0.028). In eyes with anterior corneal astigmatism smaller than 0.55D of WTR astigmatism and PCA\ngreater than 0.35D of WTR astigmatism showed greater shifting of steep axis and also increment of refractive\ncylinder powers.\nConclusions: In eyes with superior corneal thickness greater than 714.5 �¼m and PCA greater than 0.35D of WTR\nastigmatism, steep meridian incision may cause a significant torsional effect and off-steep meridian change,\ncontributing to an increment of postoperative residual manifest astigmatism after cataract surgery.
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