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John C. Merriam, Lei Zheng; Is Surgically-Induced Astigmatism After A 2.2 Mm Temporal Corneal Incision Significant?. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6222.
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This retrospective study compares the magnitude of the vector of surgically-induced astigmatism (SIA) following a temporal 2.2 mm incision with the magnitude of the vector calculated from the keratometry readings of control, non-surgical eyes.
The surgical group includes 269 eyes from 173 patients who had uncomplicated cataract surgery and intraocular lens implantation with a temporal 2.2 mm incision with topical anesthesia. The control eyes were the unoperated fellow eyes of 239 patients who had cataract surgery. The surgeon measured pre- and postoperative corneal curvature with a manual keratometer, and these values were used to calculate the magnitude of the vector for both the operated and control eyes. For this study, the date of surgery for one eye was assumed to be the sham date of "surgery" for the fellow non-surgical eye, and the magnitude of the vector was calculated at each "post-operative" time interval for 18 months. A one-way ANOVA test was used to compare the magnitude of the vector at all follow-up times within each group. The "two sample t-test" was used to compare the magnitude of the vector of the 2.2 mm incision group and the non-surgical eyes at each follow-up time.
The magnitude of the vector for the non-surgical eyes does not differ at any follow-up interval. The magnitude of the vector following a 2.2 mm incision is greater only at one day after surgery than at all other post-operative times. However, the magnitude of the vector following a 2.2 mm incision is statistically greater (P<0.05) than that for control eyes at the one day, one week, and two week intervals after surgery. After one month the magnitudes of the vectors of the surgical and non-surgical groups are not statistically different.
Although recovery following a temporal 2.2 mm incision is rapid, this incision does induce small but measurable change in corneal curvature which persists for about 2 weeks after surgery.
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