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Sirikishan Shetty, Eugene Park, John Ladas, Stacy Bang; Effect of clear corneal incisions on posterior corneal astigmatism. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1597.
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© ARVO (1962-2015); The Authors (2016-present)
Posterior corneal astigmatism is now believed to contribute significantly to the total astigmatism of the cornea, but the effect of surgically induced posterior corneal astigmatism in sutureless cataract surgery has not been previously studied. We performed a prospective observational clinical study to test our hypothesis that a clear corneal incision will significantly affect posterior corneal astigmatism, thus affecting total corneal astigmatism.
Patients were approved for cataract surgery by 1 of 2 operating surgeons prior to participation in this preliminary study. 10 eyes of 8 patients (57 to 84 years old) were included. Inclusion criteria consisted of the following: no significant corneal pathology, no prior ocular trauma or surgery, no contact lens use within 2 weeks of surgery, and good quality scans. Additionally, based on LenStar measurements of the steep axis of astigmatism, only those patients who were determined to have clear corneal incisions at 90 degrees or 180 degree were included. The Oculus Pentacam was used to obtain preoperative corneal scans within 6 months of surgery. A 4mm diameter corneal zone was utilized to calculate the posterior and true net corneal astigmatism. Cataract extraction with phacoemulsification was performed using a 2.75mm superior (4 eyes) or temporal (6 eyes) clear corneal incision. A postoperative Pentacam scan was obtained 1-6 months after surgery. A 2-tailed paired T-test was used for statistical analysis.
The average preoperative posterior and true net corneal astigmatism was 0.21 and 0.82, respectively. The average change in posterior astigmatism and true net astigmatism was 0.09 (p-value 0.04) and 0.37 (p-value 0.30), respectively. There was no statistically significant difference after surgery in the subgroup analyses of eyes with superior or temporal incisions.
Our results show that there is a significant change in posterior corneal astigmatism after surgery. The effect of clear corneal incisions on posterior corneal astigmatism may affect intraocular lens implant selection and incision location. Although there was not a statistically significant change in total corneal astigmatism, further study will be needed to evaluate this result.
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