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Zachary Landis, Andrew Luo, Diane Jang, Jack Quillen, Tara O'Rourke, Seth Pantanelli, Ingrid U Scott; Impact of Posterior Corneal Astigmatism on Refractive Astigmatism after Cataract Extraction with Intraocular Lens Implantation. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3684.
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© ARVO (1962-2015); The Authors (2016-present)
Corneal astigmatism is the primary source of astigmatic refractive error after cataract surgery. Total corneal astigmatism is comprised of both anterior and posterior corneal astigmatism. The purpose of this study was to characterize posterior corneal astigmatism and its effect on refractive astigmatism after cataract surgery.
Retrospective consecutive case series of eyes that underwent optical biometry and topography with good image quality metrics in anticipation of cataract surgery which was subsequently performed, or supervised, by a single surgeon at an academic medical center between November 2014 and November 2018. Eyes with visually significant corneal disease or prior refractive surgery were excluded. In eyes that had implantation of a monofocal intraocular lens (IOL) (EnVista MX60, Bausch & Lomb) with post-operative best-corrected visual acuity of at least 20/40, the predicted refractive astigmatism was calculated using anterior corneal and total astigmatism as measured with a dual Scheimpflug-Placido tomographer (Ziemer Gallilei G4). Actual refractive astigmatism was obtained via subjective refraction performed 4-8 weeks post-operatively, and compared to the anterior corneal and total measured astigmatism to evaluate the effect of incorporating posterior corneal astigmatism measurements into a model that seeks to explain all post-operative refractive astigmatism.
Of the 321 eligible eyes, 141 (44.2%) had with-the-rule (WTR) anterior corneal astigmatism (ACA), 113 (35.4%) had against-the-rule (ATR), and 65 (20.4%) had oblique astigmatism. Posterior corneal steepening (PCS) was oriented vertically in 87.5% (n=281), horizontally in 5.3% (n=17), and obliquely in 7.2% (n=23). The mean magnitude of PCS was -0.25 when ACA was ATR and -0.37 when ACA was WTR (p=0.0001). For the subset of eyes in which a monofocal MX60 IOL was implanted and a post-operative refraction was available (n=283), the mean difference vector between actual and predicted refractive astigmatism was 0.44 D at 5°when only ACA was considered and 0.24 D at 9°when PCS was also considered (p < 0.0001).
PCS magnitude is greatest in eyes with WTR ACA and least in eyes with ATR ACA. The post-operative refractive astigmatism can be predicted more accurately when posterior corneal astigmatism is considered as part of the analysis.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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