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In this study, the authors analysed a dataset of 122 eyes of 122 patients with pre- and postoperative measurements of corneal astigmatism with IOL Master 700. A standardised 2.5mm superior corneal incision was utilised. The corneal power vector component in the 0/90-degree meridian decreased by around a quarter of a dioptre (-0.26D for keratometry and -0.28D for total keratometry; 0.01D change in corneal back surface). The changes at oblique meridians (45/135 degrees) were by around 0.3D. In all these cases, the flattening was restricted to the corneal front surface only. Furthermore, stabilisation of the corneal architecture is not finished by three months postoperatively, and further changes in astigmatism should be expected even up to six months. The authors conclude that with a corneal incision from the superior meridian, the corneal power reduces by around 0.25D, mostly as a result of a change in corneal front surface curvature. The reduction of corneal power in the corneal incision axis is mostly counterbalanced by a steepening in the orthogonal meridian in such a way that on average, we see only a very slight reduction of overall corneal power from preoperative to one month follow-up.

Surgically induced astigmatism after cataract surgery – a vector analysis.
Langenbucher A, Szentmary N, Cayless A, et al.
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Kurt Spiteri Cornish

Sheffield Teaching Hospitals NHS Trust, London, UK.

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