Change on the horizontal and vertical meridians of the cornea after cataract surgery.

PURPOSE To compare the course and magnitude of change on the horizontal and vertical meridians of the cornea after 5 different incisions for cataract: extracapsular cataract extraction (ECCE), 6 mm superior scleral tunnel (6Sup), 3 mm superior scleral tunnel (3Sup), 3 mm temporal scleral tunnel (3Temp), and 3 mm temporal corneal incision (3Cor). METHODS Retrospective chart review of 665 cases of preoperative regular astigmatism. The preoperative keratometry (K) reading was subtracted from the postoperative K reading to determine mean net change on each meridian at 1 day, 1 week, 2 weeks, 1 month, 1.5 months, 2 months, 4 months, 6 months and 12 months and at 6 month intervals thereafter. After the superior incisions, the temporal changes on each meridian are well described by an analytic model with an initial and final plateau. The changes after the temporal incisions are described by a linear equation. RESULTS After each superior incision, the steepness and length of the transition from the initial to final plateau for each meridian depend on incision length. Considering the uncertainty of measuring K, the corneal meridians stabilized 4.5 months after ECCE, 1.2 months after 6Sup, and 0.3 months after 3Sup. No significant change was detected on the horizontal and vertical meridians after 3Temp and 3Cor. CONCLUSION The magnitude and the duration of changes on the horizontal and vertical meridians of the cornea after cataract surgery depend on both incision length and location. Small temporal incisions induce less change than superior incisions.