Cataract Surgery Alters Corneal Biomechanics and IOP

Journal Highlights

American Journal of Ophthalmology, November 2018

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Using the updated Corvis ST tonom­eter, Hirasawa et al. studied the effects of cataract surgery on corneal biome­chanics and intraocular pressure (IOP). They noted a decrease in the stiffness parameter at applanation 1 (SP A1) and increases in deformation amplitude maximum (DA max) and integrated radius, suggesting that the cornea is less stiff following cataract surgery.

This prospective, interventional case series included 39 patients (39 eyes) with cataract. Measurements with the Corvis ST tonometer were obtained before surgery and at 1 week, 1 month, and 3 months postoperatively; param­eters included DA max, DA ratio max (1 mm and 2 mm), integrated radius, SP A1, Ambrosio relational thickness to the horizontal profile (ARTh), Corvis biomechanical index, central corneal thickness, noncorrected IOP, and biomechanically corrected IOP. In addition, they measured IOP with Goldmann applanation tonometry and a noncontact tonometer. The linear mixed model was used to compare measurements for each time point, with and without adjustment for biome­chanically corrected IOP and central corneal thickness.

All IOP measurements decreased over time. Increased central corneal thickness was noted at 1 week and 3 months. Although the Corvis biome­chanical index was elevated at 1 week, it returned to preoperative status by 1 month. A decrease in ARTh was observed at 1 week and 1 month; this parameter returned to its preoperative level by 3 months. DA max and inte­grated radius had increased by month 3, and SP A1 had decreased by this time.

The authors advise caution when applying these results to clinical practice. They noted that 1 week following surgery may be too soon to use the Corvis biomechanical index to identify keratoconus.

The original article can be found here.