Changes in corneal hysteresis after clear corneal cataract surgery

PURPOSE: To assess the changes in corneal hysteresis (CH) as measured by the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, New York, USA) to describe the influence of clear corneal cataract surgery on corneal viscoelastic prop, erties and intraocular pressure (lop) measured by noncontact tonometry (NCT) and Goldmann applanation tonometry (GAT). DESIGN: Retrospective, interventional, comparative study. METHODS: One hundred and one eyes of 101 consec,utive patients who underwent routine clear corneal cataract surgery were evaluated. CH, NCT, and central corneal thickness (CCT) were measured by ORA before surgery and at postoperative day 1. A control group of 48 pseudophakic eyes (surgery > 3 months previously) was included. * RESULTS: CCT increased from 556.82 +/- 32.5 mu m before surgery to 580.26 +/- 45.5 mu m after surgery (P < .001; control, 555.16 +/- 42.33 mu m). Mean CH decreased from 10.35 +/- 2.5 mm Hg before surgery to 9.20 +/- 1.9 mm Hg after surgery (P < .001; control, 10.47 +/- 1.63 mm Hg). NCT values rose from 17.85 +/- 3.8 mm Hg before surgery to 20.10 +/- 6.3 mm Hg after surgery. GAT values were 14.85 +/- 2.8 mm Hg before surgery and 15.24 +/- 4.1 mm Hg after surgery (P = .52). There was no significant difference of CCT or CH between the preoperative values and the values of the control group (CCT, P = .986; CH, P = .166), in contrast to the difference between postoperative values and the values of the control group (CCT, P = .005; CH, P = .031). CONCLUSIONS: At day I after clear corneal cataract surgery, CH is diminished, whereas CCT is increased significantly. Postoperative corneal edema leads to a change of corneal viscoelastic properties, resulting in a lower damping capacity of the cornea. It is supposed that GAT and NCT measurements are significantly different because of postoperative changes in viscoelastic properties of the cornea.