Goldmann applanation tonometry after Intacs corneal ring segments

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Abstract
To evaluate the change of intraocular pressure (IOP) after implantation of Intacs (KeraVision) corneal ring segments using Goldmann applanation tonometry (GAT). Multicenter clinical trial for U.S. Food and Drug Administration application conducted at 10 U.S. sites. One-year follow-up data from a phase III clinical trial (n = 359) were reviewed. Intraocular pressure was measured by GAT preoperatively and 1 week and 1, 3, 6, and 12 months after Intacs implantation. The untreated fellow eyes were controls. Change from baseline (preoperative) IOP was calculated and tested for correlation with age and change from baseline in mean keratometry, manifest refraction spherical equivalent (MRSE), and pachymetry (central corneal thickness). Mean IOP in treated and control groups was compared through month 6. At all postoperative examinations, mean IOP in the Intacs eyes was significantly lower (-0.39 to -1.75 mm Hg; all P </=.02) than at baseline. Change from baseline in mean IOP of treated eyes did not correlate with age or change from baseline in mean keratometry values, MRSE, or central corneal thickness. At 1, 3, and 6 months, mean IOP was significantly less (-0.38 to -0.53 mm Hg; all P </=.002) in Intacs eyes than in control eyes. Implantation of Intacs slightly lowered IOP measurements by GAT, without correlation to other tested parameters. Postoperative IOP differences between Intacs and control eyes were statistically but not clinically significant. Goldmann applanation tonometry accurately measured IOP at the center of the cornea in eyes with Intacs.