IOP after ICRS™ implantation for myopic correction

Purpose. To assess the impact, if any. of ICRS (Intrastromal Corneal Ring Segment) implantation on intraocular pressure (IOP), patients enrolled in the U.S. Phase II and European ICRS clinical trials were evaluated. Methods. Individuals with IOP measurements outside the normal 10 to 21 mmHg range, or with a history of glaucoma, were excluded from the trials. To date, 148 U.S. patients and 47 European patients have received the ICRS in one eye. An approximately equal distribution of five ICRS thicknesses (0.25, 0.30, 0.35, 0.40 and 0.45 mm) were implanted. IOP was measured in both eyes preop and at each postop exam using a TonoPen XL, or equivalent hand-held tonometer. Results. Using available U.S. Phase II trial data, the mean (SEM) IOP were calculated {Preop: 15.5 mmHg (0.29); Day 1: 14.3 mmHg (0.31); < Month 2: 17.4 mmHg (0.32); and Month 3: 13.3 mmHg (0.35)]. The percentage of individual patients falling within the normal range was also calculated [Preop: 99% (101/102); Day 1: 96% (96/98); < Month 2: 90% (91/101); Month 3: 91% (90/99)]. All patients with an increase/decrease outside the normal range at Month 3 exhibited a similar increase/decrease in the nonoperative eye. The was no statistically significant ICRS thickness effect at any of the time points (p >0.36). Conclusions. The mean IOP values remained well within the normal range at all time points. The increase and decrease in TOP relative to baseline for all patients appeared to be transient in nature and without a systemic pattern. The ICRS does not appear to compromise normal IOP status and is well-tolerated by the cornea. Data collection is ongoing, and combined results from the European and U.S. trials will be reported. Cf 268.