Vance Thompson, Theo Seiler, Alex Sacharoff, Daniel Durrie, Alberto Aran, Ronald Barnet, David Dulaney, Art Hurt, P. Mann, Harold Sawelson, Myron Yanoff, David Muller
We update the continued progress of laser thermokeratoplasty (LTK) clinical trials being conducted in the U.S. for the treatment of hyperopia and hyperopic astigmatism. Data from the Phase II hyperopia investigations on 25 patients and from Phase I astigmatism trials on 30 patients is reviewed. From the hyperopia Phase IIa study, the near uncorrected visual acuity of 13 patients for whom complete follow-up results are available at 1 year shows that all 13 patients gained 2 or more lines of visual acuity (Ave. gain 3.5 lines), which indicates a significant improvement in near vision. A survey given to these hyperopia patients finds 8% could read without glasses preoperatively versus 58.3% at 1 year post-operatively. The preoperative uncorrected visual acuity of those patients treated for astigmatism in the Phase I trial showed 2 out of 30 patients or 6.7% seeing better than 20/40 versus 10 out of 27 patients or 37% at one year post-op. The one year data in both studies indicates that after an initial period of partial regression of effect, the residual correction remains relatively stable between 6 months and 1 year. Continued follow-up will be carried out to see if the corrections remain stable beyond 1 year.
We describe the results of a 30 patient Phase I clinical trial using the Laser Thermokeratoplasty (LTK) treatment for correction of hyperopic astigmatism. We report the results for 29 patients who have reached 2 months post-operative. The average pre-op cylinder was reduced from -3.06 Diopters (D) to -1.21 D. Average spherical equivalent (SE) refractive error was reduced from +2.28 to +1.34 D. Six patients have reached 4 months post-op; the average cylinder of these patients has been reduced from -1.92 to -0.79 D while the average SE has been reduced from +1.29 to +0.31 D. Although patients had varying degrees of astigmatism pre-op, all treatments were performed with identical parameters (intended to correct a small amount of astigmatism) to enable us to determine the effect of the procedure without the influence of other factors such as varying zone diameter or laser fluence. The predictability and stability of the LTK procedure are supported by a recent study of 20 patients treated in Germany by Seiler for low to moderate degrees (2 - 4 D) of hyperopia. After 6 months post-op, 16 of 20 patients are within +/- 1 D of the attempted correction. Longer-term follow-up will be necessary to determine the ultimate refractive stability of the LTK procedure.
We report on two clinical trials, one involving 10 patients in the United States and the other in Berlin, Germany with 15 patients, all treated for hyperopia with a new laser surgical procedure known as laser thermokeratoplasty (LTK). The procedure involves making a circular array of corneal coagulations using an Ho:YAG laser, fiber-optic handpiece, and contact focusing tip. The extent of steepening of central corneal curvature is controlled by the diameter of the treatment zone. The LTK procedure induces an immediate and significant reduction in hyperopic refractive error. Although the clinical investigations are at an early stage, results of the clinical trials indicate that the LTK procedure may prove to be a reliable means of effecting a permanent change in refraction in patients suffering from hyperopic refractive disorders.
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