Radial keratotomy increases outflow facility in the porcine eye in vitro

Purpose. To investigate the biomechanical effect induced by radial keratotomy on outflow facility in paired, enucleated whole porcine eyes. Methods. Freshly enucleated porcine eyes were perfused at a constant pressure of 10 mm Hg. Radial keratotomy (RK), with a 3.5 mm central clear zone and eight radial incisions, was performed using a diamond knife with the blade length set at 100% of the paracentral corneal thickness, as measured by pachymetry. The fellow eye of each pair received sham RK as a control. Results. Seven pairs of eyes were perfused (RK group n = 7, control n = 7). There was no significant difference in the mean baseline of outflow facility between the paired experimental and control eyes preoperatively (p = 0.5). After RK, outflow facility increased by 46% (p < 0.001) in the treatment group, compared to a 7% (p < 0.04) increase in the control group, resulting in a 39% increase in outflow facility attributed to RK (p < 0.001). Conclusions. Radial keratotomy produced a statistically significant acute increase in outflow facility in freshly enucleated porcine eyes. We believe that this increase results from steepening of the peripheral corneal curvature and the concomitant stretching of the iridocorneal angle. Further studies are needed to evaluate this effect in human eyes and in vivo.