Biological Lenticule Implantation for Correction of Hyperopia: An Ex Vivo Study in Human Corneas

PURPOSE: To evaluate changes in corneal tomography after stromal lenticule implantation ex vivo, with respect to the dependency of the lenticule thickness and implantation depth on the corneal curvature and the postoperative biomechanical strength at increased chamber pressure. METHODS: Twenty-eight human donor corneas underwent pocket implantation of refractive stromal lenticules. Four groups were created by the combination of two implantation depths (110 and 160 µ m) and two lenticule thicknesses (95 µ m = 4.00 diopters [D], 150 µ m = 8.00 D). Sagittal keratometry and total corneal refractive power (TCRP 4mm,apex,zone ) were obtained for the front and back curvature with Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) at chamber pressures of 15 and 40 mm Hg. RESULTS: The anterior curvature steepening was comparable between the 4.00 D and 8.00 D groups ( P > .141), but more pronounced with 110 µ m implantation depth ( P < .038). The posterior curvature flattened significantly more after implantation of 8.00 D than 4.00 D lenticules ( P < .002), but was similar at 110 and 160 µ m implantation depths ( P > .071). Average ΔTCRP for the 4.00 D and 8.00 D groups was 3.10 ± 0.60 and 5.30 ± 1.66 diopters (D) at 110- µ m depth, respectively ( P = .003), but 1.99 ± 0.79 and 3.36 ± 1.45 D at 160- µ m depth, respectively ( P = .066). The relative correction achieved was 66% to 78% at 110- µ m depth and 42% to 50% at 160- µ m depth, but similar when using 4.00 D and 8.00 D lenticules. Increased chamber pressure caused significant anterior and posterior curvature steepening after implantation in all four groups ( P < .001), but not before implantation ( P > .632). CONCLUSIONS: The power of the implanted lenticule must be higher than the intended correction, and customized to the chosen implantation depth. Biomechanical strength seems to decrease after lenticule implantation. [ J Refract Surg. 2018;34(4):245–252.]