Experimental Results of Preparing Laser-shaped Stromal Implants for Laser-assisted Intrastromal Keratophakia in Extremely Complicated Laser in situ Keratomileusis Cases

ABSTRACT PURPOSE: To evaluate the feasibility of lasershaped stromal implants from a donor eye for correcting extreme high hyperopia with irregular astigmatism and an exceptionally thin corneal bed. METHODS: Thirty-one fresh enucleated porcine eyes were used. The procedure was initiated with mechanical de-epithelialization followed by a lamellar cut with a microkeratome, resulting in a hinged flap (thickness 150 µm, diameter 9.5 mm). The cornea was photoablated with PRK treatment for +8.00 D sphere (hyperopic lenticule group) and -5.00 D sphere (myopic group) by a scanning spot excimer laser. A customized scanning software algorithm was used to create a circumferential cut with a 6.5-mm internal diameter. The lenticule was removed from the stromal bed and measured by a surface profiling system. A clinical case was performed on a patient with previous LASIK and highly irregular hyperopic astigmatism to verify the clinical utility of the experimental setup. RESULTS: Under the microscope, lenticules seemed round, regular, and transparent. The average surface profile of porcine corneas demonstrated good parabolic shape with individual variations as large as 30 µm, probably due to the corneal size and curvature differences between the porcine eye and the human eye-for which the microkeratome is designed. The patient underwent a topographyguided treatment after laser-assisted intrastromal keratophakia (LAIK) and 1-month follow-up showed an increase of UCVA, BSCVA, and central corneal thickness. CONCLUSIONS: The use of modern scanningspot excimer lasers and microkeratomes enabled us to produce stromal lenticules of good quality, which might be acceptable to implant into a human eye. [J Refract Surg 2002;18:S639-S643] W e have witnessed the rapid development of surgical methods for the correction of myopia, hyperopia, and astigmatism. Although most patients who undergo refractive surgery are elective first time patients, there is also an emergent group of secondary iatrogenic hyperopic and astigmatic patients after complicated laser treatments with a decreased residual corneal thickness. The first techniques of adding more corneal tissue for refractive purposes were keratophakia, epikeratophakia, and keratomileusis. They were introduced by Barraquer in the 1950s and were used during the 1980s, but due to the complexity of the procedure and equipment, the inaccuracy of refractive results, postoperative complications, and delayed visual rehabilitation 1 , they are rarely performed today, even after recent studies of the laser assisted lenticule lathing. 2 Another alternative with promising but inconclusive results is provided by artificial lenses made of different materials (flint glass, polymethylmethacryate, polysulfone, and hydrogel) that are implanted in the stroma