Electron microscopic examination of prelathed, lyophilized tissue used for epikeratophakia in humans

Morphologic changes secondary to cryolathing and lyophilization have been described in tissue lenses used for epikeratophakia. We report the electron microscopic findings of an aphakic tissue lens which could not be used because of sudden preoperative myocardial infarction of the patient. Scanning electron microscopy revealed the presence of three distinct zones (peripheral, intermediate, and central) on the stromal side of the lens. The surface of the central zone appeared to be the smoothest, as a consequence of the different angle of lathing. The Bowman's layer side of the tissue lens exhibited a uniform, smooth surface. Transmission electron microscopy revealed a largely normal collagenous structure of both stroma and Bowman's layer. Interfibrillary distances were within normal limits. Several giant stromal spaces of various dimensions filled with homogeneous material were observed. Variably preserved keratocytes were a regular finding among the lamellae. Our findings confirmed some of the structural changes previously observed in tissue lenses not used for epikeratophakia in humans. The limited size of a smooth central zone of the posterior surface could explain some postoperative complaints such as persistent glare phenomena, as well as prolonged visual rehabilitation time, especially in those cases where centration of the epi-lens onto the recipient cornea is not optimal.