Keratophakia and keratomileusis: comparison of pathologic features in penetrating keratoplasty specimens

Two patients, one who had had two keratophakia procedures, and another who had had keratophakia, followed by a keratomileusis procedure both eventually required a penetrating keratoplasty. In the keratoplasty specimen bearing an intrastromal lenticle from a keratophakia procedure performed nine months earlier, no viable keratocytes were found in the in situ lenticle. The lenticle's stroma stained paler with methylene blue and toluidine blue than the host's surrounding stroma, probably due to the absence of proteoglycan synthesis. The interface scar between the lenticle and the host's stroma displayed metabolically active keratocytes, amorphous basement membrane-like material, banded basement membrane material or long-spacing collagen of 1000 A periodicity, microfibrillar collagen of 100 A diameter, and, only in focal areas, more mature-appearing collagen of 200 A diameter. In the keratomileusis-bearing penetrating keratoplasty specimen, complete repopulation of the keratomileusis' stroma by the host's keratocytes had been accomplished after seven months. The absence of any significant tinctorial differences between the keratomileusis' stroma and the host's stroma indicated that these keratocytes were functioning and able to produce proteoglycans. The interface scar between the keratomileusis' stroma and the host's stroma was similar to that in the keratophakia specimen, except for the lesser presence of mature collagen of 2000 A diameter. An explanation is not clearly obvious for the more rapid keratocytic repopulation of the keratomileusis' stroma in comparison with the lenticle's stroma in keratophakia. Both patients had successful penetrating keratoplasties, with postoperative visual acuities of 20/40 and 20/20, owing to the fact that the earlier corneal surgeries had not compromised the integrity of the anterior chamber structures.