[Keratoconus].

OBJECTIVE: To describe the human corneal histopathology after laser in situ keratomileusis, photorefractive keratectomy, astigmatic keratoplasty, clear corneal refractive lens surgery, conductive keratoplasty, and intrastromal corneal ring segment placement. DESIGN: Retrospective histopathologic study and selected literature review. METHODS: Ninety-four postmortem corneas from 49 patients and 10 corneal button specimens from 6 patients with previous refractive surgery were collected from eye banks and refractive surgeons in North America. This observational case series evaluated the pathologic findings in the wounds of these corneas in the context of previous studies. RESULTS: Three histopathologic types of corneal wound-healing responses were present in corneas after refractive surgery. The first was an epithelial cell modification that reestablished a smooth anterior corneal surface through basal epithelial cell hypertrophy, by epithelial hyperplasia, or both. The second was the production of a hypercellular fibrotic stromal scar, and the third was the production of a hypocellular primitive stromal scar. Although only the hypercellular fibrotic stromal scar could be identified on gross examination, all three wound responses were identified with light, electron, and immunofluorescence microscopy. Confocal microscopy also identified these three processes but with less detail and resolution. CONCLUSION: Understanding the locations, clinical appearance, and functional attributes of these wound-healing responses will help guide evolving techniques or adjunctive treatments.

Cornea↗

PubMed2005

Femtosecond laser-assisted posterior lamellar keratoplasty: initial studies of surgical technique in eye bank eyes.

OBJECTIVE: To perfect the technique of femtosecond laser-assisted cutting of the lamellar corneal disc in posterior lamellar keratoplasty. DESIGN: Experimental study. METHODS: The femtosecond laser was used to make the posterior corneal lamellar interface and trephine (side) cut in 20 eye bank globes and 9 eye bank corneoscleral buttons. Laser parameters were energy 7.4+/-0.1 microJ (lamellar cut) and 8.7+/-0.1 microJ (trephination cut), spot size 2.4 microm, firing rate 15 kHz, and trephination diameter 6.0 to 8.0 mm. The thicknesses of the excised corneal discs were measured with a digital micrometer and compared with values calculated from the laser treatment parameters and the preoperative ultrasound pachymetric readings. The cut surfaces were examined by light microscopy and scanning electron microscopy. In globes, the corneal disc was removed from the eye after laser treatment through a blade incision in the peripheral cornea. In corneoscleral buttons, the posterior disc was peeled off the cornea with forceps after laser treatment on an artificial anterior chamber device. In simulated transplantation, the excised corneal disc was placed into the posterior stromal bed in 7 globes. RESULTS: The femtosecond laser was successful in making posterior lamellar and trephination cuts in cornea. The cut surfaces were of very good quality with straight, orthogonal edges, albeit with a mild stucco texture of the lamellar stromal surfaces. In 3 globes, the lamellar surface showed shallow concentric ridges. The measured thickness of the excised discs was 55+/-61 microm thicker than the preoperatively predicted values. CONCLUSIONS: These preliminary studies show that the femtosecond laser can make nonmechanical cuts for posterior lamellar keratoplasty with relative ease and reliability, thus facilitating the most technically difficult step in this surgery.

Cornea↗