Variations in corneal wound healing after radial keratotomy: possible insights into mechanisms of clinical complications and refractive effects.

Ultrastructural and histopathologic analysis was performed on three human corneal specimens for variable and complicated refractive outcomes 1-2 years after radial keratotomy. Specimens were obtained immediately postsurgery after microkeratome resection with homoplastic lamellar keratoplasty (two cases) and penetrating keratoplasty (one case) for correction of glare, severe astigmatism, overcorrection, and/or double vision. All three cases showed variability of wound healing and delayed corneal wound healing sites; epithelial retention cysts, and/or absence of stromal scar collagen that was not dependent on the length of time after surgery. Two of the three radial keratotomy specimens also contained extensive duplication of the superficial corneal epithelial basal lamina. When present, the thickened basal lamina (3-6 microns in thickness) was seen between all incisions evaluated and appeared to extend from the central optical zone out to the periphery of the lamellar button. The one full-thickness keratoplasty specimen showed focal loss of underlying endothelial cells with occasional migrating cells seen by scanning electron microscopy. These data support previous findings that delayed corneal wound healing with epithelial retention cysts remains the most common histopathologic alteration after radial keratotomy. The effects of variations and delay in wound healing between individuals could explain the lack of predictability of refractive outcome and continuing refractive instability in long-term follow-up after single or repeat radial keratotomy surgeries.