Ultraviolet Laser Engraving For Thermally Neutral Preparation Of Corneal Allogenic Intrastromal Ring Segments – An Ex Vivo Proof-Of-Concept

Building on our previously published diode engraving laser method for low-cost preparation of corneal allogenic intrastromal ring segments (CAIRS), we introduce a next-generation approach employing an ultraviolet (UV) laser for “cold-light” photoablation of donor corneal tissue applicable not only to CAIRS fabrication but also to lamellar keratoplasty. Unlike continuous-wave visible diode lasers that generate a narrow peripheral thermal rim, short-wavelength UV irradiation enables precise stromal dissection through predominantly photochemical mechanisms with minimal heat diffusion.

Preclinical ex vivo laboratory study performed on human donor corneas unsuitable for transplantation, obtained from a certified eye bank. Tissue preparation and UV laser photoablation were conducted under controlled laboratory conditions. No live implantation or clinical intervention was performed.

Human donor corneas unsuitable for transplantation were obtained from an eye bank, stored in Optisol-GS, and equilibrated to room temperature. Epithelium and Descemet’s membrane were removed, and controlled dehydration (30–60 min) was performed. A computer-guided 355-nm pulsed UV laser enabled line-by-line cold photoablation below photocoagulation thresholds. Stromal rings (6.0 mm inner, 8.0 mm outer diameter, 1.0 mm width) were created and bisected into CAIRS segments. Lamellar discs (~8.0 mm) were similarly trephined. Gross and histologic evaluation assessed edge quality and thermal effects. No live or clinical implantation was performed in this preliminary stage. 

UV laser engraving successfully generated uniform stromal ring segments from all donor corneas without mechanical tearing or edge irregularities. no evidence of subsurface heat-induced coagulation zones. In contrast to the mild brown discoloration occasionally observed at the margins of blue-diode laser cuts, the UV-engraved segments showed no visible pigmentation or tissue shrinkage. The engraved edges maintained a translucent appearance with sharply preserved lamellar structure. The workflow was comparable to the diode method in setup and duration, yet achieving cleaner tissue margins. Segments were semi-rigid and easily handled following air-drying.

This technique not only advances CAIRS fabrication but may also be adapted as a low-cost, cold-light platform for lamellar keratoplasty, offering highly controlled stromal layer separation with minimal thermal damage.