Novel application of diode engraving laser for preparing corneal allogenic intrastromal ring segments: a comparative study with femtosecond laser and manual trephine.

Corneal allogenic intrastromal ring segments (CAIRS) provide a biocompatible option for the treatment of keratoconus and ectatic disorders, however surgical outcomes rely heavily on pre-operative planning and precise donor tissue preparation. Femtosecond (FS) lasers ensure micron-level accuracy but are costly and often inaccessible, whereas manual trephines are more affordable but limited to fixed geometries and variable thickness. This study evaluated a low-cost automated handheld portable diode engraving laser as a novel alternative for CAIRS preparation. In an ex vivo feasibility study, human donor corneal buttons unsuitable for optical transplantation customized into CAIRS segments using a consumer-grade blue diode engraver (LaserPecker L2, 5 W, 450 nm). Dimensional accuracy, thickness variation with controlled dehydration, stromal interface quality on anterior-segment OCT, and collateral thermal effects were evaluated. As a proof of concept, A diode-engraved laser cut segment was implanted in a keratoconus patient following femtosecond-assisted tunnel creation, and the postoperative visual and tomographic outcomes were documented. Twenty semicircular segments were created without failure. The Mean inner diameter was 6.48 ± 0.05 mm, the outer diameter was 8.01 ± 0.06 mm, and width measured 0.76 ± 0.05 mm (coefficient of variation < 5%). Three engraving passes consistently achieved full stromal penetration (~ 450 μm). Dimensional reproducibility was comparable published FS laser data, while device cost (~ USD 1,200) was over ten-fold lower. Manual trephination proved less precise and lacked customization capability. Preliminary histological analysis confirmed that thermal effects were confined to a narrow coagulation rim with no evidence of deeper stromal alteration. In vivo, a 39-year-old patient improved from UCVA 20/150 to 20/40 and BCVA 20/80 to 20/25, with Kmax reduced from 57.5 D to 44.0 D at one month, and no compications were observed. A consumer-grade diode engraving laser can reliably produce customized CAIRS segments with high precision, minimal collateral damage, and substantially lower cost than FS platforms. This proof-of-concept clinical case demonstrates its potential as an accessible, customizable, and affordable alternative for CAIRS preparation in resource-limited settings.