Microscopic characterization of collagen modifications induced by low-temperature diode-laser welding of corneal tissue
✍ Scribed by Paolo Matteini; Francesca Rossi; Luca Menabuoni; Roberto Pini
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 332 KB
- Volume
- 39
- Category
- Article
- ISSN
- 0196-8092
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
Background and Objective
Laser welding of corneal tissue that employs diode lasers (810 nm) at low power densities (12–20 W/cm^2^) in association with Indocyanine Green staining of the wound is a technique proposed as an alternative to conventional suturing procedures. The aim of this study is to evaluate, by means of light (LM) and transmission electron microscopy (TEM) analyses, the structural modifications induced in laser‐welded corneal stroma.
Materials and Methods
Experiments were carried out in 20 freshly enucleated pig eyes. A 3.5 mm in length full‐thickness cut was produced in the cornea, and was then closed by laser welding. Birefringence modifications in samples stained with picrosirius red dye were analyzed by polarized LM to assess heat damage. TEM analysis was performed on ultra‐thin slices, contrasted with uranyl acetate and lead citrate, in order to assess organization and size of type I collagen fibrils after laser welding.
Results
LM evidenced bridges of collagen bundles between the wound edges, with a loss of regular lamellar organization at the welded site. Polarized LM indicated that birefringence properties were mostly preserved after laser treatment. TEM examinations revealed the presence of quasi‐ordered groups of fibrils across the wound edges preserving their interfibrillar spacing. These fibrils appeared morphologically comparable to those in the control tissue, indicating that type I collagen was not denatured during the diode laser corneal welding.
Conclusions
The preservation of substantially intact, undenatured collagen fibrils in laser‐welded corneal wounds supported the thermodynamic studies that we carried out recently, which indicated temperatures below 66°C at the weld site under laser irradiation. This observation enabled us to hypothesize that the mechanism, proposed in the literature, of unwinding of collagen triple helixes followed by fibrils “interdigitation” is not likely to occur in the welding process that we set up for the corneal suturing. Lesers Surg. Med. 39:597–604, 2007. © 2007 Wiley‐Liss, Inc.