Femtosecond laser-assisted keratoplasty: full and partial-thickness cut wound strength and endothelial cell loss across a variety of wound patterns.

PURPOSE: To evaluate wound strength for patient safety during transport and endothelial viability when partial and complete femtosecond laser-assisted keratoplasty (FLAK) incisions are made in cadaveric corneas. METHODS: 19 human corneoscleral rims were divided into six groups, mounted on an anterior chamber maintainer and cut with a femtosecond laser programmed to the following patterns: 'zigzag' (A), 'mushroom' (B) and 'top hat' (C) in both full (1) and partial (2) thicknesses. The pressure required to produce leakage from the corneal incision was then measured. Eight additional corneas were cut with the 'zigzag' pattern: four full and four partial thickness, prepared and transported per standard eye bank protocol, and analysed for endothelial cell loss with trypan blue staining and digital image analysis. RESULTS: Mean leakage pressure in mm Hg for group A1 was 110 (SD 94); group A2, 1180 (SD 468); group B1, 978 (SD 445); group B2, 987 (SD 576); group C1, 710 (SD 474); group C2, 1290 (SD 231). There was a significant difference in leakage pressure between groups A1 and A2 (p=0.05), groups A1 and B1 (p=0.05), and groups A1 and C1 (p=0.05). Mean percentage endothelial damage after full-thickness cuts was 8.40 (SD 2.34) and 5.30 (SD 1.33) in partial-thickness cuts (p=0.11). CONCLUSIONS: Partial thickness zigzag, top hat and mushroom-style partial FLAK incisions left an intact tissue wall with high resistance to rupture, whereas full-thickness cuts were more variable. Laser trephination and eye bank handling protocol for donor FLAK buttons leads to moderate peripheral endothelial cell loss in tissue with both complete and partial cuts.

In vitro evaluation of endothelial cell loss using the Neusidl Corneal Inserter.

PURPOSE: To determine the immediate endothelial cell loss (ECL) resulting from insertion of a precut donor button using the Neusidl Corneal Inserter (NCI) and compare it with the previously published ECL resulting from insertion of a folded donor button using non-coapting forceps. METHODS: Ten corneas were precut for Descemet stripping automated endothelial keratoplasty and trephinated to a diameter of 8.0 mm (n = 5) or 8.5 mm (n = 5). Each tissue was placed onto the platform of a new NCI spatula and inserted into a cadaveric whole globe through a 5.2 mm incision. The tissue was carefully removed and stained with trypan blue and alizarin red to detect damaged endothelium. ECL was estimated using Adobe Photoshop planimetry. Mean ECL was compared with previously reported studies of forceps insertion with a one-sample t test, using SPSS v. 19. Geographic patterns of ECL were also documented. RESULTS: Mean ECL was 15.6% (95% confidence interval, 13.8-17.4). We were unable to detect a difference in ECL compared with previous insertion methods studied (P < 0.001). The pattern of damage from the NCI was different than that previously seen with forceps insertion. CONCLUSION: Immediate endothelial damage resulting from use of the NCI for insertion of Descemet stripping automated endothelial keratoplasty tissue is comparable with that seen with a standard forceps technique, but with a different damage pattern.

The endothelial safety of using a gentian violet dry-ink "S" stamp for precut corneal tissue.

PURPOSE: To determine the endothelium damage resulting from the application of "dry" gentian violet (GV) stromal markings on corneas precut for Descemet stripping automated endothelial keratoplasty (DSAEK) using a Moria "S" Stamp. METHODS: Five precut corneas had the stromal graft bed marked with GV using the Moria "S" stamp and 6 precut corneas were left unmarked as controls. After applying the ink to the stamp, care was taken to allow the alcohol carrier to dry for 10 seconds before applying the dry dye to the stromal surface. Tissue was then trephinated and stained with calcein AM to assess endothelial viability. Grafts were photographed and digital pixel planometry, using an established analysis technique, was used to compare the damage between the control and experimental groups. RESULTS: The mean percent cell damage of corneas treated with GV "S" stamp (n = 5) was 8.6% (range 4.4-12.9), and it was 8.1% (range 3.9-15.1) in the DSAEK control set (n = 6). Median percent cell damage was 6.7% among GV-treated corneas and 7.4% among control corneas. The distributions were not significantly different between groups (Mann-Whitney U test = 15.0, two-tailed P = 1.0). Moreover, no "S" pattern of damage was seen in any study eye. CONCLUSIONS: There were no significant differences in endothelial damage between the 2 groups. GV stromal markings may be applied without undue damage to the endothelium using the dry-ink technique described.