Evaluation of interface quality in organ-cultured lamellar corneal transplants

An optional surgical technique for obtaining lamellar donor grafts: a pilot study

Background

To evaluate the surface quality and thickness uniformity of lamellar donor grafts using an optional surgical technique called reversed manual dissection (RMD) in porcine corneas.

Methods

Twenty-four paired porcine corneas (48 eyes) were numbered 1 to 24 and divided into 6 groups. All left corneas were assigned to conventional manual dissection (CMD), and all right corneas were assigned to RMD. Each group contained 8 corneas. For Groups I, II, and III, 30, 50, and 70% of the entire corneal thickness was dissected using CMD. For groups IV, V, and VI, 70, 50, and 30% of the entire corneal thickness was dissected using RMD. The residual stromal thickness was examined by anterior segment optical coherence tomography (ASOCT) to assess the thickness uniformity and scanning electron microscopy (SEM) to assess the surface quality.

Results

The thickness uniformity of the lamellar grafts between each paired group was not significantly different (p > 0.05). The qualitative surface roughness grading (QiSR) evaluated by masked observers through SEM was significantly higher in the RMD groups (p < 0.001). The quantitative surface roughness grading (QnSR) acquired from the Mountains software was significantly lower in the RMD groups (p < 0.001).

Conclusions

RMD is an optional surgical technique for obtaining porcine lamellar grafts. The thickness uniformity of RMD is comparable to that of CMD, and a smoother surface with fewer ridges and roughness is achieved compared to CMD.

"OSMO-UT-DSAEK" using THIN-C medium

BACKGROUND

When performing ultra-thin Descemet's stripping automated endothelial keratoplasty (UT-DSAEK), the quality of the stromal interface and stromal thickness seem to be critical for visual outcome. The aim of this study was to investigate whether additional osmotic deswelling prior to UT-DSAEK improves the quality of the cut surface and leads to a more reliable and deeper cut in UT-DSAEK ("OSMO-UT-DSAEK").

METHODS

Seventeen human donor corneas not usable for transplantation were used in this experiment. After standard deswelling with culture Medium II, ten corneas were randomly assigned to be additionally deswollen within THIN-C medium. The other remaining seven corneas were put back into culture Medium II. All corneas were placed in an artificial anterior chamber system (Moria); a double path cutting procedure using a microkeratome (Moria) was then performed. Corneal thickness was measured by ultrasound biomicroscopy and in paraffin-embedded slides, followed by histological grading of the cut surface.

RESULTS

Stromal interface smoothness significantly improved after preconditioning in THIN-C medium (Pearson P = 0.019). The correlation of the corneal thickness obtained by UBM (mean 706 ± SD 208 μm) and histology (mean 530 ± SD 159 μm) was not significant (Pearson r = 0.11, P > 0.05, mean difference 247, 95 % CI [+50;+304]). We found no significant correlation between the microkeratome setting and the actual thickness of the lenticule measured in histological analysis in both media as well as for the first and second cut (first cut: Pearson r = 0.9, P = 0.1, 95 % CI [-10;+96], second cut: Pearson r = 0.9, P = 0.4, 95 % CI [-10;+22]).

CONCLUSION

Preconditioning of corneas with THIN-C medium significantly improved the quality of the graft interface in UT-DSAEK, but did not significantly improve the cut precision of the microkeratome.