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Comparative pilot study: DALK results using -70ºC frozen stromas versus standard 4ºC preserved corneas

Poster Details

First Author: M.Naveiras SPAIN

Co Author(s):    C. Lisa   A. Meana   J. Merayo   J. Alfonso           

Abstract Details


To evaluate one year results after Deep Anterior Lamellar Keratoplasty (DALK) in severe keratoconus, using two methods for stroma preservation: Progressive freezing to -70ºC versus standard 4ºC deswelling medium.


Instituto Oftalmológico Fernández-Vega. Oviedo. Spain


Prospective case – control study. 4 frozen stromas (cases) were initially obtained from corneas preserved in Tissue-C (Alchimia, Padova, Italy) at 31ºC and denuded of endothelium and Descemet's membrane during preparation of DMEK. The remaining intact stroma was subjected to slow freezing -1º / hour to -70 ° C in a 10% glycerol 10% dextran 80% DMEM medium. Implantation was deferred for subsequent implant according to validated protocols for amniotic membrane. The 4 standard corneas (controls) were preserved in Eusol deswelling medium (Alchimia, Padova, Italy) for 4-7 days. DALK surgeries were conducted by modified Melles technique, guided by intraoperative pachymetry.


The 8 cases were documented for a year. BCVA at 9 months was 0.33 in both groups; at 12 months was 0.45 ± 0.2 in cases and 0.50 in controls. Both groups had a case with maximum 0.7 vision. At one year, Kmax / Kmin was 45.2 / 43.1 in cases and 49.9 / 46.2 in controls. Pachymetry was 529 ± 82.7 in cases and 578 ± 32.4 in controls. Confocal microscopy in the case group suggested progressive quiescence of keratocytes and reinnervation after the sixth month, in addition to turbidity and persistent microfolds at the interface.


Simultaneous production of endothelial grafts and denuded stroma from the same cornea is viable and can double the efficiency of the donation process. Endothelial grafts can be deferred up to 28 days and stromal grafts up to five years. The surgical complexity is greater with frozen stromas, but the results one year are safe and equivalent in selected cases of keratoconus. Longer follow-up studies are needed to assess long-term transparency in frozen stroma and define the optimal indication of frozen tissue.

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