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Peter B. Thomas, Achyut N. Mukherjee, Madhavan S. Rajan; Pachymetry Controlled Stromal Pre-conditioning of Human Donor Corneas For Micro-thin Endothelial Keratoplasty. Invest. Ophthalmol. Vis. Sci. 2012;53(14):57.
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Human donor corneas in culture have varying thicknesses which results in poor repeatability in achieving thin endothelial grafts for the purpose of endothelial keratoplasty. In this study, we describe the novel technique of pre-conditioning donor corneal thickness prior to microkeratome dissection to facilitate thin Descemet’s stripping automated endothelial keratoplasty (Micro-thin DSAEK).
In an experimental study, thirteen human donor corneas were randomised to conventional DSAEK (n=7) and micro-thin DSAEK (n=6) groups. Corneas in both groups were mounted onto an artificial anterior chamber (Moria inc., Doylestown, PA), de-epithelialized, and their central thicknesses (CCT) determined using a handheld pachymeter. Corneas in the micro-thin DSAEK group were subjected to pachymetry controlled anterior stromal dehydration using a custom air flow device with sterile airflow velocity of 3.8m/s for 15 second increments. A target CCT of 530µm was aimed for, and a 350µm microkeratome head was then used to cut the DSAEK graft with standardisation of intraocular pressure and speed of keratome passage. Corneas in the conventional DSAEK group were cut using a 350µm Moria microkeratome head without pre-conditioning of CCT. Anterior lamella and endothelial graft thicknesses were evaluated using OCT. Endothelial viability was assessed using trypan blue and Alizarin red staining. Histology was undertaken on all grafts in the study.
The initial CCT was 608µm (+/-83µm) in the conventional DSAEK group, and 637µm (+/- 39µm) in the micro-thin DSAEK group. Controlled stromal dehydration in the micro-thin group resulted in CCT of 531µm (+/-6µm). The pre-conditioning duration in the micro-thin group was 72s (+/-26s) resulting in anterior stromal thinning of 106µm (+/-38µm). Microkeratome dissection provided endothelial graft thickness of 177µm (+/-33µm) in the conventional DSAEK group, and 106µ (+/-32µm) in the micro-thin DSAEK group (p < 0.05). There was no significant difference in endothelial cell loss between the two groups. Histology confirmed anterior stromal compaction and decreased anterior stromal vacuolation in the micro-thin group with normal pre-Descemet’s stroma and keratocyte density.
Pachymetry controlled stromal dehydration of human donor corneas to a prescribed thickness of 530µm is a rapid and predictable method to achieve 100µm endothelial grafts. These support the surgical procedure of Micro-thin DSAEK with resultant clinical advantages of faster visual recovery, better acuity and decreased risk of graft detachment.
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