Impact of Donor Age on Endothelium-Descemet Membrane Layer Harvesting and Roll Formation
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PURPOSE: Descemet membrane endothelial keratoplasty (DMEK) is an alternative to Descemet's stripping automated endothelial keratoplasty (DSAEK) to surgically replace diseased corneal endothelium. Although graft rejection incidence has been reported to be drastically lower in DMEK, wide adoption may be limited by two factors. Harvesting the endothelium-Descemet membrane layer (EDM) can be difficult, and tight EDM scrolling can hinder unfolding once inserted into the patient's eye. Anecdotally, surgeons have noticed the use of younger donors has exacerbated these factors. We sought to correlate donor age with EDM stripping difficulty and scroll tightness. METHODS: EDM scrolls were harvested by a cornea-fellowship trained ophthalmologist masked to donor age from 26 corneoscleral buttons. An 11.5 mm partial trephination was used instead of blunt dissection for a consistent and even outer cut. 7.0 to 8.25 mm EDM scrolls were prepared using the SCUBA technique in Optisol GS. VisionBlue(r) (.06 % trypan blue) staining was used to harvest and assess EDMs. The surgeon subjectively rated stripping difficulty on a 1 to 5 scale (easiest to unable to strip) based upon DM adherence to underlying stroma and radial tear formation. Three different methods were used to characterize scrolling severity: scroll width, normalized scroll surface area (scroll width × scroll length/surface area of EDM), and tendency for EDM scroll formation (referred to as scroll rating). A scroll rating of 1 corresponded to opposite ends of the EDM not touching, 2 when EDM ends touch, 3 when the EDM forms one complete scroll and 4 when more than one scroll formed. RESULTS: Mean donor age was 59±14 years (15-69 range). Mean diameter of EDM scroll was 7.9±.23 mm (7.0-8.25 range). Stripping difficulty was shown to be inversely correlated with donor age (p<.05). The three methods to determine scrolling severity had different results. Inverse relations between donor age was significant for scroll rating (p<.05), nearly significant for normalized surface area (p=.0508), and not significant for scroll width (p<.10). CONCLUSIONS: Our data supports that the use of older corneas should reduce the surgical difficulty of DMEK procedures. The study showed a significant decrease in the subjective category of stripping difficulty with the use of older donors. In addition, there may be a decreased scrolling tendency based on an inverse correlation between age and scroll rating (p<0.05) and a positive correlation between age and normalized scroll surface area (p=0.0508).