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Jeffrey D Holiman, Yan Li, Christopher Stoeger, David Huang; The Effects of a Novel Processing Technique on Donor Cornea Clarity Following Hypothermic Storage. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5134.
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© ARVO (1962-2015); The Authors (2016-present)
A new process involving 4 C storage, transfer to recombinant human serum albumin (rHSA) in 20 C storage and subsequent terminal sterilization by electron beam irradiation was developed for long term storage of donor corneas. This study is to objectively assess the change in transparency in corneas that have undergone this processing.
Corneas suitable for anterior lamellar keratoplasty were selected in an eye bank. The corneas were first stored 4 C for 11 to 13 days. The tissues were warmed to 20 C, epithelium and endothelium were removed. Next, tissue was trephined to 8.0 mm diameter and placed on a glass slide for dark field photomicroscopy. After photography, the corneas were placed in 20% rHSA and irradiated by electron beam. Following ≥ 72 hours after irradiation, the corneas were re-imaged for post processing comparison. Dark field photos were obtained under the same light condition and microscopy settings. Customized software coded with Matlab (software version R2012a) was designed to access the corneal clarity change in dark field photos. The photos were converted into grayscale images with a normalized brightness range of 0 to 1 (0 equaled the brightness of a clear slide, 1 equaled the brightness of an opaque frosted slide). The brightness of central 10 mm2 (range [9.5, -10.5] mm2) of cornea was averaged for each dark field photo. Hyper-reflection regions (due to air bubble, etc.) captured in the photos were excluded for brightness calculation. The transparency of the tissue was defined as (1 - averaged brightness).
Six corneas were included in this study (age ranged 61-69 years). The average corneal transparency was 91.2% ± 3.1% (range [86.8%, 96.0%]) before processing and 91.1% ± 1.3% (range [88.6%, 92.2%]) after processing. The average change in clarity following processing was 0.10% less transparent, 4 of 6 tissues showed a slight decrease of clarity (2.7% less transparent), 2 of 6 tissues showed an improvement in clarity (4.0% more transparent).
The limitations in analysis technique were due to variability in mechanical removal of cellular debris and subtle wrinkles due to natural curvature of each cornea. Small changes in clarity were detected in tissues that had undergone this novel treatment for long term ambient temperature storage of donor corneas. For future studies, minimizing shadows from tissue folds will increase the sampling area.
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