Corneal findings after death: a preliminary OCT study on an animal model

Purpose : The aim of this study was to describe by means of a portable OCT the postmortem morphological changes of the central cornea in an animal model (Ovis aries). Methods : The design involved the analysis of 30 eyes (15 heads) of female, adult sheep (> 2 years) sacrificed at a local slaughterhouse. The eyes, after decapitation, were examined in situ, without enucleation. Ocular globes were stored at known temperature (within a range of 12–22 °C) and humidity (within a range of 50–60%). The instrumental analysis was executed using a portable spectral-domain OCT (SD-OCT) system (iVue SD-OCT, Optovue Inc, Fremont, CA) calibrated to the corneal mode. OCT imaging was performed at the following time-points since death: immediately (within 15minutes), at the 30th minute, at the 1st, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th, 9th, 10th, 11th, 12th, 15th, 18th, 21st, 24th, 30th , 36th ,42nd, 48thhour, and later (< 72nd). Pachymetric map, morphological and ultrastructural analysis (epithelium, stroma, and endothelium) were performed for each time-point. Results : After initial thinning and epithelial hyper-reflectivity, stromal thickness increased from the 2nd up to the 6th hour. Subsequently, a new trend of thinning was observed in association with a demarcation line between anterior and posterior stroma. At the same time, in 33% of samples, epithelium disappeared and endothelium was characterized by an increase of reflectivity. After the 12th hour, a recurrence of corneal swelling was detected in association with the delamination of stromal tissue. Since the 24th hour, epithelium disappeared in 50% of cases and anterior chamber depth progressively decreased. At the 48th hour, corneal tissue showed the onset of putrefaction processes: the appearance of hyper-reflective dots in anterior chamber, irido-corneal contact, and the massive vacuolization of the posterior stroma until the total delamination. Conclusions : The portable OCT system is a useful approach for in situ, postmortem corneal examination, and may be potentially applied for the selection of donor cornea in transplantology and the determination of post-mortem intervals in forensic medicine.