Elsevier

Experimental Eye Research

Volume 169, April 2018, Pages 20-27
Experimental Eye Research

Morphological analysis of corneal findings modifications after death: A preliminary OCT study on an animal model

https://doi.org/10.1016/j.exer.2018.01.013Get rights and content

Abstract

The aim of this work was to describe, for the first time, the morphological modifications, in a three-dimensional mode, of the central cornea at different intervals since death. The study design involved the analysis of 30 eyes (15 heads) of female, adult sheep (>2 years) sacrificed at a local slaughterhouse. The eyes, after animal decapitation, were examined in situ, without enucleation. Ocular globes were stored at well-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 different time-points since death. Pachymetric map, morphological and ultrastructural analysis (epithelium, stroma, and endothelium), were performed for each time-point. After an initial thinning of tissues and an enhancement of epithelial reflectivity, stromal thickness increased from the 2nd up to the 6th hour. Subsequently, a new trend incorneal thinning was observed in association with the appearance ofone or more demarcation lines between the anterior andposterior stroma. After the 12th hour, a recurrence of corneal swelling was detected in association with thedelamination of stromal tissue. Since the 24th hour, the epithelium disappeared in 50% of cases and the anterior chamberdepth progressively decreased. At the 48th hour, various ocular structures showed the onset of putrefaction processes, such as theappearance of hyper-reflective dots in anterior chamber, iridocorneal contact, and the massive vacuolization of theposterior stroma until the total delamination. The portable OCT system is a useful approach for in situ postmortem corneal examination, and it may be potentially applied for the selection of donor cornea in transplantology and for the determination of post-mortem intervals in forensic medicine.

Introduction

Corneal morphological changes in early postmortem intervals are well-known phenomena described in literature since 1846 (Letheby, 1846, Couch et al., 1964). At present, despite the importance of understanding the nature and timing of modification in the ophthalmological (for transplantation purposes) and in the forensic medicine scenario, no studies have been performed in order to analyze the morphological changes of the cornea by means of imaging techniques in a predetermined scheduled post-mortem timing.

The OCT technology is now of daily use in ophthalmology to investigate the retina, the anterior segment and the ocular surface (Huang et al., 1991, Napoli et al., 2016a, Napoli et al., 2014a, Napoli et al., 2014b). This type of approach allows clinicians to have in a few seconds an accurate, contactless, three-dimensional and morphological image of the cornea. Application of this device in postmortem samples may be useful to obtain real-time, in situ and recorded data, without tissue manipulation (Cafaro et al., 2015, Napoli et al., 2016b).

The aim of this study was to describe, for the first time, the morphological modifications, in a three-dimensional mode, of the central cornea at different intervals since death. In our preliminary study we decided to use an animal model for three orders of reasons: firstly, due to the availability of samples in a wide lapse of post-mortem time ranging from very early (15–30 min) to late one (more than 48 h); secondly, since the chosen model combines greater dimensions of the ocular globe (compared to humans) with a greater availability of samples in the territory on which the study was conducted; and finally, due to the possibility to use waste products from alimentary purposes without any ad hoc animal sacrifice.

Section snippets

Materials and methods

The design involved the analysis of 30 eyes (15 heads), from female adult sheep (2–5 years old), that passed the standard controls for food consumption, sacrificed at a local slaughterhouse. The eyes, after animal decapitation, were examined in situ, without enucleation; the heads were stored at a controlled environment both in temperature and humidity. Sheep corneas were clear and without any visible pathology at time of death.

The instrumental analysis was performed using a portable

Results

All OCT results were summarized in Table 1, Table 2 and Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7.

In our samples, the horizontal and vertical diameter of the corneas were found to be of 17.7 ± 1.4 mm [mean ± standard deviation] and 12.3 ± 1.3 mm, respectively.

Morphological findings were analytically described for each postmortem interval as follows.

Discussion

In our study we described, on an animal model, the morphological corneal changes at different postmortem intervals (PMIs) detectable by using a portable OCT. The repeatability and reproducibility of this system, on the same animal model, to evaluate post-mortem central corneal thickness (CCT) has been demonstrated in our preliminary study (Napoli et al., 2016b). The validity of sheep cornea as a model has been demonstrated by previous authors on the basis of important common features with human

Conclusions

In conclusion, portable OCT is a promising, accurate tool to investigate the ultrastructural changes of the cornea after death in order to understand the structure and function of tissue layersand the time-related processes for forensic and ophthalmological purposes.

Conflicts of interest

The authors declare no competing financial interests.

Contributions

Conceived and designed the experiments: P.E.N. and M.N. Performed the experiments: P.E.N. and M.N. Analyzed the data: P.E.N. and M.N. Contributed reagents/materials/analysis tools: P.E.N., M.N., E.d.A., R.D., E.L. and M.F. Wrote the paper: P.E.N., M.N., E.d.A. and M.F.

References (41)

  • A. Damian et al.

    Optical coherence tomography-based topography determination of corneal grafts in eye bank cultivation

    J. Biomed. Optic.

    (2017)
  • A. Daxer et al.

    Collagen fibril orientation in the human corneal stroma and its implications in keratoconus

    Invest. Ophthalmol. Vis. Sci.

    (1997)
  • C. Dogaroiu et al.

    Postmortem corneal changes evaluated by fluorescent staining

    Rom. J. Leg. Med.

    (2014)
  • H.F. Edelhauser

    Endothelial and stromal response to injury: corneal biophysics workshop

    Corneal Biomech. Wound Heal. NIH

    (1989)
  • R.D. Freeman

    Oxygen consumption by the component layers of the cornea

    J. Physiol.

    (1972)
  • S.B. Han et al.

    Applications of anterior segment optical coherence tomography in cornea and ocular surface diseases

    J. Ophthalmol.

    (2016)
  • D. Huang et al.

    Optical coherence tomography

    Science (N. Y.)

    (1991)
  • N. Hutchings et al.

    Swelling of the human cornea revealed by high-speed, ultrahigh-resolution optical coherence tomography

    Invest. Ophthalmol. Vis. Sci.

    (2010)
  • W. Kawashima et al.

    Estimating the time after death on the basis of corneal opacity

    J. Forensic Res.

    (2015)
  • A.A. Khodadost et al.

    The survival and rejection of epithelium in experimental corneal transplants

    Invest. Ophthalmol. Vis. Sci.

    (1969)
  • Cited by (29)

    • Post-mortem ocular changes and time since death: Scoping review and future perspective

      2021, Legal Medicine
      Citation Excerpt :

      In particular, the translation of modern clinical and computational technologies into the forensics field seems to be highly promising; for example, the application of OCT technology opens a frontier for noninvasively estimating the time since death. In fact, Nioi et al. recently showed how OCT application serves to demonstrate a clear, progressive degenerative path across all corneal tissues, with distinctive putrefactive signs and hyper/hyporeflectance patterns during the first 72 h after death [17]. However, more evidence on this topic and further validation in humans are needed.

    • A computational approach to estimate postmortem interval using opacity development of eye for human subjects

      2018, Computers in Biology and Medicine
      Citation Excerpt :

      Although RGB color space only has color information, other color spaces include information on light intensity, color depth, purity of color, etc. There are studies reporting morphological postmortem alterations of the cornea on animal and human subjects [42, 43], however, we refer to the anterior surface of the eye for PMI prediction with a practical approach. Some methods proposed in literature for PMI estimation are not practical.

    • IMAGE-BASED RGB SCORING OF CORNEAL OPACITY FOR ESTIMATION OF POSTMORTEM INTERVAL

      2023, International Journal of Medical Toxicology and Legal Medicine
    View all citing articles on Scopus

    This is the first study that reveals the ultrastructural changes of the cornea in various postmortem intervals, which will have considerable impact in transplantology and forensic scenario.

    1

    These authors contributed equally to this work.

    View full text