Morphological analysis of corneal findings modifications after death: A preliminary OCT study on an animal model☆
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)
- et al.
The hydration of proteoglycans of bovine cornea
Biochim. Biophys. Acta
(1975) Molecular mechanisms underlying the corneal endothelial pump
Exp. Eye Res.
(2012)- et al.
Human corneal anatomy redefined: a novel pre-Descemet's layer (Dua's layer)
Ophthalmology
(2013) On the observance of method in conducting post-mortem examinations: especially when they are intended for legal purposes
Lancet
(1846)The significance of oxygen during contact lens wear
Contact Lens Anterior Eye
(2014)- et al.
Morphological and histological changes in eye lens: possible application for estimating postmortem interval
Leg. Med.
(2015) - et al.
Relation between optical coherence tomography and optical pachymetry measurements of corneal swelling induced by hypoxia
Am. J. Ophthalmol.
(2002) - et al.
The importance of measuring intraocular pressure using a tonometer in order to estimate the postmortem interval
Am. J. Forensic Med. Pathol
(2010) - et al.
On the cornea of healthy Merino sheep: a detailed ex vivo confocal, histological and ultrastructural study
Anat. Histol. Embryol.
(2015) - et al.
The use of cadaver tissues in transplantation
N. Engl. J. Med.
(1964)
Optical coherence tomography-based topography determination of corneal grafts in eye bank cultivation
J. Biomed. Optic.
Collagen fibril orientation in the human corneal stroma and its implications in keratoconus
Invest. Ophthalmol. Vis. Sci.
Postmortem corneal changes evaluated by fluorescent staining
Rom. J. Leg. Med.
Endothelial and stromal response to injury: corneal biophysics workshop
Corneal Biomech. Wound Heal. NIH
Oxygen consumption by the component layers of the cornea
J. Physiol.
Applications of anterior segment optical coherence tomography in cornea and ocular surface diseases
J. Ophthalmol.
Optical coherence tomography
Science (N. Y.)
Swelling of the human cornea revealed by high-speed, ultrahigh-resolution optical coherence tomography
Invest. Ophthalmol. Vis. Sci.
Estimating the time after death on the basis of corneal opacity
J. Forensic Res.
The survival and rejection of epithelium in experimental corneal transplants
Invest. Ophthalmol. Vis. Sci.
Cited by (29)
Post-mortem ocular changes and time since death: Scoping review and future perspective
2021, Legal MedicineCitation 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 MedicineCitation 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 MedicineResearch Progress on Estimation of Postmortem Interval Based on Ocular Tissues Structure
2023, Journal of Forensic MedicineResearch Progresses and Application Prospects of Optical Coherence Tomography in Forensic Science
2023, Laser and Optoelectronics Progress
- ☆
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.