Quantitative measures of corneal transparency, derived from objective analysis of depth-resolved corneal images, demonstrated with full-field optical coherence tomographic microscopy

• Published in: PloS one 2019-08, Vol.14 (8), p.e0221707-e0221707
• Main Authors: Bocheux, Romain, Pernot, Pascal, Borderie, Vincent, Plamann, Karsten, Irsch, Kristina
• Format: Article
• Language: English
• Subjects: Aging; Algorithms; Attenuation; Bioengineering; Biology and Life Sciences; Coherence; Computation; Cornea; Cornea - diagnostic imaging; Cornea - pathology; Corneal transplantation; Data acquisition; Data analysis; Decay; Decay rate; Engineering and Technology; Engineering Sciences; Evaluation; Heterogeneity; Humans; Image Processing, Computer-Assisted; Imaging; Infection; Information management; Lasers; Life Sciences; Light; Localization; Mathematical analysis; Medicine and Health Sciences; Microscopy; Novels; Numerical analysis; Objective analysis; Ophthalmology; Optical tomography; Optics; Photonic; Physical Sciences; Research and Analysis Methods; Scattering; Signal and Image processing; Stroma; Surgery; Tomography; Tomography, Optical Coherence; Transparence; Transparency; Trauma
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0221707

Loss of corneal transparency, as occurs with various pathologies, infections, immune reactions, trauma, aging, and surgery, is a major cause of visual handicap worldwide. However, current means to assess corneal transparency are extremely limited and clinical and eye-bank practice usually involve a subjective and qualitative observation of opacities, sometimes with comparison against an arbitrary grading scale, by means of slit-lamp biomicroscopy. Here, we describe a novel objective optical data analysis-based method that enables quantifiable and standardized characterization of corneal transparency from depth-resolved corneal images, addressing the demand for such a means in both the laboratory and clinical ophthalmology setting. Our approach is based on a mathematical analysis of the acquired optical data with respect to the light attenuation from scattering processes in the corneal stroma. Applicable to any depth-resolved corneal imaging modality, it has been validated by means of full-field optical coherence tomographic microscopy (FF-OCT or FF-OCM). Specifically, our results on ex-vivo corneal specimens illustrate that 1) in homogeneous tissues, characterized by an exponential light attenuation with stromal depth (z), the computation of the scattering mean-free path (ls) from the rate of exponential decay allows quantification of the degree of transparency; 2) in heterogeneous tissues, identified by significant deviations from the normal exponential z -profile, a measure of exponential-decay model inadequacy (e.g., by computation of the Birge ratio) allows the estimation of severity of stromal heterogeneity, and the associated depth-dependent variations around the average ls enables precise localization of the pathology.