Evaluation of animal corneal stroma as a human model: A raman spectroscopic analysis of biochemical composition

Comparative studies of human and animal corneal structures using Raman spectroscopy are limited. We compared the Raman spectra of human and animal corneal stroma to evaluate the suitability of animal corneas as experimental models and to assess the feasibility of Raman spectroscopy for characterizing biochemical differences. Raman microspectroscopy (700–4000[Formula: see text]cm[Formula: see text]) was performed on seven fresh porcine corneas, six fresh rabbit corneas, and 12 human corneal stromal lenticules obtained from patients who underwent small incision lenticule extraction. Four machine learning algorithms — Support Vector Machine (SVM), K-Nearest Neighbors (KNN), Random Forest (RF), and Decision Tree (DT) — were used to classify the data. Ten characteristic peaks were identified in the human corneal stroma, including prominent peaks at 937[Formula: see text]cm[Formula: see text] (proline/valine/type I collagen), 1243[Formula: see text]cm[Formula: see text] (collagen amide III), 1448[Formula: see text]cm[Formula: see text] (collagen/phospholipids), 1663[Formula: see text]cm[Formula: see text] (DNA/proteins), 2940[Formula: see text]cm[Formula: see text] (lipids/proteins), and 3330[Formula: see text]cm[Formula: see text] (water). Eleven peaks were observed in the porcine and rabbit corneas. Using raw spectra, the SVM, KNN, and RF models achieved 100% classification accuracy (area under the receiver operating characteristic (ROC) curve, 1.00 for both test and validation sets). The DT model showed the lowest performance (approximately 33% accuracy for human data; [area under the ROC curve, 0.67 [Formula: see text]]). Human myopic corneal stroma differed from the animal models in regions linked to nucleic acids and water content. The porcine cornea more closely resembled the human cornea than the rabbit cornea, indicating it as a more appropriate analog. Raman spectroscopy is a useful tool for interspecies comparisons and elucidating the biochemical composition of diseased corneas.