Abstract
PURPOSE: To investigate the feasibility of transplanting cyanobacteria species Synechocystis sp. PCC6803 into the corneal stroma as a novel photosymbiotic biotherapy. METHODS: A suspension of cyanobacteria was injected into the central stroma of female New Zealand white rabbit corneas under sterile conditions. Postoperative care included topical application of Tobra Dex eye drops and gel three times daily for 7 days. Corneal optical coherence tomography (OCT) was performed to assess the distribution of cyanobacteria and any structural changes. Histopathological analysis, including SYTOX Green staining and confocal microscopy, was conducted to evaluate cyanobacterial survival and host tissue response. RESULTS: After 7 days of transplantation, brown-colored cyanobacteria remained localized within the corneal stroma without inducing significant corneal edema, neovascularization, or structural damage. OCT imaging identified hyperreflective regions corresponding to cyanobacterial colonization. Histological analysis confirmed a substantial number of viable cyanobacteria persisting within the stromal matrix, with only a small proportion of nonviable cells detected. No overt inflammatory response or adverse effects on corneal transparency were observed. CONCLUSIONS: This pilot study demonstrates the survival of cyanobacteria within the corneal stroma. These findings provide preliminary evidence supporting the feasibility of ocular surface photosymbiosis as a novel therapeutic approach for hypoxia-related corneal diseases. Further studies are needed to quantify oxygen production and evaluate long-term safety.