Management of fungal corneal ulcer by corneal collagen cross-linking technique

Abstract

Background Fungal corneal ulcer is a visual-threatening eye disease,and drug therapy has a limiting efficacy.Corneal transplantation or eye enucleation sometimes is necessary to the severe patients.Corneal collagen cross-linking (CXL) is an effective method for some corneal diseases,but the study on CXL for fungal corneal ulcer is lack.Objective This study was to evaluate the clinical effectiveness and safety CXL for fungal corneal ulcer.Methods Fifteen 8-week-old healthy New Zealand white rabbits were used in this study and other 5 rabbits served as normal controls.Fungal corneal ulcer models were established in the right eyes of other 10 rabbits by infecting sickle bacteria liquid after corneal scratching and removing corneal epithelium,then decellularized ostrich corneal patch covered the defected cornea.The models were randomly divided into the non-treatment group and the CXL treatment group.Corneal lesions were examined under the slit lamp microscope every day,and cornea was pictured by laser scanning confocal microscope on the 3rd,7th,14th,21st and 28th day individually after CXL.All rabbits were sacrificed and corneal tissues were obtained 4 weeks after treatment,and the collagen fiber diameter and fibrocytes were observed under the scanning electron microscope.Results Fungal corneal ulcer models were successfully established by corneal scratching and decellularized ostrich cornea covering.The gray ulcer lesions and hypbae like bean pod were seen by slit lamp microscope and laser scanning confocal microscope 3 days after modeling.Corneal ulcer deepened and expanded 1 week later,and there were a large number of spore and hyphae criss-crossing as short rod in shallow stroma.Inflammatory cells were observed in corneal endothelial cells and ocular anterior chamber.In the CXL treatment group,the range of corneal epithelial deficiency was less than that in the nontreatment group on the 3rd,7th,14th,and 21st (all at P＜ 0.05).The diameters of collagen fibers were (24.6± 1.8) nm,(24.9 ± 1.9) nm and (43.0 ± 7.4) nm in the normal control group,non-treatment group and CXL treatment group,showing a significant difference among the 3 groups (F =27.05,P =0.00),and the collagen diameters were thicker in the CXL treatment group than those in the normal control group and non-treatment group (t =5.40,-5.30,both at P＜0.05),and fibrocytes were seen among the collagen fibers.No significant difference was found in the collagen diameters between the non-treatment group and normal control group,and the fibrocytes were less in the non-treatment group.Conclusions CXL therapy can treat fungal corneal ulcer by enhancing collagen,promoting fibrocytes proliferation,suppressing fungus and inflammatory response and accelerating tissue repair. Key words: Corneal collagen cross-linking; Fungus; Corneal ulcer/therapy; Laser scanning confocal microscope; Collagen fiber; Disease model/animal; Rabbit