Cross-linking of scleral collagen in the rabbit using riboflavin and UVA.

Abstract

PURPOSE:

Scleral biomechanical weakness and thinning is known to be one of the main factors in the pathogenesis of progressive myopia. We tried to strengthen rabbit sclera by cross-linking scleral collagen using ultraviolet A (UVA) and the photosensitizer riboflavin.

METHODS:

Circumscribed 10 x10 mm sectors of the posterior--equatorial sclera of six chinchilla rabbit eyes were treated in vivo using a UVA double diode with 4.2 mW/cm(2) UVA at 370 nm and applying 0.1% riboflavin-5-phosphate drops as photosensitizer for 30 min. 1 day postoperatively biomechanical stress--strain measurements of three treated scleral strips were performed using a microcomputer-controlled biomaterial testing device and compared to non-treated contralateral control sclera. In addition, three treated eyes were examined histologically by light microscopy, TUNEL staining and electron microscopy to evaluate side-effects.

RESULTS:

Following the cross-linking treatment, the ultimate stress was 11.87+/-1.8 MPa versus 3.63+/-0.40 in the controls (increase of 227.9%, p=0.014), Young's modulus 27.67+/-4.16 MPa versus 4.9+/-.15 MPa in the controls (increase of 464.7%, p=0.021) and ultimate strain 92.2+/-7.43% versus 165.63+/-19.09% in the controls (decrease of 54.52%, p=0.012). Histologically, serious side-effects were found in the entire posterior globe with almost complete loss of the photoreceptors, the outer nuclear layer and the retinal pigment epithelium (RPE).

CONCLUSIONS:

Our new method of scleral collagen cross-linking proved very effective in increasing the scleral mechanical strength; the new treatment may represent an option for strengthening scleral tissue in progressive myopia. However, serious side-effects were observed in the outer retina. In future studies these side-effects could be avoided by reducing the irradiation dose below the cytotoxic level of the retina. Before its clinical application, the new method should be tested in a myopia animal model.

• Authors: Gregor Wollensak, Elena Iomdina, Dag-Daniel Dittert, Olga Salamatina, Gisela Stoltenburg
• Journal: Acta ophthalmologica Scandinavica (Acta Ophthalmol Scand) Vol. 83 Issue 4 Pg. 477-82 (Aug 2005) ISSN: 1395-3907 [Print] Denmark
• PMID: 16029274 (Publication Type: Journal Article)

Chemical References

• Cross-Linking Reagents
• Photosensitizing Agents
• Collagen
• Riboflavin

Topics

• Animals
• Biomechanical Phenomena
• Collagen (chemistry, metabolism, ultrastructure)
• Cross-Linking Reagents
• Female
• In Situ Nick-End Labeling
• Microscopy, Electron
• Photoreceptor Cells, Vertebrate (drug effects, radiation effects, ultrastructure)
• Photosensitizing Agents (pharmacology, toxicity)
• Rabbits
• Radiation Injuries, Experimental (pathology)
• Retinal Diseases (pathology)
• Riboflavin (pharmacology, toxicity)
• Sclera (drug effects, radiation effects)
• Ultraviolet Rays (adverse effects)