(569a) Helping the Corneal Stroma Stay in Shape (Invited Talk)

The cornea of the eye is a remarkable collagen-based hydrogel that is 78%wt water, yet it has the strength to serve as a stable optical element despite continuous tension imposed by intraocular pressure. The corneaâ??s balance of clarity and permeability with mechanical strength is maintained by the constant degradation and replacement of its constituents. When these are out of balance either due to excessive degradation or insufficient replacement, the cornea begins to bulge outward (e.g. keratoconus). Through a Caltech-UCSF collaboration we have developed a gentle method to reinforce the tissue using photoactivated crosslinking of the biomolecules already present in the stroma. The crosslinking is activated by visible light (using green light to activate the photosensitizer eosin Y), which shows low toxicity to the cells in the corneal stroma (keratocytes) and behind it (corneal endothelial cells). To progress to the clinic, we are exploring novel, minimally invasive ways to penetrate the corneaâ??s epithelial barrier for drug delivery. This talk will present the visible-light photocrosslinking method, the reason that it motivates drug delivery to the stroma without disruption of the epithelium, and the approach we are exploring to achieve it.