Abstract: Equi-dosed time-fractionated pulsed UVA is employed to irradiate a class of riboflavin/collagen mixture in the presence of copious oxygen to cause rapid crosslinking causing gelation of the riboflavin/collagen mixture in situ and to effect adhesion to underlying structure specifically ocular tissue such as scleral and corneal tissue. Irradiation according to an embodiment of the invention results in depletion of dissolved oxygen at a rate inversely related to irradiance and more particularly depletion of dissolved oxygen occurs rapidly during the process of generation/cross-linking of reactive oxygen species (ROS), specifically singlet oxygen, such that the pulsed fractionation of UVA radiation exposure increases cross-linking efficiency by allowing the re-diffusion of oxygen during pauses in exposure.