Biodegradable implants have been steadily gaining popularity, offering safer, more efficient alternatives to common therapeutics. Currently, most ocular implants that are used for sustainable drug delivery are non-biodegradable. In addition to the eye being a sensitive area, the likelihood of complications increases when multiple surgeries are performed to remove the implant as well as insert it. Biodegradability of the implant can eliminate these removal complications.

Using COMSOL® Multiphysics, we modeled the delivery of betamethasone phosphate (BP) from a biodegradable implant that is placed in the scleral layer of a human eye. As a glucocorticoid, BP is used to reduce inflammation in the tissue layers surrounding the sclera. We used a 2D axisymmetric geometry to represent the eye with the implant and focused on the delivery of BP to the retina.

The implant’s bulk erosion and mass transfer dynamics resulted in an initial spike of BP release followed by a slow, gradual depletion of the remaining drug. The initial size and location of the implant in our model were taken from those of similar implants tested in rabbit eyes. Upon finding that BP concentration exceeded the desired range in the retina, we optimized the location and size of our implant for drug delivery in the human eye. After optimization, an effective concentration in the retina was maintained for 34 days. The model was validated with experimental data for BP release from implants in the rabbit eye, which is an accurate model for drug pharmacokinetics in the human eye. Our results suggest that this biodegradable ocular implant is a viable option for drug delivery in the human eye.