pSivida Corp., of Watertown, Mass., amended its existing agreement with New York-based Pfizer Inc. to focus solely on a sustained-release implant for ocular hypertension and glaucoma. The product will deliver the drug latanoprost using a system based on pSivida's Durasert technology. Pfizer will pay $2.3 million initially, and pSivida will develop the glaucoma candidate through Phase II trials. At that point, Pfizer can exercise an option for $20 million to develop and commercialize the product globally. In that event, pSivida would be eligible for milestone payments worth up to $146.5 million, plus double-digit royalties.