The best solution is laser surgery so you don't need glasses. Barring that you can use Rain-X on the outside face of your lenses to encourage the water to bead off and an anti-fog compound on the inside to reduce fogging. A front fender will help reduce splatter from below and a viso may help some with direct rain. I have not had much success with visors. Riding at any speed limits their effectiveness.

However, no matter what you do, riding in the rain with glasses is a pain.