"Posterior" is the back surface of the lens and "subcapsular" because it is beneath the lens capsule, which is a small "sac", or membrane, that encloses the lens and holds it in place. » Is cataract ...

Prolonged use of corticosteroids may result in glaucoma with damage to the optic nerve, defects in visual acuity and fields of vision, and in posterior subcapsular cataract formation. Use caution ...