The assertion discusses difficulty in reading and close work, which is commonly seen in patients with primary open angle glaucoma. This is a result of the increasing difficulty in focusing, often due to changes in the ciliary muscle's function as the disease progresses.
The reason explains that the constant pressure on the ciliary muscle, a key part of the eye responsible for focusing, leads to accommodative failure. This matches the assertion as the patients experience difficulty in reading and require frequent changes in presbyopic glasses.
Thus, both statements are correct, and the reason correctly explains the assertion.