Which type of glaucoma is known for developing slowly over many years?

Primary open-angle glaucoma is characterized by a gradual increase in intraocular pressure over time, leading to optic nerve damage and vision loss if not properly managed. This type of glaucoma often develops silently, with patients usually not experiencing noticeable symptoms until significant optic nerve damage has occurred. Over the years, peripheral vision may diminish without the individual being aware, making routine eye examinations crucial for early detection.

In contrast, acute angle-closure glaucoma arises suddenly and presents as a medical emergency, often with severe symptoms such as eye pain, headache, nausea, and vomiting. Normotensive glaucoma is defined by optic nerve damage and vision loss occurring in the presence of normal intraocular pressures, which does not directly correlate with the slow developmental nature characteristic of primary open-angle glaucoma. Secondary glaucoma occurs due to other underlying conditions or factors, leading to elevated intraocular pressure but does not inherently possess the gradual progression seen in primary open-angle glaucoma. Thus, the slow development of primary open-angle glaucoma sets it apart as the correct answer.