What is the medical term for decreased vision in dim light or darkness?

Nyctalopia is the medical term that specifically refers to decreased vision in dim light or darkness, commonly known as night blindness. This condition occurs when the eyes are unable to adapt properly to low-light environments, which can be due to various factors such as vitamin A deficiency, retinal diseases, or inherited disorders.

The other terms listed relate to different visual impairments: Hemeralopia refers to difficulty seeing in bright light, Astigmatism is a refractive error caused by an irregularly shaped cornea, and Glaucoma is a group of eye conditions that damage the optic nerve, often due to high intraocular pressure, leading to loss of vision. Understanding these distinctions helps clarify why nyctalopia is the correct term for diminished vision in low-light situations.