Night blindness refers to the difficulty in seeing in low-light conditions or darkness, resulting from the dysfunction of certain vision cells, specifically the rods in the retina. Our eyes' ability to adapt quickly from bright to dark environments and see in dimly lit areas is essential for healthy vision. When this ability is compromised, the condition is commonly known as night blindness or, medically, as nyctalopia. This issue can arise from various diseases that lead to the degeneration of the retina's rods, the sensory cells responsible for low-light vision. Additionally, it can be caused by an inherited problem with visual purple, or rhodopsin, the pigment found in the retina's rods. A deficiency in vitamin A can also lead to this problem, as rhodopsin is maintained only in the presence of this vitamin. Night blindness is a classic symptom of vitamin A deficiency, a condition first described by English physician William Heberden (1710-1801). Heberden also identified other significant medical conditions, such as angina (severe chest pain due to insufficient oxygen supply to the heart) and the presence of nodules in small joints, known as Heberden's nodes, found at the last joint of the finger. Vitamin A can be sourced from animal livers, milk, and yellow and green leafy vegetables, which contain carotenes—substances that the body converts into vitamin A. Night blindness is also known by other terms such as day sight, nocturnal vision impairment, nyctalopia, and nyctanopia.
