- Nyctalopia, commonly referred to as night blindness, is a condition characterized by impaired vision in low-light or dark environments.
- Individuals with nyctalopia experience difficulty adjusting their eyesight when moving from bright areas to dimly lit spaces, and they may struggle with activities such as driving at night or walking in poorly illuminated places.
- Rather than being a disease in itself, nyctalopia is typically a symptom of an underlying condition, most commonly linked to retinal disorders or nutritional deficiencies—particularly vitamin A deficiency.
- The physiological basis of nyctalopia lies in the dysfunction of rod cells in the retina. Rod cells are responsible for vision in low-light conditions and contain rhodopsin, a light-sensitive pigment made from vitamin A (retinal) and a protein (opsin). Inadequate availability or production of rhodopsin impairs the rods’ ability to detect light, thereby reducing night vision. When vitamin A is deficient—due to malnutrition, malabsorption syndromes, liver disease, or prolonged fat-restricted diets—the regeneration of rhodopsin is compromised, leading to night blindness.
- In addition to nutritional causes, nyctalopia is often associated with genetic and degenerative retinal diseases. One of the most common is retinitis pigmentosa, a hereditary disorder in which the photoreceptor cells in the retina gradually degenerate, typically starting with rod cells, thereby causing progressive nyctalopia. Other conditions such as congenital stationary night blindness, X-linked retinoschisis, and choroideremia also feature night blindness as a primary symptom. Additionally, glaucoma medications like certain carbonic anhydrase inhibitors may cause reversible night vision disturbances.
- Clinically, nyctalopia may present as a subjective complaint—patients often describe an inability to see in dim environments, a longer adjustment period when moving from light to dark, or difficulty recognizing objects in the dark. In inherited retinal diseases, night blindness may begin in childhood or adolescence and gradually worsen over time, potentially leading to tunnel vision and even complete blindness. In contrast, vitamin A deficiency–related nyctalopia is usually more acute and reversible if promptly treated.
- Diagnosis of nyctalopia involves a combination of clinical history, dietary assessment, and ophthalmologic evaluation. Eye exams may include fundoscopy, visual field testing, electroretinography (ERG) to assess rod and cone function, and dark adaptation tests to quantify the eye’s ability to adjust to darkness. Serum vitamin A levels can help confirm deficiency in cases where dietary intake or malabsorption is suspected.
- Treatment depends on the underlying cause. In cases due to vitamin A deficiency, oral or intramuscular vitamin A supplementation typically results in rapid improvement of night vision, often within days. For inherited retinal disorders, there is no definitive cure, but vision aids, genetic counseling, and low-vision rehabilitation services can help manage symptoms and improve quality of life. In all cases, addressing modifiable risk factors—such as improving diet, treating malabsorption disorders, and managing contributing medications—is essential.
