Night blindness, also known as nyctalopia, is the inability to acclimatize to dim lighting conditions. Some people become more nearsighted at night as the pupil dilates in dark conditions, a condition called spherical aberration. When a person is unable to see well enough to distinguish distinct images in low lighting conditions, night blindness results.

People with night blindness (also called impaired dark adaptation) have poor vision in the darkness, but see normally when adequate light is present.

Night blindness is mostly a symptom of several underlying diseases or conditions, especially untreated nearsightedness.

This occurs because an individual with myopia will become even more nearsighted as the pupil dilates at night. On the other hand, patients being treated with glaucoma medications, which constrict the pupil, will also frequently have night blindness, because the small pupil allows minimal light to enter the eye. Retinitis pigmentosa, a retinal degenerative disorder, may also be associated with night blindness. Some other less common causes of night blindness include the retinal disorders such as gyrate atrophy.

Types of night blindness -