Low vision is a term commonly used among eye care professionals to mean partial sight, or sight that isn't fully correctable with surgery, pharmaceuticals, contact lenses or glasses.
Low vision can result from a variety of diseases, disorders, and injuries that affect the eye.
Low vision can also be caused by heredity.
Many people with low vision have age-related macular degeneration, cataracts, glaucoma, or diabetic retinopathy.
Age-related macular degeneration accounts for almost 45 percent of all cases of low vision.
Following are some of the most common causes of low vision:

• Albinism.
  Albinism results from a lack of pigment.
  Some forms of albinism affect only the eyes (ocular) while other forms affect skin and hair color as well as the eyes (oculocutaneous).
  Albinism is hereditary.
  
• Aniridia.
  Aniridia is the partial or total absence of the iris of the eye.
  The lack of an iris results in acuity loss, light sensitivity and visual field loss.
  
• Aphakia.
  Aphakia is the absence of the lens of the eye which prevents the ability to adjust focus between objects at different distances.
  
• Cataracts.
  Cataracts result from the lens of the eye becoming cloudy or opaque.
  The clouding can occur over the entire lens or over a small area over the lens.
  Surgical removal of the cataract can result in aphakia.
  
• Coloboma.
  Coloboma is a birth defect occurring during the development of the fetus resulting in an underdevelopment, such as a cleft in the pupil, iris, ciliary body, lens, retina, choroid or optic nerve.
  
• Glaucoma.
  Glaucoma is a condition resulting from an increase of pressure inside the eye, often from improper drainage of fluids, which can cause damage to eye structures such as the optic nerve.
  
• Macular degeneration.
  Macular degeneration involves the gradual loss of sensitivity of the central portion of the retina.
  Since this is the area of the retina responsible for detail vision, macular degeneration is often associated with the loss of central vision and the ability to see fine detail.
  
• Nystagmus.
  Nystagmus is the involuntary movement of the eyes resulting in the inability to maintain a steady fixation.
  The movement can be horizontal, vertical, circular, or mixed.
  
• Optic atrophy.
  Optic atrophy is the degeneration of the optic nerve.
  Loss of function of the optic nerve results in a decreased ability to transmit electrical signals to the visual center of the brain.
  
• Optic nerve hypoplasia.
  This is a condition in which the number of nerves within the optic nerve bundle is reduced.
  
• Retinitis pigmentosa.
  This is a progressive degeneration of the retina resulting in night blindness and peripheral field loss.
  
• Retinopathy of prematurity.
  This is a condition in which the normal growth of blood vessels in the retina is disturbed during fetal development, often due to circumstances surrounding premature birth.
  This condition can lead to an increased risk of retinal tears or retinal detachment.