Vision - night blindness
Nyctanopia; Nyctalopia; Night blindness
Night blindness is poor vision at night or in dim light.
The cornea allows light to enter the eye. As light passes through the eye the iris changes shape by expanding and letting more light through or constricting and letting less light through to change pupil size. The lens then changes shape to allow the accurate focusing of light on the retina. Light excites photoreceptors that eventually, through a chemical process, transmit nerve signals through the optic nerve to the brain. The brain processes these nerve impulses into sight.
Considerations
Night blindness may cause problems with driving at night. People with night blindness often have trouble seeing stars on a clear night or walking through a dark room, such as a movie theater.
These problems are often worse just after a person is in a brightly lit environment. Milder cases may just have a harder time adapting to darkness.
Causes
The causes of night blindness fall into 2 categories: treatable and nontreatable.
Treatable causes:
- Cataracts
- Nearsightedness
- Use of certain drugs
- Vitamin A deficiency (rare)
Nontreatable causes:
- Birth defects, particularly congenital stationary night blindness
- Retinitis pigmentosa
Home Care
Take safety measures to prevent accidents in areas of low light. Avoid driving a car at night, unless you get your eye doctor's approval.
Vitamin A supplements may be helpful if you have a vitamin A deficiency. Ask your health care provider how much you should take, because it is possible to take too much.
When to Contact a Medical Professional
It is important to have a complete eye exam to determine the cause, which may be treatable. Contact your eye doctor if symptoms of night blindness persist or significantly affect your life.
What to Expect at Your Office Visit
Your provider will examine you and your eyes. The goal of the medical exam is to determine if the problem can be corrected (for example, with new glasses or cataract removal), or if the problem is due to something that is not treatable.
The provider may ask you questions, including:
- How severe is the night blindness?
- When did your symptoms start?
- Did it occur suddenly or gradually?
- Does it happen all the time?
- Does using corrective lenses improve night vision?
- Have you ever had eye surgery?
- What medicines do you use?
- How is your diet?
- Have you recently injured your eyes or head?
- Do you have a family history of diabetes?
- Do you have other vision changes?
- What other symptoms do you have?
- Do you have unusual stress, anxiety, or a fear of the dark?
The eye exam will include:
- Color vision testing
- Pupil light reflex
- Refraction
- Retinal exam
- Slit lamp examination
- Visual acuity
Other tests may be done:
References
Cao D. Color vision and night vision. In: Sadda SVR, Sarraf D, Freund KB, et al, eds. Ryan's Retina.7th ed. Philadelphia, PA: Elsevier; 2023:chap 11.
Cukras CA, Zein WM, Caruso RC, Sieving PA. Progressive and "stationary" inherited retinal degenerations. In: Yanoff M, Duker JS, eds. Ophthalmology. 5th ed. Philadelphia, PA: Elsevier; 2019:chap 6.14.
Duncan JL, Pierce EA, Laster AM, et al. Inherited retinal degenerations: current landscape and knowledge gaps. Transl Vis Sci Technol. 2018;7(4):6. PMID: 30034950
Fenner BJ, Tan TE, Barathi AV, et al. Gene-based therapeutics for inherited retinal diseases. Front Genet. 2022;12:794805. PMID: 35069693
Thurtell MJ, Prasad S, Tomsak RL. Neuro-ophthalmology: afferent visual system. In: Daroff RB, Jankovic J, Mazziotta JC, Pomeroy SL, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 16.
Version Info
Last reviewed on: 8/22/2022
Reviewed by: Franklin W. Lusby, MD, Ophthalmologist, Lusby Vision Institute, La Jolla, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
