Day blindness

Labelled Diagram of the Eye

Labelled diagram of the structure of the retina

Day Blindness is also known as:

Day Blindness is the term used to refer to comparatively good vision in poor light but poor vision in good illumination.

An alternative definition of Day Blindness is "a visual defect characterised by the inability to see as clearly in bright light as in dim light".

The meaning of the term Day Blindness is therefore quite easy to remember from its name, though less so when the medical term "Hemeralopia" is used.


Day Blindness is usually congenital (meaning "present since birth"). However, it may sometimes be acquired (meaning occur in a person who did not have the condition previously), for example if the cones in the retina are damaged or destroyed e.g. by disease.

See for comparison Night Blindness.

More about Ophthalmology:

This section includes short definitions of many diseases, disorders, and conditions of the eyes and visual system.
For definitions of other terms in this category, choose from the list to the left (but note that this is not a complete/exhaustive list).

Other related pages include

For further information see also our pages of books about ophthalmology.

The following books may also be of interest:

The Aging Eye (Harvard Medical School)
MCQ Companion to the Eye (Textbook)
The Secret of Perfect Vision: How You Can Prevent and Reverse Nearsightedness
What Your Doctor May Not Tell You About(TM) Glaucoma: The Essential Treatments and Advances That Could Save Your Sight

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