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Day Blindness

What is hemeralopia?

Hemeralopia is commonly known as “day blindness”. More specifically, it is characterized by decreased visual acuity (sharpness of vision) when in the presence of bright light. If severe enough, some people will exhibit the tendency to avoid brightly lit areas. This behavior is known as photoaversion. As can be imagined, this condition can be detrimental to a person’s psychological, social, and even physical health.


Pronounced HEM-ER-UH-LOH-PEE-UH, the word hemeralopia is of Greek origin: hemera=day + alaos=blind + ops=eye. This is a bit of an ambiguous term, because in many foreign countries and in older English texts, the word means the exact physiological opposite, or “seeing in the day” aka “night blindness.” Hemeralopia is also known as night sight, day blindness, cone degeneration, hemeranopia, hemeralopsia, and hemerlopia.


Most often due to some type of dysfunction in the cone cells of the retina, whether from degeneration or absence of cones, is often a congenital disorder, but may be caused by other factors.

Some diseases that may bring on hemeralopia are hereditary X-linked retinoschisis, choroideremia, blue-cone monochromatism, and rod monochromatism(the last two are forms of color blindness). Other common types of color blindness often have hemeralopia as an associated condition or symptom, as both are most often caused by cone dysfunction.

Certain anticonvulsant medications, including troxidone(trimethadione), can cause hemeralopia.

It is common in albinos due the excessive glare caused by lack of pigmentation in the iris and choroid.

Cataracts can be a contributing factor because lens clouding disperses the light improperly before it reaches the retina.

Hemeralopia is occasionally a symptom of Cohen syndrome, a rare genetic condition.

In cases where the condition is idiopathic, the cause may be exposure to prolonged periods of darkness, overall malnutrition, or improper nutrition to the retina caused by some other biological factor.


Although no conventional Western treatment is known, there are some alternative treatments that may provide relief or even a cure.

Bilberry extract, particularly from the skin of a bilberry, has been shown to significantly improve hemeralopia.

Occasionally, when the cause is unknown, patients are given progressively lighter-tinted sunglasses to wear which can help improve the tolerance to light over time.

Vitamin A, riboflavin, and nicotinic acid used in combination with each other may help improve this condition. Interesting enough, even though hemeralopia is thought to be a dysfunction of the cone cells, vitamin A is used in the synthesis of rhodopsin, a chromoprotein found in the rods of the retina.

Homeopathic dilutions of troxidone(trimethadione), the same drug that has hemeralopia as a side effect, can have a curative effect for the condition.

Other “alternative” treatments may be effective in treating this condition, including acupuncture, classical homeopathy, Reiki, flower/gem essences, and other holistic treatments.