visual halo

   Also referred to as halo and halo vision. All three terms are indebted to the Greek noun halos, which means area. In biomedicine the terms halo and visual halo are used to denote a luminous or coloured circle surrounding visually perceived stimuli or objects, notably lights. Visual halos tend to be classified either as * visual illusions or as * entoptic phenomena. Etiologically, they are associated primarily with a variety of ocular conditions, including corneal lesions (either traumatic or infectious in nature, or as a complication of eye surgery or laser treatment), Sattler veil, cataract, and glaucoma. They are also associated with diabetic * hypoglycaemia, and migraine. In the past the term halo has also been used to denote what is currently known as a * corona phenomenon, i.e. a visual illusion consisting of an extra edge around an object.

   References

   Allen, R.J., Saleh, G.M., Litwin, A.S., Sciscio, A., Beckingsale, A.B., Fitzke, F.W. (2008). Glare and halo with refractive correction. Clinical & Experimental Optometry, 91, 156-160.