halo (ha´lo)

1. A reddish yellow ring surrounding the optic disk, due to a widening of the scleral ring making the deeper structures visible. 2. An annular flare of light surrounding a luminous body or a depigmented ring around a mole. See halo nevus. 3. areola (4) 4. A circular metal band used in a h. cast or h. brace, attached to the skull with pins. [G. halos, threshing floor on which oxen trod a circle; the halo round the sun or moon]
anemic h. pale, relatively avascular areas in the skin seen around vascular spiders, cherry angiomas, and sometimes in acute macular eruptions.
glaucomatous h. 1. a yellowish white ring surrounding the optic disk, indicating atrophy of the choroid in glaucoma;glaucomatous ring; 2. a h. surrounding lights, caused by corneal edema in glaucoma.rainbow symptom;
senile h. circumpapillary h. seen in choroidal atrophy of the aged.


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