Latin name it as halo... Greek name it as halos... But what is halo actually?
Refers to The Free Dictionary by Farlex said halos is:
1.a. A circular band of colored light around a light source, as around the sun or moon, caused by the refraction and reflection of light by ice particles suspended in the intervening atmosphere.
b. Something resembling this band.
2. A luminous ring or disk of light surrounding the heads or bodies of sacred figures, such as saints, in religious paintings; a nimbus.
3. The aura of majesty or glory surrounding a person or thing that is regarded with reverence, awe, or sentiment.
But lets talks about halos in optical perception. In some cases, halos is an indicator for certain diseases such as glaucoma, corneal edema, corneal inflammation, diabetes, diabetic lens osmosis, cataract and etc.
So, visual halos is seeing halos around objects or lights. So, be careful when u seeing halos but please do not misdiagnosis. :)
References:
http://www.thefreedictionary.com/haloes
http://www.wrongdiagnosis.com/sym/visual_halo.htm
