What can cause it?
Halos appear when light is scattered on its way through the eye rather than being focused cleanly on the retina. That scattering can come from the tear film, the cornea or the lens:
- An uncorrected or out-of-date prescription
- Astigmatism
- Dry eye
- Cataract
- Corneal irregularities
- Large pupils in low light
- Previous refractive surgery
- Certain intraocular lenses