Sectoral vs complete heterochromia

The difference is where the variation sits. Sectoral heterochromia occurs within a single iris — a wedge or patch of one eye is a different colour from the rest of that same eye. Complete heterochromia is a difference between the two eyes: each iris is a fairly consistent colour, but the two colours differ from one another.

Typical distribution

Sectoral produces a radial wedge running outward from the pupil, of any size from a narrow slice to nearly half the iris. Complete produces no pattern within either iris — the pattern is the pair.

Undertone

In both, the more pigmented area appears warmer or browner and the less pigmented area cooler. The distinction between the two patterns is geometric, not one of undertone.

Central or outer ring

Neither is a ring. A concentric ring around the pupil is central heterochromia, which is a third pattern again.

Lighting effects

A sectoral patch can become much more or less obvious with pupil size and viewing angle. A complete difference is more stable, though the apparent size of the difference varies if one iris is more light-responsive than the other.