Eyes & Eye-like Structures

Opiliones are either blind or have a pair of ocelli on a median turret-like projection of the prosoma.  When such eyes are present, they are a useful character for distinguishing opilionids from mites.  Unfortunately, the most mite-like opilionids are blind.  Solfugids and some water mites have their ocelli on a median ocular plate (although usually 2 pairs of ocelli) and a few spiders have ocelli on raised processes.