Definitions for "eyecup"
A small oval porcelain or glass cup, having a rim curved to fit the orbit of the eye. it is used in the application of liquid remedies to eyes; -- called also eyeglass.
An eyecup is a cluster of light-sensitive cells forming a cup-shaped depression on an animal's body. The sides of the cup cast shadows on the cells inside it. This allows the animal to detect not only light and dark, but also the direction of the light source. Eyecups can be found on seastars (starfish) and flatworms.
a small vessel with a rim curved to fit the orbit of the eye; use to apply medicated or cleansing solution to the eyeball; "an eyecup is called an eyebath in Britain"
(or eyering).  A plastic or rubber ring to help position and steady the eye correctly.  Folded down when spectacles are worn. ield Flattening.  Reduction or correction of the curvature of an image by use of a specific lens element (usually negative).
a low cost solution to improve your focusing and ensure you get the best results you can