Stare-in-the-crowd effect evolved from a necessity for fast and accurate gaze perception for complex social interactions (Emery 2000). According to this model, an eye direction detector (EDD) mechanism - a neurocognitive system responsible for the rapid detection of eyes in the environment and their gaze direction – arose as a function of the geometry created by a dark circular iris relative to the white sclera (Baron-Cohen 1994). Specifically, it is contended that the increased ratio of exposed sclera in the eye outline of humans serves to enhance the velocity and acuity of gaze direction perception (Kobayashi and Kohshima 2001). Baron-Cohen, S. (1994)
Enucleation of the eye To avoid a sunken appearance to the eye socket, an implant approximating this volume can be placed into the space of the removed eye, secured, and covered with Tenon's capsule and conjunctiva (the mucous membrane covering the natural sclera). Implants can be made of many materials with the most common being plastic, hydroxylapatite, metal alloy or glass. Later, once the conjunctiva have healed and post-operative swelling has subsided, an ocular prosthesis can be placed to provide the appearance of a natural eye. The prosthesis is fabricated by an ocularist. Its form is that of a cupped disc so that it