The Collaborative International Dictionary of English v.0.48:

Collyrium \Col*lyr"i*um\, n.; pl. E. Collyriums, L.
   Collyria. [L., fr. Gr. ?.] (Med.)
   An application to the eye, usually an eyewater.
   [1913 Webster]

WordNet (r) 3.0 (2006):

collyrium
    n 1: lotion consisting of a solution used as a cleanser for the
         eyes [syn: eye-lotion, eyewash, collyrium]