The Collaborative International Dictionary of English v.0.48:

Ophthalmoscope \Oph*thal"mo*scope\, n. [From Gr. 'ofqalmo`s the
   eye + -scope.] (Physiol.)
   An instrument for viewing the interior of the eye,
   particularly the retina. Light is thrown into the eye by a
   mirror (usually concave) and the interior is then examined
   with or without the aid of a lens. -- Oph*thal`mo*scop"ic,
   a.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ophthalmoscope
    n 1: medical instrument for examining the retina of the eye