Op"tic (?), n. [From Optic,
a.] 1. The organ of sight; an
eye.
The difference is as great between
The optics seeing, as the object seen.
Pope.
2. An eyeglass. [Obs.]
Herbert.
{ Op"tic (?), Op"tic*al (?), }
a. [F. optique, Gr. ?; akin to ? sight,
? I have seen, ? I shall see, and to ? the two eyes, ? face,
L. oculus eye. See Ocular, Eye, and cf.
Canopy, Ophthalmia.] 1. Of or
pertaining to vision or sight.
The moon, whose orb
Through optic glass the Tuscan artist views.
Milton.
2. Of or pertaining to the eye; ocular; as,
the optic nerves (the first pair of cranial nerves) which are
distributed to the retina. See Illust. of Brain, and
Eye.
3. Relating to the science of optics; as,
optical works.
Optic angle (Opt.), the angle
included between the optic axes of the two eyes when directed to the
same point; -- sometimes called binocular parallax. --
Optic axis. (Opt.) (a) A
line drawn through the center of the eye perpendicular to its
anterior and posterior surfaces. In a normal eye it is in the
direction of the optic axis that objects are most distinctly
seen. (b) The line in a doubly refracting
crystal, in the direction of which no double refraction occurs. A
uniaxial crystal has one such line, a biaxial crystal has two. -
- Optical circle (Opt.), a graduated
circle used for the measurement of angles in optical
experiments. -- Optical square, a
surveyor's instrument with reflectors for laying off right
angles.