Optic; Optical

Part of speech: adjective (a.)

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.