{ } a. [ F. optique, Gr. 'optiko`s; akin to 'o`psis sight, 'o`pwpa I have seen, 'o`psomai I shall see, and to 'o`sse the two eyes, 'o`ps face, L. oculus eye. See Ocular, Eye, and cf. Canopy, Ophthalmia. ] 1. Of, pertaining to, or using vision or sight; as, optical illusions. [ wns=2 ]
Syn. -- ocular, optic, visual. [ 1913 Webster + WordNet 1.5 ]

The moon, whose orb
Through optic glass the Tuscan artist views. Milton. [ 1913 Webster ]

2. Of or pertaining to the eye; ocular; as, the optic nerves (the first pair of cranial nerves) which are distributed to the retina; the optic (or optical) axis of the eye. See Illust. of Brain, and Eye. [ wns=3 ] [ 1913 Webster ]

3. Relating to the science of optics or to devices designed to assist vision; as, optical works; optical equipment. [ wns=1 ] [ 1913 Webster +PJC ]

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. [ 1913 Webster ]

n. (Chem.) the ability of a chemical compound to rotate the plane of plane-polarized light. This is found only in chemicals whose molecular structure does not have a plane of symmetry, and is common in biochemical compounds. -- optically active adj. [ PJC ]

n. (Communications) a cable containing multiple optical fibers. [ PJC ]

n. (Communications) A thin fiber of very pure glass used to carry signals transmitted by means of light. It has much greater information-carrying capacity than a copper wire, and in the 1990's became a dominant means of transmitting telephone communications over long distances. [ PJC ]

adv. 1. By optics or sight. [ 1913 Webster ]

2. With reference to optics. [ 1913 Webster ]

Optically active,
Optically inactive (Chem. Physics), terms used of certain isomeric substances which, while identical with each other in other respects, differ in this, viz., that they do or do not produce right-handed or left-handed circular polarization of light. See optical activity. --
Optically positive,
Optically negative. See under Refraction. [ 1913 Webster ]