optic axis n OPTICAL AXIS
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optical axis 1. a. opticus. 2. the straight line that passes through the centers of the surfaces and the centers of curvature of a lens system. In a spherical system, it is the axis of symmetry, in the eye being the line passing through the center of the cornea and of the lens of the eye; in a simple lens system it is the line perpendicular to both surfaces of the lens, the lens being regarded as a spherical segment.Medical dictionary. 2011.