jump

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Related to jumping at: Show jumping, Jumping Jacks, Horse jumping

jump

The displacement of the image of an object occurring when viewing across the borderline between two portions of different power in a bifocal or trifocal lens. The jump is eliminated by placing the optical centres on the dividing line; the lens is then called a no jump bifocal (e.g. a monocentric bifocal with a straight dividing line) (Fig. J1). Syn. image jump; prismatic jump. See monocentric.
Fig. J1 Image jump upward caused by the segment of a bifocal lens, as the direction of gaze is lowered across the dividing lineenlarge picture
Fig. J1 Image jump upward caused by the segment of a bifocal lens, as the direction of gaze is lowered across the dividing line
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
References in periodicals archive ?
"At the moment I see this as the end of jumping at Windsor, but of course one never says never," said Renton.
It followed the end of jumping at Nottingham, which had bowed to commercial pressure amid protests from jumps professionals, a year earlier.
"In recent years we've lost jumping at Nottingham and Windsor, and there are very few fixtures now at Lingfield."