Amplitude of accommodation
A measurement of the ability of an eye to focus at near, assuming the eye is optically corrected for distance.
A computer controlled instrument for determining the refractive error of the eye.
Change in apparent position of an object seen through a particular spectacle lens due to induced prismatic effect.
Sudden movement of an image when gaze is shifted across the border between the distance and the near portion of a spectacle lens.
Jackson cross cylinder
Combination of 2 equal but opposite power cylinders used in the determination of power and axis of refractive astigmatism.
Unequal magnification of retinal images in different meridians.
Oblique (marginal) astigmatism
Astigmatism induced by the tilting of a spherical lens or by viewing through the periphery of a spherical lens.
An instrument containing a collection of spherical and cylindrical lenses for the performance of retinoscopy and manifest refraction. The instrument also commonly includes the Jackson cross cylinder, Risley prisms, and other accessories.
Each centimeter of lens decentration induces 1 prism diopter (∆) of prism for each diopter of power of the lens.
Functional loss of accommodation with aging.
A manual objective method of determining and evaluating the refractive status of an eye through the observation of the movement of a retinal reflex created by a beam of light through the pupil and the optical system of the eye.
Slab-off prism (bicentric grinding)
Creation of base-up prism in the area of a bifocal to correct induced prismatic effect in downgaze through the bifocal reading segment.
The distance from the back surface of a spectacle or contact lens to the anterior surface of the cornea