Premium
Varifocal contact lenses for the correction of presbyopia
Author(s) -
Port Michael,
Refson Kathleen,
Minards Jane
Publication year - 1995
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1046/j.1475-1313.1995.9500097w.x
Subject(s) - presbyopia , accommodation , lens (geology) , astigmatism , optometry , optics , contrast (vision) , pupil , pupil size , contact lens , spherical aberration , ophthalmology , visual acuity , medicine , physics
Summary A Nissel + 1.75 D PS45 lens' label power seems to be made up of about + 0.75 D distance and + 0.75 D near addition. There are individual variations which will depend on pupil size, corneal shape, lens position and ocular aberrations. When a + 0.75 Bausch & Lomb U3 lens was used as a control, there was also a significant increase in ‘accommodation’ measured (+ 0.75 D), but this could not be explained. When two other lenses with an aspheric surface were studied, they also showed a near addition effect. In this supplementary study the changes were explained by changes in spectacle accommodation. A lens with two spherical surfaces did not show the expected increase in spectacle accommodation. Astigmatism, as a general rule, was not corrected by the PS45 lens, although the very occasional case did show some reduction. Visual acuity and contrast sensitivity at 8 cpd and 3 cpd were not significantly affected when compared to the control lens.