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  • Title: OPTX 20/20 and Press-On Optics bifocal segments: an evaluation.
    Author: Bell SM, Gurholt KJ, Yolton RL, Griffith WT.
    Journal: J Am Optom Assoc; 1997 Sep; 68(9):579-87. PubMed ID: 9308302.
    Abstract:
    BACKGROUND: OPTX 20/20 and Press-On Optics removable bifocal segments were evaluated in three areas: optical quality, effects on vision, and stability under simulated environmental conditions. METHODS: To evaluate optical quality, sphere, cylinder, and spherical equivalent powers were measured in center and peripheral portions of 10 segments, with powers ranging from +1.00 to +2.50 D. RESULTS: Twelve of 20 OPTX 20/20 segments and six of 20 Press-On Optics +1.00 and +1.50 D segments failed to pass ANSI Z80.1 standards because of unwanted cylinder powers. With regard to vision, +2.00 D OPTX 20/20 segments provided a 1 Snellen line advantage in near acuity, as compared with the Press-On Optics segments. contrast sensitivity for low- and mid-spatial frequencies was not significantly different for segments of the two types. CONCLUSION: For higher powers, the optical characteristics of the OPTX 20/20 segments are better and provide better visual acuity. For lower powers, distortion and small amounts of unwanted cylinder reduce the optical quality of the OPTX 20/20 segments. Both segment types retained adhesion to CR-39 carriers equally well and should be satisfactory for their designated purposes of providing temporary and removable adds for occasional use.
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