title: OPTX 20/20 and Press-On Optics bifocal segments: an evaluation.
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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Pacific University, College of Optometry, Forest Grove, Oregon, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Bell
authors.forename: K J
authors.initials: KJ
authors.lastname: Gurholt
authors.forename: R L
authors.initials: RL
authors.lastname: Yolton
authors.forename: W T
authors.initials: WT
authors.lastname: Griffith
mesh_terms: D000328:Adult; D004781:Environmental Exposure; D005139:Eyeglasses / Q000592:standards*; D006801:Humans; D055095:Optics and Photonics; D011305:Presbyopia / Q000628:therapy; D014792:Visual Acuity