title: Clinical performance of an innovative back surface multifocal contact lens in correcting presbyopia.
abstract: OBJECTIVE
  This prospective study was designed to subjectively and objectively evaluate the performance of an aspheric multifocal back surface rigid gas permeable (RGP) contact lens. The multifocal element of this lens design consisted of an aspheric optical zone that varied according to the patient's ametropia, corneal topography, and required reading addition.
  
  
  METHODS
  We fit 28 presbyopic subjects with an aspheric multifocal back surface RGP contact lens (age range: 45 to 68 years). Reading additions ranged from +0.75 D to +2.50 D. Subjects were assessed initially and at 2, 6, and 12 weeks for ocular changes, visual performance, and subjective responses.
  
  
  RESULTS
  We required 116 RGP lenses to achieve an acceptable fit and visual acuity in 28 subjects (55 eyes). At the final visit, the distance logMAR acuity with the multifocal contact lens (+0.12 +/- 0.10) was not statistically different (t = -0.623, P = -0.5388) from spectacle acuity at the initial visit (+0.10 +/- 0.12). The near logMAR acuity with the multifocal contact lens at the final visit (0.36 +/- 0.12) was not statistically different from that for near acuity with spectacles at the initial visit (0.33 +/- 0.13). No slit lamp signs worsened during the study. A reduction in myopia of 0.67 D was noted by the final visit. Spectacle blur was noted if the acuity at the initial refraction was compared to the acuity with the same refraction at the final visit (t = -3.287, P = 0.0028) but not when the refractive changes were incorporated (t = 1.058, P = 0.3127). All subjects rated the performance of the lenses very highly: comfort, 86%; distance acuity, 83%; near acuity, 73%; and stability of vision, 74%. Twenty-four subjects (86%) chose the multifocal contact lens as their preference.
  
  
  CONCLUSIONS
  We demonstrated that a multifocal design is able to provide acceptable distance and near correction for presbyopic patients. The aspheric geometry required can be optimized for a given patient by considering his/her degree of ametropia, as well as the corneal topography.
authors.affiliation: Department of Optometry and Vision Science, Manchester, UK.
authors.forename: C
authors.initials: C
authors.lastname: Woods
authors.forename: D
authors.initials: D
authors.lastname: Ruston
authors.forename: T
authors.initials: T
authors.lastname: Hough
authors.forename: N
authors.initials: N
authors.lastname: Efron
mesh_terms: D000368:Aged; D003261:Contact Lenses; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010349:Patient Compliance; D017060:Patient Satisfaction; D011305:Presbyopia / Q000628:therapy*; D011474:Prosthesis Design; D017755:Prosthesis Fitting; D016896:Treatment Outcome; D014792:Visual Acuity