title: Contrast sensitivity after implantation of diffractive bifocal and monofocal intraocular lenses.
abstract: OBJECTIVE
  To compare contrast sensitivity (CS) after implantation of a diffractive bifocal intraocular lens (IOL) and a monofocal IOL of similar design.
  
  
  METHODS
  Seven European centers.
  
  
  METHODS
  In this randomized, prospective study, CS was tested 5 months after cataract and IOL implantation surgery in 115 patients with a diffractive bifocal IOL and 106 patients with a monofocal IOL. It was also tested in a subgroup of 38 patients who had bilateral implantation of a diffractive bifocal IOL. Contrast sensitivity was tested using the Vision Contrast Test System (VCTS).
  
  
  RESULTS
  In patients with a best corrected visual acuity (BCVA) of 1.0 or better, the CS at all spatial frequencies (1.5 to 18 cycles/degree), both at distance and near, was slightly lower in the bifocal IOL group than in the monofocal group. Mean values were within the normal range. In patients with a BCVA of less than 1.0, the CS was lower and the difference between the bifocal and monofocal groups was less. In patients with bilateral bifocal IOLs, CS was better when tested bilaterally than when testing the better eye alone. Pupil size affected the results to a small degree. Contrast sensitivity appeared to improve over time after implantation of a diffractive bifocal IOL.
  
  
  CONCLUSIONS
  In patients with cataract and no other eye pathology, the diffractive bifocal IOL with slightly reduce the CS at all spatial frequencies. In those with reduced visual acuity after cataract surgery, CS will be reduced accordingly. In this situation, the reduction from the diffractive bifocal optic would be minor.
authors.affiliation: Eye Department, National Hospital, Oslo, Norway.
authors.forename: E
authors.initials: E
authors.lastname: Haaskjold
authors.forename: E D
authors.initials: ED
authors.lastname: Allen
authors.forename: R L
authors.initials: RL
authors.lastname: Burton
authors.forename: S K
authors.initials: SK
authors.lastname: Webber
authors.forename: K U
authors.initials: KU
authors.lastname: Sandvig
authors.forename: H
authors.initials: H
authors.lastname: Jyrkkiö
authors.forename: E
authors.initials: E
authors.lastname: Leite
authors.forename: A
authors.initials: A
authors.lastname: Liekfeld
authors.forename: B
authors.initials: B
authors.lastname: Philipson
authors.forename: A
authors.initials: A
authors.lastname: Nyström
authors.forename: J
authors.initials: J
authors.lastname: Wollensak
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002387:Cataract Extraction; D015350:Contrast Sensitivity; D005260:Female; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D014792:Visual Acuity