title: Multifocal intraocular lens differentiation using defocus curves.
abstract: OBJECTIVE
  To determine the most appropriate analysis technique for the differentiation of multifocal intraocular lens (MIOL) designs by using defocus curve assessment of visual capability.
  
  
  METHODS
  Four groups of 15 subjects were implanted bilaterally with either monofocal intraocular lenses, refractive MIOLs, diffractive MIOLs, or a combination of refractive and diffractive MIOLs. Defocus curves between -5.0 D and +1.5 D were evaluated by using an absolute and relative depth-of-focus method, the direct comparison method, and a new "area-of-focus" metric. The results were correlated with a subjective perception of near and intermediate vision.
  
  
  RESULTS
  Neither depth-of-focus method of analysis was sensitive enough to differentiate between MIOL groups (P > 0.05). The direct comparison method indicated that the refractive MIOL group performed better at +1.00 diopter (D), -1.00 D, and -1.50 D and worse at -3.00 D, -3.50 D, -4.00 D, and -5.00 D than did the diffractive MIOL group (P < 0.05). The area-of-focus intermediate zone was greater with the refractive than with the diffractive MIOL group (P = 0.005) and the near zone was better with the diffractive (P = 0.020) and "mix and match" (P = 0.039) groups than with the refractive MIOL group. The subjective perception of intermediate and near vision agreed best with the area-of-focus metric for the intermediate (r(s) = 0.408, P = 0.010) and near zone (r(s) = 0.484, P < 0.001).
  
  
  CONCLUSIONS
  Conventional depth-of-focus metrics provide a single value to quantify the useful range of vision; however, they fail to provide sufficient detail to differentiate between MIOL designs. The direct comparison method provides a large amount of information, although the results can be complex to interpret. The proposed area-of-focus metric provides a simple, but differentiating method of evaluating MIOL defocus curves.
authors.affiliation: Ophthalmic Research Group, School of Life and Health Sciences, Aston University, Birmingham, United Kingdom. phillip.buckhurst@plymouth.ac.uk
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Buckhurst
authors.forename: James S
authors.initials: JS
authors.lastname: Wolffsohn
authors.forename: Shehzad A
authors.initials: SA
authors.lastname: Naroo
authors.forename: Leon N
authors.initials: LN
authors.lastname: Davies
authors.forename: Gurpreet K
authors.initials: GK
authors.lastname: Bhogal
authors.forename: Athina
authors.initials: A
authors.lastname: Kipioti
authors.forename: Sunil
authors.initials: S
authors.lastname: Shah
mesh_terms: D003867:Depth Perception / Q000502:physiology; D005260:Female; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular / Q000145:classification*; D008297:Male; D008875:Middle Aged; D055095:Optics and Photonics; D018918:Phacoemulsification; D011474:Prosthesis Design; D019591:Pseudophakia / Q000503:physiopathology; D014792:Visual Acuity / Q000502:physiology*