title: Influence of the effective lens position, as predicted by axial length and keratometry, on the near add power of multifocal intraocular lenses.
abstract: OBJECTIVE
  To calculate the near focal distance of different multifocal intraocular lenses (IOLs) as a function of the 2 parameters that are measured before cataract surgery; that is, axial length (AL) and refractive corneal power (keratometry [K]).
  
  
  METHODS
  GB Bietti Foundation IRCCS, Rome, Italy.
  
  
  METHODS
  Noninterventional theoretical study.
  
  
  METHODS
  The IOL power for emmetropia was first calculated in an eye model with the AL ranging from 20 to 30 mm and K from 38 to 48 diopters (D). Then, the predicted myopic refraction for any given IOL add power (from +1.5 to +4.0 D) was calculated, and from this value the near focal distance was obtained. Calculations were also performed for the average eye (K = 43.81 D; AL = 23.65 mm).
  
  
  RESULTS
  The near focal distance increased with increasing values of K and AL for each near power add. The near focal distance ranged between 53 cm and 72 cm (21 inches and 28 inches) for a multifocal IOL with +2.50 D, between 44 cm and 60 cm (17 inches and 24 inches) for a multifocal IOL with +3.00 D add, and between 33 cm and 44 cm (13 inches and 18 inches) for a multifocal IOL with +4.00 D add. In the average eye, the near focal distance ranges between 36 cm (near add power = 4.00 D) and 99 cm (near add power = 1.5 D).
  
  
  CONCLUSIONS
  Longer eyes with steeper corneas showed the longest near focal distance and could experience more difficulties in focusing near objects after surgery. The opposite was true for short hyperopic eyes.
  
  
  BACKGROUND
  Dr. Hoffer receives licensing fees for the commercial use of the registered trademark Hoffer from all biometry manufacturers using the Hoffer Q formula to ensure that it is programmed correctly and book royalties from Slack, Inc., for the textbook IOL Power. None of the authors has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From the GB Bietti Foundation IRCCS (Savini, Lombardo, Serrao, Schiano-Lomoriello, Ducoli), Rome, Italy; Stein Eye Institute (Hoffer), University of California, Los Angeles, California, USA; St. Mary's Eye Center (Hoffer), Santa Monica, California, USA. Electronic address: giacomo.savini@alice.it.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Savini
authors.affiliation: From the GB Bietti Foundation IRCCS (Savini, Lombardo, Serrao, Schiano-Lomoriello, Ducoli), Rome, Italy; Stein Eye Institute (Hoffer), University of California, Los Angeles, California, USA; St. Mary's Eye Center (Hoffer), Santa Monica, California, USA.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Hoffer
authors.affiliation: From the GB Bietti Foundation IRCCS (Savini, Lombardo, Serrao, Schiano-Lomoriello, Ducoli), Rome, Italy; Stein Eye Institute (Hoffer), University of California, Los Angeles, California, USA; St. Mary's Eye Center (Hoffer), Santa Monica, California, USA.
authors.forename: Marco
authors.initials: M
authors.lastname: Lombardo
authors.affiliation: From the GB Bietti Foundation IRCCS (Savini, Lombardo, Serrao, Schiano-Lomoriello, Ducoli), Rome, Italy; Stein Eye Institute (Hoffer), University of California, Los Angeles, California, USA; St. Mary's Eye Center (Hoffer), Santa Monica, California, USA.
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Serrao
authors.affiliation: From the GB Bietti Foundation IRCCS (Savini, Lombardo, Serrao, Schiano-Lomoriello, Ducoli), Rome, Italy; Stein Eye Institute (Hoffer), University of California, Los Angeles, California, USA; St. Mary's Eye Center (Hoffer), Santa Monica, California, USA.
authors.forename: Domenico
authors.initials: D
authors.lastname: Schiano-Lomoriello
authors.affiliation: From the GB Bietti Foundation IRCCS (Savini, Lombardo, Serrao, Schiano-Lomoriello, Ducoli), Rome, Italy; Stein Eye Institute (Hoffer), University of California, Los Angeles, California, USA; St. Mary's Eye Center (Hoffer), Santa Monica, California, USA.
authors.forename: Pietro
authors.initials: P
authors.lastname: Ducoli
mesh_terms: D058452:Axial Length, Eye / Q000473:pathology*; D003315:Cornea / Q000503:physiopathology*; D058453:Emmetropia / Q000502:physiology; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008962:Models, Theoretical; D018918:Phacoemulsification; D012029:Refraction, Ocular / Q000502:physiology*