title: Calculation of posterior chamber intraocular lens (IOL) size and dioptric power for use in pet rabbits undergoing phacoemulsification.
abstract: OBJECTIVE
  To calculate the size and dioptric power of a posterior chamber intraocular lens (IOL) to achieve emmetropia in adult rabbits and to compare the dioptric power calculation results using a proprietary predictive formula to a retinoscopy-based method.
  
  
  METHODS
  Three wild rabbit cadavers, seven pet rabbits with cataracts and ten healthy pet rabbits.
  
  
  METHODS
  Implant size was calculated using a capsular tension ring (CTR) (Acrivet®, Berlin, Germany). Published and cadaveric biometric data were used in the predictive formula. An IOL power-escalation study compared the predicted values to the refraction results of one pet rabbit (P1) fitted with a + 41D canine IOL (Acrivet®) and six pet rabbits (P2-P7) fitted with prototype IOLs (Acrivet®). Retinoscopy of 10 healthy pet rabbits served as controls.
  
  
  RESULTS
  A 13.5 mm CTR fitted in all rabbits and permitted the use of a 13 mm IOL. The predicted IOL power ranged between +24D and +25D. The +41D IOL resulted in a refraction error of +8D. Progressive recalculation through a calibration formula led to the insertion of three +49D IOLs in two pet rabbits and a refraction of +6D to +8D, followed by seven +58D IOLs in four pet rabbits and a refraction median of 0D (range: -1.5D to +1D).
  
  
  CONCLUSIONS
  A 13 mm prototype IOL of +58D achieves emmetropia and is of adequate size for rabbits. The combined use of a CTR and retinoscopy is a useful method to calculate the size and refractive power of a new, species-specific, veterinary IOL.
authors.affiliation: The Royal Veterinary College, Department of Clinical Science and Services, University of London, Hawkshead lane, North Mymms, Herts, AL9 7TA, UK.
authors.forename: Rick F
authors.initials: RF
authors.lastname: Sanchez
authors.affiliation: Chirurgische Ophthalmologie, Carl Zeiss Meditec AG, Standort, Berlin, Germany.
authors.forename: Ronald
authors.initials: R
authors.lastname: Becker
authors.affiliation: The Royal Veterinary College, Department of Clinical Science and Services, University of London, Hawkshead lane, North Mymms, Herts, AL9 7TA, UK.
authors.forename: Charlotte
authors.identifier: http://orcid.org/0000-0001-9974-1244
authors.initials: C
authors.lastname: Dawson
authors.affiliation: The Royal Veterinary College, Department of Clinical Science and Services, University of London, Hawkshead lane, North Mymms, Herts, AL9 7TA, UK.
authors.forename: Natàlia
authors.initials: N
authors.lastname: Escanilla
authors.affiliation: The Royal Veterinary College, Department of Clinical Science and Services, University of London, Hawkshead lane, North Mymms, Herts, AL9 7TA, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Lam
mesh_terms: D000818:Animals; D002138:Calibration; D058453:Emmetropia; D019654:Lens Implantation, Intraocular / Q000379:methods / Q000662:veterinary; D007910:Lenses, Intraocular; D009907:Optometry; D057805:Pets; D018918:Phacoemulsification / Q000662:veterinary*; D057972:Posterior Eye Segment / Q000033:anatomy & histology*; D011817:Rabbits / Q000601:surgery*; D012029:Refraction, Ocular; D042262:Retinoscopy / Q000662:veterinary
keywords: IOL development; IOL diameter; capsular tension ring; cataracts; refraction; retinoscopy