title: Opacification of hydrophilic acrylic intraocular lens attributable to calcification: investigation on mechanism.
abstract: OBJECTIVE
  To identify the nature and to investigate the biochemical mechanisms leading to late opacification of implanted hydrophilic acrylic intraocular lenses (IOLs).
  
  
  METHODS
  Retrospective laboratory investigation.
  
  
  METHODS
  setting: Department of Ophthalmology, Medical School, Department of Chemical Engineering, Laboratory of Inorganic and Analytical Chemistry, University of Patras and FORTH-ICEHT, Greece. study population: Thirty IOLs were explanted one to 12 years postimplantation attributable to gradual opacification of the lens material. observation procedures: Materials analysis was done using scanning electron microscopy (SEM) equipped with a microanalysis probe (EDS), confocal microscopy, x-ray diffraction (XRD), and Fourier transform infrared (FTIR) for the identification of the substances involved in the opacified lenses.
  
  
  RESULTS
  SEM investigation showed plate-like as well as prismatic nanoparticle deposits of calcium phosphate crystallites on the surface and in the interior of opacified IOLs. The plate-like deposits exhibited morphology and particle size typical for octacalcium phosphate (OCP), while the respective characteristics of the prismatic nanocrystals were typical of hydroxyapatite (HAP). EDS analysis confirmed the chemical composition of the deposits. Aqueous humor analysis showed that the humor is supersaturated with respect to both OCP and HAP, favoring the formation of the thermodynamically more stable HAP, while the formation and kinetic stabilization of other transient phases is also very likely. In vitro experiments using polyacrylic materials confirmed the clinical findings.
  
  
  CONCLUSIONS
  Hydrophilic acrylic IOLs' opacification may be attributed to the deposition of calcium phosphate crystallites. HAP is the predominant crystalline phase of these crystallites. Surface hydroxyl groups of the polyacrylic materials facilitate surface nucleation and growth.
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Patras, Rion, Patras, Greece. s.gartag@med.upatras.gr
authors.forename: Sotirios P
authors.initials: SP
authors.lastname: Gartaganis
authors.forename: Dimitra G
authors.initials: DG
authors.lastname: Kanellopoulou
authors.forename: Ephigenia K
authors.initials: EK
authors.lastname: Mela
authors.forename: Vassiliki S
authors.initials: VS
authors.lastname: Panteli
authors.forename: Petros G
authors.initials: PG
authors.lastname: Koutsoukos
mesh_terms: D000180:Acrylic Resins; D000368:Aged; D000369:Aged, 80 and over; D001082:Aqueous Humor / Q000737:chemistry / Q000378:metabolism; D002114:Calcinosis / Q000209:etiology* / Q000378:metabolism; D002130:Calcium Phosphates / Q000737:chemistry / Q000378:metabolism; D003263:Contact Lenses, Hydrophilic / Q000009:adverse effects*; D020878:Device Removal; D017886:Durapatite / Q000737:chemistry / Q000378:metabolism; D004577:Electron Probe Microanalysis; D005260:Female; D006801:Humans; D019654:Lens Implantation, Intraocular; D008297:Male; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D018918:Phacoemulsification; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D012189:Retrospective Studies; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D000180:Acrylic Resins; D002130:Calcium Phosphates; D017886:Durapatite; C020243:calcium phosphate