title: Spring constants of capsular tension rings.
abstract: OBJECTIVE
  To determine the spring constants of several types of capsular tension rings (CTRs).
  
  
  METHODS
  Department of Ophthalmology, Johannes Gutenberg-University, Mainz, Germany.
  
  
  METHODS
  Fourteen models of CTRs provided by 9 companies were tested; all were 11.0 mm in diameter. The CTRs were positioned in a special retainer of a material-testing machine and compressed at a constant speed of 10.0 mm per minute. The distance and force values were recorded, and each CTR model was tested 3 times using a new specimen each time. The resulting measurements were used to calculate a mean spring constant for each CTR model.
  
  
  RESULTS
  All tested CTRs showed linear proportionality between force and compression distance. Test results were repeatable and precise. Capsular tension rings of the same model had comparable mechanical properties, and different models had different mean spring constants ranging from 0.8162 to 4.5501 mN/mm.
  
  
  CONCLUSIONS
  The spring constant of a CTR is a suitable mechanical characteristic to facilitate the choice of CTR model. A CTR with a low spring constant may be advantageous for the management of zonular dialysis, whereas a CTR with a higher spring constant may reduce capsular bag shrinkage more effectively.
authors.affiliation: Department of Ophthalmology, Johannes Gutenberg-University, 55101 Mainz, Germany. kurz@augen.klinik.uni-mainz.de
authors.forename: Sabine
authors.initials: S
authors.lastname: Kurz
authors.forename: H Burkhard
authors.initials: HB
authors.lastname: Dick
mesh_terms: D001672:Biocompatible Materials; D019245:Compressive Strength / Q000502:physiology*; D006801:Humans; D007903:Lens Capsule, Crystalline / Q000601:surgery; D019904:Polymethyl Methacrylate; D019736:Prostheses and Implants
chemical_list: D001672:Biocompatible Materials; D019904:Polymethyl Methacrylate