title: Lens parameter changes under in vitro and ex vivo conditions and their effect on the conjunctiva.
abstract: OBJECTIVE
  To quantify changes in contact lens parameters induced by lens wear and determine whether these changes are associated with contact lens-induced conjunctival staining (CLICS).
  
  
  METHODS
  In vitro: Lens diameter, sag, edge shape, base curve of six contact lens brands (balafilcon, comfilcon, etafilcon, lotrafilcon B, omafilcon and senofilcon) measured at 21°C and 35°C (eye temperature). Ex vivo: Diameter of lenses collected from a prospective, randomised, contra-lateral, cross-over clinical trial from 36 subjects wearing all lens types for 1 week daily wear, measured in 35°C PBS after removal. Ocular surface was examined for lens-induced conjunctival staining by masked examiner.
  
  
  RESULTS
  In vitro: Changes in diameter and base curve outside ISO tolerance were found with etafilcon A and omafilcon A. Ex vivo: Comfilcon A and etafilcon A had greatest shrinkage in diameter (0.18mm) and base curve (0.11mm steeper) with temperature increase from 21°C to 35°C. Senofilcon A, lotrafilcon B and balafilcon A maintained most stable parameters between 21°C and 35°C. Changes in diameter and base curve from lens wear were not correlated with CLICS (p>0.49). Multivariate analysis showed significantly greater levels of lens induced staining were associated with lens modulus (p<0.001) and knife (p<0.001) and chisel (p<0.001) edge shapes.
  
  
  CONCLUSIONS
  Parameter changes induced by lens wear were associated with increasing temperature, but these changes in lens diameter and base curve did not induce CLICS. Modulus and edge shape were associated with increased CLICS. The susceptibility of etafilcon A and omafilcon A lenses to parameter changes might be related to their high water content.
authors: Brien Holden Vision Institute, Sydney, Australia. j.ozkan@brienholdenvision.org
authors: Jerome
authors: J
authors: Ozkan
authors: Klaus
authors: K
authors: Ehrmann
authors: David
authors: D
authors: Meadows
authors: John
authors: J
authors: Lally
authors: Brien
authors: B
authors: Holden
authors: Percy Lazon
authors: PL
authors: de la Jara
mesh_terms: D000328:Adult; D003228:Conjunctiva / Q000293:injuries* / Q000473:pathology*; D003261:Contact Lenses / Q000009:adverse effects* / Q000145:classification*; D055119:Elastic Modulus; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006244:Hardness; D006801:Humans; D008297:Male; D013696:Temperature; D016896:Treatment Outcome