title: Cytotoxicity of rigid gas-permeable lens care solutions.
abstract: OBJECTIVE
  Reports on cytotoxic effects of rigid gas-permeable lens multipurpose solutions, which remain important because of increasing popularity of orthokeratology, are limited. This study determined cytotoxic effects of rigid gas-permeable lens multipurpose solutions on human corneal epithelial cells and assessed the proliferation rate at different levels of cell membrane damage.
  
  
  METHODS
  The human corneal epithelial cells were exposed to multipurpose solutions containing chlorhexidine gluconate (0.003%) and polyaminopropyl biguanide (PHMB) (0.0005%) (MPS-A), PHMB (0.0005%) (MPS-B) and PHMB (0.0001%) (MPS-C) for one, five and 10 minutes. Following staining with Annexin V-FITC/7-AAD, cell viability and membrane integrity were assessed by flow cytometry. Effects of exposure to concentrations of 10 to 40 per cent multipurpose solutions for 12 hours on the metabolic rate of human corneal epithelial cells were assessed by 3-(4-,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell proliferation assay. Recovery rates were assessed after re-culture for 96 hours at 37°C.
  
  
  RESULTS
  MPS-A exposure caused the highest percentage of early and late necrotic cells for all exposure times and was significantly higher than other multipurpose solutions (p < 0.0001). After 10 minutes exposure, almost 40 per cent of cells in MPS-A but less than five per cent in MPS-B or MPS-C, were in late necrotic stage. After 12 hours of exposure, cell activity was significantly reduced in a dose-response manner for MPS-A treated cells only (p > 0.05). After 96 hours of re-culture, all exposed cells showed some reduction in viability but the effects of exposure to 30 and 40 per cent MPS-A resulted in loss of viability.
  
  
  CONCLUSIONS
  The presence of chlorhexidine appeared to increase cytotoxicity of multipurpose solutions for rigid gas-permeable lenses. This was apparent in both increased levels of necrotic cells on initial exposure and reductions in viability after prolonged exposures at lower dilutions. Multipurpose solutions containing PHMB as a preservative, while not causing acute cytotoxicity, did affect cell viability following exposure to diluted solutions. This indicated it is inadvisable to expose the cornea to multipurpose solutions but rather to rinse lenses with saline before insertion and use artificial tears for rewetting.
authors: School of Optometry, The Hong Kong Polytechnic University, Hong Kong SAR, China.
authors: Camus Kar Man
authors: CK
authors: Choy
authors: Pauline
authors: P
authors: Cho
authors: Maureen V
authors: MV
authors: Boost
mesh_terms: D000891:Anti-Infective Agents, Local / Q000493:pharmacokinetics / Q000633:toxicity; D001645:Biguanides / Q000493:pharmacokinetics / Q000633:toxicity; D002463:Cell Membrane Permeability / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002710:Chlorhexidine / Q000031:analogs & derivatives / Q000493:pharmacokinetics / Q000633:toxicity; D018639:Contact Lens Solutions / Q000493:pharmacokinetics* / Q000633:toxicity*; D019573:Epithelium, Corneal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D005434:Flow Cytometry; D005740:Gases; D006801:Humans; D011310:Preservatives, Pharmaceutical / Q000493:pharmacokinetics / Q000633:toxicity
chemical_list: D000891:Anti-Infective Agents, Local; D001645:Biguanides; D018639:Contact Lens Solutions; D005740:Gases; D011310:Preservatives, Pharmaceutical; C064420:polyaminopropylbiguanide; C010882:chlorhexidine gluconate; D002710:Chlorhexidine
keywords: cornea; cytotoxicity; human corneal epithelium; multipurpose solutions; rigid gas-permeable lens solutions