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McCanna D et al. Use of a human corneal epithelial cell line for screening the safety of contact lens care solutions in vitro. Eye & Contact Lens, 2008; 34;1: 6-12

Mowrey-McKee M et al. Comparative cytotoxicity potential of soft contact lens care regimens, The CLAO Journal, 2002; 28(3): 160-164

Tchao R et al. Comparison of contact lens multipurpose solutions by in vitro sodium fluorescein permeability assay. The CLAO Journal, 2002; 28:3:151-156

Levy B & Orsborn G. Clinical Risks: Myths and Truths. Interpreting the evidence-based data about contact lens care. Contact Lens Spectrum, January 2008

Deeper Evaluation
There are other methods of assessing eye health than corneal staining. Biocompatibility-based testing provides a deeper level evaluation at the cellular level.

Corneal Staining Biocompatibility testing
Superficial Cellular level detail
Transient Indication of metabolic activity
Asymptomatic Indication of cell integrity
Visible to the naked eye Invisible to the naked eye

Biocompatibility-based tests include:

  1. AlmarBlue - a metabolic dye that measures the respiratory activity of cells1
  2. Sodium-fluorescein permeability assay - higher sodium-fluorescein permeability is related to breaks/disruption in the tight junctions between cells, suggesting damaged or compromised cells1,3
  3. Confocal microscopy - looks at deeper levels of the corneal epithelium that are not visible through a slit lamp or even a scanning electron microscope5


Scanning electron microscopy of human corneal epithelial cells.

These cells are closely juxtaposed with each other, and the ridges between two cells represent tight junctions.1

Cytotoxicity testing: a pre-clinical measure
Often confused, cytotoxicity is not a method of evaluating eye health but instead a pre-clinical evaluation of solution toxicity.2 Cytotoxicity assays conducted in vitro or in animals assess the effect of different compounds on cells from different tissues (biocompatibility) of contact lens solutions before moving to human clinical testing to determine if a cytotoxic component exists.4

Product testing requirements
All products are required to undergo in vitro cytotoxicity testing as part of the regulatory guidance guidance from governing authorities such as the European Medicines Agency and other global standards organisations.2

References

  1. McCanna D et al. Use of a human corneal epithelial cell line for screening the safety of contact lens care solutions in vitro. Eye & Contact Lens, 2008; 34;1: 6-12
  2. Mowrey-McKee M et al. Comparative cytotoxicity potential of soft contact lens care regimens, The CLAO Journal, 2002; 28(3): 160-164
  3. Tchao R et al. Comparison of contact lens multipurpose solutions by in vitro sodium fluorescein permeability assay. The CLAO Journal, 2002; 28:3:151-156
  4. Levy B & Orsborn G. Clinical Risks: Myths and Truths. Interpreting the evidence-based data about contact lens care. Contact Lens Spectrum, January 2008
  5. Bantseev V, McCanna D, Driot J-Y, Ward K, Sivak, J: Biocompatibility of Contact Lens Solutions Using Confocal Laser Scanning Microscopy and the In Vitro Bovine Cornea. Eye and Contact Lens, 33 (6, Part 1 of 2):308-316

www.truthaboutstaininggrid.com is intended as a scientific resource for eye care practitioners developed by Bausch & Lomb