Overview
ISO 18189:2016 - "Ophthalmic optics - Contact lenses and contact lens care products - Cytotoxicity testing of contact lenses in combination with lens care solution" - specifies an in vitro test method to assess potential cytotoxic effects from interactions between contact lenses and lens care solutions. The standard focuses on direct-contact testing to detect lens-mediated release or concentration of solution ingredients (e.g., preservatives) that could harm ocular cells. (Note: standalone cytotoxicity of a lens or solution is covered by ISO 10993‑5.)
Key topics and requirements
- Test principle: direct-contact cytotoxicity using contact lenses pre‑soaked in the lens care solution and placed onto a confluent monolayer of L‑929 cells.
- Sample preparation: lenses are incubated in ~10 ml of the care solution (or DPBS for lens controls) for 24 h ± 2 h at room temperature with gentle agitation; lenses may be cut (pinwheel) before testing.
- Cell system and culture: L‑929 fibroblast cells (ATCC NCTC clone 929), seeded to form subconfluent monolayers in Minimal Essential Medium (MEM) with 5% serum; incubations at 37 °C ± 1 °C and 5% ± 1% CO2.
- Controls and acceptance criteria:
- Positive control: latex (1 cm × 1 cm), expected grade ≥ 3 in all four replicates.
- Negative control: high density polyethylene (HDPE, 0.5 mm thick, 1 cm × 1 cm), expected grade ≤ 1.
- Lens control: lens soaked in DPBS, expected grade ≤ 1.
- Test validity requires these control criteria be met.
- Endpoint and scoring: after 24 h ± 2 h contact, remove specimens, stain with Trypan Blue, and assess cell morphology and zone of lysis. Reactivity grades range 0 (none) to 4 (severe); grades > 2 indicate cytotoxic effect.
- Measurement guidance: Annex A describes measuring the zone of cell lysis and plate layout.
Applications and users
ISO 18189 is used by:
- Contact lens and lens care solution manufacturers for product development and compatibility testing.
- Biocompatibility and analytical laboratories performing preclinical in vitro testing.
- Regulatory and quality assurance teams preparing safety dossiers and ensuring compliance with ophthalmic device safety expectations.
- R&D teams evaluating interactions across conventional and silicone hydrogel lens materials with representative multipurpose solutions.
Practical benefits include early identification of adverse lens/solution interactions, reduced risk in clinical testing, and support for regulatory submissions.
Related standards
- ISO 10993‑5 - Biological evaluation of medical devices - Tests for in vitro cytotoxicity (general guidance).
- ISO 18369‑1 - Contact lens vocabulary, classification, and labelling (referenced for terms and definitions).
Keywords: ISO 18189, cytotoxicity testing, contact lenses, lens care solutions, in vitro test, L‑929 cells, ISO 10993‑5.
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