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How the most common preservative affects the Meibomian lipid layer
1Augenklinik des Städtischen Klinikums, Ludwigshafen, D-67063, Germany
Orbit (Amsterdam, Netherlands)
|June 5, 2002
Summary
Benzalkonium chloride in eye drops can harm the Meibomian lipid layer. Concentrations above 0.005% disrupt lipid film spreading and stability, suggesting clinical avoidance.
Area of Science:
- Ophthalmology
- Surface Chemistry
- Tear Film Dynamics
Background:
- Preservatives like benzalkonium chloride are common in ophthalmic solutions.
- The impact of benzalkonium chloride on the Meibomian lipid layer, crucial for tear film stability, is not well-understood.
Purpose of the Study:
- To investigate the in vitro effects of varying benzalkonium chloride concentrations on the Meibomian lipid layer.
- To determine a critical concentration of benzalkonium chloride that adversely affects the Meibomian lipid layer's morphology and spreading properties.
Main Methods:
- Meibomian gland secretion was applied to an aqueous subphase containing benzalkonium chloride (0.001% to 0.1%).
- Brewster Angle Microscopy was used for direct optical control of lipid film spreading and quality.
- Experiments were conducted at pH 5.5 and 20°C, mimicking ocular surface conditions.
Main Results:
- Benzalkonium chloride was tolerated at concentrations up to 0.005%.
- Higher concentrations (> 0.005%) led to domain formation and unstable lipid films.
- These findings were confirmed using a modified method involving post-spreading benzalkonium chloride injection.
Conclusions:
- A critical concentration of benzalkonium chloride exists that impairs the spreading and alters the morphology of the Meibomian lipid layer.
- Ophthalmic solutions containing benzalkonium chloride above 0.005% should be reconsidered for clinical use due to potential harm to the ocular surface.