Modern Contact Lens Care: A Comprehensive Guide for Eye Care Practitioners

Contact lens technology and hygiene have progressed significantly over the past few decades. However, complications such as microbial keratitis, contact lens discomfort (CLD), and inflammatory responses still affect many wearers, often due to inadequate or inappropriate lens care. As practitioners, it is essential to stay informed about the latest disinfection systems, the science behind solution ingredients, and the regulatory landscape to provide the best patient outcomes.

This blog offers a detailed overview of modern contact lens care systems, with practical insights into their efficacy, compatibility, and clinical considerations.

The Ideal Contact Lens Care System: What Are We Aiming For?

According to Jones and Senchyna (2007), an ideal care product should:

Be rapidly effective against a broad spectrum of pathogens

Be non-toxic and biocompatible with ocular tissues

Be compatible with all lens materials

Condition lens surfaces for improved wettability and comfort

Minimize deposit formation from tear film components

Be easy to use and affordable

Achieving all these goals in a single product is challenging, but ongoing innovation continues to bridge the gap.

Understanding Modern Contact Lens Disinfection Systems

1. Multipurpose Disinfecting Solutions (MPS/MPDS)

These are the most commonly used systems due to their convenience. MPS solutions combine cleaning, rinsing, disinfecting, and storing functions.

Core Components:

Disinfectants: PHMB, PQ-1, MAPD, and Alexidine. Some combinations enhance anti-fungal and anti-amoebic activity.

Buffers & Tonicity Agents: Maintain pH and osmolarity.

Surfactants: Remove debris and improve wettability.

Demulcents: Enhance comfort during insertion.

Viscosity Agents: Control the thickness for better handling and comfort.

Chelating Agents: Enhance disinfectant efficacy by sequestering metal ions.

Clinical Considerations:

Disinfectant Cytotoxicity: PQ-1 based solutions show higher cytotoxicity in vitro, while PHMB has been linked to more clinical cases of solution-induced corneal staining (SICS).

Uptake and Release Dynamics:

Larger molecules are less readily absorbed into lenses.

Positively charged preservatives (e.g., PQ-1) interact strongly with negatively charged lens materials.

Surface tension and blink rate influence ocular exposure.

2. Hydrogen Peroxide (H₂O₂) Systems

Hydrogen peroxide remains the gold standard in antimicrobial efficacy. Modern systems use 3% H₂O₂ and a one-step neutralization process (via tablet or platinum disc catalyst).

Key Benefits:

Superior efficacy against bacterial, fungal biofilms, and Acanthamoeba cysts/trophozoites

Minimal residual toxicity after neutralization

No need for preservatives, reducing the risk of allergic responses

Improved end-of-day comfort compared to MPS

Challenges:

Requires strict patient compliance to avoid instilling unneutralized peroxide

Slightly more cumbersome regimen compared to MPS

Studies (e.g., Gabriel et al., 2021; Nichols et al., 2019) show that H₂O₂ outperforms MPS in antimicrobial activity, especially against biofilms and Acanthamoeba, with less corneal staining.

3. Povidone-Iodine Systems

A relatively newer addition, these systems combine:

Outer Core: Povidone-iodine (broad-spectrum antimicrobial)

Inner Core: Ascorbic acid and protease (neutralization and protein removal)

Advantages:

Effective disinfection within 4 hours

Continued antimicrobial activity for 7 days

Well-tolerated by users

Limitations:

May require additional surfactant cleaning

Aesthetic aversion to the temporary brown discoloration during disinfection

Katsuhide Yamasaki et al. (2018, 2021) demonstrated their efficacy against Pseudomonas biofilms and support their safety.

The Role of Surfactants: More Than Just Cleaning

Modern MPS solutions use Poloxamines (Tetronics) and Poloxamers (Pluronics) to enhance wettability and remove lipid/protein deposits. However, some components—especially Tetronic 1107—have been implicated in fluorescein hyperfluorescence and may contribute to SICS in sensitive wearers (Franklin et al., 2013).

Understanding these interactions is crucial, especially for symptomatic wearers or those with a history of solution intolerance.

The Biofilm Challenge: Hidden Threat in Lens Cases

Plastic lens cases are particularly vulnerable to biofilm formation, where microorganisms alter their metabolic states, increasing resistance to disinfectants.

Clinical Strategies to Mitigate Biofilm:

Encourage patients to replace their lens cases regularly

Promote mechanical cleaning with solutions

Use silver nanoparticle-impregnated cases—these release silver ions gradually, preventing bacterial adhesion and biofilm formation (Datta et al., 2019; Vijay et al., 2020)

Povidone-Iodine systems have also shown vapor-phase activity against biofilms during the neutralization process.

Acanthamoeba Keratitis: A Unique Disinfection Challenge

Acanthamoeba is a particularly hardy organism, existing in both active trophozoite and dormant cyst forms. Up to 90% of Acanthamoeba keratitis (AK) cases occur in contact lens wearers, and current MPS/MPDS products are largely ineffective against this organism.

What Works:

3% Hydrogen Peroxide: Effective against both forms.

Povidone-Iodine: Some efficacy against cysts.

Experimental Approaches:

Cellulase + chlorhexidine combo (Abjani et al., 2017) – promising but needs safety validation.

UV disinfection (Lonnen et al., 2014) – early-stage but effective in lab settings.

Best Practices:

Strong patient education—no water contact, no topping off solutions

Encourage daily disposable lenses when feasible

Advocate for regulatory updates in ISO protocols to test against Acanthamoeba

Regulatory & Testing Standards: The ISO Landscape

A wide array of ISO standards governs microbiological efficacy and biocompatibility:

ISO 14729: Standalone antimicrobial efficacy

ISO 18259: Efficacy in presence of lenses and lens cases

ISO 11986: Uptake and release testing of preservatives

ISO 18189 & 9394: Biocompatibility and cytotoxicity assessments

ISO 19045: Acanthamoeba encystment potential (but lacks efficacy requirements)

Despite this robust framework, no ISO standard currently mandates efficacy testing against Acanthamoeba cysts and trophozoites—a major gap in patient protection.

Practical Advice for Eye Care Practitioners

Individualize Recommendations:

Consider lens material, wear schedule, ocular health, and patient compliance when recommending care systems.

Avoid one-size-fits-all solutions.

Educate on Compliance:

Reinforce lens hygiene, case replacement, and hand washing habits.

Highlight the dangers of water exposure and topping off solutions.

Evaluate Symptoms Carefully:

Investigate SICS or discomfort not just in terms of lens fit, but also the biochemical interactions of solutions with the lens material.

Encourage Up-to-Date Practices:

Stay current on solution formulations and ISO standards.

Consider offering hydrogen peroxide systems to high-risk patients or those with recurring issues.

Final Thoughts

Modern contact lens care has made substantial advancements—but new challenges, especially from resistant pathogens like Acanthamoeba and biofilm-forming bacteria, require constant vigilance. As clinicians, we must balance evidence-based recommendations with practical, individualized care.

Hydrogen peroxide and povidone-iodine systems offer exciting opportunities to improve patient outcomes, particularly in cases where traditional MPS products fall short. At the same time, our role in educating patients and advocating for stronger testing protocols is more critical than ever.

Let’s move beyond convenience to compliance, and from generic recommendations to precision care.

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