Making Corneal Sensation Testing Accessible: Bench Validation of a Low-Cost Adjustable Monofilament Aesthesiometer

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Medical Devices

Background:

• Corneal sensation testing is crucial for diagnosing and monitoring neurotrophic keratopathy.
• The gold-standard Cochet-Bonnet (COBO) aesthesiometer is expensive and not widely available.
• Current alternatives like cotton wisps are qualitative and lack sensitivity.

Purpose of the Study:

• To evaluate a generic adjustable monofilament corneal aesthesiometer (GAMCA) for its ability to replicate COBO performance.
• To assess the feasibility of fabricating a low-cost corneal aesthesiometer using commodity materials.

Main Methods:

• A GAMCA was constructed for approximately £10.28, featuring an adjustable nylon monofilament.
• Two devices were validated against published COBO reference pressures using precision balance and corneal phantom testing.
• Agreement was analyzed using Bland-Altman analysis, regression, and correlation statistics.

Main Results:

• The GAMCA demonstrated a consistent pressure-length relationship, aligning with beam mechanics.
• Near-perfect rank-order correspondence with COBO was observed (Pearson's r = 0.998-0.999).
• Acceptable repeatability and bias were noted across different humidity levels.

Conclusions:

• A cost-effective corneal aesthesiometer replicating COBO principles can be built for about 1% of the cost.
• The GAMCA shows preserved rank-order fidelity and acceptable repeatability.
• This device is suitable for community screening, ward-based settings, and resource-limited environments, warranting further clinical validation.