In-Office Procedures · Diagnostic
Corneal Sensitivity Testing
Corneal esthesiometry measures corneal nerve function, the part of the workup the tear film tests miss. It is how you separate a numb, neurotrophic surface from a hypersensitive, neuropathic one.
Key points
- Esthesiometry quantifies corneal sensitivity, a direct marker of corneal nerve health.
- Reduced sensitivity points toward neurotrophic keratitis.
- Pain out of proportion to signs points toward neuropathic ocular pain.
- The Brill esthesiometer is a portable, non-contact, air-pulse device with five stimulus levels.
What it is
Esthesiometry measures the threshold at which the cornea perceives a stimulus. The traditional method is the Cochet-Bonnet filament, which touches the cornea with a nylon thread of variable length. The Brill Corneal Esthesiometer is described as the first portable, non-invasive esthesiometer, using a calibrated puff of air rather than contact.
How it works
The device delivers controlled air pulses at five graded intensities toward the cornea. The lowest intensity the patient reliably perceives reflects corneal sensitivity. Because it is non-contact, it avoids the surface contact and variability of filament testing, and it can be mounted on a slit lamp or used hand-held.
The science
Corneal nerves sense the environment, drive reflex tearing, and regulate the blink, the loop often called the lacrimal functional unit. When sensation drops, in neurotrophic states after refractive or cataract surgery, herpetic disease, diabetes, or long-term drop use, that feedback loop and surface healing are impaired. At the other extreme, neuropathic ocular pain presents as significant pain with minimal visible signs, sometimes called pain without stain.
Clinical evidence
- TFOS DEWS III (2025) recognizes neurosensory abnormalities as part of dry eye disease, supporting assessment of corneal sensation when symptoms and signs diverge. American Journal of Ophthalmology
- Brill Engines describes the first portable, non-invasive corneal esthesiometer, using controlled air-pulse stimuli at five levels. Brill Engines
Where it fits
Reach for sensitivity testing when symptoms and signs diverge, when neurotrophic risk is present, or around ocular surgery. A numb cornea points toward neurotrophic support and protection, while a hypersensitive one points toward neuropathic pain pathways, two problems that look similar but are managed very differently. The Brill device is manufacturer-direct; we point you to Brill Engines for purchase and training.
Sources are linked inline above. Device descriptions reference FDA clearance status, published peer-reviewed studies, and manufacturer data. Clinical outcomes are not a guarantee of individual results. Review full prescribing information, the IFU, and FDA clearance documentation for each device before use.
