In-Office Procedures · Diagnostics
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 device using controlled air pulses.
- It runs at five stimulus levels and works on a slit lamp or hand-held.
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 graded intensities, five levels, toward the cornea. The lowest intensity the patient reliably perceives reflects corneal sensitivity. Because it is non-contact, it avoids the surface contact and length-by-length variability of filament testing, and it can be mounted on a slit lamp or used hand-held. Brill Engines product information.
The science behind it
Corneal nerves are central to the ocular surface. They 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. Consistent with TFOS DEWS III neurosensory findings.
Where it fits
Reach for sensitivity testing when symptoms and signs diverge, when neurotrophic risk is present, or around ocular surgery. The result changes management: 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 treated very differently.
Sources: Brill Engines product information; TFOS DEWS III neurosensory framework.
Two patients can describe the same misery. Nerve testing tells you whether you are treating a cornea that feels too little or one that feels too much.
Frequently asked questions
Do you sell this device?
Corneal esthesiometry is a manufacturer-direct device. We point you to Brill Engines for purchase and training.
When should I reach for it?
Consider it for neurotrophic risk such as post-surgical, herpetic, or diabetic eyes, and for patients with strong pain and minimal staining.
Is it contact or non-contact?
The Brill device uses controlled air pulses, so it is non-contact, unlike the traditional Cochet-Bonnet filament.
What does a low reading mean?
Reduced corneal sensitivity suggests impaired corneal nerve function and raises the possibility of neurotrophic disease, which changes how you protect and treat the surface.
How does it compare with the Cochet-Bonnet?
Both assess sensitivity. The air-pulse approach is non-contact and graded, which many clinicians find more repeatable and more comfortable for the patient.
