Congenital Insensitivity to Pain: A Case Report With Corneal Esthesiometry and In Vivo Confocal Microscopy
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Updated: Oct 14, 2025
Author Spotlight: Establishing a Practical and Cost-Effective Protocol for Corneal Sensitivity Testing in Clinical Settings
Published on: August 2, 2024
Jeremy D Keenan1,2, John A Gonzales1,2, Stephen G Waxman3,4
1Department of Ophthalmology, University of California, San Francisco, San Francisco, CA.
Purpose:
To report the findings of a comprehensive eye examination from an individual with congenital insensitivity to pain because of loss-of-function mutations in the SCN9A gene.
Methods:
Ophthalmologic examination and confocal microscopy were performed on a patient with congenital insensitivity to pain.
Results:
A 39-year-old man with compound heterozygous mutations in the SCN9A gene underwent examination. Cochet-Bonnet esthesiometry readings averaged 38 mm (SD 8 mm) in the right eye and 55 mm (SD 7 mm) in the left eye. Other corneal findings included mild conjunctival lissamine green staining, nonvisually significant corneal scars, mild anterior basement membrane dystrophy, and a tear breakup time of 3 seconds in each eye. In vivo confocal microscopy of the corneal subbasal nerve plexus revealed relatively normal corneal nerve morphology, but a reduction in corneal nerve fiber density.
Conclusions:
An individual with loss-of-function mutations in SCN9A had reduced corneal nerve fiber density but normal corneal mechanoreception.
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