Evaluation of Corneal Sensitivity: Tools We Have.

Corneal sensitivity is an important indicator of corneal health and innervation. Corneal hypoesthesia may be an early indicator of corneal diseases such as neurotrophic keratopathy. Various instruments have been used to measure corneal sensitivity, the first being the Cochet-Bonnet aesthesiometer. Over the years, new devices employing different stimuli have been developed, such as the gas-based Belmonte aesthesiometer, the Swiss liquid-jet aesthesiometer, and the most recently released corneal Brill aesthesiometer. In this review, the progress and advancement of aesthesiometers since their introduction is described. The mechanism, advantages, and disadvantages of these aesthesiometers are discussed and compared. We also report the relationship between corneal sensitivity and corneal innervation in various conditions, including diabetes mellitus, Fuchs' endothelial dystrophy, dry eye disease, glaucoma, keratoconus, herpes simplex keratitis, post-refractive surgery, and ocular graft-versus-host disease. Through this review, we aim to highlight the importance of the assessment of corneal sensitivity and innervation in the diagnosis, treatment, and monitoring of anterior and posterior segment ocular disorders.