Selective changes in human corneal sensation associated with herpes simplex virus keratitis

Area of Science:

• Ophthalmology
• Neuroscience
• Corneal Physiology

Background:

• Herpes simplex virus (HSV) keratitis is a common cause of corneal blindness.
• Understanding the impact of HSV keratitis on corneal sensitivity is crucial for managing ocular surface disease.
• Previous studies have indicated potential alterations in corneal sensation following HSV infection.

Purpose of the Study:

• To quantify corneal sensitivity to mechanical, chemical, heat, and cold stimuli in patients with a history of HSV keratitis.
• To compare sensory responses between affected eyes, fellow eyes, and healthy controls.
• To elucidate the specific sensory modalities affected by HSV keratitis.

Main Methods:

• Corneal sensitivity was assessed in 16 patients with unilateral HSV keratitis and 10 healthy controls using the Belmonte gas esthesiometer.
• Mechanical, chemical (CO2), heat, and cold stimuli were applied to the central cornea.
• Subjective intensity perception and sensory thresholds were evaluated for each stimulus type.

Main Results:

• Corneal sensitivity to mechanical and heat stimuli was significantly reduced in eyes with HSV keratitis.
• Patients with HSV keratitis showed impaired ability to identify the intensity of mechanical, chemical, and heat stimuli.
• Corneal sensitivity to cold stimulation was not significantly altered in HSV keratitis patients.

Conclusions:

• HSV keratitis leads to significant impairment of corneal sensitivity to mechanical and thermal (heat) stimuli.
• Findings suggest axonal damage and/or altered ion channel expression in corneal nerve terminals.
• Corneal cold-sensitive nerve terminals appear to be relatively preserved following HSV keratitis.