Abstract
Purpose: :
To determine and compare mechanical, chemical and thermal sensitivity in patients with keratoconus.
Methods: :
120 eyes of 63 patients were divided in three groups. Corneal sensitivity was measured with Belmonte's non-contact gas esthesiometer (Ocular Pain Meter, Deriva, Spain). Mechanical (air jets at flow rates from 0 to 200 mL/min, reaching the corneal surface at 34 °C), chemical (air containing 0% to 80% CO2 at subthreshold flow rates and temperature at the cornea of 34°C), and thermal stimuli (cooled air at subthreshold flow rates changing corneal basal temperature +/-1 °C) were applied to the cornea to determine the sensitivity threshold for each stimulus modality.
Results: :
Control group consisted in 24 eyes from 12 patients with normal corneas, mean age of 38.62 + 11.83 years. Mean mechanical thresholds: 84.16 + 38.52 mL/min, chemical thresholds: 31.87 + 13.00% CO2, and thermal hot stimuli thresholds: 23.66 °C. Keratoconus non-contact lens users group: 49 eyes from 27 patients, mean age of 31 + 8 years. Mean mechanical thresholds: 92.02 + 32.06 mL/min, chemical thresholds: 36.97 + 14.61 % CO2, and thermal hot stimuli thresholds: 23.97 °C. Keratoconus contact lens users group: 47 eyes of 24 patients, mean age of 33 + 11 years. Mean mechanical thresholds: 109.46 + 41.52 mL/min, chemical thresholds: 37.93 + 16.91 CO2, and thermal hot stimuli thresholds: 24.38°C.
Conclusions: :
Keratoconus patients showed corneal hypoesthesia after mechanical and chemical stimulation, increased in contact lens users.
Keywords: cornea: clinical science • keratoconus • perception