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J. Merayo, A. Portero, D. Galarreta, N. Cortes, G. Rodriguez-Zarzuleo, V. De Juan, R. Martin, A. Mayo; Measurement of Corneal Sensitivity in Normal, Contact Lenses and Keratoconus Patients With the Belmonte Ocular Pain Meter (bpm), a Commercial Model of the Belmonte Non-Contact Gas Esthesiometer in Normal, Contact Lenses and Keratoconus Patients. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4347.
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To determine mechanical, chemical, and thermal sensation using the BPM, a commercial model of the Belmonte noncontact gas esthesiometer in normal, contact lens wear and keratoconus patients.
Both eyes of five normal subjects (3 males, 2 females, aged 26,4 years), 5 contact lens wearers (2 males, 3 females, aged 25,2 years) and 5 keratoconic patients with contact lens wear (3 males, 2 females, aged 28,2 years) were explored. Corneal sensitivity was measured with a newly developed commercial model of the Belmonte non contact gas esthesiometer (Belmonte’s Ocular Pain Meter (BPM), Deriva Sl, Valencia, Spain). Mechanical (air jets at flow rates from 0 to 200 mL/min, reaching the corneal surface at 34º C), thermal (cooled or warmed air at subthreshold flow rates changing corneal basal temperature +/-1 ºC), and chemical stimuli (air containing 0% to 80% CO2 at subthreshold flow rates and temperature at the cornea of 34 ºC) were applied to the center of the cornea to determine the sensitivity threshold for each stimulus modality. Patients indicated when the stimulus was felt and its thermal quality (cool or warm).
Thresholds in the normal, contact lenses and keratoconus groups were : Mechanical thresholds: 51,5 ± 10,81 ml/min, 59,5 ± 16,23 ml/min, and 68 ± 20,71 ml/min respectively; chemical thresholds: 63,1 ± 13,78 % CO2, 61,5 ± 14,73 % CO2 and 72 ±10,32 % CO2 respectively; thermal hot stimuli thresholds: 37,35 ± 1,8 ºC, 39,42 ± 0,62ºC and 39,18 ± 1,79ºC respectively and finally thermal cold stimuli thresholds: 32,28 ± 0,95ºC, 30,30 ± 0,73ºC and 29,79 ± 2,39ºC respectively.Differences in mechanical and chemical thresholds between the three groups did not reach statistical significance levels. Thermal cold thresholds were significantly lower in contact lenses (p<0,02) and keratoconus (p<0,005) eyes than in normal corneas, but not between them. Termal hot stimuli thresholds were significantly higher in patients with contact lenses (p<0,01) and with keratoconus (p<0,03) than in control patients, but not between them.
Contact lens wear with or without keratoconus change thermal sensitivity of the cornea and eventually could make an alteration of the ocular surface homeostasis.
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