Esthesiometer

Abstract: PURPOSE The aim of this investigation was to evaluate a prototype noncontact pneumatic esthesiometer for measuring sensitivity of the eye. METHODS To evaluate the instrument's repeatability, central corneal sensitivity was recorded on two separate occasions with a 24-h interval between the two measures. In a separate experiment, corneal edema was induced with a thick hydrogel lens, and the eye was closed and patched. Corneal sensitivity was measured before wearing the lenses for 3 h, immediately after lens removal, and 15 min later. Corneal sensitivity also was measured before the instillation of a single drop of proparacaine (Alcaine, 0.5%) and at 2 and 18 min later. Sensitivity was measured at the corneal apex and at a temporal conjunctival location 3 mm from the limbus. RESULTS A high correlation was found between days 1 and 2 (r = 0.90; p = 0.0001). The coefficient of repeatability (COR = 0.87 mm Hg) showed that 95% of the difference between test and retest measures were between +/-0.87 mm Hg. Corneal sensitivity decreased by 55% after lens-induced corneal swelling and by 159% after instillation of the topical anesthetic. Central corneal sensitivity was found to be significantly higher than that of the temporal conjunctiva (p = 0.0001). CONCLUSION We conclude that this pneumatic esthesiometer provides repeatable and reliable measures of ocular-surface sensitivity.

Abstract: Purpose We used a prototype gas esthesiometer to measure corneal threshold sensitivity values for mechanical, chemical, and thermal stimuli. We also evaluated the reproducibility of the esthesiometer measurements, the influence of previous corneal symptoms, and the safety of this technique. Methods Forty healthy subjects participated in the study. Mechanical, chemical, and thermal (hot and cold) thresholds were determined at the center of the cornea using a prototype Belmonte's gas esthesiometer. To determine reproducibility of the results, the sensitivity thresholds were measured for each eye on 2 days. Corneal fluorescein staining and bulbar hyperemia after completion of the tests were analyzed. Results There were no differences for any sensitivity threshold between eyes or between the first and second esthesiometries. The reproducibilities of mechanical and hot thresholds were higher than for chemical and cold thresholds. Men had significantly higher chemical intensity thresholds than did women (men: 23.50 ± 5.10; women: 10.20 ± 2.16, P = 0.021). There were no alterations of the ocular surface after completion of the measurements. Conclusions Mechanical, chemical, and thermal corneal sensitivity thresholds in the central cornea have been established in healthy men and women of different age groups. The use of the Belmonte gas esthesiometer is safe and reproducible, with the highest reproducibility in determining mechanical and hot thresholds.

Abstract: Purpose The purpose of this study is to determine the association between corneal sensitivity measured using a pneumatic esthesiometer and eye color quantified objectively. Methods Twenty subjects had ocular surface sensitivity measured using a Belmonte esthesiometer. An ascending method of limits followed by the method of constant stimuli were used to estimate 1) cold detection thresholds, 2) discomfort detection thresholds (both using pneumatic stimuli at 20 degrees C, 3) mechanical detection thresholds using pneumatic stimuli at 50 degrees C (ocular surface temperature approximately 33 degrees C), and 4) percent CO2 chemical detection thresholds using 50 degrees C pneumatic stimuli at flow rates set at half of each subject's pneumatic detection threshold (therefore detected by the chemical content and not the mechanical content). Eye color was estimated 1) clinically by two observers ranking the color (light to dark) of digital images of each subject's iris, 2) photometrically by measuring iris luminance, and 3) using chromaticity obtained from a Photo Research 650 spectroradiometer with controlled illumination. Correlation and linear and nonlinear regression analyses were used to examine relationships between variables. Results There were no associations between eye color (determined clinically or objectively) for mechanical and chemical detection thresholds (best r = 0.15, all p > 0.05). There was a significant linear association between 20 degrees detection thresholds and eye color (r = 0.39), which was substantially improved with a two-line function (part level and part increasing linearly, r = 0.65). Conclusions We were generally unable to demonstrate the relationship between eye color and sensitivity reported previously using a Cochet-Bonnet esthesiometer. However, for a subset of subjects with palest irises, there appears to be a linear association between eye color and sensitivity to cooling stimuli.

Abstract: E-mail: Olesya_zavoloka@yahoo.com Purpose: To develop a novel non-contact corneal esthesiometer and to determine the efficacy of this meter in assessing the neurotrophic status of the cornea in type I diabetic mellitus (T1DM) patients with bacterial keratitis. Material and Methods: We developed a novel non-contact corneal esthesiometer and determined the efficacy of this meter in assessing the neurotrophic status of the cornea based on examination of 30 T1DM patients with bacterial keratitis and 30 healthy individuals. Results: A corneal sensitivity assessment technique using our novel non-contact corneal esthesiometer was found to be non-invasive, accurate and repeatable. The use of low-temperature air jets in non-contact esthesiometry results in improved accuracy. Corneal sensitivity examination at nine specified points and calculation of mean corneal sensitivity threshold allows for a more comprehensive corneal function assessment, with account of the peripheral cornea. Conclusion: A significantly decreased corneal sensitivity was found in T1DM patients with bacterial keratitis. Our newly developed non-contact corneal esthesiometer was found to be effective in assessing the neurotrophic status of the cornea in T1DM patients with bacterial keratitis.