A novel method to evaluate residence time in humans using a nonpenetrating fluorescent tracer.
Invest Ophthalmol Vis Sci
; 43(4): 1032-9, 2002 Apr.
Article
em En
| MEDLINE
| ID: mdl-11923244
ABSTRACT
PURPOSE:
The purpose of these investigations was to develop an improved method for measuring precorneal residence time (RT) and to demonstrate its efficacy with novel formulations.METHODS:
A biomicroscope was adapted for use as a clinical fluorometer. Using a nonpenetrating fluorescent probe (FITC-dextran, 70,000-73,000 molecular weight [MW]), RT was estimated as the time to return to baseline (gross RT) and from parameters derived from least-squares regression fits to the decay data (area under the curve [AUC], elimination rate, and time for 50% of the signal to be eliminated [T(50)]). One rabbit and two human studies were conducted. The studies were randomized, double-masked, and controlled. Repeatability in humans was examined in 15 subjects (six determinations per subject, n = 90 total).RESULTS:
The FITC-dextran tracer did not penetrate into corneal tissue. The rabbit gross RTs were 14.5, 15.0, and 16.0 minutes for three low-viscosity solutions (eta = 2.7-7.7 mPa/sec) and 22.5 minutes for a more viscous solution (eta = 357 mPa/sec). For a high-viscosity (eta approximately equal 30,000 mPa/sec) gel in humans, the method demonstrated approximately a twofold increase in gross RT and AUC compared with buffered saline. Repeatability of the method appeared acceptable, with intersubject variability the most significant factor affecting precision.CONCLUSIONS:
The new method is safe and convenient and offers comprehensive RT data. Furthermore, it appears to differentiate among formulations. However, as with other tear-influenced parameters, there is significant variability. Thus, sufficient sample sizes are necessary for meaningful comparative investigations.
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Base de dados:
MEDLINE
Assunto principal:
Dextranos
/
Fluoresceína-5-Isotiocianato
/
Córnea
/
Técnicas de Diagnóstico Oftalmológico
/
Corantes Fluorescentes
Tipo de estudo:
Clinical_trials
/
Prognostic_studies
Limite:
Adult
/
Animals
/
Female
/
Humans
/
Male
/
Middle aged
Idioma:
En
Revista:
Invest Ophthalmol Vis Sci
Ano de publicação:
2002
Tipo de documento:
Article
País de afiliação:
Estados Unidos