ABSTRACT
The volume of tears in the eye depends on the rate of production and the rate of elimination by drainage and evaporation. A mechanism for the regulation of tear production mediated through changes in tear tonicity has been suggested. High evaporation of tears with a patent drainage system has been thought to be related to reduced tear volume, increased tonicity and an eventual stimulus to production. In this study no significant correlation was found between tear evaporation, measured by a modified evaporimeter system, and tear production, as measured by the turnover rate with a scanning fluorophotometer. This result suggests that regulation of tear production through the mechanism of tonicity change may not be the only, or principal, mechanism in the normal eye.
Subject(s)
Tears/metabolism , Adult , Female , Fluorophotometry , Humans , Lacrimal Apparatus/physiology , Male , Tears/physiologyABSTRACT
We found a correlation between accommodative amplitude and lens fluorescence in a small population of subjects of nearly the same age. This supports the hypothesis that aging changes of the lens, including presbyopia, are related to lens growth.
Subject(s)
Accommodation, Ocular/physiology , Fluorescence , Lens, Crystalline/physiology , Adult , Aging/physiology , Fluorophotometry , Humans , Lens, Crystalline/growth & development , Pilot ProjectsABSTRACT
A Beer-Lambert analysis of fluorophotometric scans of ocular lenses has been carried out. It is shown that an assumption of a single flourophor allows us to calculate the distribution of this fluorophor along the central lens axis. For the great majority of lenses in our study, covering a wide range of ages, our results are in essential agreement with published results on excised lenses. For a small subset of lenses in the study the assumption of a single fluorophor is found to be unsatisfactory. In these cases a reasonable symmetry assumption allows us to estimate the distribution of an additional agent which removes light from the entering or exiting beams without contributing to the fluorescence. The fact that this agent is restricted to the lens nucleus and that it occurs in lenses in which nuclear changes are clinically evident suggests that it is an expression of nuclear cataract.
Subject(s)
Aging/metabolism , Fluorophotometry , Lens, Crystalline/metabolism , Adult , Aged , Aged, 80 and over , Fluorescence , Humans , Mathematics , Middle AgedABSTRACT
Measurement of tear turnover rate using an automated scanning fluorophotometer (FluorotronR) was compared to Schirmer test results without anesthesia in young adults with no known ocular disorder. After the instillation of fluorescein, tear film fluorescence, expressed as fluorescein concentration equivalent, decreased exponentially in a linear fashion with time. The mean tear turnover rate was 30% per minute. Contact lens wearers had higher mean tear turnover rates when compared with non-contact lens wearers, but differences were not statistically significant. Half of tested eyes demonstrated total wetting of Schirmer Tear Test StripsR. Higher mean tear turnover rates were associated with complete wetting of the Schirmer test strips. There was no significant correlation between Schirmer paper wetting of less than 30 mm and fluorescein turnover rate.
Subject(s)
Tears/metabolism , Adult , Contact Lenses , Female , Fluoresceins , Humans , Male , PhotofluorographyABSTRACT
Lenticular autofluorescence in a diabetic population was quantitated by scanning ocular fluorophotometry. Measurements were made through the lens along the optical axis. The profile of the scan from front to rear was characterized by anterior and posterior juxtacortical peaks and a central plateau. Maximum fluorescence values were compared with those of nondiabetic control subjects. Fluorescence increased linearly with age in both populations, but was significantly higher in the diabetic population of all ages. Posterior to anterior fluorescence peak ratios decreased as a parabolic function of age in both populations, but peak ratios were lower in the diabetic population. We conclude that in vivo measurements of lens autofluorescence correlate with premature lenticular senescence in diabetes.
Subject(s)
Diabetes Mellitus/metabolism , Fluorescence , Lens, Crystalline/metabolism , Adolescent , Adult , Aged , Aging , Cataract/diagnosis , Cataract/metabolism , Child , Crystallins/metabolism , Female , Fluorometry , Humans , Male , Middle Aged , Spectrometry, FluorescenceABSTRACT
We quantitated blue-green light transmission and autofluorescence of the human crystalline lens in vivo, using an automated scanning fluorophotometer (Fluorotron) coupled with a lens system designed for high resolution of the ocular anterior segment. Lenses were scanned through the dilated pupil along the optical axis, generating a fluorescence profile consisting of anterior and posterior juxtacortical peaks and a central plateau. Fluorescence increased linearly with increasing age. We calculated percent transmission of excitation (410-500 nm) and emission (510-670 nm) as the ratio of posterior to anterior juxtacortical peaks. Light transmission decreased as a parabolic function of age and was correlated with both fluorescence increase and observed lens brunescence.
