The measurement of blood flow in the ocular fundus is of scientific and clinical interest. Investigating ocular blood flow
in the choroid may be important to understand the pathogenesis of numerous ocular diseases, such as glaucoma or agerelated
macular degeneration (AMD). Laser Doppler flowmetry (LDF) was applied to measure relative velocity, volume
and flux of red blood cells in the tissues of human eye. Its main application lies in the possibility of assessing alterations
in blood flow early in the course of diseases. The purpose of the present study was to investigate the effect of pupil
dilatation with one drop of 1% tropicamide on blood flow in the foveal region of the choroid of the human fundus. The
blood flow parameters were measured in 24 eyes during 30 minutes (one measurement in every 3 minutes) after the
application of the drop. Since the Doppler parameters depend on the scattering geometry, which may change as the pupil
dilates; an artificial pupil of 4mm in diameter was placed directly in front the eye. Following the administration of
tropicamide the mean pupil diameter was increased from 3.29 mm to 8.25 mm (P<0.0001, Paired student t-test). In
comparison to the baseline values, the data shows no significant increases were observed in velocity, volume, and flow
with 4 mm artificial pupil (0.2%, 1.3%, 0.8% respectively) and a statistically significant increases were observed
without artificial pupil (10.7%, 13.9%, 12.8% respectively) following the application of tropicamide.
Laser Doppler flowmetry (LDF) is a technique used to measure relative average velocity, number and flux (number
times velocity) of red blood cells in vessels or capillaries. In this study, the effect of topical timolol on the choroidal
circulation was investigated in 12 healthy subjects. Maximum velocity of red blood cells and volumetric blood flow rate
in sub-foveal choroids are determined in each eye just before instillation of drops and then every 30 min upto 2 hours.
Average intraocular pressure (IOP) decreased significantly in the timolol-treated eyes compared to that of placebo-treated
eyes. Nevertheless no significant differences in choroidal blood hemodynamic between timolol and placebo-treated
eyes were observed.
Ocular fundus reflectometry is a technique aimed at the in-vivo measurement of the reflectance of the tissues of the
ocular fundus. Studies have demonstrated a correlation between optical and physiological properties of such tissues in
humans and the existence of a control mechanism, called neuro-vascular coupling (NC), which adjusts local blood
perfusion to support vision-induced neural activity. We developed an instrument for functional imaging of the neural
tissues of the ocular fundus based on reflectance measurements to study the NC. The images acquired with the
instrument needed processing to work out reflectance time-courses. The algorithm exploited previously requires long
computational time, provides poor discrimination of objects and need manual intervention. We have developed a fully
automatic algorithm based on differential multiscale framework for the processing of the images of the ocular fundus
with reduced computational time. This algorithm is reasonably efficient to determine relative translational displacement
(translation and rotation) between the images and also to remove the geometric distortion. Simulation results performed
on the fundus images show that differential multiscale framework based image registration reduces computational times
up-to one fourth of the time required by the general purpose algorithm, and provides better alignment precision.
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