Measurement of the pulsatile ocular dynamics of the
human eye for glaucoma diagnosis.
Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 131 p.
The objective of this thesis work is to design a non-invasive diagnostic instrument
to study the biomechanical properties of the eye and test the potential of this
instrument for the early diagnosis of glaucoma.
G1aucoma is an eye disease in which the vision loss is permanent. The present
diagnostic methods are unable to detect glaucoma in its initial stages. It
commonly takes several years following the onset of the disease in order to
identify people with glaucoma. A new diagnostic instrument that could detect
glaucoma at its onset is highly desirable. It has been shown in numerous studies
that pulsatile ocular blood flow plays a major role in glaucoma. The ocular blood
flow drives the mechanical pulsations of the eye. As both ocular blood flow and
ocular biomechanics are altered in glaucoma, it can be assumed that the
mechanical pulsations driven by ocular blood flow would also be altered. A
device capable of measuring such pulsations could potentially be used as a new
diagnostic tool for glaucoma.
In previous works, the pulsatility of the eye has been measured using tonometer-based
technologies, which measure the variations in the intra ocular pressure at
the cornea. These instruments do not measure mechanical displacement of ocular
tissues. Furthermore, most of the tonometer-based technologies have to make
contact with the eye in order to perform such measurements. As contact
techniques are not preferred for the reasons such as infection and damage to the
eye, technologies that require no contact with the eye were sought. Technologies
such as ultrasonic transducers, laser interferometry and low-coherence
interferometry have been used to measure one or the other aspect of the ocular
pulsations. Ultrasonic transducers were shown to measure the corneal axial
displacements, but could not be applied to measure the pulsations of the interior
ocular tissues, such as the retina. In glaucoma it could be more interesting to
measure the pulsatility of the retina rather than that of the cornea. Therefore
technologies such as laser interferometry and low coherence interferometry have
been applied by sorne research groups.
In this thesis work, a device based on Fourier-domain low-coherence
interferometry was developed. The device was first tested on live animals, such as
rabbits and rats, and then further tested on human subjects recruited at the
Research Center of the Hospital Maisonneuve-Rosemont. The developed device
could measure simultaneously the pulsations of the comea and the retina. In the
later part of the thesis work, a comparative study between glaucoma and nonglaucoma
subject was performed.
The results obtained suggest that the pulsations of the ocular tissues, such as the
comea and the retina, are larger in patients with glaucoma compared to normal
subjects. The developed device provides for the first time an opportunity to study
the pulsations of the comea and the retina simultaneously and at video rate, with a
displacement resolution as small as 400 nm. This allows the researchers and the
clinicians to measure the biomechanical properties of the eye and study their role
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