| Abstract |
Decreased quality of vision, may be detrimental for the quality of life. The optical
system of the eye, is responsible for the formation of the retinal image, and the quality of
the optical system of the eye, determines the quality of vision. In young and healthy eyes,
cornea and crystalline lens are practically transparent and the image formed in the retina,
is mainly affected by aberrations and diffraction from the pupil. Pathologies, injuries and
age related changes in the optical system of the eye can raise scatter phenomena, that
possibly have an impact on visual performance. Light scatter, is also an outcome of the
refractive surgery, which in our days is often used for the correction of refractive errors
of the eye Light-tissue interaction is an interesting subject for scientific community in
vision science.
Aim of this thesis, is the study of light scatter in the human eye. A new physical
model is proposed, based on glass microspheres (Jaygo Co.) dissolved in 20% collagen
solution. Collagen solution consists of collagen from porcine skin and Carraggeenan
Kappa. Objective single pass measurements were performed on scatter samples of the
new model, with optical setups that were developed for the purpose of this thesis.
Analyzing the 4th Purkinje image, is considered to be a new promising method, that was
developed for scatter measurement in vivo. In addition psychophysics measurements of
light scatter were performed, in contact lenses containing microspheres, developed by
Menicon Co. This model may be used for the calibration of scatter-measuring systems as
well as for future psychophysical measurements.
Objective scatter measurements were performed based on optical setups that were
developed, and scattered light was measured after a single pass from the scattering
medium. Scattering samples of different thickness, consisted of glass microspheres,
dissolved in collagen solution, in different concentrations. Scatter contact lenses were
also developed from Menicon Co., containing glass microspheres. Double pass
measurements performed, using a modified commercial wavefront analyzer, Wavelight
Allegretto available in the V.E.I.C (Vardinogianion Eye Institute of Crete) for clinical
use. At the same time, a new setup was developed, in order to measure light scatter in the
human eye in vivo, based on analyzing 4th Purkinje image. The final step of scatter
measurements was to perform psychophysics measurements of light scatter in healthy
eyes, wearing scatter contact lenses with the commercial straylight meter C-Quant 80000,
Oculus, kindly granted from Tom van den Berg.
A linear relation was found between BR (part of the light that does not meet any
scatterer on its optical path) and microspheres concentration. This relation was validated
from a second setup developed for the study of scatter profile, based on single pass
measurements as well. A small deviation was found between the BR estimated from
single and double pass experiments. This difference may be attributed to the different
assumptions in the calculations employed in the two methods. Low scatter levels were
produced from the scatter contact lenses measured by means of single pass experiments,
and the results were validated from the psychophysics measurements. Objective and
subjective measurements could be only qualitative and not quantitative related, due to the
different metrics used. The results from in vivo scatter measurements showed that small
modifications in the developed setup, can lead the analysis of the 4th Purkinje to a new
promising method for scatter measurements in the human eye.
The results of this study showed that the proposed physical model can reproduce
light scatter that is usually measured in human eyes, the first period after refractive
surgery. Scatter contact lenses, reproduced light scatter that clinical often expect in the
early stages in pathology eyes. These results were validated from psychophysics
measurements performed with C-Quant Straylight meter. At the end, analyzing 4th
Purkinje showed up to be a new promising method for the in vivo scatter measurement in
human eyes.
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Ένα φυσικό μοντέλο που προσομοιώνει την σκέδαση στον κερατοειδή μετά από επεμβάσεις διαθλαστικής χειρουργικής βασισμένο σε μοκροσφαιρίδια γυαλιού εμποτισμένα σε διάλυμα κολλαγόνου
