| Abstract |
Τhe definition of ocular scattering is the incident change of the propagating
direction of light due to the non- uniformities of the optical medium of the eye (tears,
cornea, lens, vitreous humor) . The ocular scattering can cause blur vision, loss of
colours and loss of contrast of the retinal image. Ocular scattering is measured
through optical set-ups such as the double pass set-up which is purposed to measure
scattering directly and quantifying it via the point spread function (PSF).
There have been many attempts for the mathematical description of scattering. The
inception was made by Stiles and Holladay in 1930 where they proposed the
description of scattering with a function containing the PSF. The function that is
commonly used in the literature the last few years is the Commission International d’
Eclairage (CIE) glare function (1999) proposed by Voss and Van den Berg. The CIE
glare function involves parameters of the eye such as age and iris pigmentation ,and is
evolved by psychophysical measurements in a major number of normal eyes.
The difficulty of the project lies in the direct measurement of the PSF with the help
of a point source due to the small intensity of the scattered light in angles bigger than
a few minutes of arc. For this purpose, the method of optical integration is evolved
with which it is proven that the ratio between the PSF within a disc of radius r , and
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the total PSF is equal to the ratio between the intensity in the center of the disc of
radius r and the intensity of a disc with a theoretically infinite radius.
The primary purpose of the study was the implementation of the optical integration
method for measuring scattering data held by double pass set-ups.
Certain functions were chosen and evaluated for the outright description of PSF ,
which were predicated in non psychophysical characteristics, with independent
variables that fit unexceptionably to the CIE glare function. The function that was
chosen finally was the sum of two individual functions, one of which describes the
PSF peripheral portion and the other which describes the PSF central portion. On the
other hand, a coefficient A was assigned, which was called the scattering coefficient
and denotes the percent of the scattered light .
The main question in this subject was whether there is a possible way of analytical
calculation and estimation of the distribution of light in the retinal plane after the first
pass. After calculation, it was observed that such a problem is unsolvable. Therefore,
the obtained PSF from double pass data was estimated in arithmetic means via the
convolution theorem.
By collecting experimental data from single and double pass measurements the
functions were evaluated and fitted in the data sets. The fitting in the data sets was
held by the implementation of the optical integration method. Thus, scattering was
evaluated and measured in angles bigger that 1 degree , where scattering has the
primary role over the properties of vision.
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Μέθοδοι οπτικής ολοκλήρωσης για τη μέτρηση της σκέδασης σε διατάξεις διπλής διέλευσης
