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Identifier 000414485
Title Light scatter in eye and its impact on vision
Alternative Title Η ενδοφθαλμία σκέδαση και επίδραση της στην όραση
Author Sahin, Onurcan
Thesis advisor Σιγανός, Χαράλαμπος
Παλλήκαρης ,Ιωάννης
Τσιλιμπάρης, Ιωάννης
Reviewer Ταρουδάκης, Μιχαήλ
Τσατσάκης, Αριστείδης
Δετοράκης, Ευστάθιος
Παπαζογλου, Δημήτριος
Abstract Introduction The vision is the most fundamental and the most complex sense in the evolution progress. Although, the complete process of the visual function has not been fully understood, there are several essential factors take part in the vision. The optics of the eye, the retina, and the visual cortex should be considered as a complete structure while evaluating the visual performance. The interaction between the light and the structures of the eye determine the quality of the retinal image which is the key factor for the visual performance. Two different interaction mechanisms of the light and the eye exists. The first mechanism is the optical interactions, which is detailed as optical properties of the eye and the second mechanism is detailed as the material properties of the eye. It is very important to understand and distinguish the difference between these two mechanisms. In order to have the good vision or in other words good retinal image quality, having the best refraction is as important as having transparent optics and clear optical way. Amount of the irregularities or defects induce straylight in the eye. Although, effects of intraocular scattering exist for ages and observed in the clinical practice, the knowledge and understanding of the intraocular scattering is not as good as the understanding of the refraction or aberrations. We believe that a complete analysis of visual performance will only be completed with analyzing the intraocular straylight. In this thesis, a novel optical device for measuring forward intraocular scattering with double pass method is developed and results are shown. The relevant chapters focus on several studies which worked on measuring, quantifying and understanding of the straylight phenomenon. Methods The proof of concept, repeatability, functionality of the device was tested with either in test or clinical conditions. The first study on the proof and concept and constancy evaluations were performed on an artificial eye and previously documented lenses. The straylight difference were evaluated of the artificial eye between different hard contact lenses which induce different amount of straylight. The second study was performed with an artificial eye for determining the effect of defocus on the measurements. The measurements were collected by changing the position of the retina which was corresponding inducing myopia or hyperopia. Additionally, the repeatability and the effect of axial alignment of the pupil camera was tested by taking consecutive measurements from the different axial positions from a healthy eye of a subject. In the third study, the scattering difference between healthy subjects and the effect of different diffusing filters which induce straylight were measured. Measurements with and without lenses and were evaluated. The final studies were performed under clinical conditions with healthy subjects and cataract patients. Optical and psychophysical measurements were performed as well as the LOCS III grading in these studies. Correlation between two methods of measuring intraocular scattering and LOCS III grading system were evaluated. Results Outcomes of these study showed the system is capable of detecting the amount straylight between different scatterers. The results also showed that the system is capable of detecting different amounts of straylight on human eyes and the system is immune for measuring patients with refractive error which is smaller than the 5D. The measurements of the optical and psychophysical measurements showed %80,3 and %84,4 (p<0,01) correlation. Furthermore, the psychophysical measurement and optical measurement showed 0,17 and 0,16 statistical significant difference (P<0,001). In addition, Bland-Altman analysis also confirmed that the bias was significant. The analysis of optical measurements between different groups of cataract gradings revealed significant differences between all groups (P<0,004). Conclusion Development of this novel device, which is described in this thesis, gives advancement for the clinical routine beyond the aberrations and reflections. Besides the subjective methods of grading cataract, this method gives fast, relevant, sensitive and significant information for the effects of the forward scattering. This device could be a step forward in the clinical routine and helps clinicians for the objective evolution of the material properties of the eye.
Language English
Issue date 2018-03-28
Collection   Faculty/Department--School of Medicine--Department of Medicine--Doctoral theses
  Type of Work--Doctoral theses
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