published_or_final_version / Anatomy / Master / Master of Philosophy

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

No description available.

This dissertation documents the development of a new illumination technique for use in the studies of retinal oximetry and fundus spectroscopy. Intravitreal illumination is a technique where the back of the eye is illuminated trans-sclerally using a scanning monochromator coupled into a fiber optic illuminator. Retinal oximetry is the processof measuring the oxygen saturation of blood contained in retinal vessels by quantitative measurement of the characteristic color shift seen as blood oxygen saturation changes from oxygenated blood (reddish) to deoxygenated blood (bluish). Retinal oximetry was first attempted in 1963 but due to a variety of problems with accuracy and difficulty of measurement, has not matured to the point of clinical acceptabilityor commercial viability.Accurate retinal oximetry relies in part on an adequate understanding of the spectral reflectance characteristics of the fundus. The use of intravitreal illumination allows new investigations into the spectral reflectance properties of the fundus. The results of much research in fundus reflectance and retinal oximetry is detailed in thisdocument, providing new insight into both of these related fields of study.Intravitreal illumination has been used to study retinal vessel oximetry and fundus reflectometry resulting in several important findings that are presented in this document. Studies on enucleated swine eyes have provided new insight into the bidirectional reflectance distribution function of the fundus. Research on live swine hasshown accurate measurement of retinal vessel oxygen saturation and provided the first in vivo spectral transmittance measurement of the sensory retina. A secondary discovery during this research suggests that vitrectomy alters the retinal vasculature,a finding that should spawn new research in its own right.

No description available.

Electroretinoraphic signals (ERGs) are affected when recorded under isoflurane anesthesia in the operating room. We explored the effect of isoflurane and propofol in ex vivo guinea pig retinal preparations using a multielectrode array to record simultaneously ERGs and retinal ganglion cell (RGC) activity. The viability and light-response characteristics of the model were documented. In the presence of isoflurane, the ERG and RGC activity was reduced in a dose-dependent manner, even at sub-clinical doses; the OFF responses were consistently more affected. Propofol had minimal effects: at subclinical doses, a small excitation was measured while a concentration a hundred times stronger than the clinical concentration was required to measure a significant decline in EGR and RGC signals. This study confirms the usefulness of the guinea pig model to study clinically relevant retinal issues and shows that propofol is a better anesthetic to use in the operating room when retinal investigations are required.

Retinal ganglion cells (RGCs) undergo continued maturation after birth. RGC development can be influenced by light, but for most RGCs this requires the development of functional retinal circuits that occurs up to 2 weeks after birth. A subpopulation of RGCs express melanopsin (MRGCs) making them intrinsically photosensitive at birth. I hypothesized that this intrinsic photosensitivity could affect the morphology of MRGCs during the postnatal (PN) developmental period (PN 3 to adult). I took advantage of the Clomeleon-expressing transgenic mouse line that, combined with melanopsin immunohistochemistry, allowed for the systematic identification of the M2 MRGC at different PN periods. The pattern of development of the M2 MRGC, characterized through the analysis of 6 morphological parameters, was similar to that described for other types of RGCs. Thus, despite being intrinsically photosensitive, M2 MRGCs did not show substantial developmental differences from other RGC types

No description available.

Purpose: The RTVue-100 is a new instrument for measuring retinal blood flow (RBF), but image quality needs to be optimized in order for valid blood flow results. The primary aim of this thesis was to assess the presence of learning effects with novice and experienced operators. Methods: Twelve upper-year optometric students from the University of Waterloo, School of Optometry and Vision Science, were trained in operating RTVue-100. Nine healthy participants, with a mean age (?? SD) of 25.7 ?? 3.8 years, underwent OCT imaging. Using the Doppler OCT of Retinal Circulation (DOCTORC) software, images were assessed by computer for various image quality parameters. Results: Paired samples t-tests showed significant statistical differences between the novice and experienced operators for the following image acquisition parameters: total acquisition time (TAT), number of attempts to complete total scan protocol, and number of valid images. Mean values for TAT and the number of attempts decreased, whereas the mean number of valid images increased from novice to experienced level. Conclusions: The results confirm that there are learning effects observed within the image acquisition process using the RTVue-100 SD-OCT.

Purpose: To investigate venous total retinal blood flow (TRBF) and retinal blood flow (RBF) in the superior and the inferior retinal hemifields in primary open angle glaucoma (POAG) patients with, and without, disc hemorrhage (DH). Methods: RBF measurements were obtained from 10 POAG with DH and 19 POAG without DH using Doppler SD-OCT (RTVue) as well as bi-directional laser Doppler flowmetry (CLBF). Results: RBF was not different between the superior and inferior hemifields for either of the two groups. Venous TRBF in the POAG with DH group was significantly lower than in the age-matched stable POAG without DH group (p=0.009). In the POAG with DH group, venous TRBF was significantly lower in the DH eye compared to contralateral eye without DH (p=0.015). Conclusions: Venous TRBF was significantly lower in the POAG with DH group compared to both the POAG without DH group and the contralateral eye of the POAG with DH group.