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Vascularity of mammalian retinae : a comparative anatomical study of mammals with and without intraretinal blood vessels

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Buttery, Robert Gordon (1990) Vascularity of mammalian retinae : a comparative anatomical study of mammals with and without intraretinal blood vessels. PhD thesis, University of Tasmania.

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Abstract

The physical requirements necessary for the perception of light have produced peculiar
adaptions to the way in which the eye is nourished. In many mammals there is a dual blood
supply to the retina derived from both choroidal and intraretinal circulations. Interestingly,
some species have only a choroidal blood supply. This study has addressed the coping
strategies of those retinae which lack intraretinal blood vessels. Placental guinea pigs and
diprotodont marsupial brushtail possums and sugar gliders, all of which lack retinal circulation
(avascular retinae) have been compared with placental rats and polyprotodont marsupial
quolls, Virginia opossums and Tasmanian devils, all of which possess intraretinal blood
vessels (vascular retinae). Functional angiographic study has documented vascular patterns
and demonstrated the close arteriovenous pairing within the polyprotodont marsupial retina.
Avascular retinae are thinner than their vascular counterparts. The difference is not great
(170Am versus 220gm): The limitation in thickness is borne by most retinal laminae but more
so by those layers furthest from the choroidal supply. Morphological analysis suggests that
spatial visual acuity is comparable in vascular and avascular species. Corrosion casting and
microscopy of the ocular vasculature has shown that the choroid of the avascular species
examined has no obvious morphological specialisations which might offset the lack of retinal
vessels. However, the metabolic pathways within the inner layers of avascular retinae are
markedly different, with limited oxidative metabolism as indicated by the activity of the
mitochondrial enzyme, cytochrome oxidase. However, ATPase activity, as a measure of
overall energy consumption, is known to be high within the inner layers of the avascular
guinea pig retina (Ueno et al. 1981). This suggests that low cytochrome oxidase activity need
not mean limited functional metabolic capacity. As a morphological accompaniment of
oxidative activity, ultrastructural analysis would suggest that mitochondrial numbers may be
reduced within the inner retinal layers of avascular retinae when compared with similar
regions in vascular retinae. Central to these observations is the clinical question of whether
the human retina can mimic the coping strategies of avascular retinae following pathological
disruption of its intrinsic vasculature.

Item Type: Thesis (PhD)
Keywords: Retina, Retina
Copyright Holders: The Author
Copyright Information:

Copyright 1990 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Library has additional copy on microfiche. Thesis (Ph.D.)--University of Tasmania, 1991. Includes bibliographical references (p. 271-308)

Date Deposited: 25 Nov 2014 00:45
Last Modified: 21 Jun 2016 03:02
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