Structural damage to the rabbit retina and choroid from light exposure

McKechnie, Nicol M (1981) Structural damage to the rabbit retina and choroid from light exposure. PhD thesis, University of Glasgow.

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This thesis reports the findings of an investigation into the effects of various intensities of white light on the morphology of the rabbit retina and choroid as studied by light and electron microscopy. The exposure period was one hour in all the experimental procedures. The light levels employed ranged from an estimated retinal illumination of 20.4mWcm-2 to 84.4mWcm-2. These levels of illumination are similar to those experienced by human retinae during procedures such as indirect ophthalmoscopy, (Calkins and Hochheimer, 1980). The experimental procedures were divided into two categories:- An investigation into the appearance of the retina and choroid immediately after exposure to various intensities of white light. Alterations in retinal and choroidal structure were assessed by both light and electron microscopy. In addition, it was attempted to quantify changes in the cellular components of the outer nuclear layer by a random point counting system. 2) An investigation, by light and electron microscopy, into the morphology of the retina and choroid at various times after a damaging light exposure with special consideration of the fate of the cellular debris produced by light damage. To assess the immediate effects of light exposure, the eyes of nineteen adult Dutch rabbits were subjected to one of six light intensities. The estimated retinal illumination levels were 84.4, 38.6, 32.8, 28.9, 23.2 and 20.4mWcm-2. Following exposure to the two lowest light intensities the retinal and choroidal tissues appeared normal. At slightly higher levels of retinal illumination (28.9mWcm-2 to 38.6mWcm-2) there were disturbances of the receptor cells' outer segments as well as slight distension of the pigment epithelium's smooth endoplasmic reticulum and mitochondria. Cone receptor cells were slightly more susceptible to damage than rod receptor cells. With higher light intensity both the degree and variability of damage increased markedly. At the retinal illumination level of 38.6mWcm-2 the morphology of the receptor cells and pigment epithelial cells was highly variable. These cells could appear swollen with both their cytoplasmic organelles and their nuclei being swollen, also, conversely, they could be shrunken, their cytoplasm becoming densely stained and their nuclei pyknotic. The choroid, at these light intensities, was usually normal in appearance but occasionally there did appear to be a slight inflammatory response in the vessels of the choriocapillaris. This response was usually confined to the appearance of degranulating platelets and a few polymorphonuclear leucocytes and monocytes. Very occasionally the vessels of the choroid were filled with impacted red cells. These regions of choroidal abnormality were usually associated with the regions of most extreme retinal damage. At the highest level of illumination (84.4mWcm-2) damage to the inner retina was variable in appearance. Damage to the receptor cells and pigment epithelial cells was present and often very severe. As was seen in animals exposed to lower light intensities, regions of severe retinal damage were associated with areas of choroidal abnormality. The quantification of the cellular components of the outer nuclear layer yielded disappointing results. The results of the point counting system did seem to reflect the appearance of individual tissue blocks. However, the variation within retinae (block to block) and between animals was so great that there could be no meaningful correlations. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: W S Foulds
Keywords: Ophthalmology
Date of Award: 1981
Depositing User: Enlighten Team
Unique ID: glathesis:1981-71974
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 May 2019 15:11
Last Modified: 24 May 2019 15:11

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