The effect of total acute ischaemia on the structure and function of the rabbit retina and the pattern of post-ischaemic recovery


This thesis describes the function and structure of the rabbit retina during and after periods of total acute ischaemia. The function of the retina was determined by eleotroretinography while the retinal structure was investigated by light and electron microscopy. Following a 2 hour period of dark adaptation, total acute ocular Ischaemia was induced in one eye of each rabbit by raising the intraocular pressure above the systemic systolic blood pressure for varying periods (15, 30, 60, 90 and 120 minutes). The contralateral eye acted as the control. One group of animals were killed immediately after the period of ischaemia and investigated histologically. In another group of animals, the intraocular pressure was returned to normal for up to 4 hours, the function of the retina was monitored throughout by electroretinography under scotopic conditions. Groups of animals were killed one and 4 hours after the return of the ocular circulation to determine the histological pattern of post-ischaemic recovery. Light and electron microscopy revealed that the individual cell types making up the retina possessed different tolerances to ischaemia. The visual cells were the least resistant to ischaemia, being susceptible to periods of ischaemia longer than 30 minutes. The Muller cells, the ganglion cells and the RPE were the most resistant to ischaemia, often showing only mild changes following 4 hours recovery from 90 and 120 minutes ischaemia. The neural cells of the inner nuclear layer exhibited an intermediate tolerance to ischaemia showing severe degenerative changes following periods of ischaemia longer than 60 minutes. A prominent feature of the ischaemic retina was the presence of macrophages in the subretinal space. The macrophages appeared to be actively engaged in the removal of outer segment debris. These cells were not a feature of the post-ischaemic retina. During the recovery phase the RPEwas able to increase its phagocytic activity. This appeared to be the main mechanism for the removal of outer segment debris during the post-ischaemic phase following periods of ischaemia not longer than 60 minutes. The histological changes arising from periods of ischaemia induced by high intraocular pressure may have arisen from the effects of ischaemia, the mechanical effect of pressure or a combination of the two factors. Post-mortem retinal tissue was investigated to determine the effects of total acute ocular ischaemia not involving raised intraocular pressure. There was a marked similarity between the pressure-induced ischaemic tissue and post-mortem tissue which suggested that the mechanical effects of raised intraocular pressure were small compared to the effects of ischaemia. Following total ocular Ischaemia, some recovery of ERG was found in all eyes exposed to ischaemia of up to 120 minutes, although after longer periods of ischaemia; recovery of the ERG was delayed and incomplete. (Abstract shortened by ProQuest.)

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oaioai:theses.gla.ac.uk:72635Last time updated on 7/9/2019View original full text link

This paper was published in Glasgow Theses Service.

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