Anatomical and Functional Correlates in Ischaemic Retinal Vein Occlusion

Abstract

Ischaemic retinal vein occlusion (iRVO) is a potentially blinding condition, incompletely understood, carrying a higher risk of complications and poorer prognosis than non-ischaemic RVO (niRVO). This PhD project was designed to improve the understanding of iRVO and further the knowledge on this disease. For this purpose, this PhD thesis comprised systematic reviews (chapters II and III), a retrospective observational clinical study (chapter IV), and a cross-sectional, prospective, pilot, clinical study (chapter V). Current treatments for RVO, including anti-vascular endothelial growth factor (anti-VEGF) drugs and laser photocoagulation, target the complications of RVO, namely macular oedema and neovascularisation, respectively. Anti-VEGFs are being used for iRVO and niRVO. However, randomised controlled trials that proved their efficacy did not include patients with iRVO and, thus, the efficacy in this group was previously unknown. Work conducted in this thesis suggests that anti-VEGFs are indeed beneficial in iRVO, justifying their use in this group. However, due to the low level of presenting vision classically found in people with iRVO, the expected visual outcome following anti-VEGFs is lower than in niRVO. This information is important for the counselling of patients prior to treatment. Work undertaken in this thesis showed that reduced retinal function occurs at sites of retinal lesions result of RVO. As lesions resolved, function recovers, even if not to the full extent. Reperfusion of ischaemic retina, however, was rarely observed and, even if it occurred, functional loss remained irreversible. Factors determining reperfusion remain unknown. Results suggest also that damage of retinal cells as a result of ischaemia in RVO may occur early and become irreversible soon after the onset of the disease. Hence, when available, early intervention may be required for functional recovery. Experimental animal models of RVO, are available and can facilitate the understanding of this condition and development of new treatments.