Anatomical and Functional Correlates in Ischaemic Retinal Vein Occlusion

  • Meiaad Khayat

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Ischaemic retinal vein occlusion (RVO) is a potentially blinding condition that is not fully understood, and entails a higher risk of developing complications and poorer prognosis than non-ischaemic RVO. This PhD project was designed to improve the level of understanding on ischaemic RVO as well as to further the knowledge on this disease. For this purpose, this PhD thesis comprises of three main components: systematic reviews (chapters II and III), a retrospective observational clinical study (chapter IV), and a cross-sectional/ prospective pilot observational clinical study (chapter V).

The systematic reviews aim at compiling current knowledge on ischaemic RVO and identifying gaps on the understanding of this retinal disease based on published literature (Chapter II) and on experimental animal models of RVO (Chapter III). The retrospective observational clinical study compares baseline characteristics as well as outcomes following treatment between patients with ischaemic and those with nonischaemic RVO. Finally, the pilot cross-sectional observational clinical study evaluates anatomical and functional correlates, point to point, at areas of retinal ischaemia along with other structural lesions in patients with newly diagnosed RVO.

Ischaemia secondary to RVO is strongly associated with development of neovascular complications and poor visual prognosis. Prognostic parameters to differentiate patients who would develop extensive areas of ischaemia from those who would not is still to be explored. Available current treatments target the complications of RVO and are being used clinically for both ischaemic and nonischaemic RVO, although data from randomised clinical trials (RCTs) refers only to the latter group of patients. In fact, intravitreal anti-VEGF, in particular, proved to be as beneficial in ischaemic forms of RVO as in non-ischaemic forms. However, due to the low baseline vision classically found in the ischaemic form, final vision remains lower than in non-iRVO despite significant improvement of vision achieved following treatment in most patients, suggesting damage of the retina that cannot be restored with current treatment. This information is useful for the counselling of patients with ischaemic RVO prior to initiating anti-VEGF therapy. Reperfusion of ischaemic retina was observed in very few cases following anti-VEGF therapy. Factors determining reperfusion are still unknown and need to be investigated. Restoration of function, however, could not be seen in reperfused retina within six months of followup. A new treatment to reperfuse ischaemic retina before loss of retinal function occur is urgently needed as damage of retinal cells as a result of ischaemia in RVO may be irreversible, and this needs to be further investigated and better understood. Experimental animal models, although imperfect, are available and can be utilised to facilitate the understanding of this potentially blinding condition.
Date of AwardJul 2020
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsKing Abdulaziz University-Rabigh
SupervisorNoemi Lois (Supervisor) & Michael Williams (Supervisor)

Keywords

  • Retinal vein occlusion
  • RVO
  • retinal vein obstruction
  • retinal vein thrombosis
  • retinal ischaemia
  • retinal capillary non-perfusion
  • anti-vascular endothelial growth factor
  • anti-VEGF
  • reperfusion

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