Novel Developments in Perimetry, Ocular Coherence Tomography and Vision Restoration Therapies

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Abstract

This thesis presents the outcomes of research work whose focus lies on the development and investigation of new approaches in 3 technologies: perimetry, ocular coherence tomography and retinal implants for the purposes of vision restoration. The thesis is separated in 3 sections: Section 1 consists of a series of studies related to perimetry and glaucoma. The initial investigation of the rate of VF deterioration in patients with different stages of glaucomatous loss showed the relatively low proportion of patients with rapid progression highlighting the effectiveness of current treatment plans. However, the large proportion of patients with advanced field loss presented for the first time emphasised the need for earlier detection of the disease. The following studies focused on the development and evaluation of a new computer based visual field (VF) self administered test for enhanced case-finding of eyes with glaucomatous VF defects. Online VF self-tests were identified and undergone usability evaluation to identify design and testing features that are more attractive to users; such a feature, for example, was the presentation of multiple stimuli. The results of that study were implemented into the design of the new test: a multiple stimulus supra-threshold (i.e. 10dB above age-matched normal threshold) algorithm to test a 20 location subset of the 24-2 pattern with a multisampling (i.e. 3 seen or missed, maximum 5 trials) technique. The performance evaluation of the new test reported specificity at 97% and sensitivity at 85-90%, depending on the stage of loss. Section 2 introduces the new technology of non invasive angiography by means of ocular coherence tomography. Five studies utilising ocular coherence tomography angiography (OCTA) report and discuss the newly acquired knowledge of the eye̢۪s vasculature in pathologies, such as diabetic retinopathy or age-related macular degeneration. OCTA proved to be a quick and non invasive mean for angiographic analysis, although drawbacks, such as artefacts or limitations in image acquisition and processing, make it harder to introduce OCTA as a replacement of fundus fluorescein angiography (i.e. the clinical standard for the visualisation of the eye̢۪s vasculature). At the end of the section, the potentials of this new technology and future research pathways are thoroughly discussed. The last section describes a clinical trial that evaluates the safety and efficacy of the Argus II retinal implant in patients with advanced non-exudative age related macular degeneration. The presented results emphasise the structural alterations that the implantation caused and the inability of the functional testing to detect any benefits of the Argus II system to the implanted eyes. The section concludes with a critical review of the study̢۪s protocol, highlighting its strengths and weaknesses.

Keyword(s)

glaucoma; ocular coherence tomography; teleophthalmology; visual field

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