Multimodal imaging: simultaneous structural and functional assessment of the retina

Walker, Sinead Marie (2010) Multimodal imaging: simultaneous structural and functional assessment of the retina. PhD thesis, University of Glasgow.

Abstract

Many sight threatening conditions with significant socio-economic effects such as diabetic retinopathy and age related macular degeneration adversely affect retinal structure and function, particularly that of the macula, the central part of the retina. It is consequently paramount to have effective methods of assessing macular structure and function to aid early disease diagnosis and to help assess the success of new and existing treatments. Current methods of investigating retinal structure and function have limitations and no clinical technique can simultaneously assess local retinal structure and function objectively. The aim of the work presented in this thesis was to develop a new technique, multimodal imaging (MMI), which integrated two existing clinically valuable modalities: optical coherence tomography/scanning laser ophthalmoscope (OCT/SLO), a non-invasive technique that provides high resolution imaging of the retinal surface and substructure in vivo; and multifocal electroretinogram (mfERG), an electrophysiological test that assesses local retinal function.

Technical development of the MMI system included identification of a stimulator suitable for integration into the OCT/SLO system; experimentation to facilitate effective delivery of a mfERG stimulus within the OCT/SLO and accurate synchronisation of stimulus delivery and data acquisition; creation of software allowing concurrent visualisation of live structural and functional data; and integration of post-processing techniques to help extract low amplitude signals from noise. Experiments were conducted using different mfERG stimulus parameters in order to determine the optimum spatial resolution, temporal resolution, stimulus intensity and stimulus frequency to employ during MMI recordings. The influence of scattered light and lateral interactions with neighbouring retinal areas on functional data elicited using MMI was investigated. MMI recordings were conducted on a cohort of healthy control subjects to identify local normal ranges of retinal thickness and functional measures. In order to allow comparison of MMI data recorded on separate occasions, the repeatability and reproducibility of the system was determined. An integrated method of presenting MMI data was developed to allow simple visualisation of the structural and functional data yielded using the technique. Finally, the clinical viability of MMI was assessed by testing a group of patients with macular hole, a full thickness defect in macular tissue, and by assessing the potential application of the technique in other disorders. MMI was well tolerated clinically and provided interesting information on relationships between retinal structure and function in various disease states. Data obtained from macular hole patients suggested further research is warranted to determine whether prognostic indicators of postoperative visual outcome may be identified using MMI.

The research presented in this thesis developed a clinically viable new modality capable of simultaneously assessing local macular structure and function. Further work on integrating a high speed, high resolution OCT imaging system into MMI, using an eye tracker and optimising data post-processing techniques would improve the system and could facilitate higher resolution assessment of local macular structure and function which may further enhance the clinical usefulness of MMI.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: ophthalmology, retina, optical coherence tomography, electrophysiology, multifocal electroretinogram
• Subjects: Q Science > QC Physics; R Medicine > RE Ophthalmology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health
• Supervisor's Name: Keating, Dr. David
• Date of Award: 2010
• Embargo Date: 28 October 2013
• Depositing User: Mrs Sinead Walker
• Unique ID: glathesis:2010-2230
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 01 Nov 2010
• Last Modified: 10 Dec 2012 13:53
• URI: https://theses.gla.ac.uk/id/eprint/2230