Quantifying ocular inflammation in uveitis using optical coherence tomography

Liu, Xiaoxuan ORCID: 0000-0002-1286-0038 (2021). Quantifying ocular inflammation in uveitis using optical coherence tomography. University of Birmingham. Ph.D.

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Abstract

Inflammation is the key underlying physiological process in uveitis. It drives the onset of acute flares, causes permanent structural damage and can result in sight-threatening complications. Being able to accurately detect and measure changes in inflammatory activity is crucial for managing uveitic flares and rationalising therapeutic decisions. Unfortunately, many of the current methods for quantifying inflammation are imperfect, due to the fact that they are based on subjective and unreliable clinician estimates.

In this thesis, I evaluated the potential for imaging-based technologies such as optical coherence tomography (OCT) to measure key markers of intraocular inflammation in uveitis. Whilst several key markers of inflammation are recognised, this thesis focuses on those with an existing clinical standard, which can be used as a comparator or reference test (anterior chamber cells, anterior chamber flare and vitreous haze).

I conducted a series of systematic reviews evaluating potential instrument-based techniques for measuring anterior chamber cells, anterior chamber flare and vitreous inflammation, respectively. These identified OCT and laser flare photometry as potential instruments for measuring anterior chamber cell and flare, and OCT and retinal photography for measuring vitreous inflammation. However, the interpretation of results in each review was limited by relatively few studies and the inclusion of highly heterogenous uveitic patient populations, varying severities of disease, and lack of a standardised image acquisition protocol.

Second, in the prospective study, OCTAVE (OCT-assisted vitreous evaluation), I found that our custom OCT-based vitreous analysis technique (EQUIP) demonstrated good repeatability in healthy and uveitic eyes, was able to detect vitreous inflammation and was associated with the current clinical vitreous haze grading. The EQUIP measurement was able to predict visual acuity whereas the current standard method (clinician grading 3 using the National Eye Institutevitreous haze scale) could not. Whilst these results were encouraging, there remains substantial overlap in the OCT measurement between NEI vitreous haze grades. It is not clear whether this is due to poor signal-to-noise ratio of the OCT technique, or a sign of poor reliability of the comparator (clinician-based grading using the NEI vitreous haze scale). Further investigation through longitudinal studies may be able to answer this question.

In summary, OCT has demonstrated potential for quantifying inflammation for multiple key measures in uveitis. However, a key limitation for the validation of all instrument-based measures has been the lack of a reliable reference test.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):