Towards a functional visual field assessment for low vision

Subhi, Hikmat (2017) Towards a functional visual field assessment for low vision. Doctoral thesis, Anglia Ruskin University.

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Abstract

Visual field assessment is not only important to monitor disease progression, but also to reflect and predict functional difficulty in the real world. Despite this, no test currently available is optimised for determining functional consequences of visual field loss. The aim of this study is to determine the locations within the visual field that best reflect functional difficulty, and to use this information to develop an appropriate method of assessing field loss which reflects its functional consequences. For the first experiment, fifty two participants with peripheral field loss undertook binocular assessment of visual fields using the 30-2 and 60-4 SITA Fast programs on the Humphrey Field Analyser. The mean threshold within different areas of the visual field was used as the main outcome measure. Self-reported difficulties with activities of daily living were assessed using the Dutch ICF Activity Inventory. Greater visual field loss was associated with greater perceived difficulty, and both central (0-30 deg) and peripheral (30-60 deg) visual field areas were similarly related to self-reported function. The results of this experiment suggested that in order to accurately determine the functional consequences of visual field loss, it is necessary to consider the visual field beyond 30 degrees. These findings informed the development of custom visual field assessments in Experiment 2. Fifty participants with peripheral field impairment undertook three custom binocular visual field tests on the Octopus 900 that assessed the field out to 60 degrees from fixation: a threshold, 10dB supra-threshold, and a 10dB kinetic assessment. The mean threshold, percentage of stimuli seen, and visual field area were used as the main outcome measures for analysis. Visual field scores were compared to overall self-reported function assessed during the Dutch ICF Activity Inventory, and mobility function assessed using the Independent Mobility Questionnaire. Results were also compared to currently available methods of assessing functional visual field including integrated visual fields, and Esterman tests. Perceived function related similarly to binocular threshold, suprathreshold, kinetic, and Esterman visual field scores suggesting that as long as a functional visual field test is performed binocularly and includes assessment of eccentricities to 60 degrees, the paradigm used to assess the visual field makes little difference to the test’s ability to predict function. Quick tests using a kinetic or suprathreshold paradigm are more favoured by patients however. A binocular visual field assessment that utilises a suprathreshold or kinetic paradigm, and that assesses the visual field past 30 degrees is effective at reflecting the functional abilities of patients with peripheral visual impairment.

Item Type: Thesis (Doctoral)
Keywords: visual impairment, visual field, visual function, self-report, mobility function
Faculty: Theses from Anglia Ruskin University
Depositing User: Lisa Blanshard
Date Deposited: 27 Mar 2019 12:01
Last Modified: 14 Nov 2019 16:10
URI: http://arro.anglia.ac.uk/id/eprint/704206

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