Mapping residual visual function in hemianopia
Research type
Research Study
Full title
Mapping residual visual function in hemianopia
IRAS ID
246976
Contact name
Matt J Dunn
Contact email
Sponsor organisation
Research Governance Team, Cardiff University
ISRCTN Number
ISRCTN00000000
Clinicaltrials.gov Identifier
Clinicaltrials.gov Identifier
N/A, N/A
Duration of Study in the UK
2 years, 11 months, 18 days
Research summary
Research Summary
Homonymous hemianopia (HH), a loss of one half of the visual field in the same relative position in both eyes, is a common vision deficit arising from damage to the brain. Damage to primary visual cortex is typically the cause of this deficit, although damage in other visual areas of the brain can lead to HH. HH gives rise to a number of day-to-day problems which can significantly impact on the patient’s quality of life. The inability to drive, navigate surroundings and even difficulties with reading are all extensively reported by people with hemianopia.
A subset of individuals with HH display spared central vision in their otherwise ‘blind’ hemifield, a phenomenon referred to as ‘macular sparing’. The area of spared vision in the ‘blind’ hemifield is typically detected with conventional perimetry in clinical practice. Many reasons for this retained visual function have been proposed, including lesions of primary visual cortex being incomplete, the involvement of brain pathways that are unaffected by the damage (the leading candidate being one that is associated with motion processing), or macular sparing being an artefact arising from the use of inappropriately designed (yet standard) stimuli employed in standard visual field testing.
The aim of this study is to investigate the basis of macular sparing. We will use perimetry coupled with eyetracking to monitor and control for eye movements. This will reveal whether apparent macular sparing is an eye-movement artefact. We will investigate the scaling of target diameter as a function of eccentricity. This allows us to determine if vision in the non-central visual field is present but typically missed during standard visual field testing (perimetry). We will use motion displays to probe sensitivity to motion in the blind field. This will allow us to assess the role of a spared motion pathway in macular sparing. We will investigate which areas of the brain have been damaged using MRI brain scanning. This will allow us to understand the role of specific brain regions in macular sparing.
This study will use a combination of standard techniques: perimetry, psychophysics (simple judgements), MRI and non-invasive eyetracking.
Summary of Results
The study did not take place due to the COVID pandemic.
REC name
Wales REC 3
REC reference
19/WA/0003
Date of REC Opinion
28 Feb 2019
REC opinion
Further Information Favourable Opinion