Objective Assessment of Macular Function at Retinal and Cortical Levels

Summary

Research questions/hypotheses: About 15% of the population over 40 years of age are affected by diseases of the retina. Accurate measurement of the extent of visual field impairment is of highest importance for disease subtype diagnosis and severity classification. The current gold-standard approach for the assessment of macular sensitivity is microperimetry (MP) where the patient is asked to report whether or not visual stimuli presented at different positions within the visual field are detected. While this technique is a very straightforward approach and simple in its application, it is important to note that MP is psychophysical in nature and requires constantly high attentional performance of the patient throughout the examination period. As many patients suffering from retinal diseases are well over 65 years of age, they are unable to maintain such high levels of attention over longer periods and, thus, MP results may be biased. Retinotopic assessment using population receptive field (pRF) mapping based on functional magnetic resonance imaging (fMRI) offers an alternative by allowing for objective visual field testing, independent of patient performance. We have shown previously in healthy subjects that pRF allows for accurate detection of simulated central scotomata down to 2.35 degrees radius. Also, pilot data in patients with retinal scotomata showed strong correspondence between pRF and MP results, i.e. macular regions with reduced macular sensitivity and atrophy of outer retinal layers correlated well with pRF coverage maps showing reduced density of activated voxels. The aim of this project is to determine whether pRF mapping could serve as an alternative visual field testing method by: (1) assessing test-retest reproducibility of pRF and MP in clinical populations with stable retinal diseases (Stargardt disease, geographic atrophy) over a four-week period; (2) assessing visual field changes over a one-year period in patients suffering from acute retinal scotomata (branch retinal artery occlusions, full-thickness macular holes). All pRF mapping will be accompanied by MP measurements to allow for a direct comparison of the two techniques.

Scientific/scholarly innovation/originality of the project: The present project applies a novel approach for linking retinal function assessed with MP and pRF mapping in a representative patient population with acute and chronic retinal diseases. The project seeks to contribute to best practice methods for using fMRI to assess macular dysfunction both for documentation of the natural course of the disease and during therapy in a study setting.

Methods: fMRI uses pRF mapping to provide retinotopic data (pRF coverage maps) that are then correlated with the results of conventional ophthalmic testing including MP, visual acuity and contrast sensitivity testing, reading performance, optical coherence tomography and autofluorescence imaging.

Conditions

• Macula; Degeneration, Congenital or Hereditary
• Retina Disorder

Interventions

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functional magnetic resonance imaging (fMRI)

Retinotopic mapping using functional magnetic resonance imaging (fMRI) is based on MR images acquired with blood-oxygenation-level-dependent (BOLD) contrast to reveal areas of neuronal activity in the visual cortex

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Microperimetry (MP)

MP allows localized testing of retinal sensitivity of foveal, parafoveal and even more peripheral macular regions

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Optical coherence tomography (OCT)

Optical Coherence Tomography (OCT) is a non-invasive diagnostic technique that renders an in vivo cross sectional view of the retina.

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Blue light fundus autofluorescence imaging (FAF)

Fundus autofluorescence imaging (FAF), is a non-invasive diagnostic technique focusing on the fluorescent properties of pigments in the retina to generate images.

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Visual testing

Best-corrected visual acuity will be measured using Early Treatment Diabetic Retinopathy Study (ETDRS) charts. Reading acuity and reading speed will be examined using Radner Reading Charts. Reading acuity is measured in logRAD unit (= reading equivalent of logMAR) and in critical font size (critical reading size), reading speed is measured in words per minute (wpm). Contrast sensitivity will be determined using Pelli-Robson contrast sensitivity charts.

Sponsors & Collaborators

• Medical University of Vienna

  lead OTHER

Eligibility

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2018-05-15

Primary Completion

2020-03-16

Completion

2020-06-15