Table 1.
Synopsis of visual pathway assessment methods and outcome parameters
| Functional vs. structural | Information | Findings and correlations | |
|---|---|---|---|
| Low-contrast visual acuity (LCVA) | Functional (global) | Sensitive to functional global visual impairment and “real world” visual impairment | - LCVA correlates with visual impairment of reading, facial recognition and driving [64] |
| - LCVA is associated with vision-related quality of life [65] | |||
| Vision-related quality of life | Functional (global) | Global functional assessment of patients’ disability related to vision | - Vision-related quality of life correlates with reduced LCVA [19, 61, 65] and OCT retinal damage [19] |
| Optical coherence tomography (OCT) | Structural (retina - anterior visual pathway) | Identification of structural changes within the retinal tissue | - RNFL thinning correlates with LCVA [66] |
| - RNFL thinning correlates with brain atrophy [67] | |||
| - RNFL correlates with 7 T optic radiation thinning [22] | |||
| Pattern visual evoked potentials (VEP) and multifocal visual evoked potentials (mfVEP) | Functional (anterior and posterior visual pathway) | Detection of demyelination and loss of axons resulting in latency delay and/or conduction block | - Early VEP prolongation predicts subsequent retinal axonal loss [68] |
| - VEP over time correlates with visual cortex fMRI [69] | |||
| - VEP latency correlates with optic nerve MTR [70] | |||
| Pattern electroretinography (ERG) and multifocal electroretinography (mfERG) | Functional (retina-anterior visual pathway) | Measurement of electrical responses of retinal cell types | - mfERG correlates with LCVA and RNFL [71] |
| Magnetic resonance spectroscopy (MRS) | Structural (posterior visual pathway and visual cortex) | Quantification of metabolites (e.g., N-acetyl-aspartate) within voxels | - MRS correlates with RNFL thinning in ON [23] |
| Magnetization transfer ratio (MTR) | Structural (anterior and posterior visual pathway) | Measurement of myelin content within anatomical structures | - Optic nerve MTR correlates with VEP latency following optic neuritis [70] |
| Functional MRI (fMRI) | Functional (visual cortex) | Changes in cortical activation-based BOLD effect | - fMRI negatively correlates with VEP after ON [69] |
| - Cortical activation correlates with visual motion perception [72] | |||
| Ultrahigh field MRI at 7 T | Structural (posterior visual pathway) | Delineation of the optic radiation in T2* imaging | - Correlations of OR thinning with OCT RNFL and OR lesion load [22, 62, 63] |
LCVA low-contrast visual acuity, OCT optical coherence tomography, RNFL retinal nerve fiber layer, 7 T 7 Tesla, NMOSD neuromyelitis optica spectrum disorders, MS multiple sclerosis, mfVEP multifocal visual evoked potentials, fMRI functional MRI, MTR magnetization transfer ratio, mfERG multifocal ERG, MRS magnetic resonance spectroscopy, ON optic neuritis, BOLD blood-oxygen-level dependent, OR optic radiation