TableĀ 2

Clinical measures of optic nerve function and structure

Structure/ functionInvestigational techniqueMeasurementChange in optic neuritis affected eyes
FunctionHigh-contrast visual acuityHigh-contrast resolutionWorsens acutely and improves over time4
FunctionLow-contrast visual acuityLow-contrast resolutionWorsens acutely and improves over time4
FunctionColour visionBlue-yellow and red-green defects discriminationAbnormalities in colour discrimination that correlate with RNFL thickness29
FunctionERGPhysiological integrity of cone and rod responsesNo difference in full field ERG.75 Loss of OHNC of multifocal ERG17
FunctionVEPDemyelination of the visual pathwayLatency delay that improves in a fraction of affected individuals over time22
StructureFundus photographyShows structure of inner surface of the eye (retina, optic disc, macula and fundus)Optic disc pallor, atrophy
StructureMRIOptic nerve atrophy, tissue injury, blood-brain barrier breakdown
StructureDTIImaging of white matter damage and integrity of visual white matter tractsAxonal and demyelinating injury to optic nerve and postgeniculate white matter33 76
StructureMTRMyelination status and axonal content of the optic nerveDemyelinating injury77
StructureSLPMeasure RNFL thicknessShows a decrease in retardance in eyes with axonal injury associated with visual field loss78
StructureOCTMeasure RNFL thicknessRNFL thickness decreases with MS and decreases further with MS-related ON79; shows acute thickening due to edema25
FunctionmfERGMeasures the transformation of slow membrane conduction in unmyelinated ganglion cell axons to fast saltatory conduction in myelinated axons
FunctionONHC of the mfERGTransient effects of conduction block due to reversible demyelinationLoss of this response signifies loss of myelination at the lamina cribosa and disrupted transition from membrane to saltatory transmission17
FunctionmfVEPSensitive measure of axonal damageAbnormal latency80
FunctionPupillometryMeasurement of pupil diameter as an indicator of neural inhibitory mechanismsPupillary reflex metrics impaired81
  • DTI, diffusion tensor imaging; ERG, electroretinogram; mfERG, multifocal ERG; mfVEP, multifocal VEP; MS, multiple sclerosis; MTR, magnetisation transfer imaging ratios; OCT, optical coherence tomography; ONHC, optic nerve head component; RNFL, retinal nerve fibre layer; MTR, magnetisation transfer imaging ratios; SLP, scanning laster polarimetry; VEP, visual evoked potential.