2010 BC Guide in Determining Fitness to Drive

21.17 Visual field impairmentsTypes of visual field defects 13Type Description CausesLoss of all or part of thesuperior or inferior half of theAltitudinalvisual field, but in no casefield defectdoes the defect cross thehorizontal medianArcuate scotomaBinasalfield defect(uncommon)BitemporalhemianopiaBlind-spotenlargementCentral scotomaHomonymoushemianopiaConstriction ofthe peripheralfields leavingonly a smallresidual centralfieldA small, arcuate-shaped fieldloss due to damage to theganglion cells that feed into aparticular part of the opticnerve head, which follows thearcuate shape of the nervefiber pattern; the defect doesnot cross the horizontalmedianLoss of all or part of themedial half of both visualfields; the defect does notcross the vertical medianLoss of all or part of thelateral half of both visualfields; the defect does notcross the vertical medianEnlargement of the normalblind spot at the optic nerveheadA loss of visual function inthe middle of the visual field,typically affecting the foveacentralisLoss of part or all of the lefthalf or right half of bothvisual fields; the defect doesnot cross the vertical medianLoss of the outer part of theentire visual field in one orboth eyesMore common: Ischemic optic neuropathy, hemibranchretinal artery occlusion, retinal detachmentLess common: Glaucoma, optic nerve or chiasmal lesion,optic nerve colobomaMore common: GlaucomaLess common: Ischemic optic neuropathy (especiallynonarteritic), optic disk drusen, high myopiaMore common: Glaucoma, bitemporal retinal disease(e.g., retinitis pigmentosa)Rare: Bilateral occipital disease, tumor or aneurysmcompressing both optic nervesMore common: Chiasmal lesion (e.g., pituitary adenoma,meningioma, craniopharyngioma, aneurysm, glioma)Less common: Tilted optic disksRare: Nasal retinitis pigmentosaPapilledema, optic nerve drusen, optic nerve coloboma,myelinated nerve fibers at the optic disk, drugs, myopicdisk with a crescentMacular disease; optic neuropathy (e.g., ischemic,Leber's hereditary, optic neuritis); optic atrophy (e.g.,from tumor compressing the nerve, toxic/metabolicdisease); rarely, an occipital cortex lesionOptic tract or lateral geniculate body lesion; temporal,parietal, or occipital lobe lesion of the brain (stroke andtumor more common; aneurysm and trauma lesscommon). Migraine may cause a transient homonymoushemianopiaGlaucoma; retinitis pigmentosa or some other peripheralretinal disorder; chronic papilledema; after panretinalphotocoagulation; central retinal artery occlusion withcilioretinal artery sparing; bilateral occipital lobeinfarction with macular sparing; nonphysiologic visionloss; carcinoma-associated retinopathy; rarely, drugs13 From http://www.merck.com/mmpe/sec09/ch098/ch098a.html - Adapted from The Wills Eye Manual, Douglas J.Rhee, M.D. and Mark F. Pyfer, M.D.© 1999 by Lippincott Williams & Wilkins.279