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Show f. Gin. Neuro-ophthaJmol. 1: 277-278, \981. Editorial The VER: A Status Report An Experimental But Not Clinically Significant Tool LENORE A. BREEN, M.D. RONALD M. BURDE, M.D. The visual-evoked response (VER) is <1 nonspccific. electrophysiologic measurement th.lt rdlccts afferent visual system function. Duc to the positioning of the active electrode and the preponderance of macular projections to the occipital region, the VER primdrily measures the function of the central 30 of the ViSUdl field.h;l Otherwise, the VER is nonlocdlizing anatomically, in contr<1distinction to the brilin-stem auditory-evoked response which hils well-defined neurdl sourc('s for its first 5 wav('S.' Th(' presence of aVER revcals little about perception. but it is particuldrly useful in documenting visual function in diseases causing subclinicdl involvement of the neural pathways and in cooperative patients whose subjective responses are unreliilble or unobtdinable" As a c1iniCdI test, the VER is in its infdncy. Universal stdndilfds for perfonning a VER study do not el(ist, which hds led to difficulty in compilfing data from ldboratory to liIboratory.~··t; In addition, several recent research studies hdve documented various techniCdl and c1inicdl factors which Cdn significilntly affect the results. The type of stimulus. its contrast, brightness, size, and whether it is p~olected or televised can change the response."' An abnonndl VER from a subject's eye can become nonnal if spatial and temporal frequencies of the stimulus Me changed. I. ~.!I Other known variables are the room temperature <1nd the location of the electrodes.I'1 Ideally, before iI VER study is perfonned, the test subject should hilve a careful eye examination to correct any refractive error and to document the presence of amblyopia, visual field defects, glaucoma, and mdcular djsedse.~·II. 1"_1'1 All of these conditions, if unrecognized, coin lead to an incorrect etiological interpretdtion of an abnonnal response. The subject's age, his i1bility or desire to mdintain centTilI fjl(ation on the stimulus, dnd his pupil size dUrin~ the test Me important to interpreting the VER.~7. 10. 14 From the Departments of Ophtha!mo)oRY (LAB, RMBI, Nrurology (RMBj, ..nd Neurologin! Su.gery IRMBl. Wdshinj\ton University School of Medicine, St. Louis. Missou.i. December 198\ Several visual parameters and neurological diseases have been studied with the VER, but the clinical application has been primarily in three aredS: suspected multiple sclerosis, differentiation of orgdnic from psychogenic disease, and examination of infants. The work by HillliddY i1nd associates in 197Z introduced the use of the VER to study optic neuritis in multiple sclerosis (MS) Piltients_ I~' The most common i1bnonnillity is iI delayed latency which occurs in 75-97% of definite MS cases.~ Visua[·evoked response studies by Mallincourt and co-workers' and Neetens and associatesl " have also emphasized a decreased amplitude with an abnonnal waveform. The change in the latency in optic neuritis does not correlate with either the mill(imum visual acuity or cerebrospinal fluid abnonnalities.l~ The question of the VER's sensitivity in detecting optic neuritis has been rilised. 17 Glaser i1nd laFlamme reported a 14% "false-negdtive" rate. r; "Fdlse-positive" VER's ciln be produced with decreased visual dcuity, poor refrilction, i1mblyopia, eccentric fixation, glaucoma, ischemic and compressive optic neuropathy, and visual field defects, especially central scotomas.~, 1'-11 Due to the subjectivity of most visual tests. the VER hds been used to evaluate psychogenic ciluses of blindness.l~The presence of VER with a nonnal wdvefonn and implicit timing implies the presence of an intact visual system from the retin.ll ganglion cells to the occipital cortex. Uren J.nd co-workers conducted a study to see how voluntary defocusing of the stimulus, eccentric fil(dtion, i1nd ('ye mOvements could i1ffect the VER.I~ The VER WdS often nonexistent with voluntary defOCUSing. Eccentric fil(ation caused a significant prolongation of the latency, dnd eye movements ,1 change in amplitude. An unilttentive or uncooperative patient can therefore render the test meaningless. (Be W,lry of the results if they are abnormal when malingering is suspected.) The evaluation of infants and young children with the VER is indeed valuable. An estimation of ViSUd[ dcuity and stereopsis coin be made'" III Srebro found a decreilsed amplitude of the VER in amblyopia using a 6-Hz frequency for the stimulus, but 277 J n("lnn..1 re-sponSE' Jl .. frt'qlle-ncy of 18 Hz. ' In Jddition. slIpprrssion of lht' VER occurs WIlh bim....: ul"'r vlsion."~~1 Tht' JJtt'r"'hon of the- rrsponSE' CJn be studu:d Icmpor",lIy, dnd lmprove-me-nt with trt'dtm("nt CJn be S("f'n 10 Jmblyopl<l. I Vt"Ctor <lndl~ I~ alf tht' VER is lUst dt've-1opmli ",nd mdY be pr\'misln~ 10 vlsudl f,(Old tt'Sfmg I'..: ....t this point In lime .In Jbnonn..hty 10 the VER rt'fJeds dysfunclu> n somt'wht'rt' In Ih(' dfft'rt'nl vlsu.. r systt'm wllh no In(nnsic IOCdhzlnK voIlut", tht' rt'port by Ft'lnsod dnd dSSOCldtt"S nocwllhsl..ndmg:~l In our mmds, <II Ihls rimt' tht" 1t'St rf'm.ms ,In mlt'resting t"Xpt'nml'nl<l1 tool, .nd wIth rul' l')(ct'phons offers Vt'ry hull' tnform..tion th.r IS of vollul' in the tredlrnl'nt of .. sp<"Clfic p.llll'ni. .... rt'Cl'nl siudy by Fiort'ntml dnd co-workers has dt'monslr.tf'd tht' uSf'fulnpss of rt"Cordmg both f1i1sh and polUt'm e/t"Ctrorelinogrdm (ERG) simultilnoously with the VER in optic nt'Ne resions In both «Its and humolns.~· Thl' lIoIsh ERG is nonn.l with dt'gl'nl'r..tion of tht" rl'lin.III g.nghon ct'Us. bur Iht' p.lttem ERG IS ..bnonn.1 or .bsen!. These tests. u~ In conjunction with the VER. «In thus help to dlfft"rentl.te betw«n ,Interior ..ffl'rl'nl visu..1 systt'm dysfunction ..nd morl' postl'norly loc..tt"d It'SlonS Elf'g.Jnt combinf'd .nd comp.ar.tive .n.. lysis of tht' fl..sh ERG. tht' p.ittl'm ERG, .nd the fl..sh. p.ittt'm...nd grolting VER In diffl'rl'nt dlSE'olSE' proc(' SSt'S offt'r grl'.t hopt' for f'SI ..blishtng .. clinically v.. lu.bJe set of tools for futurl' u~. Rt'fl'rl'nCf's I. Srl'bro, R.: Thl' vlsu.Uy f'Vokf'd rnpo~. ~rch Ophlhdlmol. 96: aJ9, 1978. 2. Sokol, S.: Vlsu.ll f'vokf'd polf'nh.lls. In Elecrrodl' .lgnosis in CllnlC.l/ Neurology. M.l AminoH. Ed. Churchlllllvingstonl', Nl'w York, 1980. p.34ft 3. N.lk.amur.l, Z.; PhotopIC .nd scotopic components of the hum.n electroretln0litrJrn dnd vlsu..1evoked cor. ticdl potential. )pn.}. Oplllh<llmo/. 23: 289. 1979. 4. Regan. D.: EleClriC.J1 responses elloked from the hum.an buin. Sci. ~rn. 241(0): 134. 1979. 5 Uren. S.M., Stewart, 1'... nd Cosby, P.A.: Subject coo~r.ltlon .nd tht VISU..J evoJ.ed response. In\'esl Ophlh./mo/. V.s. Sc, 18: 048. 1979. 6 Allison. T. Goff. W R••nd Wood. C C, Audltorv. SOmollOSf'nwty••nd VISU.J evoled polent•.als In Ihe dl.gnOSIS of MurOJUlhology In Humdn EI'Ol.td Pll. lent,,,,/s, D lehm.nn .nd ( C.llI.w.y, [ds. Plenum Prns, ew York. 1<;)19, p I 7 V.n Llh. C H.M.. M.rle, G W ••nd Vdn Dol-moll. G T M V.n.tlOfl In Io1lency tlmn of VISUJlly ('Vo..L.ed (OftIColI polenh.Is 8, I Ophlh./mol 62:.!ZO. 1"7t' 8 Spekrel~. H, Ouw",er. A L, .nd Posthumus Mtytn. r L Conlt.st evol..ed poIentl..1Is .nd psy. chophys.ics .n multlpk SC"le~ls JUhtnls_ In Hutn.ln Cvolr..t'd l'oIentld/s, D lthnunn .nd E. C.U.w.y. [ds. Menum Ptt'u. New Yorl. IQ?O, p.3cl.J. o M.. llencoun, 1-, n.,n, r. lebl.nc. M_.•nd lhet. m'lh·. r An.lly",...,J vl"uJI n·\.l..d rl!'Sponses In ,,,,,h,,,I..... 1.·.....,.. H,..nlo'\.lltlOf' .\2: :10. 1080. 10. Nmens. A.• Hendroll... Y....nd V.an RomJHt)'. I.: P.llem .and nuh evoked responSt"S in disseminated .nd wlKlive optic p.llhw.y dam.age. T,Mls. OphIh./ mol. Soc. U.K. 99: 103, 1919. II. Ellenbf'rger, c.. .and Shuttlesworth, D.E.: EIKtrinJ (orre"tf'S of nonn.1 blnocul.ar VISion. ....rch. N~rol. 35; 834. 1978 12 Collins, D.W.K.• C.artolJ. W M., BI.ck. J.L, MId W.I~. M EffKts of refr<lC!lvt trror on Iht visual evokf'd rnponw Sr Mt'd./ 1: 2.31. 1979. 13 Tyler. CW. N.k.ay.m.a. K.., ....pkan..n. P..I\.• and ~I, D M VER .lssessmf'nt of vlsu.al function. Vi· S'OfI Rf'S 21: 007, 1981 14 lehm.nn. 0, .nd Skrolndles. W.: Multich..nnel m.pping of sJHtI.a1 dlSinbullons of sc.alp polmtial fields evoked by chKktrboud rtvtrwl to different retln.al .a,,'.s In Hum.n £voJct'd Pottntl./s. D. lehm. nn .nd [ C.a".aw.ay. Eds. Plenum Press. New York. 1979, p 201. 15 H.llhd.y. AM. McDon.ald. W I, and Mushin. J.: Of'I.~d vlsu.l evoktd response In optic nnlritis. Ltnctt 1: 982, 1972. 16 Bynke, H, Rosin, I.• .and Sandbf'rg-Wollht1m. M.: Correl.ahon of VISlJoIJ evokf'd potenll.als, ophlh.almologlc. al.and nturolGglul flndlOSs .fler uml.attr.al op.he ntunhs ~c1d Ophth.almol 5&: 673. 1980. 17 CI.awr, J.•nd ufl.amme. P The vlsu.l n'Oked rnponse mtlhodology .nd .pphuhon 10 optic nervt dlse.aw In Topl(s ,n NNro-Ophth.almology. H S Thompson, Ed Wllh..m & WilkinS. 8.altuTlore. 1919. p 199 HI Skdlk., H W ComJUnson of SntUtn .acuity. VIR .Ku.ty, .nd Arden gr.atlng scorn In mlculo1r .and OptIC ne~ d.se.ses. Br ) Ophlh"'mol 64: 24. 1980. 19 Ct'lesl.a. G G, Sonl. V K .•nd Rhode. W.S.: Vlsu.a1 evokf'd Sp«llVm .ruy .lnd Inlerhemlsphenc voIri.ahons ~rch Neurol 35: 078, 197&. ZOo ltnnerslr.lnd. G., Bmoculu Inler.ctlon studIed with Vlsu.ll tvoked tesponses In hum..ns with nonn.al or Imp.alred bmoculu VISion ~ct. Ophthdlmol. 56: oZ8. 1978 21. H.rttr. MR., Towle, Vl., loIkrzewski. M., .nd MOYf'r. S.M.; An obltctlvt mdlunl of binocular vision in hum.ns: Slze·specific inlerOculolr suppres. sion of visu.ll tvoked polenti.lls. EI~clrO('nCtphdlogr. CJm. Neurophyslo/. 4); 8:!5, 1977. Z!. 0ttuchl, Y: V«tor .an.llysls of p.ltem VEP. Ophth.l. Res 13: 1.51. 1081 23. Femsod, M.. Hoyt, W.F..•nd Wilson, W.B.: Supra. sln.te html.anopl. Ltncet I: 1225. 1914. Z-I flortntlni. A. MaHt"i, l.. PirchlO. M., Spinelli. D., .nd Porcl.tti. V.: The ERG In response 10 alt~matiI13 Rutlngs In JUlltnts w,th dlSt..ses of lhe peripheral vlsu.a1 poIlhw.y. Invest Ophth./mo/. Vis. Sci. 21: -IQ(). 10&1. Acknowledgment This worl.. wu supponf'd In poIn by .. gr.Jt\t &om RPSt.rch to Pl't"Vt'nl Blindness, Inc.. New York, N~ Yor~ 1000poIrtment of Ophthalmology). Wnlt' "" reprints to: Ronald M. Surde. M.D.. [)topoInmenl of OphlhalmokJsy_Box 8096, 660 South Euclid Avenut, St. louis. Missouri 63IIO. |
