Electroretinogram b/a wave ratio improvement in central retinal vein obstruction

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1 BritishJournl ofophthlmology 1994; 78: Schepens Eye Reserch Institute, 20 Stniford Street, Boston, USA Y Mtsui O Ktsumi T Hirose Retin Assocites, 100 Chrles River Plz, Boston, USA O Ktsumi T Hirose Deprtment of Ophthlmology, Hrvrd Medicl School, Boston, USA O Ktsumi T Hirose Deprtment of Ophthlmology, Fculty of Medicine, Kyoto University, Kyoto, Jpn Y Mtsui H Skue Correspondence to: Ttsuo Hirose, MD. Accepted for publiction 26 August 1993 Electroretinogrm b/ wve rtio improvement in centrl retinl vein obstruction Yoshie Mtsui, Osmu Ktsumi, Hiroshi Skue, Ttsuo Hirose Abstrct The electroretinogrm (ERG), especilly the b/ wve rtio, is considered good indictor of retinl ischemi in centrl retinl vein obstruction (CRVO). Seven CRVO ptients who showed b/ wve rtio improvement from <1 0 [negtive type (-) ERG] to 1 0 nd one from 1*07 to 1'53 were studied. Three mechnisms of chnge were observed: firstly, the b-wve mplitude incresed without n -wve mplitude decrese (group A, n=2); secondly, the b-wve mplitude incresed with n -wve mplitude decrese (group B, n=4); nd, thirdly, both decresed, but the -wve mplitude decresed more mrkedly (group C, n=2). In group A, the visul cuities improved mrkedly. In group B, the visul cuities improved in two cses in which the b-wve mplitude reched the norml rnge; the visul cuities did not improve in two cses in which the b-wve mplitude did not rech the norml rnge. In group C, the visul cuities remined poor. The negtive (-) ERG or significntly reduced b/ wve rtio is ssocited with ischemic CRVO nd did not occur becuse of the filtering effect of the hemorrhge, which my reduce the stimulus light for the ERG. Improvement of the reduced b/ wve rtio with n incresed b-wve mplitude ws ccompnied by improvements in fundus ppernce nd visul cuity in CRVO. The results suggest tht the retinl ischemi in CRVO, s reveled by the ERG nd fluorescein ngiogrm, my be reversible in some cses. (Br_J Ophthlmol 1994; 78: ) The prognosis of centrl retinl vein obstruction (CRVO) is believed to depend on the severity of the circultory disturbnce of the retin: the more severe the disturbnce, the poorer the prognosis. 2 Ablting the non-perfused retin by lser cogultion in ischemic CRVO hs been topic of discussion.3 4 Therefore, when dignosis of CRVO is mde, besides finding the possible cuse of the disese, the next step is evluting the degree of retinl ischemi. When the centrl retinl rtery is completely obstructed, cusing severe generlised retinl ischemi, the electroretinogrm (ERG) b-wve, which is generted in the neurl retinl lyers, is selectively depressed, nd the -wve, which origintes in the receptors, remins norml or becomes lrger thn norml.'6 On the other hnd, in CRVO, the ERG b-wve, both mplitude nd implicit time, nd the b/ wve rtio vry, nd the vrition is believed to depend upon the degree of retinl ischemi.i'-i" If the ERG b-wve rtio becomes very smll in the eye 191 with CRVO, similr to tht observed in centrl retinl rtery obstruction, one cn conclude tht the overll retinl ischemi is very severe. Thus, the ERG b/ wve rtio cn be used s mesure of the degree of retinl ischemi t the time of initil evlution s well s during follow up in ptients with CRVO.8 Johnson et l'2 reported tht the log K vlue of the Nk-Rushton function of the b-wve mplitude is well correlted with retinl ischemi. Aside from the ERG b-wve, 30 Hz flicker implicit time is lso reported to be sensitive indictor of retinl ischemi.""1 It hd been reported tht 5-7% of eyes with non-ischemic CRVO progress to the ischemic type' I14; menwhile, it hd not been reported tht ischemic CRVO cn become nonischemic. We report herein the clinicl findings in eight cses of CRVO in which the ERG b/ wve rtio improved during the course of observtion. Ptients nd methods We studied eight ptients (six men, two women; 35 to 76 yers of ge) with unilterl CRVO who were referred to the Retin Assocites, Boston. Of 15 ptients who showed negtive (-) type ERGs t the initil visit nd hd ERGs recorded more thn once, these eight showed improved ERG b/ wve rtios during follow up. Two ptients with dibetes mellitus nd three ptients with systemic hypertension with no chnge in the retin specific to ech disese were included in this study. The ERG ws recorded in cses 1 nd 3-7 by method described previously.'5 A Jcobson-type contct lens electrode (Dunker Lbortories Inc, Srsot, FL, USA) ws used s n ctive electrode. The reference electrode ws plced on the ipsilterl cheek, nd the ground electrodes were plced on both erlobes. The ptients' pupils were fully dilted with 1% cyclopentolte hydrochloride nd 2 5% phenylephrine hydrochloride. Thirty minutes of drk dpttion preceded the ERG recording. The light source ws stroboscopic light (Model PS-22, Grss Instrument Co, Quincy, MA, USA). The photopic b-wve ws determined with red light, nd the scotopic b-wve ws obtined with dim blue light. Photopic flicker responses were obtined with reltively bright white flickering light (intensity 8 t 32 Hz). Single white flsh responses were recorded with n ctul light intensity of 48 5 lux seconds. Responses were mplified using filter with bndpss Hz (Model 7D, Grss Instrument Co). In cses 2 nd 8, the ERG ws recorded with the LKC System UTAS E 2000 (LKC Technologies, Inc, Githerberg, MD, USA). A Burin-Allen monopolr type contct lens Br J Ophthlmol: first published s /bjo on 1 Mrch Downloded from on 7 September 2018 by guest. Protected by copyright.

2 192 Mtsui, Ktsumi, Skue, Hirose Tble 1 Results ofelectroretinogrph recording with bright white flsh nd viswl cuity Durtion -Wve b-wve Cse Age from onset mplitude mplitude b/ Wve Visul No (yers) Sex (months) (RtV) (RsV) rtio cuity 1 65 F CF CF CF 10 2% / % / / / / / M / / M CF / M / / M / CF 6 68 F CF CF 7 47 M HM HM 8 74 M CF CF HM=hnd movement; CF=counting fingers. Age-mtched normls: -wve mplitude: , , , , nd ItV t ges 26-35, 36-45, 46-55, 56-65, nd >66 yers, respectively. Age-mtched normls: b-wve mplitude: , , , , nd tv t ges 26-35, 36-45, 46-55, 56-65, nd >66 yers, respectively. Figure I The chnge ofthe electroretinogrm (ERG) results with bright whiteflsh in group A ptients. The visul cuities t the time of ech ERG recording re shown beside the b/ wve mplitude rtio. CF= countingfingers. electrode ws used s the ctive electrode. The reference electrode ws plced on the forehed, nd the ground electrodes were plced on both erlobes. The ptients' pupils were fully dilted with 1% cyclopentolte hydrochloride nd 2-5% phenylephrine hydrochloride. After 45 minutes of drk dpttion, responses to single white flsh stimuli with Gnzfeld stimultor bowl were recorded, the intensity of which ws 2-8 log cd/m2. The responses were mplified using filter with bndpss Hz. Initil ERGs were recorded between 1 nd 6 months fter CRVO onset, nd the lst ERGs were recorded between 6 nd 75 months fter 3 _ C-. ( E C- = -6 C > 400- _- E i-c %^^ /500 Group A Cse CF Cse 3 20/200 O s 6 -wve mplitude ---* b-wve mplitude b/ wve rtio CRVO onset. Pnretinl photocogultion (PRP) ws performed in cses 1 nd 7 t 11 nd 3 months, respectively, fter CRVO onset. A stndrd sequence ws used in the fluorescein ngiogrphy (FA) exmintion s reported previously.'6 The erly frmes concentrted on the disc nd mcul, the intermedite frmes on the midperipherl re in ech qudrnt, nd the lte frmes on the disc nd mcul gin. These studies were performed using Kodk Tri-X 400 ASA film (Kodk, Rochester, NY, USA), nd mesurements were mde on n Agf F071 1P positive print trnsprency. The clinicl work in this study ws performed in conformity with the tenets of the Declrtion of Helsinki. Before the ERG testing nd FA, the procedures were explined fully to ptients, nd informed consent ws obtined in ll cses. Results OVERALL ANALYSIS Tble 1 shows the results of ERG with bright white flsh in ech ptient. In ll cses (except cse 3 whose b/ wve rtio ws 1-07), the ERG b/ wve mplitude rtio incresed during follow up from <1-0 to l1-0. After nlysing the chnge of the -wve nd b-wve mplitudes, we found three vritions tht ffect the ERG b/ wve rtio: group A is comprised of those in which the b/ wve rtio incresed becuse of n incresed b-wve mplitude only; group B, those in which the -wve mplitude decresed nd the b-wve mplitude incresed; nd group C, those in which both the -wve nd b-wve mplitudes decresed, but the -wve mplitude did so more mrkedly. Group A Cses 2 nd 3. The b/ wve mplitude rtio incresed minly due to n increse of the b-wve mplitude from 457 to 510 [tv nd 319 to 450 o,tv in cses 2 (Fig 1, top) nd 3 (Fig 1, bottom X nd Fig 2, top), respectively. The -wve mpli-, tudes remined t pproximtely the sme level. c The visul cuities improved from 20/500 to 1 20/100 nd counting fingers t 6-8 feet to 20/200 in cses 2 nd 3, respectively. Regrding the t-0 75 other ERG components, the -wve pek time shortened in both cses (Fig 2, top, Tble 2). In cse 2, cpillry dropout nd fluorescein lekge initilly were prominent on FA in the midperipherl retin with severe intrretinl hemorrhge nd retinl oedem. At the time of the second ERG recording, cpillry dropout nd fluorescein lekge were not observed. Retinl hemorrhge diminished mrkedly. 15 > In cse 3, exudtes in the posterior pole nd B extensive intrretinl hemorrhge were promi- 1.0 Q nent (Fig 2, middle left). On FA, the veins were mrkedly dilted, while the presence of cpillry 0 5 dropout ws undetermined becuse of extensive retinl hemorrhge (Fig 2, middle right). Exudtes disppered during follow up with the decrese of retinl hemorrhge (Fig 2, bottom left). On FA, venous dilttion nd lekge were diminished (Fig 2, bottom right). Br J Ophthlmol: first published s /bjo on 1 Mrch Downloded from on 7 September 2018 by guest. Protected by copyright.

3 Electroretinogrm bl wve rtio improvement in centrl retinl vein obstruction 193 Group A Cse 3 55 months 1 month b.,w', / b, we 4 V 50 ms 100 OjV Figure 2 (Top) The electroretinogrm (ERG) recordings with bright whiteflsh in cse 3 (groupa) t I nd 5 5 months fter the onset ofcentrl retinl vein obstruction (CRVO). Arrows indicte the strt offlsh stimulus. The b-wve mplitude incresed, while the -wve mplitude remined t the sme level of the ERG recording 5 5 months fter CRVO onset. (Middle left nd middle right) The findus photogrph ndfluorescein ngiogrm (FA) t I month. (Bottom left nd bottom right) Fundus photogrph nd FA t S S months fter CRVO onset. (Middle left) Exudtes in the posterior pole nd extensive intrretinl hemorrhge were prominent. The optic nerve hed is congested. (Middle nght) On FA, the veins were mrkedly dilted, while the presence ofcpillry dropout ws seen but prtly covered by the extensive retinl hemorrhge. (Bottom left) Exudtes disppered duringfollow up with the decrese ofretinl hemorrhge. The optic nerve hed is less congested. (Bottom right) On FA, venous dilttion diminished. Br J Ophthlmol: first published s /bjo on 1 Mrch Downloded from Group B Cses I nd 4-6. In cse 1, the ERG results were compred from recordings done 4-5 nd 75 months fter CRVO onset. In this group, the b-wve mplitudes incresed, while the -wve mplitudes decresed. These four cses were subdivided further into two types ccording to the b-wve mplitude t the lst ERG recordings (Fig 3). In Group B1 [cses 1 (Fig 3, top left nd Fig 4, top) nd 4 (Fig 3, bottom left)], the b-wve mplitudes improved to the level of our gemtched norml controls in both cses: 278 to 405 RV (norml rnge for the ge: RV) nd 363 to 420 RV (norml rnge for the ge: RV), respectively. The -wve mplitudes decresed from supernorml to the norml level of our ge-mtched controls, 220 iiv in cse 1 nd 298 RV in cse 4, respectively. The visul cuities improved in these two cses from counting fingers t 2-3 feet to 20/100 nd from 20/25 to 20/20, respectively. All other ERG components improved in cse 1 nd improved or remined t the sme level except for the scotopic b-wve mplitude in cse 4 (Tble 2). In group B2 (cses 5 nd 6), the b-wve mplitudes incresed from 344 to 385 tv in cse 5 (Fig 3, top right) nd 100 to 158,uV in cse 6 (Fig 3, bottom right), but did not rech the level of the ge-mtched norml controls. The -wve mplitudes decresed from 422 to 319 IiV in cse 5 nd from 192 to 150 jiv in cse 6. The visul cuities remined t counting fingers in both cses. In cse 1, extensive cpillry dropout with microneurysms nd multiple cotton wool spots initilly were observed (Fig 4, middle left). Intrretinl lekge ssumed cystoid pttern in the fove (Fig 4, middle right). After follow up, multiple photocogultion scrs were present on 7 September 2018 by guest. Protected by copyright.

4 194 Mtsui, Ktsumi, Skue, Hirose Tble 2 Chnges ofelectroretinogrm results -Wve pek Cse Durtion from Photopic b-wve Scotopic b-wve Flicker mplitude time with white Photoptc Scotopic b-wve No onset (months) mplitude (1sV) mplitude (RlV) (RlV) flsh (ms) b-wve pek pek time (ms) time (ms) Non-recordble Non-recordble Non-recordble Non-recordble Non-recordble Non-recordble Non-recordble Non-recordble Non-recordble Non-recordble Non-recordble Non-recordble Age-mtched norml controls: Photopic b-wve mplitude: , , , nd RV t ges 26-35, 46-55, 56-65, nd 66 yers. Scotopic b-wve mplitude: , , , nd RtV t ges 26-35, 46, 55, 56, 65, nd 66. Flicker mplitude: , , , nd t ges 26-35, 46-55, 56-65, nd >66. -Wve pek time with white flsh: , , , nd ms t ges 26-35, 46-55, 56-65, nd >66. Photopic b-wve pek time: , , , nd ms t ges 26-35, 46-55, 56-65, nd 66. Scotopic b-wve pek time: % , , , nd t outside nd prtly inside the vsculr rcde (Fig 4, bottom left). On FA, cpillry dropout nd vein lekge disppered (Fig 4, bottom right). In cse 4, multiple intrretinl hemorrhge, which ws present initilly, clered during follow up. Cpillry dropout ws not observed on FA t the initil visit, while lekge from the (1 > s _ >v-v ~g) -o - Co. E ns 4) Cse I-2-0 '-K 300 ~~~~~~20/ f1-0 CFIC Cse 4 r 0Cu I 20/ optic disc nd dilttion of the retinl veins were prominent. FA ws not repeted. In cse 5, exudtes in the posterior pole nd extensive retinl hemorrhge observed initilly disppered during follow up. A pigmentry scr in the mcul ppered during follow up. Extensive cpillry dropout nd micro- Group B ).2 il * 0 *, EC.0 >500, -V.0 l 5 co c o-- -wve mplitude -0 b-wve mplitude ---M-- b/ wve rtio,'20/20 - C 1-67 i D co Q L.. > E ! > 120 D0 I O c6s 20/400 Cse X 0 co I., I I I, CF/, Cse 6 -- F Ax CF ( X Figure 3 The results ofthe electroretinogrm (ERG) with bright whiteflsh in group B ptients. The visul cuities t the time ofech ERG recording re shown beside the b/ wve mplitude rtios. The twofigures on the left (cses I nd 4) re group Bl, nd the two on the right (cses S nd 6) re group B2. CF=countingfingers co D >1 > ~~~~~~~~._ 300 _ ^ Br J Ophthlmol: first published s /bjo on 1 Mrch Downloded from on 7 September 2018 by guest. Protected by copyright.

5 Electroretinogrm bl wve rtio improvement in centrl retinl vein obstruction 195 Group B Cse months 75 months b \/ b \Oms 1100 RV y 50 ms 4L Figure 4 (Top) The electroretinogrm (ERG) recordings with bright whiteflsh in cse I (group B) t4s5 nd 75 months fter the onset ofcentrl retinl vein obstruction (CRVO). Arrows indicte the strt offlsh stimulus. The b-wve mplitude incresed, nd the -wve mplitude decresed t the ERG recording 75 months ftercrvo onset. (Middle left nd middle right) Thefundus photogrph ndfluorescein ngiogrm (FA) t 1 month. (Bottom left nd bottom right) Fundusphotogrph ndfa t 55 months fter CRVO onset. (Middle left nd middle right) Initilly, extensive cpillry dropout with microneurysms nd multiple cotton wool spots were present nd intrretinl lekge ssumed cystoid pttem in thefove. (Botom left) Afterfollow up, multiple photocogultion scrs were present outside nd prtly inside the vsculr rcde. (Middle right) Chorioretinl trophy ws observed in the mcul. (Bottom right) On FA, cpillry dropout nd vein lekge disppered. Br J Ophthlmol: first published s /bjo on 1 Mrch Downloded from neurysms were observed in the posterior pole on FA t the time of the initil ERG recording. However, FA ws not repeted in this ptient. In cse 6, exudte in the posterior pole disppered, nd retinl hemorrhge decresed during follow up. FA ws not performed becuse of ptient llergy to fluorescein. Group C Cses 7 nd 8. The -wve nd b-wve mplitudes with bright white flsh both decresed in these cses, with the decrese of the -wve mplitude lrger thn tht of the b-wve mplitude: 224 to 133 [iv in cse 7 (Fig 5, top nd Fig 6, top), nd 426 to 298 [tv in cse 8 (Fig 5, bottom). As result, the b/ wve mplitude rtio incresed. The -wve pek time shortened in both cses (Tble 2). The visul cuities remined hnd movement in cse 7 nd counting fingers in cse 8. In cse 7, exudte ws extensive round the disc. The retin in the mculr re ws oedemtous initilly (Fig 6, top left). Extensive cpillry dropout ws observed on FA t the time of the initil ERG recording (Fig 6, bottom right). The intrretinl hemorrhge decresed, the exudte disppered, nd mculr degenertion developed during follow up (Fig 6, bottom left). However, FA ws not repeted. on 7 September 2018 by guest. Protected by copyright.

6 196 Mtsui, Ktsumi, Skue, Hirose Figure S The results ofthe electroretinogrm (ERG) with bright whiteflsh in group C ptients. The visul cuities t the time ofech ERG recording re shown beside the bl wve mplitude rtio. PRP=pnretinl photocogultion; HM=hnd moveent; CF=countingfingers. co 1. A Q: 0 _ 0 ) U. L.-V 220' CPRP Group C Cse s" 1.o H274-< ~07 il)nl D t [-0- -wve mplitude -* b-wve mplitude ---<"--- b/ wve rtio In cse 8, the retin in the mculr re ws oedemtous initilly, nd mculr degenertion ppered during follow up. Cpillry dropout ws not observed in either the first or second FA. The mount of retinl hemorrhge decresed but ws still extensive t the time of the second ERG recording. Cse report A 65-yer-old femle ptient (cse 1) (Fig 7) noticed decrese of vision in her right eye, nd 1 month lter, she ws dignosed with CRVO nd treted with systemic steroids. She ws reexmined by us 2 months fter CRVO onset. She hd been suffering from dibetes mellitus, but hd no dibetic retinopthy in either eye. At the first ERG recording, 2 months fter the onset of CRVO, both the -wve nd b-wve mplitudes were supernorml, nd the b/ wve mplitude rtio ws The vein ws mrkedly engorged nd tortuous. Multiple intrretinl hemorrhges nd cotton wool exudtes were observed. Visul cuity ws counting fingers t 4-5 feet. At the time of her second ERG recording 21/2 months lter, both the -wve nd b-wve mplitudes, but especilly the ltter, decresed, nd the b/ wve mplitude rtio decresed to Retinl hemorrhge nd exudtes were mrked. However, t the third ERG recording 8 months fter onset, the b-wve mplitude incresed from 278 to 446 [iv, more mrked chnge thn the increse in the -wve mplitude (363 to 367 lv). Accordingly, the b/ wve mplitude rtio incresed lo 1V22. Visul cuity remined counting fingers t 6-8 feet. The mount of retinl hemorrhge nd exudtes decresed. Group C Cse 7 2 months 7 months t b 50 ms 100 I1V Br J Ophthlmol: first published s /bjo on 1 Mrch Downloded from Figure 6 (Top right) The electroretinogrm (ERG) recordings with bright whiteflsh in cse 7 (group C) t 2 nd 7 months fter the onset ofcentl retinl vein obstruction (CRVO). Arrows indicte the strt offlsh stimulus. Both the -wve nd b-wve mplitudes decresed t the ERG recording 7 months fter CRVO onset. (Top left nd bottom right) Thefundus photogrph nd fluorescein ngogrm (FA) t 2 months. (Bottom left) The fundus photogrph t 7 months fter CRVO onset. (Top left) The rein in the mculr re ws oedemtous initilly. (Bottom right) Extensive cpillry dropout ws observed on FA t the time ofthe initilerg recording. However, FA ws not repeted. (Bottom left) The intrretinl hemorrhge decresed, the exudte disppered, nd mculr degenertion developed duringfollow up. on 7 September 2018 by guest. Protected by copyright.

7 Electroretinogrm bl wve rtio improvement in centrl retinl vein obstruction 197 -o ' E 'I) VD c c6 Cse 1 Figure 7 The time course of the electroretinogrm (ERG) -wve nd b-wve mplitudes nd b/ wve At the fourth ERG recording 10 months fter mplitude rtio with bright CRVO onset, the b/ wve mplitude rtio whiteflsh in cse 1. The incresed to 1 44, nd her visul cuity improved visul cuities t the time of to 20/300. Brrge photocogultion ws perech ERG recording re shown beside the b/ wve formed with green lser 11 months fter onset mplitude rtios. PRP=pnretinl CF=countingfingers. becuse of the presence of mrked nd wide- spred cpillry dropout in the posterior pole FA (Fig 4, middle right). The fifth ERG recording, fter lser tretment showed decrese in both the -wve nd b-wve mplitudes temporlly. The visul cuity incresed to 20/200. Retinl hemorrhge diminished nd exudtes were bsorbed, while vsculr nstomosis ws observed on the disc. At the sixth ERG recording 14 months fter lser tretment (30 months fter CRVO onset), both the -wves nd the b-wves incresed (217 to 311 FtV nd 396 to 513 [tv, respectively). Retinl hemorrhge nd the vsculr nstomosis on the disc disppered. During the 4 yer follow up, three dditionl ERGs were recorded, with similr findings. Finlly, 75 months fter onset, the b/ wve mplitude rtio incresed to The b-wve mplitude incresed nd the -wve mplitude decresed compred with the ERG results t 4 5 months from onset when the b/ wve mplitude rtio ws < 1-0. On FA, cpillry dropout, which ws observed until 42 months fter CRVO onset, could not be observed t 62 months (Fig 4, bottom right). The visul cuity improved to the 20/100-20/70 rnge. All other ERG components incresed in mplitude but remined below norml (Tble 2). Discussion After nlysing the ERG recordings of the eight cses in which the b/ wve mplitude rtio ws below 1-0, then incresed during the follow up period, we observed three ptterns of chnge in the ERG b/ wve rtio: firstly, n incresed b-wve mplitude (group A); secondly, n incresed b-wve mplitude ssocited with decresed -wve mplitude (group B); nd thirdly, decresed -wve nd b-wve mplitudes, the former more mrked, resulting in n incresed b/ wve rtio (group C). The -wve mplitude remined t lmost the sme level in group A nd decresed in groups B nd C. Considering the improvement of the ERG, FA, fundus ppernce, nd visul cuity, we speculte tht the degree of retinl ischemi ctully decresed nd the retinl function showed significnt improvement in two group A ptients nd two group B1 ptients in whom the b-wve mplitude improved to the level of the norml controls. These cses suggest tht ischemic CRVO my improve to less ischemic CRVO. On the other hnd, in the two ptients in group B2, the b-wve mplitude incresed but did not rech the level of the norml controls. The visul cuities remined poor, lthough retinl hemorrhge nd exudtes decresed in both cses. In this group, the b-wve mplitude seemed to be n importnt fctor: the greter the improvement of the b-wve mplitude to the level of the norml ge-mtched controls the more ctive the compenstion ginst ischemi (the recovery of retinl blood flow). In group C, the retinl function ws not thought to be improved, becuse both the -wve nd b-wve mplitudes decresed. The visul cuities remined poor in these cses. Although the ERG b-wve mplitude, which reflects the overll retinl function, is not direct predictor of visul cuity, we reported recently tht when the b-wve mplitudes or the b/ wve rtios were decresed on the initil ERG recordings soon fter the onset of CRVO, the visul cuities were poor (worse thn 20/200) in ll cses fter follow up of more thn 1 yer. 17 Therefore, the ptients should be followed crefully, becuse the follow up periods of five of the eight cses (60%) in this study were less thn 1 yer. According to the clssifiction of Hyreh,' the visul prognosis of ischemic CRVO is poor; however, tht of non-ischemic CRVO is fvourble. According to our results, we believe tht n improvement of retinl function nd chnge in the degree of retinl ischemi from ischemic CRVO to less ischemic CRVO cn occur. To our knowledge, such n occurrence in CRVO hs not been reported, with the exception of n improvement in b-wve mplitude from negtive (-) type ERG reported in metllosis bulbi.'8 In experimentl reserch using monkeys, Hyreh et l'9 reported tht hemorrhgic CRVO (ischemic CRVO) occurred when the centrl retinl vein occlusion is ccompnied by trnsient (6-7 5 hours) centrl retinl rtery occlusion. When both the centrl retinl vein nd rtery re occluded completely, retinl cpillry oblitertion occurred without development of hemorrhgic or venosttic (non-ischemic) CRVO. Kurchi nd couthors"o reported tht temporl retinl circultory disturbnce in Tkysu's disese cused trnsient decrese of b-wve mplitude: temporl negtive (-) type ERG insted of permnent chnge. Hyreh et l reported tht retinl dmge fter trnsient centrl retinl rtery occlusion ws reversible if the retinl ischemi ws less thn 97 minutes nd the ERG b-wve ws reversible for up to 135 minutes of ischemi.2' Therefore, under certin conditions, retinl impirment cused by trnsient ischemi might be reversible - for Br J Ophthlmol: first published s /bjo on 1 Mrch Downloded from on 7 September 2018 by guest. Protected by copyright.

8 198 Mtsui, Ktsumi, Skue, Hirose exmple, when the period of ischemi is short, when the degree of ischemi is moderte, or combintion of these. The ERG b-wve is generted in the middle retinl lyer in which the blood supply is provided minly by the retinl circultion. Accordingly, the b-wve mplitude is believed to be good indictor of the retinl circultion. Among our eight cses, the b-wve mplitude returned to norml in four (groups A nd B1); the visul cuities improved in ll of them. The b-wve mplitudes improved but did not rech the level of the norml ge-mtched control in two cses (group B2) nd decresed in two cses (group C). In these four cses, the visul cuities remined poor. We report here tht improvement of retinl function in ischemic CRVO ccompnied with visul cuity improvement cn occur, nd is correlted with the recovery of the b-wve mplitude recorded with bright white flsh. A ntionwide CRVO study is under wy tht will provide informtion bout how the ERG would be helpful to mnge this disese. Prt of this work ws presented t the nnul meeting of the Assocition for Reserch in Vision nd Ophthlmology, Srsot, Florid, 5 My We pprecite the support of Chrles L Schepens, MD. Elizbeth W Lrson nd Chrlene J Skldzien provided technicl ssistnce. Lynd C Chrters edited the mnuscript. This investigtion ws supported in prt by grnt from the Ntionl Institutes of Helth (EY ). 1 Hyreh SS. Clssifiction of centrl retinl vein occlusion. Ophthlmology 1983; 90: Hyreh SS. So-clled 'centrl retinl vein occlusion'. I. Pthogenesis, terminology, clinicl fetures. Ophthlmologic 1976; 172: Mgrgl LE, Brown G, Augsburger JJ, Prrish RII. Neovsculr glucom following centrl retinl vein obstruction. Ophthlmology 1981; 88: Mgrgl LE, Brown G, Augsburger JJ, Donoso LA. Efficcy of pnretinl photocogultion in preventing neovsculr glucom following ischemic centrl retinl vein obstruction. Ophthmology 1982; 89: Krpe G, Uchermnn A. The clinicl electroretinogrm. VII. The electroretinogrm in circultory disturbnces of the retin. Act Ophthlmol 1955; 33: Thler A, Heilig P. EOG nd ERG comprison in ischemic retinopthy. Ophthlmic Res 1977; 9: Krpe G, Germnis M. The prognostic vlue of the electroretinogrm in thrombosis of the retinl veins. Act Ophthlmol 1962; 70 (suppl): Sbtes R, Hirose T, McMeel JW. Electroretinogrphy in the prognosis nd clssifiction of centrl retinl vein occlusion. Arch Ophthlmol 1983;.101: Hyreh SS, Klugmn MR, Podhisky P, Kolder HE. Electroretinogrphy in centrl retinl vein occlusion. Correltion of electroretinogrphic chnges with pupillry bnormlities. Grefes Arch Clin Exp Ophthlmol 1989; 227: Breton ME, Quinn GE, Keene SS, Dhmen JC, Brucker AJ. Electroretinogrm prmeters t presenttion s predictors of rubeosis in centrl retinl vein occlusion ptients. Ophthlmology 1989; 96: Kye SB, Hrding SP. Erly electroretinogrphy in unilterl centrl retinl vein occlusion s predictor ofrubeosis irides. Arch Ophthlmol 1988; 106: Johnson MA, Mrcus S, Elmn MJ, McPhee TJ. Neovsculriztion in centrl retinl vein occlusion: electroretinogrphic findings. Arch Ophthlmol 1988; 106: Morrell AJ, Thompson DA, Bruckner AJ, Quinn GE. Electroretinogrphy s prognostic indictor of neovsculristion in CRVO. Eye 1991; 5: Minturn J, Brown GC. Progression of nonischemic centrl retinl vein obstruction to the ischemic vrint. Ophthlmology 1986; 93: Hirose T, Wolf E, Hr A. Electrophysiologicl nd psychologicl studies in congenitl retinoschisis of X-linked recessive inheritnce. In: Lwwill T, ed. ERG, VER, nd psychophysics. The Hgue: Junk Publishers, 1977; 13: Weiter JJ, Delori F, Dorey K. Centrl spring in nnulr mculr degenertion. Am J Ophthlmol 1988; 106: Mtsui Y, Ktsumi 0, McMeel JW, Hirose T. Prognostic vlue of electroretinogrm (ERG) in centrl retinl vein obstruction (CRVO). Invest Ophthlmol Vis Sci 1991; 32 (suppl): Knve B. Electroretinogrphy in eyes with retined introculr metllic foreign bodies. Act Ophthlmol 1969; 47 (suppl): Hyreh SS, Vn Heuven WAJ, Hyreh MS. Experimentl retinl vsculr occlusion. I. Pthogenesis of centrl retinl vein occlusion. Arch Ophthlmol 1978; 96: Kurchi Y, Hirose T, Yonemur D. ERG in pulseless (Tkysu's) disese. Jpn J Ophthlmol 1966; 10 (suppl): Hyreh SS, Kolder HE, Weingeist TA. Centrl retinl rtery occlusion nd retinl tolernce time. Ophthlmology 1980; 87: Br J Ophthlmol: first published s /bjo on 1 Mrch Downloded from on 7 September 2018 by guest. Protected by copyright.