Sir,
We agree with Mahroo’s1 helpful suggestions on the utility of electroretinography (ERG) in suspected transient retinal artery occlusion (TRAO) cases.
TRAO is a recently proposed clinical entity supported by OCT findings.2, 3 The ERG features of TRAO are yet to be described, and may be sought as part of a prospective case-finding study. Two limitations of Ganzfeld ERG in TRAO are: (1) branch pattern TRAO may not be detected; and (2) b-wave attenuation on ERG reverses fully after 30 min in experimental models of transient retinal ischaemia.4 ERG evidence of widespread ischaemia may vanish before testing takes place.
However, if there is perimetric or OCT evidence of ongoing retinal ischaemia when ERG is performed, it is likely that ERG abnormalities would be detectable. If the ischaemic changes extend beyond the obviously affected area of the retina, the Ganzfeld ERG might provide evidence of retinal ischaemia in the form of b-wave amplitude reduction and increased 30-Hz photopic flicker implicit time.
The multifocal ERG (mfERG) may provide evidence of localised ischaemic changes and might have contributed to the diagnosis in cases 2 and 3.2 Branch retinal artery occlusion attenuates the N1, P1, and N2 components in the distribution of ischaemic retina on mfERG.5 mfERG is capable of identifying wider retinal dysfunction than that suggested clinically.6 It has been used to demonstrate functional recovery following retinal artery occlusion7 and to detect subclinical retinal dysfunction in Susac’s syndrome.8 Pattern ERG may also demonstrate reduced amplitude or delayed P50 in cases of macula-involving TRAO, and may have supported a diagnosis in case 1.2
The mechanism underlying TRAO is unknown. If vasospasm or thromboembolism was responsible, it is conceivable that retinal ischaemia may persist beyond the specific occlusive episode and may be detectable on ERG or mfERG. It is also possible that reperfusion after prolonged TRAO would produce ERG changes, although we are not aware of this having been studied in human subjects.
Although a normal ERG may not exclude TRAO, it may therefore be considered in suspected TRAO when OCT findings are inconclusive or where persistent retinal ischaemia is suspected.
References
Mahroo O . Electroretinography can provide objective assessment of inner retinal function prior to atrophic change on OCT. Eye (Lond) 2015; 29 (11): 1513.
Yusuf IH, Fung TH, Wasik M, Patel CK . Transient retinal artery occlusion during phacoemulsification cataract surgery. Eye (Lond) 2014; 28 (11): 1375–1379.
Yusuf IH, Fung TH, Wasik M, Patel CK . Reply: transient retinal artery occlusion during phacoemulsification cataract surgery. Eye (Lond) 2015; 29 (4): 591–592.
Block F, Schwarz M, Sontag KH . Retinal ischemia induced by occlusion of both common carotid arteries in rats as demonstrated by electroretinography. Neurosci Lett 1992; 144 (1-2): 124–126.
Ohshima A, Hasegawa S, Takada R, Takagi M, Abe H . Multifocal electroretinograms in patients with branch retinal artery occlusion. Jpn J Ophthalmol 2001; 45 (5): 516–522.
Wildberger H, Junghardt A . Local visual field defects correlate with the multifocal electroretinogram (mfERG) in retinal vascular branch occlusion. Klin Monbl Augenheilkd 2002; 219 (4): 254–258.
Inomata K, Shinoda K, Ohde H, Tsunoda K, Hanazono G, Kimura I et al. Transcorneal electrical stimulation of retina to treat longstanding retinal artery occlusion. Graefes Arch Clin Exp Ophthalmol 2007; 245 (12): 1773–1780.
van Winden M, Salu P . Branch retinal artery occlusion with visual field and multifocal erg in Susac syndrome: a case report. Doc Ophthalmol 2010; 121 (3): 223–229.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Competing interests
The authors declare no conflict of interest.
Rights and permissions
About this article
Cite this article
Yusuf, I., Smith, R. & Patel, C. Transient retinal artery occlusion: the potential utility and limitations of electroretinography. Eye 29, 1513–1514 (2015). https://doi.org/10.1038/eye.2015.117
Published:
Issue Date:
DOI: https://doi.org/10.1038/eye.2015.117