A comparison of multifocal ERG and frequency domain OCT changes in patients with abnormalities of the retina

Abstract

To compare the ability of the multifocal electroretinogram (mfERG) and frequency domain optical coherence tomography (fdOCT) to detect retinal abnormalities. A total of 198 eyes (100 patients) were referred by neuro-ophthalmologists to rule out a retinal etiology of visual impairment. All patients were evaluated with static automated perimetry (SAP) (Humphrey Visual Field Analyzer; Zeiss Meditec), mfERG (Veris, EDI) and fdOCT (3D-OCT 1000, Topcon). The mfERG was performed with 103 scaled hexagons and procedures conforming to ISCEV standards (Hood DC et al. (2008) Doc Ophthalmol 116(1):1-11). The fdOCT imaging included horizontal and vertical line scans through the fovea. Local mfERG and fdOCT abnormalities were compared to local regions of visual field sensitivity loss measured with SAP and categorized as normal/inconclusive or abnormal. 146 eyes were categorized as normal retina on both fdOCT and mfERG. The retina of 52 eyes (36 patients) was categorized as abnormal based upon mfERG and/or fdOCT. Of this group, 25 eyes (20 patients) were abnormal on both tests. However, 20 eyes (13 patients) were abnormal on mfERG, while the fdOCT was normal/inconclusive; and 7 eyes (7 patients) had normal or inconclusive mfERG, but abnormal fdOCT. Considerable disagreement exists between these two methods for detection of retinal abnormalities. The mfERG tends to miss small local abnormalities that are detectable on the fdOCT. On the other hand, the fdOCT can appear normal in the face of clearly abnormal mfERG and SAP results. While improved imaging and analysis may show fdOCT abnormalities in some cases, in others early damage may not appear on structural tests.

Fig. 1

Patient 1. a 30-2 SAP demonstrates dense nasal scotoma with inferior extension in the right eye. b mfERG with reduced amplitude and increased latency throughout most of the field for the right eye (blue waveforms). c fdOCT horizontal line scans of the left and right eyes demonstrate loss of the inner segment–outer segment (IS/OS) junction in the temporal retina of the right eye. a–c Red boxes identify corresponding regions of the retina

Fig. 2

Patient 2. a 24-2 SAP demonstrates paracentral scotomas in left and right eyes. b mfERG with reduced amplitude and increased latency in both eyes. c fdOCT demonstrates loss of the IS/OS junction, most prominent in the temporal retina of both eyes (red boxes). a–c Red boxes identify corresponding regions of the retina

Fig. 3

Patient 3. a 24-2 SAP demonstrates central scotomas (more pronounced inferiorly) in both eyes. b mfERG with marked reduction in amplitude and slight increase in latency in both eyes. c fdOCT demonstrates subtle disorganization of the IS/OS junction (red arrows) in both eyes; yellow arrow identifies shadow created by blood vessels. Red boxes (a and b) correspond to the fdOCT scan (c) through the retina 5° superior to the fovea

Fig. 4

Patient 4. a 10-2 SAP demonstrates dense central scotomas in both eyes. b mfERG with reduced amplitude and latency at the upper limit of normal throughout the central 10°. c fdOCT with normal appearance in both eyes. a–c Red boxes identify corresponding regions of the retina

Fig. 5

Patient 5. a 24-2 SAP is without significant abnormalities, but with reduced foveal sensitivity in the right eye (33 dB). b mfERG with slightly reduced amplitude of foveal waveform in the right eye (blue waveform). c fdOCT demonstrates thickening of outer retina in the right eye. a–c Red boxes identify corresponding regions of the retina

Fig. 6

Patient 6. a 10-2 SAP demonstrates scotoma in the right eye. b mfERG with slightly reduced waveform amplitude in the region corresponding to the SAP defect (red box). c fdOCT demonstrates dramatic thinning of the nasal retina in the right eye. a–c Red boxes identify corresponding regions of the retina

Fig. 7

fdOCT of 5 patients with normal mfERG results, but abnormal fdOCT results. fdOCT demonstrates: a macular hole, b premacular fibrosis, c macular hole status post surgical repair, d disorganization of inner segment–outer segment junction (unknown diagnosis/lost to follow-up), e loss of inner segment-outer segment junction (no definitive diagnosis)

Fig. 8

fdOCT of two patients presumed to have Stargardt disease: a fdOCT demonstrates clear loss of inner segment–outer segment junction at the fovea, b fdOCT demonstrates subtle reduction in density of inner segment–outer segment junction