Purpose
In addition to visual fields (VF), multifocal electroretinograms (mfERGs) and frequency-domain optical coherence tomography (fdOCT) scans are used to rule out a retinal etiology. To assess when the mfERG is needed in addition to the fdOCT, we evaluated results from patients with suspected retinal disease.
Methods
50 eyes from 40 patients (53.8 yrs.) with reliable abnormal 24-2 or 30-2 VFs (Zeiss Meditec) suspected of having a retinal abnormality were evaluated using fdOCT scans (Topcon Inc, Japan) and mfERGs (Veris, EDI, CA). All patients had 9 mm horizontal and vertical line scans as well as macular cube and disk volume scans. The mfERGs were recorded with Burien-Allen electrodes and a display with 103 hexagons. For each eye, the fdOCT and mfERG results were reviewed by 2 experienced observers and classified as normal, inconclusive, or abnormal. A result was classified as abnormal only if the abnormality was topographically consistent with the VF findings. The mfERG was considered abnormal if the amplitude was significantly decreased and/or the latency was delayed. The fdOCT was considered abnormal if the outer retinal layers (i.e. receptor plus inner nuclear layer) were markedly decreased in thickness and/or showed marked distortions.
Results
Fifteen of the 50 eyes were abnormal on fdOCT (outer retina) in topographical agreement with the VF. Of the remaining 35, 32 eyes were normal on fdOCT (outer retina): 21 of these were also normal on mfERG while 5 were abnormal, and 6 were inconclusive. In addition, 3 eyes were classified as inconclusive on fdOCT and required further testing with mfERGs, all of which were then classified as abnormal. Of the 32 eyes with normal fdOCT (outer retina), 16 had inner retinal (ganglion cell and/or retinal nerve fiber layer) damage.
Conclusions
Given that fdOCT is faster and easier to perform than the mfERG, to rule out retinal disease, patients should be tested first with the fdOCT, which can also pick up optic nerve disease. Because a normal fdOCT does not necessarily rule out retinal damage, it should be followed with the mfERG test. [1,2] In the population studied here, this strategy would have reduced the need for mfERGs by 30%. 1. Dale et al. Doc Ophthalmol, 2009 120:175. 2. Talamini et al. Doc Ophthalmol 2011, pp. 187-192.
Keywords: 688 retina •
509 electroretinography: clinical •
612 neuro-ophthalmology: diagnosis