Abstract
Purpose :
Multiple pathological processes occur in Birdshot chorioretinopathy with considerable variability making assessing activity and understanding disease mechanisms challenging. Exploring how structural and functional measurements may correlate may offer valuable insights. In this study we sought to explore correlations between macular optical coherence tomography (OCT) parameters and the 30 Hz photopic flicker electroretinogram (ERG), which derives from cone-driven inner retinal neurons.
Methods :
Birdshot patients seen in a single tertiary referral uveitis service underwent spectral domain OCT examination (6mm square scans using the Topcon 3D-OCT system, Topcon Corporation, Tokyo, Japan) and 30 Hz photopic flicker ERG recording using a hand-held device (RETeval, LKC Technologies, Inc., Gaithersburg, MD, USA). Correlation between anatomic parameters (central subfield thickness and macular volume) and functional parameters (amplitude and implicit time) was quantified.
Results :
Recordings were made from 12 patients (24 eyes). Mean (SD) age was 63 (5.7) years. Mean (SD) central subfield thickness was 238 (52.7) microns and mean (SD) macular volume was 6.92 (0.88) mm3, Mean (SD) ERG amplitudes and implicit times were 22.4 (13.7) and 29.3 (3.5) respectively. Correlation coefficients and p values were as follows: for OCT central subfield thickness and ERG amplitude, 0.51 (p=0.01); for central subfield thickness and ERG implicit time, -0.22 (p=0.3); for macular volume and ERG amplitude, 0.83 (p<0.0001); for macular volume and implicit time, -0.42 (p=0.04).
Conclusions :
With more severe disease, retinal atrophy is expected together with reduced amplitude and increasingly delayed electrical activity, so the positive correlations with amplitude and negative correlations with implicit time are as expected. Interestingly, the correlation between ERG amplitude and macular volume was strong and highly significant. Loss of macular volume is likely to reflect irreversible loss of tissue and of function, hence a reduced ERG amplitude may be an indicator of this. The less strong correlation with implicit time supports the notion that this can reflect dysfunction rather than tissue loss, raising the possibility of reversibility, and hence implicit time changes may be more useful to guide treatment.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.