Abstract
Purpose :
To evaluate the relationship between the pattern electroretinogram (pERG) and the pattern visual evoked potential (pVEP), measures of retinal ganglion cell and cortical function, respectively, in patients who have mild to severe thyroid eye disease (TED) without clinical evidence of optic neuropathy.
Methods :
The pERG and pVEP were recorded from 5 TED subjects and 4 age-similar, visually-normal controls. Study subjects had no clinical evidence of optic neuropathy, including normal visual fields, visual acuity better than 20/25, normal color vision, and no relative afferent pupillary defects. The pERG and pVEP were elicited by a contrast reversing checkerboard and were recorded simultaneously using conventional techniques. The pERG amplitude was measured from the P50 peak to the N95 trough, whereas the pVEP amplitude was measured from the N75 trough to the P100 peak, per convention.
Results :
The pERG and pVEP amplitudes were reduced below the normal control range in two of the five TED subjects. The pERG amplitude was below the normal mean by as much as 53%, whereas the pVEP amplitude was reduced below the normal mean by as much as 67%. Despite the small sample size, there was a strong correlation between the pERG and pVEP amplitudes for the TED subjects (r = 0.88, p = 0.047). The pERG implicit time (P50) was delayed beyond the normal control range in two of the five TED subjects and the pVEP (P100) was delayed in three of the five TED subjects. The pERG implicit time delays were as great as 14 ms beyond the normal mean, whereas the pVEP P100 was delayed by as much as 21 ms beyond the normal mean. There was a moderate correlation between the pERG and pVEP implicit times for the TED subjects that did not reach statistical significance in this small sample of subjects (r = 0.59, p = 0.30).
Conclusions :
These preliminary results indicate that both pERG and pVEP amplitude can be reduced in TED patients who have otherwise normal optic nerve function. Likewise, the timing of these responses can be substantially delayed. These measurements appear to represent early optic nerve dysfunction and may be of use as objective, non-invasive outcome measures in future clinical trials.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.