Abstract
Purpose :
The Snellen chart, used to estimate visual acuity (VA) in the clinical setting, has limitations necessitating the development of additional techniques for measuring VA. We conducted a prospective, non-interventional medical device study to test the hypothesis that sVEP VA will be equivalent to the Snellen VA for patients with ON and AMD.
Methods :
After informed consent, 18 ON patients (21 eyes), 44 AMD patients (55 eyes), and 28 control participants (56 eyes) were enrolled. Patient inclusion criteria were a precise ON or AMD diagnosis, a best-corrected visual acuity (BCVA) better than 20/400, and the ability to adhere to the VEP testing process. Exclusion criteria were a BCVA worse than 20/400 and an inability to follow the VEP protocol. All control participants had a normal eye exam, a BCVA of 20/25 or better, and the ability to comply with the VEP protocol. All participants had their VA estimated using the Snellen chart. The Diagnosys D-341 Attaché- Envoy System was used for sVEP VA recordings. ON and AMD patients also had standard automated perimetry testing and Cirrus optical coherence tomography (OCT). The Wilcoxon signed-rank test and Spearman’s rank-order correlation were used to assess the differences between the sVEP and Snellen acuities and the relationship between the VAs and the foveal threshold and the average ganglion cell layer (GCL) thickness.
Results :
The sVEP and Snellen VAs were significantly different in normal subjects, ON, and AMD patients (P-values = 0.003, 0.05, and 0.007, respectively). Based on these findings, sVEP cannot replace Snellen for VA assessment in these patient populations. In ON patients, sVEP and Snellen acuities were not significantly correlated with the foveal threshold. However, sVEP VA was strongly correlated with the average GCL thickness (r = -0.878, P= 0.001). In AMD patients, neither sVEP nor Snellen was correlated to the foveal threshold. Still, both sVEP and Snellen acuities showed a significant negative correlation to average GCL thickness (r = -0.575, P= 0.01), (r = -0.739, P= 0.00), with the Snellen showing a stronger correlation.
Conclusions :
Our results show that sVEP and Snellen are not interchangeable for VA estimation in normal subjects, ON, and AMD patients. It remains to be determined which of the two tests is more accurate at predicting VA.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.