Psychophysically determined full-field stimulus thresholds (FST) in retinitis pigmentosa: relationships with electroretinography and visual field outcomes

The purpose of this study is to describe the relationships between full-field stimulus threshold (FST), electroretinography (ERG), and visual field (VF) outcomes in retinitis pigmentosa (RP). Data from 47 patients with RP (n = 94 eyes) were evaluated. Patients were submitted to comprehensive ophthalmological examination including measurement of best-corrected visual acuity (BCVA), 30-2 threshold static VF, and microperimetry. Full-field ERG (ISCEV standard) was recorded, and achromatic FST was measured using a Diagnosys Espion system with the ColorDome (TM) LED full-field stimulator (Diagnosys LLC, Lowell, MA, USA). BCVA mean +/- A SD was 0.31 +/- A 0.03 logMAR, and FST mean +/- A SD was -18.45 +/- A 9.53 dB. No significant correlation was found between BCVA and FST. In contrast, statistically significant correlations were found between FST and static 30-2 VF mean deviation (r = -0.389; P < 0.01), microperimetry mean threshold (r = -0.607; P < 0.01). Dark and light-adapted ERGs were detectable in 28 and 48 eyes, respectively. Nevertheless, considering only the eyes with recordable ERG responses, moderate correlations were found between combined dark-adapted a-wave amplitude (r = -0.560; P < 0.01), b-wave amplitude (r = -0.643; P < 0.001), 30-Hz flicker response (r = -0.501; P < 0.01), and FST, and high correlation with FST for cone b-wave amplitude (r = -0.715; P < 0.01). FST could be successfully determined in RP patients with a wide range of vision loss. FST results showed stronger correlations with full-field ERG amplitude than with sensitivity measured with visual field tests. FST is as an alternative to VF or ERG for assessment of retinal function in patients unable to do visual fields or with non-detectable ERGs.