Abstract
Purpose: :
To describe the relationships between full-field stimulus threshold (FST), electroretinography (ERG), and visual field (VF) outcomes in Retinitis Pigmentosa (RP) patients with VF showing typical concentric constriction, but stable fixation.
Methods: :
Baseline data from 38 consecutive patients with RP (n = 76 eyes) enrolled in a clinical trial were retrospectively evaluated. Patients were submitted to comprehensive ophthalmological examination including measurement of best-corrected visual acuity, 30-2 threshold static, and automated kinetic VF (OCTOPUS 900), and microperimetry (MAIA - CenterVue). Full-field and multifocal ERG (ISCEV standard), and achromatic FST were recorded using Diagnosys Espion system with the ColorDomeTM LED full-field stimulator (Diagnosys LLC, Lowell, MA).
Results: :
BCVA mean ± SD was 0.38 ± 0.30 logMAR, and FST was -19.6 ± 10.5 dB (min: -45.7; max: -0.14 - normal range: -66 to -54 dB). Interestingly, FST was the only normally distributed variable measured in this population (Shapiro-Wilk W test). No significant correlation was found between BCVA and FST. Static 30-2 VF mean deviation (MD) was -23.9 ± 5.6 dB, and a weak, but statistically significant correlation between FST and MD (r = -0.37; P = 0.0016) was observed. Similar results were found for microperimetry mean threshold (r=-0.55; P0.05). Dark and light-adapted ERGs were not recordable in 58 (76%), and 46 (60%) eyes respectively. Nevertheless, considering only the eyes with recordable ERG responses, strong correlations were found between combined dark-adapted response b-wave amplitude (r = 0.80; P<0.001), cone response b-wave amplitude (r=-0.84; P<0.0001) and the FST.
Conclusions: :
FST could be successfully determined in RP patients with a wide range of vision loss; the test is easy to perform and takes between 1.5 and 3 minutes. Interestingly, FST results showed stronger correlations with full-field ERG amplitude than with sensitivity measured with visual field tests. FST should be considered as an alternative to VF or ERG for assessment of retinal function in retinal diseases.
Keywords: retinitis • retinal degenerations: hereditary • electroretinography: clinical