ET-1 plasma levels, choroidal thickness and multifocal electroretinogram in retinitis pigmentosa

To assess the relationship between both photoreceptor function and choroidal thickness and endothelin-1 (ET-1) plasma levels in patients with early stage retinitis pigmentosa (RP).

We compared 24 RP patients (14 males and 10 females), 25 to 42 years of age (mean age: 34±7 years) with 24 healthy controls (12 males and 12 females) aged between 28 and 45 years (mean 36±6.8 years). All patients underwent visual field test, electroretinogram and multifocal-electroretinogram and choroidal thickness measurement by using spectral domain optical coherence tomography.

RP patients had a visual acuity of 0.95, a mean defect of the visual field of -7.90±1.75 dB, a pattern standard deviation index of 6.09±4.22 dB and a b-wave ERG amplitude of 45.08±8.24 μV. Notably RP subjects showed significantly increased ET-1 plasma levels and reduced choroidal thickness compared with controls: respectively, 2.143±0.258 pg/ml vs. 1.219±0.236 pg/ml; p<0.002 and 226.75±76.37 μm vs. 303.9±39.87 μm; p<0.03. Spearman's correlation test highlighted that the increase of ET-1 plasma levels was related with the decrease of choroidal thickness (r=-0.702; p<0.023) and the increase of implicit time in both ring 2 (r=-0.669; p<0.034) and ring 3 (r=-0.883; p<0.007) of mfERG.

Increased ET-1 plasma levels may play a key role in the impairment of retinal and choroidal blood flow due to the vasoconstriction induced by ET-1. This could lead to worsening of the abiotrophic process of the macular photoreceptors.