Purpose: Although extensive clinical research has been performed on structural analysis of sickle cell (SC) retinopathy, functional aspects have been poorly investigated. Our purpose was to report full-field electroretinogram (ffERG) findings in patients with early SC retinopathy according to the following hemoglobin types: HbSS or HbSC (homozygous or heterozygous mutations, respectively).
Methods: In this monocentric retrospective observational study, patients affected by nonproliferative SC retinopathy were included from November 2014 to April 2016. Patients were separated into one of the following three groups: HbSS, HbSC, and control. All groups underwent full ophthalmologic examination (fundus examination) and ffERG. For SC patients, additional imaging testing was also performed (fluorescein angiography and spectral domain optical coherence tomography).
Results: A total of 24 eyes from 12 patients (6 HbSS and 6 HbSC) and 12 eyes from 6 controls were included. The HbSS group exhibited a dramatic decrease of the b-wave amplitudes for all dark-adapted (DA) ffERG responses when compared with the control group (P = 0.02, P = 0.003, P = 0.005, respectively, after DA 0.01, DA 3.0, and DA 10.0 cd.s.m-2 stimulations) and decreased a-wave amplitudes for light-adapted responses (P = 0.03 after light-adapted 3.0 cd.s.m-2 stimulations). The a-Wave amplitudes were significantly reduced for all dark-adapted and light-adapted responses in HbSC group compared to the control group (P = 0.03, P = 0.01, P = 0.03, respectively, after DA 3.0, DA 10.0, and light-adapted 3.0 cd.s.m-2 stimulations). The HbSS+HbSC groups presented decreased a-wave amplitudes for DA and light-adapted responses and decreased b-wave amplitude after DA 0.01 and 10.0 cd.s.m-2 stimulations when compared to the control group.
Conclusions: These results could suggest an early involvement of the inner retinal cells in the disease process in HbSS patients and of the outer retinal cells in HbSC patients. This could provide new insights on the pathophysiology of the retinal affection in HbSS/HbSC SC disease.