Abstract
Purpose: :
To investigate the clinical significance of the photopic negative response (PhNR) of the electroretinogram (ERG) and to determine the relationship of the PhNR with optical coherence tomography (OCT) findings in patients with non proliferative diabetic retinopathy (NPDR).
Methods: :
Sixty-one eyes of 36 patients with NPDR at different stages and eleven age-matched controls underwent ophthalmic examination including visual acuity (VA), the photopic cone ERG and Cirrus spectral domain OCT (Carl Zeiss Meditec, Dublin, CA). Patients who had panretinal photocoagulation therapy were excluded. PhNRs were elicited by white stimuli (2.4297 cd.s/m2 ) with a white background (31.9417 cd.s/m2 ). Central retinal thickness (CRT) and retinal nerve fiber layer thickness (RNFLT) around optic disc were taken from OCT results. The amplitudes, implicit times of PhNR and CRT, RNFLT of OCT were compared at the different stages of NPDR.
Results: :
The visual acuity (VA) were significantly reduced as NPDR progressed (p=0.010). The amplitudes of PhNR were significantly attenuated with a progression of NPDR (p=0.009). The implicit times of PhNR were also significantly delayed (p=0.000). However, in anatomical aspect, CRT remained unchanged despite advancing stages of retinopathy (p=0.704). RNFLT tended to be decreased with advancing stages, but it was not statistically significant (p=0.411). No statistically significant correlation was observed between PhNR components; amplitude, implicit time and anatomical components; CRT and RNFLT.
Conclusions: :
With the progression of NPDR, the amplitudes of PhNR were progressively decreased and implicit times were delayed, whereas, CRT and RNFLT did not show the specific tendency. The results showed that functional changes might precede anatomical changes; PhNR could be a valuable tool in detecting the progression of NPDR.
Keywords: electroretinography: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • diabetic retinopathy