The Light-adapted Full-field ERG Luminance-response Series in Proliferative Diabetic Retinopathy Treated with Intravitreal Ranibizumab and Multispot Laser Panretinal Photocoagulation

Abstract

Purpose : To investigate the effects of intravitreal Ranibizumab (IVR), combined or not with conventional (ETDRS) or Multispot Laser Panretinal (PASCAL) photocoagulation (PRP) on light-adapted full-field ERG luminance-response series in eyes with proliferative diabetic retinopathy (PDR).

Methods : Laser-naive PDR patients that required PRP were randomly and prospectively assigned to receive IVR or IVR combined to PASCAL or EDTRS. PRP was performed at baseline in 1 (PASCAL) or 2 (ETDRS) sessions. In eyes with macular edema, macular laser was associated to IVR at baseline and IVR was repeated monthly, or quarterly if neovascularization was detected on angiography. Best-corrected visual acuity (BCVA), fluorescein angiography: to measure the leakage area (FLA), and OCT were performed at baseline and every 4 weeks after treatment. Full-field light-adapted electroretinography (Diagnosys LLC) was recorded using a 30 cd/m² background and a sequence of six flashes stimuli from 0.1 to 30 cd.s/m². B-wave amplitude data were fit with a sum of a logistic-growth and a Gaussian function (photopic hill equation). Reported parameters: V_Max: sum of maximal amplitude from the two components, and μ: flash strength at the peak of the Gaussian component, in cd.s/m².

Results : IVR=13, PASCAL=15, and ETDRS=15 eyes finished 48-weeks follow-up. There was a significant BCVA improvement of 0.1 to 0.3 logMAR in all groups (P<0.05), and FLA reduced significantly without between-groups differences. Overall, significant a- and b-wave amplitudes reductions were observed for dark- and light-adapted ERG for ETDRS and PASCAL, but only minor dark-adapted b-wave reduction was found for IVR, up to 48 weeks. Parameter V_Max reduced significantly (P<0.05) after treatment (week 12, 24 and 48 respectively) on groups ETDRS (33%, 40% and 42%) and PASCAL (34%, 30% and 33%), while a significant reduction was observed only on week 48 for IVR (13%, 13%, 22%). Parameter μ increased (~ 0.2 cd.s/m²) significantly on ETDRS and PASCAL.

Conclusions : Parameters derived from luminance-response series were used to report cone-driven function damage on PDR eyes treated with PRP, and highlighted that IVR alone seems to avoid, at least partially, these changes. Future studies should investigate correlations between these parameters and other retinal structure/functional changes.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.