Evaluation of inner retinal function assessed with a novel handheld instrument (RETeval) using flicker electroretinography after anti-VEGF treatment in patients with diabetic macular oedema

Background Electroretinographic studies have suggested that anti-VEGF treatment apart from its positive impact on the diabetic macular oedema may have a more generalised impact on the entire retinal function. A portable, handheld, flash and flicker electro retinography (ERG) recording system has recently been developed (RETeval™ LKC Technologies, Gaithersburg, MD) that makes it possible to record ERGs more rapidly and less invasively than the conventional ERG systems. We evaluate ERG measurements by the RETeval device before and after treatment with intravitreal anti-VEGF injections in eyes with diabetic macular oedema associated with mild nonproliferative diabetic retinopathy. Methods Prospective pilot study of 7 eyes of 5 patients with type II diabetes treated for macular edema by intravitreal ranibizumab injections in Jules Gonin University Eye Hospital in Lausanne, Switzerland. ERGs were recorded with the RETeval system before treatment and 1 month after the 3rd injection. Measurements included responses to photoptic flicker and ERG recording according to various protocols including photopic negative response (PhNR), ERGs recorded by sinusoidal light stimulus and the RETeval specific diabetic retinopathy Assessment Protocol. Additionally, fluorescein angiography was performed on each patient before and after treatment. Results All patients demonstrated significant improvement of visual acuity and resolution of macular oedema after treatment. We found no significant differences of the amplitudes and implicit times of ERGs after intravitreal injection of anti-VEGF with most of the protocols applied bar ERGs recorded by sinusoidal light stimulus. The mean implicit time of the flicker ERGs recorded by sinusoidal light stimulus was shortened significantly from 30.2 msec (SD: 0.6) at baseline to a mean of 29 msec (SD:0.76,) after the last intravitreal injection (p< 0.05; paired t-test). Additionally, the RETeval specific diabetic retinopathy Assessment Protocol designed to aid in the detection of vision threatening diabetic retinopathy including clinically significant macular oedema, could detect improvement in 71% of our cases. Conclusion In the present study we found no significant difference of the amplitudes and implicit times by most protocols applied bar shortening of the implicit times after ranibizumab treatment using a sinusoidal light stimulus. It is believed that sinusoidal stimulus is sensitive to inner-retinal function though its significance is not yet clearly elucidated. Additionally, the RETeval specific DR Assessment Protocol could detect improvement in the majority of our cases. The RETeval device offers a novel, quick and easily accessible method of objective electroretinographic measurements though the significance of its clinical role warrants further studies