Abstract
PurposeTo determine the changes in the multifocal electroretinogram (mfERG) at 1 year in a clinical series of diabetic macular edema (DME) patients treated with ranibizumab (RNBZ) using a pro re nata protocol.MethodsWe analyzed a clinical series of 35 eyes of 35 patients with DME at baseline and after treating them with RNBZ over 1 year, in order to determine the change in the macular function, which was assessed by means of the response density and the implicit time of the first-order kernel (FOK) P1 wave of the mfERG at the foveola (R1), fovea (R2) and parafovea (R3). These electrophysiological parameters were studied taking into account different independent variables, such as DME type, degree of diabetic retinopathy (DR), level of preservation of both the ellipsoid zone (IS/OS) and the external limiting membrane (ELM) and changes in central retinal thickness (CRT) and total macular volume (TMV). We also studied the relationship between the response density and the best-corrected visual acuity (BCVA).ResultsEyes with cystic and spongiform DME showed better response density with respect to the serous type (p < 0.001) at baseline. Similarly, eyes with high IS/OS and ELM preservation rates showed higher initial response density compared to the others (p < 0.001). Eyes with moderate DR had better response density compared to those with severe and proliferative DR (p = 0.001). At the beginning of the study, those eyes with proliferative and severe DR showed longer implicit times with respect to those with moderate DR (p = 0.04). The response density significantly increased in eyes that anatomically restored the IS/OS and the ELM after being treated with RNBZ (both p < 0.001). Similarly, eyes with spongiform DME further improved the response density with respect to those with cystic and serous DME (p < 0.001). On the contrary, eyes with hard exudates showed less improvement in their response density at the end of the study (p < 0.001). We observed a significant relationship between BCVA and the response density achieved at the end of the study (p = 0.012). Eyes with severe and proliferative DR significantly shortened implicit time compared to those with moderate DR (p = 0.04).ConclusionsThe multifocal electroretinogram allowed us to differentiate groups of eyes with DME according to their electrophysiological profile, both initially and after being treated with RNBZ. Ranibizumab increased the response density in all DME types included in the study, with a maximum response in those eyes with spongiform type. Once treated with RNBZ, the macular electrophysiological activity improved in eyes that had a well-preserved ellipsoid zone and ELM. The presence of hard exudates was a limitation to the response density achieved at the foveola.
Highlights
Diabetic macular edema (DME) is the leading cause of visual acuity loss in diabetic patients [1]
Nobody presented with mild diabetic retinopathy, and severe and proliferative diabetic retinopathy affected 40% of the patients
The multifocal electroretinogram can be used to study the functional status of the macula divided into rings in an objective manner
Summary
Diabetic macular edema (DME) is the leading cause of visual acuity loss in diabetic patients [1]. Optical coherence tomography (OCT) is the technique most often used during follow-up for DME and helps to determine the need for continued treatment. There are different pathophysiological mechanisms involved in the genesis of DME. Several studies have emphasized the role of vascular endothelial growth factor (VEGF) after having observed an increase in its levels in the vitreous of patients with diabetic retinopathy (DR). It increases the retinal vascular permeability that can lead to DME [2]. The majority of treatments for DME target VEGF to block its action. Several studies have demonstrated its safety and efficacy in the treatment of this disease [3, 4]
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