ERG provides insight into duration of the intravitreal dexamethasone implant

(Image credit: AdobeStock/Anton)

An Egyptian research team led by Aya Refaat Ali Mohammed, MD, reported that multifocal electroretinography (mfERG) was valuable for demonstrating the effect of one dose of the intravitreal dexamethasone implant (Ozurdex, Allergan).¹ Mohammed is a resident in Ophthalmology, Minia Health Insurance Hospital, Minya, Egypt. She was joined in this study by clinicians from the Faculty of Medicine, Minia University, Minya.

The investigators conducted a prospective interventional study to determine the therapeutic anatomic and functional effects of one intravitreal dexamethasone implant in eyes with refractory diabetic macular edema (DME) based on optical coherence tomography (OCT) images, the best-corrected logarithm of the minimum angle of resolution visual acuity (logMAR BCVA), and mfERGs.

They explained that OCT reveals several morphologic changes that could affect the treatment outcome of DEX implants for DME,² one of these being disorganization of the retinal inner layers.³ OCT also can be used to identify biomarkers for plana vitrectomy and peeling of the internal limiting membrane in naïve DME.⁴ Ultra-wide-field scanning laser ophthalmoscopy is another imaging modality for diabetic retinopathy.⁵ The association between retinal structural and functional alterations in patients with DME has rarely been thoroughly investigated using OCT and mfERG together,⁶ they explained.

Twenty eyes of 20 patients (15 men, 5 women; mean patient age, 62.83 ± 6.34 years) with refractory DME were included. All had been treated with six intravitreal injections of anti-vascular endothelial growth factor (VEGF) therapy. OCT was performed to measure the central retinal thickness (CRT) exceeding 300 μm. Four weeks after the administration of the final anti-VEGF injections, the eyes were treated with one dexamethasone implant.

The study were the changes in the CRT, logMAR BCVA, p1 amplitude of ring 1 on the mfERGs, and the intraocular pressure (IOP) recorded before the implant was injected and then 2, 4, and 6 months after the implant was injected. The mean duration of diabetes was 16.7 ± 2.21 years.

Visualized treatment effects

The investigators reported that during the 2-month follow-up, they observed significant reductions in the CRT, logMAR BCVA, and increases in the p1 of ring 1 on the mfERGs (P = 0.046, P < 0.001 and P < 0.001, respectively).

At the 4-month evaluation, the were not statistically significant (P = 0.99, P < 0.56, P < 0.58, respectively), and by 6 months, all parameters at almost returned to the level before injection of the implant (P = 0.93, P = 0.99 P = 0.81, respectively). The IOPs did not increase significantly at 2, 4, or 6 months (P < 0.06, P = 0.35, and P = 1.0, respectively).

There were significant negative correlations between the mfERG and OCT parameters before and 6 months after DEX injection (P = 0.000).

“One intravitreal injection of the dexamethasone implant in patients with refractory DME induced significant anatomic and functional improvements, but these improvements only lasted for short periods of up to 4 months. This treatment exhibited an excellent safety profile. However, at 6 months, the therapeutic effect was null. This study highlighted the use of mfERG as a sensitive biomarker of treatment efficacy,” the authors concluded.

References

1. Mohammed ARA, Othman MFS, Khairat YM, Abdelrahman AAM. Use of a multifocal electroretinogram to evaluate the therapeutic effect of a single intravitreal dexamethasone implant, Ozurdex^®, for refractory diabetic macular oedema. Int J Retin Vitr. 2025;11; https://doi.org/10.1186/s40942-025-00652-x

2. Zur D, Iglicki M, Busch C, et al. OCT biomarkers as functional outcome predictors in diabetic macular edema treated with dexamethasone implant. Ophthalmology. 2018;125:267–75. https://doi.org/10.1016/j.ophtha.2017.08.031.

3. Zur D, Iglicki M, Sala-Puigdollers A, et al. Disorganization of retinal inner layers as a biomarker in patients with diabetic macular oedema treated with dexamethasone implant. Acta Ophthalmol. 2020;98:e217–23. https://doi.org/10.1111/aos.14230.

4. Iglicki M, Lavaque A, Ozimek M, et al. Biomarkers and predictors for functional and anatomic outcomes for small gauge Pars plana vitrectomy and peeling of the internal limiting membrane in Naïve diabetic macular edema: the VITAL study. PLoS ONE. 2018;13:e0200365. https://doi.org/10.1371/journal.pone.0200365.

5. Tang F, Luenam P, Ran AR, et al. Detection of diabetic retinopathy from Ultra-Widefield scanning laser ophthalmoscope images: A multicenter deep learning analysis. Ophthalmol Retina. 2021;5:1097–106. https://doi.org/10.1016/j.oret.2021.01.013.

6. Khojasteh H, Riazi-Esfahani H, Khalili Pour E, et al. Multifocal electroretinogram in diabetic macular edema and its correlation with different optical coherence tomography features. Int Ophthalmol. 2020;40:571–81. https://doi.org/10.1007/s10792-019-01215-4.