Intravitreal Dexamethasone Shows Minimal Effect on Choroidal Structure in Refractory DME

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Switching to an intravitreal dexamethasone implant may improve best-corrected visual acuity (BCVA) and central macular thickness (CMT) in eyes with diabetic macular edema (DME) refractory to anti-vascular endothelial growth factor (VEGF) injections, according to new findings.¹

The results showed an absence of a significant effect on subfoveal choroidal thickness and choroidal vascularity index in the short term with the implant, suggesting its greater effect on retinal layers in eyes with resistant DME.

“This result may indicate that, in previous anti-VEGF therapy-received eyes, intravitreal dexamethasone implant affects the retinal layers more potentially than the choroid,” wrote the investigative team, led by Serdar Bilici, MD, department of ophthalmology, Zonguldak Bulent Ecevit University Faculty of Medicine.

Despite its status as a first-line treatment for DME, many patients have shown an inadequate response to anti-VEGF agents. The complex pathogenesis of the disease means inflammatory mediators other than VEGF play a role. Evidence has suggested intravitreal steroids could be a useful alternative treatment in case of poor response.²

Choroidal abnormalities in patients with diabetes may cause severe functional damage to the retina and a decrease in visual acuity. As a biomarker, the choroidal vascularity index has shown a good correlation with the severity of diabetic retinopathy and could be a sensitive marker of choroidal vascular change in eyes with DME. Choroidal vascularity index changes with anti-VEGF or steroid treatment have been previously evaluated — however, the effect of intravitreal dexamethasone implant in eyes with DME refractory to anti-VEGF therapy has not been investigated.¹

Led by Bilici, the retrospective study included 23 eyes of 14 patients treated with intravitreal dexamethasone implant due to refractory DME, despite ≥3 consecutive monthly intravitreal anti-VEGF therapy, at the investigator’s site between September 2021 - June 2022. All patients underwent an ophthalmic evaluation before and 3 months after implant, including the measurement of BCVA, fluorescein angiography, and enhanced depth imaging - optical coherence tomography (EDI-OCT).

For analysis, choroidal images were binarized into the luminal area and total choroidal area. The investigative team calculated subfoveal choroidal thickness and choroidal vascularity index.

Study participants had a mean age of 64 years and received a mean number of 7.5 previous intravitreal anti-VEGF injections. Upon analysis, investigators found the mean BCVA was statistically significantly improved in the short-term after intravitreal dexamethasone implant, from 0.94 to 0.81 LogMAR (P = .02).

Meanwhile, the mean CMT for all eyes decreased significantly from 464.9 ± 168.3 µm at baseline to 371.0 ± 127.0 µm at the final visit after intravitreal dexamethasone implant (P = .01).

Although the analysis showed a slight decrease in subfoveal choroidal thickness after implant, the change was not statistically significant (P = .51) at the end of the follow-up period. In addition, the mean choroidal vascularity index of eyes with refractory DME showed no significant change from baseline to the final visit (P = .35).

Overall, there were significant improvements in CMT and BCVA after the switch to the implant, with no systemic or ocular complications, particularly cataract progression. However, Bilici and colleagues noted the short follow-up and small sample size may have contributed to the findings, particularly the lack of effect on the choroidal structure.

“A prospective multicenter clinical study with larger sample size and longer follow-up period may be warranted in the future to reveal the longitudinal effect of intravitreal dexamethasone on choroidal vasculature,” investigators wrote.

References

1. Bilici S, Serbest E, Ugurbas SH. Short-term Effects of Intravitreal Dexamethasone Implant on Choroidal Structure in Eyes with Refractory Diabetic Macular Edema. Beyoglu Eye J. 2023;8(3):193-197. Published 2023 Sep 13. doi:10.14744/bej.2023.73644
2. Schmidt-Erfurth U, Garcia-Arumi J, Bandello F, Berg K, Chakravarthy U, Gerendas BS, et al. Guidelines for the management of diabetic macular edema by the European society of retina specialists (EURETINA) Ophthalmologica. 2017;237:185–222