Baseline Central Subfield Thickness Predicts Visual Response to DEX Implant

Baseline central subfield thickness, as measured using optical coherence tomography (OCT), can predict visual outcomes for patients who have received a dexamethasone implant (DEX-I) to treat diabetic macular edema (DME), according to a study published in International Journal of Retina and Vitreous. The research also shows a second biomarker, baseline subfoveal neuroretinal detachment (SND), can be a negative prognostic factor for increased CST 4 months after DEX-I injection.

Researchers reviewed clinical records of 33 eyes of 33 patients (mean age 68.2±9.7 years) who had type 2 diabetes mellitus and DME. Advanced DME was present in 21 eyes, early DME in 5 eyes, severe stage DME in 5 eyes, and atrophic maculopathy in 2 eyes. Analysis took place from March 2020 to September 2022.

Of the cohort, 18 (54.5%) achieved gains of 5 or more Early Treatment Diabetic Retinopathy Study (ETDRS) letters at 1 month. Cube average thickness (CAT), cube volume (CV), and intraretinal cystoid space (ICS) larger than 200 µm all dropped after injection (each P <.001). For the full study cohort, mean baseline central subfield thickness was 487.0±142.0 µm. However, for those who gain 5 or more ETDRS letters after 1 month of DEX-I injection, mean baseline central subfield thickness was 531.2±153.9 µm (P =.048).

In a panel regression model, SND displayed a negative predictive relationship with increased CST after 4 months. A stepwise logistic regression analysis confirmed thicker baseline central subfield thickness is associated with better visual acuity by 1 month (coefficient 0.01, CI 0.00 to 0.01, P =.044). Regarding safety, no major adverse events occurred, although 5 individuals (15.15%) had increased intraocular pressures (IOP) after 1 month.

“Our results suggest that thicker CST at baseline may be a predictor for visual improvement at one month, and subfoveal neuroretinal detachment SND may be a
negative prognostic factor for CST increase at 4 months,” the research team explains. “Regarding the remaining biomarkers examined in this study, including ICS, DRIL, SHF, HF, EZ/ELM alteration, and VMT, we did not observe any significant association with visual improvement at either 1 or 4 months, even after stratifying by naïve and treated eyes.”

Previous research indicated that an absence of disorganization of inner retinal layers (DRIL) at baseline predicted better structural results, but researchers have not shown any association between DRIL levels and functional outcomes for these patients.

Limitations of this investigation include its retrospective design, small cohort, and that 63.6% of the cohort exhibited advanced DME. Inadequate test power reduced generalizability.