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Intravitreal dexamethasone sodium phosphate challenge to predict implant response in refractory diabetic macular
Rodrigo Pessoa Cavalcanti Lira1, Michelle Maria Teixeira Figueiredo Paiva1, Gabriel Rocha Lira1
1Universidade Federal de Pernambuco, Recife, PE, Brazil.
Purpose:
To evaluate the accuracy of a short-term intravitreal dexamethasone sodium phosphate challenge in predicting the anatomical response to a sustained-release dexamethasone implant (Ozurdex) in patients with refractory diabetic macular edema.
Methods:
This prospective, non-randomized, Phase 2 pilot study enrolled 12 pseudophakic eyes with diabetic macular edema refractory to anti-vascular endothelial growth factor (anti-VEGF) therapy. Participants underwent a challenge phase (Day 0) consisting of a single intravitreal injection of 0.08-mg dexamethasone sodium phosphate, followed by a maintenance phase (Day 7), during which all subjects received a 0.7-mg dexamethasone implant. The primary outcome was concordance between the anatomical response at Day 3 (post-dexamethasone sodium phosphate) and Day 60 (post-implant), defined as a ≥10% reduction in central macular thickness. Secondary outcomes included achieving a clinically "dry" macula (central macular thickness ≤300 μm) at Day 60, changes in best-corrected visual acuity, safety outcomes (intraocular pressure), and spectral-domain optical coherence tomography biomarker analysis.
Results:
The dexamethasone sodium phosphate challenge induced significant macular drying by Day 3 (median central macular thickness reduction, -21 μm; p=0.002). A positive response to dexamethasone sodium phosphate strongly predicted response to the dexamethasone implant, with a positive predictive value and specificity of 100%. The negative predictive value was 80%. Irreversible biomarkers, including disorganization of retinal inner layers and ellipsoid zone disruption, were more prevalent among nonresponders (60% vs. 28.6%). Safety outcomes were acceptable; 16.7% of patients developed ocular hypertension, which was successfully managed with topical therapy.
Conclusion:
A short-term dexamethasone sodium phosphate challenge is a safe, low-cost, and highly specific predictor of dexamethasone implant efficacy. This "test-and-treat" strategy may optimize resource allocation in resource-constrained settings by identifying responders before high-cost implantation.
