Abstract
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.
Keywords: Diabetic retinopathy; Macular edema; Dexamethasone; Drug implants; Biomarkers, pharmacological
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