Comparison of Patients with Diabetic Macular Edema Undergoing Early versus Late Switch from Intravitreal Anti-VEGF Therapy to Dexamethasone Implant.

Abstract

Objectives: To compare anatomical and functional outcomes in patients with diabetic macular edema who exhibited a suboptimal response to intravitreal anti-VEGF therapy and underwent early (<6 months) versus late (≥6 months) switch to an intravitreal dexamethasone implant.

Methods: This retrospective comparative study included 141 eyes of 141 patients with diabetic macular edema. Patients received at least three consecutive anti-VEGF injections without adequate anatomical or functional response and were subsequently switched to a dexamethasone implant. Patients were divided into two groups: early switch (<6 months) and late switch (≥6 months). Best-corrected visual acuity, central macular thickness, optical coherence tomography biomarkers, intraocular pressure, lens status, number of injections, and complications were analyzed.

Results: Of 141 patients (79 females, 62 males; mean age 65.3±8.9 years), 49 were in the early switch group and 92 were in the late switch group. At baseline, best-corrected visual acuity was marginally better in the late switch group (p=0.049), while baseline central subfield thickness was comparable (p=0.35). After switching, both groups showed a significant reduction in central subfield thickness (p<0.01), with no difference between the groups (p=0.58). Best-corrected visual acuity improved significantly in both groups; however, visual gain was greater in the early switch group (p=0.038). The mean number of total intravitreal injections was significantly higher in the late switch group (p<0.01). Mean intraocular pressure increased from 16.3 to 18.0 mmHg in both groups (p<0.01), with no intergroup difference. Thirty-one patients required cataract surgery during follow-up, without correlation with switch timing. Optical coherence tomography biomarkers revealed that patients with ellipsoid zone disruption had poorer BCVA outcomes, while those with subfoveal serous detachment exhibited greater central subfield thickness reduction (p<0.05).

Conclusion: Early switch from anti-VEGF to a dexamethasone implant in refractory diabetic macular edema provides superior functional outcomes and reduces treatment burden compared with late switch, despite similar anatomical improvements.