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

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 bio-markers 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).
DISCUSSION AND 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.

Keywords: anti-VEGF, dexamethasone implant, diabetic macular edema, switch