Structural, Functional Improvements Seen Following Dexamethasone Injections

Significant improvements in central macular thickness and visual acuity were observed following intravitreal dexamethasone injection for the treatment of diabetic macular edema (DME), according to research results published in Retina. 

Researchers conducted a retrospective review to evaluate subfoveal choroidal thickness (SFCT) changes following dexamethasone injection therapy in patients with DME, as well as the relationship between functional and anatomical treatment responses and optical coherence tomography (OCT) parameters. Included patients had either type 1 or type 2 diabetes, clinically identified naïve or refractory DME, and were undergoing their first dexamethasone injection. 

The study took into account 81 eyes of 70 patients (48.1% men; mean age, 58.19 years ± 10.13 years). Of these, 75 were followed for up to 14 weeks. 

A total of 30 DME eyes were treatment naïve, while 51 were refractory to previous anti-VEGF injections (mean number of previous injections, 2.66 ± 1.17). Also, 37 eyes had proliferative diabetic retinopathy, among which 83.8% were treated with panretinal photocoagulation. 

Mean preoperative central macular thickness was approximately 473.35 µm at baseline. This decreased significantly to approximately 298.50 µm and 386.49 µm at weeks 7 and 14, respectively (P <.001 for both). Mean preoperative SFCT also significantly decreased following dexamethasone injection (299.81 ± 116.60 µm at baseline vs 269.30 ± 104.32 µm at week 7 vs 278.10 ± 112.07 µm at week 14). 

A subgroup analysis demonstrated no significant difference in SFCT, central macular thickness, best corrected visual acuity, or their respective changes at weeks 7 and 14 between patients who were naïve and patients who were refractory. Outcome measures also did not differ significantly between patients with proliferative or nonproliferative diabetic retinopathy, or eyes with or without previous platelet-rich plasma or macular laser treatments. 

Eyes that demonstrated a good functional response at weeks 7 or 14 had greater SFCT reduction at week 7 compared with eyes without a good functional response at the same stage (P =.047 and P =.021, respectively). 

In terms of OCT parameters, eyes with subretinal fluid at baseline demonstrated significantly greater SFCT reduction at week 7 (P =.039); a significantly higher proportion of eyes with baseline subretinal fluid had good functional response at week 7 than in eyes without subretinal fluid (P =.033), and eyes with a continuous ellipsoid zone/interdigitation zone layer had significantly lower SFCT at week 7 and better best corrected visual acuity at baseline, week 7, and week 14. 

Study limitations include those inherent to the retrospective nature, including the use of OCT scans at week 7 and week 14 instead of monthly; data should be cautiously interpreted compared with studies based on a 3- or 6-month timeframe. Additionally, diurnal variation in SFCT may have affected OCT image results. 

“Greater SFCT reductions, especially in the early stages after dexamethasone injection therapy, may predict better anatomical and functional treatment responses and correlate with OCT features known as predictors of treatment responses,” the research shows. “Further studies with larger sample sizes and better control of possible confounders are warranted.” 

Reference

Moon KY, Choi SY, Song JH. Changes in subfoveal choroidal thickness following intravitreal dexamethasone implant therapy for diabetic macular edema. Retina. Published online December 10, 2020. doi:10.1097/IAE.0000000000003029