Effectiveness of dexamethasone implants in treating diabetic macular edema with hard exudates: a clinical observation

Objective

This study seeks to explain the relationship between systemic conditions and hard exudate formations in diabetic macular edema patients. Besides, the study aimed to quantitatively examine changes in the area, location, and impact on visual function of hard exudates following intravitreal dexamethasone implant injections.

Methods

A retrospective analysis was conducted, including 40 patients (40 eyes) diagnosed with non-proliferative diabetic retinopathy and concurrent macular edema between January 1, 2022, and January 1, 2024. Preoperative evaluations included glycated hemoglobin, lipid profile, and renal function examinations. Based on the location of HE, patients were divided into two groups: Group A, with HE in 1 mm of the central fovea, and Group B, with HE outside 1 mm of the central fovea. Selected eyes were subject to pre- and postoperative examinations, including best-corrected visual acuity (BCVA), intraocular pressure, slit-lamp biomicroscopy, scanning laser ophthalmoscopy (SLO), optical coherence tomography, and multifocal electroretinography. Following screening and examination, patients received an immediate intravitreal injection of the DEX implant, with an injection administered at the four-month mark. Hard exudate (HE) areas were measured utilizing SLO fundus imaging.

Results

Total cholesterol, low-density lipoprotein, and triglyceride levels were found to be positively correlated with the presence of HE. Following surgical intervention, all patients demonstrated an improvement in BCVA. The mean BCVA increased from a preoperative measurement of 0.79 ± 0.04 to 0.39 ± 0.02 at the 6 month follow-up, indicating a statistically significant difference (p < 0.001). The baseline HE area for the entire patient cohort was 2.28 ± 0.22. One month post-operation, the HE area exhibited a slight increase to 2.27 ± 0.22. However, by the 6 month follow-up, the HE area had significantly decreased to 0.8 ± 0.87, representing a 35.09% reduction from the baseline measurement (p < 0.001). It is worth noting that Patient P1 did not exhibit a statistically significant difference between preoperative and six-month postoperative HE area (p = 0.032). Preoperative BCVA measurements for Group A and Group B were 0.81 ± 0.03 and 0.77 ± 0.03, respectively, with no statistically significant intergroup difference (p = 0.333). The baseline HE area for Group A was 2.61 ± 0.16, which decreased to 0.38 ± 0.20 at the six-month follow-up, representing a 14.60% reduction from the baseline total area. For Group B, the baseline HE area was measured at 1.95 ± 0.09, then decreasing to 1.21 ± 0.13 at the six-month follow-up, indicating a 62.05% reduction from the baseline total area. A statistically significant difference in the postoperative 6 month HE area was observed between Group A and Group B (p < 0.001). In Group A, the reduction in HE area (initial HE area-final HE area) was positively correlated with the improvement in P1 (initial P1-final P1) (r = 0.610, p = 0.004). In Group B, a similar positive correlation was found (initial HE area-final HE area with initial P1-final P1) (r = 0.488, p = 0.029). In Group B, the reduction in HE area (initial HE area-final HE area) correlated positively with the improvement in BCVA (initial BCVA-final BCVA) (r = 0.615, p = 0.004). Additionally, in Group B, the reduction in HE area (initial HE area-final HE area) was positively correlated with the improvement in CMT (initial CMT-final CMT) (r = -0.725, p< 0.001). Aggravated cataracts were observed in thirteen eyes during a follow-up examination 6 months later.

Conclusion

HE formation is associated with lipid levels. Dexamethasone implants demonstrate effectiveness in reducing HE areas in the short term, reducing macular edema, improving retinal structure, and enhancing visual function. The incidence of postoperative complications such as cataracts and glaucoma remains low.