Diabetic macular edema is one of the leading causes of avoidable blindness in diabetic adults. In the current study, the prevalence of diabetic macular edema was 26.3% (95% CI: 19.7–34.6). This is consistent with other studies conducted in Kenya 33.3% (22) and Saudi Arabian 20.3% (23). However, it is greater than the global mata-analyses 7.48% (24), Australia 7.6% (25) ,Tunisia 8.7% (26), Norway 3.9% (27), India 5.78% (28), and South Africa 3.2% (29). This variation in studies could be due to differences in diabetic management, methodology, risk comorbidities, diagnostic method, quality of glycemic control, and diabetic patients' health seeking behavior The prevalence of clinically significant macular edema in our study was 6.56%. This corresponds to the findings of a study conducted in China 4% (30). However, it is higher than studies in southern India (1.4%) (31) and South Korea 1.6% (32) but lower than a study in Brazil (9.4%)(2). This study's variation could be attributed to the quality of care provided to diabetic patients as well as the diagnostic method used. 43.4% of those polled had a problem with their visual acuity. Approximately 90% of those with macular edema had a problem with visual acuity.
In multivariate logistic regression, poor glycemic control, hypertension, and a long duration of diabetic illness were associated with diabetic macular edema. The odds ratio for developing diabetic macular edema was three times higher among those with poor glycemic control (AOR (95% CI: 2.97 (1.86,9.76)) than in those with good glycemic control. This result is consistent with the findings of a study in Japan(33), Southern Iran (34), Tanzania (35) and Jimma University Hospital (36). As a result of ischemia, hyperglycemia produces aberrant retinal blood vessel proliferation. In an attempt to supply oxygenated blood to the hypoxic retina, these blood vessels grow. Patients with diabetes can develop DME, which is characterized by retinal thickening in the macular area, at any moment during the course of DR. DME occurs when the blood-retinal barrier breaks down due to microaneurysms and dilated hyperpermeable capillaries.(37–39). DME can be reduced by 46% with strict glycemic control (47). Glycemic control should be established early in the disease's progression and maintained for as long as possible (48).
The odds ratio for developing diabetic macular edema in hypertensive patients was two and a half times higher (AOR (95% CI: 2.55 (1.86,9.76)) than in non-hypertensive patients. This is consistent with research in Japan (40), Tunisia (26), Kenya (22), and Jimma University Hospital (36). Hypertension induces choriocapillaris occlusion, which causes pigment epithelial necrosis and a rupture of the outer hemato-retinal barrier, resulting in retinal edema. This is why, in diabetic patients, tight blood pressure control at target pressure (150/85 mmHg) reduced the risk of microvascular illness by 37%, the rate of DR progression by 34%, and the risk of visual acuity deterioration by 47%(41).
Long-term diabetes was also linked to diabetic macular edema in our study. Patients who had been diabetic for more than ten years were three times more likely to develop diabetic macular edema (AOR (95% CI: 3.15 (1.78,8.52)) than their counterparts. This conclusion is supported by research conducted in Brazil (20), England (42), Chain (43), Kenya (44), Tanzania (35), Zimbabwe (45),and Khartoum (46).
Strength and Limitations of the study
Even though this study had several strengths, including fundus examinations performed by skilled ophthalmologists and the use of optical coherence tomography were two of them. It's also the first study to look into the scope of macular edema in Ethiopia and the factors that contribute to it. Another aspect of this study was the huge sample size and number of independent factors. Using a cross-sectional study design, average fasting blood sugar was another drawback in this study area due to a lack of HbAlc facilities.