Purpose: Diabetic retinopathy is considered the ghost cause of vision deterioration; it is attributed to elevated oxidative stress. Antioxidants, like melatonin, were found to be affected in
diabetic retinopathy. In the present paper, we aim to explore melatonin levels in various stages of
diabetic retinopathy. Method: Patients with diabetic retinopathy were recruited and divided into 3
groups (non-proliferative diabetic retinopathy (NPDR), proliferative diabetic retinopathy (PDR), and
advanced diabetic eye disease). One control group was recruited (diabetics without diabetic
retinopathy). Each participant was subjected to full ophthalmological examination, internal medicine evaluation, fluorescein angiography F/A, as well as optical coherence tomography (OCT) to
classify the stage of diabetic retinopathy. The laboratory evaluation of melatonin, bilirubin, aspartate transferase AST, alanine transferase ALT, fasting plasma glucose FBG, hemoglobin A1c
HA1c, and lipid profile were done. Data were collected and analyzed. Results: Each group < br />includes 60 participants. We found no different sex distribution in the four groups as (P value
=0.77), age in the four groups was as follows 58.35±8.56, 55.77±14.43, 59.3±10.73, 60.98±
7.60 years with (P =0.06). For diabetes-associated variables like duration, fasting glucose
levels, HA1c, and medications (insulin or oral hypoglycemic), we found this result; increased
duration of diabetes with raised levels of FBG, HA1C, and insulin treatment were linked with
severe diabetic retinopathy affection (P value <0.0001). When assessing the plasma melatonin
levels, the mean melatonin levels were decreased significantly with increased severity of diabetic
retinopathy (86.04 ± 2.71, 73.05 ± 6.91, 25.82 ± 2.89, 24.28 ± 2.37 pg/ml) in the studied groups
NDR, NPDR, PDR and advanced diabetic retinopathy with (P-value < 0.0001). Decreased
melatonin could be a risk factor for diabetic retinopathy. As regards total bilirubin, its mean values
decreased significantly with increasing severity of DR (P-value < 0.0001). Conclusion: There
is a relation between the levels of serum melatonin and the severity of diabetic retinopathy.