Purpose: The aim of our study was to compare the level 
of Endothelin 1 in plasma and vitreous between type 1 
and type 2 diabetes mellitus and control group and 
understand its role in diabetic retinopathy. 
Design: Prospective randomized case control study. 
Methods: This study was conducted on three groups. 
Group 1 were type I diabetic patients, Group 2 were type 
II diabetics and group 3 were controls (complete healthy 
non-diabetic
 individuals).
 Full ophthalmological 
examination was done to all our cases. Endothelin level 
in vitreous and plasma was estimated together with 
glycated hemoglobin HbA1c and other parameters were 
estimated in all patients and controls. 
Results: Plasma Endothelin 1 level was significantly 
elevated in diabetics compared to controls (normal 
subjects). Vitreous endothelin 1 was significantly lower 
in diabetics compared to controls. There was a positive 
correlation between glycated hemoglobin HbA1C and 
serum Endothelin-1 ET-1 level in both type 1 and 2 
diabetes mellitus. Endothelin 1 level is elevated in poorly 
controlled diabetic patients. 
Conclusion: Endothelin-1 plays an important role in 
mediating retinal changes in diabetics.