The eye seems disproportionately large given the size of the head. Or perha Ops it's the angle of the eye that bothers me. ... Or the shape. Other than the eyes, the art is pretty awesome. I especially like her mane blowing in the wind. And the hue/ tint gradations.
it's always so hard for me to imagine derpy serious with her eye problem..sad is do-able,but never SERIOUSLY anything, mad, pure unfiltered relief, jealousy, or even a neutral glance..you kind of cheated,but that's why i love this so much, you've taken derpy past a joke character and made her into something beautiful and powerful looking