First of all, you need bright and clear eyes to look young. If you have vitreous opacity, you may look old and ill.
Secondly, young eyes have elastic eyelids and eye skin. If you have eye bags under your eyes, you may appear to be at least 10 years older that your age.
Thirdly, thick eyelashes make your eyes biger and younger. You know why women like to wear false eyelashes.
Last but not the least, you should have affirmative and vibrant eye expression. Eyes are the windows of one's soul. If you have a young attitude, your eyes can tell it.