See my answer above. Likely you have a droopy upper eyelid (ptosis) making that eye look smaller. See an Eye MD ophthalmologist that specializes in oculoplastic surgery. I note you are from India, perhaps going to a medical school with a Department of Ophthalmology would work well for you.
JCH MD
Dear Sir,
My Age is 22 year's and by birth my left eye is smaller than the right eye. there any chance of getting clear of these problems. waiting for your suggestions.
See an ophthalmolgist. The most likely condition that causes this is a droopy upper lid (ptosis). If it is a problem (likely not after all these years) surgery can often improve.
Find an Eye MD in the USA at www.aao.org
JCHMD