Hello,


Once you will complete your Diploma, you can appear for Lateral entry examination through which you can further do Bachelor's course in Optometry where you will get admission in 3rd year and then Master's and then you can also do Doctorate.
You can appear for a common entrance exam  called EYECET for admission.
Premiere institutes like AIIMS conduct separate entrance exams for B.Sc in Optometry.

I hope this helps.