Safe size of corneal graft with less chances of failure is -
With the help of a corneal trephine (7.5 mm to 8 mm in size)a paial thickness incision is made in the hostcornea . Then, anterior chamber isentered with the help of a razor blade knife andexcision is completed using corneo-scleral scissors. REF:Comprehensive ophthalmology,AK Khurana,4th edition,pg no.125.
7.5 mm
5.5 mm
6.5 mm
4.5 mm
Cornea and sclera