<prompt> Safe size of corneal graft with less chances of failure is -7.5 mm5.5 mm6.5 mm4.5 mm  <response>: With the help of a corneal trephine 7.5 mm to 8 mm in sizea 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. 