1. To obtain the certificate of attending ophthalmology, you need to have certain knowledge and skills in ophthalmology and pass the corresponding examination. Only reviewing for six months can't meet the test requirements, and it takes longer to study and practice.

2. To obtain the certificate of ophthalmologist, you need to have certain clinical experience and skills. Students are required to be able to deal with some common ophthalmic diseases independently in practical work, and it takes some practical exercise to meet the requirements. Therefore, it is difficult to master enough knowledge and skills only by reviewing for half a year, and it takes longer to study and practice.