Abstract: Medical service providers are faced with the problem of how to make decisions when they are unable to reach an agreement due to the lack of scientific evidence or there are conflicting evidence on a certain issue. Making consensus is one of their solutions. This review introduces two common consensus formation methods, namely Delphi process and nominal group technique. Delphi process collects the opinions of relevant experts on a given problem through a questionnaire and makes repeated evaluation. Nominal group technique is to collect the views of relevant experts on a given problem through structured meetings and conduct repeated evaluation. (Int Rev Ophthalmol, 2021,45：369-373)

Key words: consensus making, Delphi process, nominal group technique, research methodology