Ridologii susțin că nu diagnosticează anumite boli, ci mai degrabă că acestea “evidențiați” acele sisteme și organe din organism care sunt sănătoase și cele care sunt descrise ca “hiperactiv” sau “inflamat.” These are said to point to a tendency in the patient towards certain illnesses, to reflect past medical problems, or to predict health problems which may be developing.Since iridology is not a method of treatment, its practitioners have often studied other branches of alternative medicine, such as naturopathy, and used the study of the iris as a diagnostic first step. Iridology is practiced more widely in Europe (especially in the UK and Germany), where there are approximately 20,000 practitioners, than in the United States, which has only a tenth of that number.