Iridology is the study of the iris for determining the part of the body that has a health problem. There are no links between homeopathy and iridology so it can only be regarded objectively as a complementary therapy that should be investigated on its own. Otherwise it turns into a means of short-cutting the hard work of repertorization and case taking. There is a great seduction to eliminating the diagnostic work of classical homeopathy and multi-therapeutic holistic practitioners are not likely to take time to know it well. On the other hand you have a practitioner like Cyrus M. Boger who said that sometimes he knows the remedy by looking at the eye. Remember, though, he was a master homeopath first.
Proponents of iridology attribute its start at about 1861 to Ignatz von Peczely, a Hungarian physician who at 11 years old accidentally broke the leg of an owl and noticed a black stripe in the lower part of the owl's eye form. Nils Liljequist of Sweden also saw changes in his iris color when he was sick or injured and published a paper on the subject ten years later. In 1893 he published an atlas with 258 black and white drawings and 12 colored double-iris drawings called "Diagnosis From The Eye".
In the mid-20th century, Léon Vannier a very well-known and published French homeopath urged his students to use iridology only after case taking and the remedy had been chosen. He said iridology can sometimes be useful to complement case taking in searching for information but not in choosing the remedy. He did not follow classical homeopathy as we know it but derived many of his theories directly from Hahnemann. Hahnemann did not use iridology.