There are a number of rare ophthalmological conditions that individual clinicians may only see every 1 to 2 years. By themselves, these conditions contribute very little to national visual morbidity but are often of great inherent interest to the ophthalmological community as a whole for a number of reasons.

Firstly, it is evident that certain rare diseases provide fundamental models that would help in the understanding of the pathogenesis of other commoner disorders. In the field of uveitis, for instance, comprehension of the mechanisms that underlie sympathetic ophthalmia would not only improve the management of this disease in those rare patients that contract it, but also might throw light on the pathogenesis of many disorders that result in intraocular inflammation from whatever cause. Similarly, the rapid identification of patient pedigrees in uncommon genetic disorders and the application of modern molecular genetic techniques to these rare cases could have a major impact in the field of prenatal screening and, ultimately, in their possible cure. Secondly, the ability to identify rare complications of common diseases or …