Iris crystals in chronic uveitis

Purpose. Crystals on the iris of patients with chronic uveitis are a rare clinical sign. They are thought to represent unusually large Russell bodies (spherical, immunoglobulin containing structures derived from plasma cells). We present a series of 18 uveitic eyes with iris crystals. Methods. A photographic survey of 18 eyes of 16 patients was undertaken. Demographic details and clinical features including the natural history of the iris crystals were documented. Immunoglobulin subclasses were also measured. A histopathological review of all iridectomy specimens obtained in our centre from patients with chronic uveitis over a three year period was also undertaken. Results. The mean age of patients was 37 years. There were 11 females and 5 males, with 12 patients Caucasian, 3 Indo-Pakistani and 1 Afro-Caribbean. Ten patients had Fuchs' Heterochromic Cyclitis (FHC) and the other uveitis entities included chronic anterior uVeitis and panuveitis with retinal vasculitis. One patient had Behcet's disease and another presumed ocular tuberculosis. Iris crystals were noted bilaterally in two cases. There was no correlation between severity of clinical signs and presence of iris crystals. No significant change in the number, size or position of the iris crystals was seen over a mean follow up period of 20 months in spite of some patients receiving topical and/or systemic therapy. In our review of the histology of iridectomy specimens obtained from patients with chronic uveitis, none showed evidence of Russell body formation. Conclusions. This is the largest documented series of iris crystals. This clinical sign appears to be rare, though the minute size of the lesions may result in under-reporting. Previous literature suggests that Russell bodies are common features of the histopathology of chronic uveitis but our observations do not support this. The majority of cases in our series occur in FHC which is known to have raised levels of immunoglobulin in the aqueous.