Purpose: We identified a pattern of concentric circular transillumination defects (TIDs) in a few patients with exfoliation syndrome (XFS) using an infrared detection system. This pattern of iris abnormality has also been observed in a mouse model of XFS. The objective of the current study is to determine whether concentric iris TIDs are specific to XFS and may have some diagnostic utility for identifying early cases of disease.
Materials and methods: A total of 68 volunteers from the University of Iowa Glaucoma Clinic with normal eyes (n=21) or diagnoses of either XFS (n=12), pigment dispersion syndrome (PDS) (n=8), or primary open-angle glaucoma (POAG) (n=27) were enrolled in the study. The irides of these subjects were each examined by 4 ophthalmologists masked to their diagnosis, using infrared videography. The presence of concentric, circular TIDs on the videos was graded as none (grade 0), possible (grade 1), definite (grade 2), or prominent (grade 3) by 4 examiners. We searched for an association between the presence of concentric bands of transillumination and the diagnosis of XFS after removing the effect of different raters was evaluated using the Cochran-Mentel-Haenszel test. We performed the same analysis for PDS and for POAG.
Results: The presence of any concentric, circular iris TIDs (grades 1 to 3) was detected in a mean of 38% normal subjects, 35% POAG patients, 53% PDS patients, and 77% of XFS patients. When the frequency of concentric, circular iris transillumination (grades 1 to 3 pooled) was compared between each of the patient groups and normal controls, a significant difference was detected between XFS patients and controls (P=0.000019). No significant difference was detected between POAG and controls (P=0.64) or between PDS and controls (P=0.20). Furthermore, prominent concentric, circular iris transillumination (grade 3) was only observed in XFS.
Conclusions: Detection of concentric, circular iris TIDs with an infrared system is easy, inexpensive, rapid, and relatively specific in XFS. Future larger studies will be needed to confirm the findings of this small pilot study. Furthermore, this examination technique has the potential to help physicians to make earlier diagnoses of XFS and to better plan for future surgeries to minimize risk of complication.