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Editors Selection IGR 9-3

Clinical Forms of Glaucoma: Iris transillumination defects in exfoliation syndrome

Comment by Robert Ritch & Syril Dorairaj on:

50264 Circumferential Iris Transillumination Defects in Exfoliation Syndrome, Fingert JH; Burden JH; Wang K et al., Journal of Glaucoma, 2013; 22: 555-558

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Fingert and co-workers earlier identified a pattern of concentric circular transillumination defects (TIDs) in patients with XFS, a pattern also found in the LYST mouse model,¹ and have now extended their study to determine whether these TIDs are specific to XFS and whether infrared videography can be used as a diagnostic modality for identifying early XFS. They compared XFS, PDS, POAG and normal controls and concluded that prominent concentric circular iris TIDs were observed only in XFS and not in PDS, POAG, or controls. They also concluded that infrared videography examination technique has the potential to help physicians to make earlier diagnoses of XFS.

Prominent concentric circular iris TIDs were observed only in XFS and not in PDS, POAG, or controls

Iris transillumination defects have been previously associated with XFS, either as circumferential defects in the sphincter region² or as a diffuse 'starry-sky' appearance.³ Iris changes are an early and consistent feature of XFS eyes and involve all iris structures and cell types. XFM is produced by and accumulates on the surface of the posterior pigment epithelium, which exhibits marked degenerative changes with focally ruptured cell membranes and liberation of melanin granules. These cells take on a shrunken, triangulated appearance, giving rise to a saw-tooth appearance of the pigment epithelium, which manifests as concentric folds. It is these folds which presumably give rise to the concentric transillumination pattern described by the authors.

The authors' second conclusion regarding the ability of infrared iris transillumination to facilitate early diagnosis of XFS is hypothetical and warrants future prospective studies. Early iris changes noted in fellow eyes may account for the clinical signs characteristic of early stages, such as pigment dispersion into the anterior chamber after dilation, peripupillary atrophy, trabecular pigmentation, Sampaolesi line, and pigment particles dotting the iris sphincter region.² Finding these signs in eyes of patients with no manifest exfoliation deposits on the lens in either eye warrants continued follow up and, at the current time, the possibility of typing patients for the high risk single nucleotide polymorphisms in the LOXL1 gene which underlie the vast majority of XFS cases.

Fingeret et al. have added yet another sign of XFS to the diagnostic armamentarium. Careful examination of high-risk patients through imaging could improve early detection of subclinical abnormalities characteristic of XFS. One drawback is that infrared videography may not be readily available to most clinicians. Further investigation may reveal a simpler mode of visualization using slit-lamp techniques, extending the diagnostic ability for early detection of this disease, which is the most common recognizable cause of open-angle glaucoma worldwide. It may also further the value of screening family members of affected individuals.

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