Iridoschisis^*: A Clinical and Histopathologic Study

L’iridoschisis est une pathologie dégénérative rare au cours de laquelle le stroma irien antérieur se clive spontanément du feuillet postérieur. Le feuillet antérieur se dissocie alors en fibrilles flottant dans l’humeur aqueuse. Nous rapportons le cas d’un homme de 57 ans, chez lequel nous avons découvert fortuitement une atrophie irienne unilatérale isolée. Les causes fréquentes d’atrophie irienne (herpès, dispersion pigmentaire, traumatisme...) sont éliminées. Au cours du suivi, l’atrophie évolue avec une augmentation du nombre des lésions ainsi qu’une bilatéralisation de celles-ci. Nous illustrons ce cas clinique par l’imagerie actuelle optical coherence tomography (OCT) et ultrasound biomicroscopy (UBM) mettant en évidence l’amincissement irien antérieur, non transfixiant, imagerie non encore rapportée à notre connaissance, dans la littérature. La connaissance de cette entité est importante puisque son association fréquente au glaucome en impose son dépistage dans le même temps.

Iridoschisis is a rare degenerative disease characterized by the separation of the anterior iris stroma from the posterior layer. The anterior layer splits into strands, and the free ends float freely in the anterior chamber. We report the case of a 57-year-old man, in whom we incidentally discovered isolated unilateral iris atrophy. The patient had no history of the common causes of atrophy (herpes, pigment dispersion, ocular trauma, etc.). During follow-up, the atrophy gradually worsened, with an increase in the number and bilaterality of the lesions. Ultrasound biomicroscopy (UBM) and optical coherence tomography (OCT) of anterior chamber showed thinning of the anterior iris and cleavage of the iris into two layers, an imaging result which, to our knowledge, has not yet been reported in the literature. Familiarity with iridoschisis is important, due to its frequent association with glaucoma, so that appropriate screening can be carried out at the time of diagnosis and on follow-up.

Iris anomalies associated with congenital or early-childhood glaucoma include stable primary developmental abnormalities such as those associated with the Axenfeld-Rieger spectrum and aniridia. Secondary generalized iris atrophy from uncontrolled intraocular pressure is another potential iris finding in pediatric glaucoma. We document an unusual pattern of acquired peripheral circumferential iris degeneration in 2 unrelated children with otherwise-controlled congenital glaucoma. Genetic testing revealed a common homozygous CYP1B1 mutation in one (p.Gly61Glu) and a novel heterozygous FOXC1 deletion in the other (p.Tyr81_Pro95del).

We present a technique to manage iridoschisis. This technique for anterior iridectomy of the affected iris fibers avoids intraoperative obstruction of the phaco tip and prevents postoperative complications such as corneal decompensation and glaucoma. Before the capsulorhexis is created, a vitreocutter is inserted in the anterior chamber and used to cut the iris strands at the site of the iridoschisis, making an anterior sectorial stromal iridectomy and preserving the iris pigment epithelium. Phacoemulsification is then performed. After the pupil is constricted with carbacol, remnants of the loose anterior iris fibers are excised with the vitreocutter and the scleral incision is sutured.

Flexible iris hooks, or retractors, can be used to facilitate cataract removal by phacoemulsification in patients with primary iridoschisis. This rare condition is associated with fibrillary degeneration of the iris, narrow drainage angles, and cataract. In addition to their conventional use as iris retractors, iris hooks can control the degenerate fibrillary iris stroma to improve the view and access to the lens, preventing further damage during phacoemulsification and cortical cleanup. Iris hooks are widely available, easily handled, and can transform a difficult case into one that is almost routine.

Iris fluorescein angiography is a valuable technique for clucidating a wide range of eye pathologies, among them developmental anomalies, degenerative disease, retinal vascular occlusions, diabetic microangiopathy, uveitis of various etiologies, glaucoma, tumor, and surgical or accidental trauma. In fact, IFA is more sensitive than biomicroscopy in the evaluation of iris abnormalities. Moreover, it provides indirect but reliable information on the retinal circulation when this cannot be examined directly. Some of the most important clinical applications involve the early detection of iris new vessels, cataract management in diabetic patients, and monitoring of iris tumors. Equipment, procedures, and fluorescein angiographic patterns in normal and disease states are described and extensively illustrated. More widespread use of this valuable technique is encouraged.