Abstract
Iris integrity is required to regulate both the amount of light reaching the retina and intraocular pressure (IOP), with elevated IOP being a major risk factor for glaucoma. Congenital microcoria (MCOR) is an extremely rare, autosomal dominant disease affecting iris development and hindering both of these functions. It is characterized by absent or underdeveloped dilator muscle fibers and immaturity of the iridocorneal angle—where the aqueous humor is drained—which play a central role in IOP regulation. The dilator muscle anomaly is manifested in pinhole pupils (<2 mm) and thin transilluminable irises, causing both hemeralopia and photoaversion. Axial myopia and juvenile open-angle glaucoma are very frequent (80% and 30% of all cases, respectively). It has been suggested that the immaturity of the chamber angle contributes to glaucoma, and myopia has been ascribed to photoaversion and elevated IOP. Though possible, these mechanisms are insufficient. The disease has been tied to chromosome 13q32.1 structural variations. In addition to compromising iris development, modification of the 13q32.1 architecture could alter signaling pathways for axial ocular length and IOP regulation. Here, we summarize the clinical, histological, and molecular features of this disease, and we discuss the possible etiology of associated anomalies.
Highlights
The iris (Figures 1 and 2) is a flat ring-shaped ocular membrane located between the cornea and the lens
The aqueous humor flows between the iris and lens, through the pupil to the anterior part of the iris, where it is drained through the trabecular meshwork (TM), a sieve-like structure lying at the juncture of the corneoscleral region with the iris periphery [1]
The association with refraction errors or glaucoma appears to be independent of the size or type of structural variation, and whether they are secondary to the iris anomalies or the modification of the regulatory architecture of chromosome 13q32.1 remains a mystery
Summary
The iris (Figures 1 and 2) is a flat ring-shaped ocular membrane located between the cornea and the lens. The dilator muscle originates from the anterior iris epithelium, composed of a single layer of myoepithelial cells, the basal portion of which consists in elongated smooth muscle processes [4]. The aqueous humor that provides nourishment to eyeand structures is produced by theiris, ciliary body It flows between thewhich iris and through the pupil, to the anterior part the where it epithelium layers of arelens, heavily and lightly pigmented, respectively. It flows between the iris and lens, through theciliary pupil,body, and toand theout anterior partthe of sclera the iris, where it runs (i) across the iris and anterior face of the through We will review the clinical and histological features of this disease and discuss its possible physiopathology as well as associated anomalies
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