Zonulopathy and Its Relation to Primary Angle Closure Disease: A Review.

PRCIS

This paper aims to discuss the anatomical features of zonule fibers that center the lens in the eye and summarizes the relationship between zonulopathy and PACD.

ABSTRACT

The increasing lens vault (LV) and lens thickness (LT) is a recognized mechanism for primary angle closure glaucoma (PACG). Zonulopathy, causing the abnormal lens position, is an important factor in this mechanism. Several anatomically distinct sets of zonular fibers are present in primate eyes, including ciliary zonules, vitreous zonules, and attachments between the posterior insertion zone of the vitreous zonules and the posterior lens equator (PVZ INS-LE strands). Zonulopathy, as a clinical diagnosis, exhibits zonular laxity and loss, long anterior lens zonules (LAZ). Slit lamp, gonioscopy, ultrasound biomicroscopy (UBM), anterior segment optical coherence tomography (AS-OCT) aid in the diagnosis of zonulopathy. The proportion of underdiagnosed zonulopathy among primary angle closure disease (PACD) patients before operation is high. According to the intraoperative signs, zonulopathy could be determined better. There is a high prevalence of zonulopathy among PACD patients compared with the general population. Because of the different insertion zone in lens capsules, different zonular fibers play different parts in lens position and shape. Zonular laxity and loss cause the lens to be thicker and move anteriorly, forming narrow-angle and high intraocular pressure, and then the higher intraocular pressure damages zonule fibers further and causes angle closure. Loss of vitreous zonules may make the ciliary body rotate anterior excessively and pull iris forward, leading to iridotrabecular contact. LAZ eyes tend to be hyperopic and have short axial length, increased LT and anterior lens position, plateau iris configuration, and characteristics that are consistent with elevated risk for angle closure. Zonulopathy may be a risk for PACD. A clear knowledge of zonulopathy and its relation to PACD would be helpful to the diagnosis and treatment.