Long Anterior Zonules and Angle Closure Disease

Precis: Angle closure disease was present in 59.3% of eyes with long anterior zonules (LAZ). The cause is multifactorial including a thick anteriorly positioned crystalline lens, shorter axial length, and increased lens thickness to axial length factor. Purpose: To study the profile of eyes with LAZ presenting in a glaucoma clinic in a tertiary eye care centre and understand the pathogenesis of angle closure disease in these eyes. Methods: This was a retrospective cross-sectional study. All patients with LAZ seen from January 2014 to December 2018 were included. Demographic and clinical characteristics were noted. LAZ eyes (177 eyes of 177 patients) were compared with an equal number of age and sex-matched controls. LAZ was defined as radially oriented zonular fibers (both pigmented and nonpigmented), extending central to the normal zonular termination zone on the anterior lens surface > 1mm beyond their usual insertion of 1.42 +/- 0.24mm from the lens equator onto the mid peripheral zone or central to it, as seen on slit-lamp examination, following pupillary dilation by a single examiner. Glaucoma was defined according to the International Society for Geographical and Epidemiological Ophthalmology classification. The following biometric parameters were compared: anterior chamber depth (ACD), axial length (AXL), lens thickness (LT), lens position (LP = ACD+0.5xLT), relative lens position (RLP = LP/AXL); lens thickness to axial length factor (LAF =(LT/AXL)x10). LAZ eyes without angle closure disease were also compared with controls. Results: Mean age of patients with LAZ was 64.8 +/- 8.1 years. Of these, 63.3% were females. Angle closure disease was present in 59.3% (105/177) patients. Majority of these eyes were primary angle closure suspects (PACS) (53.3%, n = 56). Significant differences were found between LAZ eyes and controls for LT (4.8 +/- 0.38mm vs. 4.49 +/- 0.40 mm, P < 0.0001), ACD (2.68 +/- 0.39mm vs. 3.0 +/- 0.32mm, P < 0.0001), AXL (22.37 +/- 0.79mm vs. 22.94 +/- 1.1, P < 0.0001), LAF (2.14 +/- 0.19 vs. 1.96 +/- 0.21, P < 0.0001), and LP (5.07 +/- 0.37 vs. 5.3 +/- 0.25, P < 0.0001). Conclusions: Angle closure was present in more than half the eyes with LAZ. Majority of these eyes were PACS or had primary angle closure. LAZ eyes had a thicker lens, shallow AC, a shorter axial length and an increased LAF as compared with age and sex matched normal controls. The presence of LAZ may be an indicator of increased risk for angle closure.