Choroidal expansion as a mechanism for acute primary angle closure: an investigation into the change of biometric parameters in the first 2 weeks

Abstract

Background/aim: Choroidal expansion with anterior movement of the lens was recently proposed as a mechanism for acute primary angle closure (APAC). The aim of this study was to compare the biometric parameters, central anterior chamber depth, limbal chamber depth, lens thickness, and lens position, within 24 hours of presentation and 2 weeks later in eyes with APAC. Methods: This was a prospective observational case series of 41 subjects with APAC. Subjects who presented with APAC were treated with medical therapy followed by laser iridotomy (LI) in both eyes once the acute attack was broken. Ocular biometry was performed in affected and fellow eyes before LI (baseline) and then 2 weeks later. Optical pachymetry was used to measure central anterior chamber depth (ACD) and the limbal chamber depth (LCD) was graded at the slit lamp. A-scan ultrasound was used to measure lens thickness (LT) and axial length (AL). Lens position (LP) was defined as ACD +KLT. Results: The majority of subjects were Chinese (83%) and female (61%), and the mean age was 60.4 (SD 10.3) years. In affected eyes, the ACD was 1.81 (0.29) mm before and 1.80 (0.28) mm 2 weeks after LI (p = 0.63), while in fellow eyes, the ACD was 1.83 (0.29) mm and 1.81 (0.38) mm, respectively (p = 0.21). There was no significant change in lens position, relative lens position, or axial length in both affected and fellow eyes over the 2 weeks. Conclusions: There was no change observed in central anterior chamber depth, lens thickness, or lens position at the time of the acute attack compared to 2 weeks later in both APAC affected and fellow eyes. The findings do not support the hypothesis of lens movement due to choroidal expansion in APAC.

Intraocular pressure elevation and choroidal thinning

“…Subsequently, the degree of glaucoma damage was not consistently associated with choroidal thickness 22. The results of our study agree with the findings by Yang et al 23 who did not find any change in the lens position, relative lens position or axial length in both affected and fellow eyes of patients within 24 h of presentation and 2 weeks later after the APAC. The authors concluded that their findings did not support the hypothesis of a lens movement due to choroidal expansion in APAC.…”

Angle closure glaucoma: a mechanistic review

“…It is conceivable that a multilevel physiological trigger may initiate a sustained choroidal expansion, which in an anatomically predisposed eye, leads to APAC and PACG. Conversely, the fact that other investigators have failed to demonstrate significant changes in biometry (ACD, lens position, RLP) before and 2 weeks after LPI [39], challenges the theory of anterior lens movement secondary to choroidal expansion as a possible mechanism for APAC. It would be interesting to perform serial UBM among those with newly diagnosed PACG post LPI to establish a temporal sequence of events.…”

Morphological changes of the anterior segment after laser peripheral iridotomy in primary angle closure

“…These changes were consistent with previous reports analysing quantitatively. [8][9][10][11][12][13][14][15][16] We did not measure the angle opening distance (AOD), because the software in AS-OCT only includes a measuring system capable of calculating distance and angle.…”

“…A large number of studies have assessed the change of anterior segment morphology using the abovementioned techniques, and most of them believed that the peripheral anterior chamber was deepened and the anterior angle was widened significantly after LPI, whereas the central anterior chamber was not changed. [8][9][10][11][12][13][14][15][16] However, all of the above methods might have some limitations. Either the accommodation or the illumination could not be controlled, or the examination would touch the eyes, thereby causing some measuring errors.…”