Angle closure glaucoma: a mechanistic review

Abstract

With recent advances in imaging techniques such as anterior segment optical coherence tomography and ultrasound biomicroscopy, there is a better understanding of nonpupil block mechanisms and novel risk factors contributing to the pathogenesis of angle closure glaucoma. Recent studies suggest that multiple anatomical and physiological factors interplay in the pathogenesis of angle closure glaucoma. The association of greater iris convexity, area and thickness with narrow angles could result in a more anterior bowing and crowding of the peripheral iris. Other novel anatomic parameters such as greater lens vault, smaller anterior chamber width, area and volume, independently increase the risk of having angle closure. Dynamic increase or lesser reduction in iris volume during dilation supports the theory of physiological predisposition to the disease process. Choroidal expansion has been demonstrated in untreated and treated, acute and chronic primary angle closure eyes. It remains unknown whether this finding is a cause or effect in this condition. With a wider availability of imaging tools and a better understanding of risk factors and mechanisms, clinicians maybe able to more accurately identify those at greater risk of developing angle closure disease and tailor their treatment according to the predominant factor(s) involved.