Anatomical and topographical characteristics of the eye in the early stages of primary angle closure disease

PURPOSE. To determine the anatomical and topographic features of the anterior and posterior segments of the eye in primary angle closure (PAC) and compare them with those in the primary angle closure suspects (PACs) and in controls.METHODS. This prospective study included 120 patients aged 41 to 80 years (60 eyes — PAC, 30 — PACs, 30 eyes — without ophthalmic pathology). The studied parameters included spherical equivalent (SE), intraocular pressure (IOP), choroidal thickness in the fovea (CTf), axial length (AL), anterior chamber depth (ACD), lens volume (LV), iris curvature and its thickness, anterior chamber angle profile: AOD500, AOD750, TISA500, TISA750.RESULTS. The PAC eyes differed from the control eyes by increased SE, LV, IOP, iris curvature, CTf, reduced ACD, AL, and the anterior chamber profile (AOD500, AOD750, TISA500, TISA750) in vertical sectors (p<0.01). Iris thickness was comparable between the groups.The PAC eyes differed from the PACs by increased SE, LV, IOP, reduced ACD, AL, AOD500 in the superior sector, and the profile of the anterior chamber angle in the inferior sector (p<0.01). Iris thickness, its curvature, as well as the profile of the anterior chamber in the upper sector and CTf were comparable.Threshold values that distinguish the PAC eyes and the PACs were determined: LV — 0.656 mm, AOD500 — 0.131 mm, TISA500 — 0.051 mm2, TISA750 — 0.093 mm2 in the lower sector and IOP 21 mm Hg. In the multifactor model adjusted for age, gender and AL, a negative correlation of iris thickness with CTf was established both in the PAC eyes and the PACs (all p<0.01), but not in the controls (all p>0.01). CONCLUSION. Parameters of the PAC eyes and the PACs significantly differ from the norm. LV and the anterior chamber profile in the inferior sector are the most informative for differentiating the PAC eyes from the PACs. Negative correlation between the iris and the choroidal thickness suggests that the choroid plays a role in the pathogenesis of primary angle closure disease.