Angle Closure and Glaucoma

Considering primary open-angle glaucoma, the main resistance to outßow is in the cribriform layer (i.e. inner wall of SchlemmÕs canal) of the trabecular meshwork that leads to changes of the optic disc and the retinal nerve Þber layer (RNFL). In primary angle-closure disease, different amounts of iris tissue form contacts with the Ð originally intact and regular Ð trabecular meshwork, mainly as a result of forward bowing of the iris due to pupillary block (Figs. 7.1, 7.2, and 7.3). This iridotrabecular contact (ITC) is a totally different cause of glaucoma. And the initial therapy is signiÞcantly different between an open-angle glaucoma and closed-angle situation. Take care to distinguish between these two different entities!

Risk factors for developing an angle closure may be changes in the anatomy of the eye, e.g. short eyes (hyperopic due to short axial length, nanophthalmus), shallow anterior chamber, lens with increased volume and/or vault (age, cataract; Fig. 7.4) or in spheroid shape (WeillMarchesani syndrome) in combination with dilated pupils (e.g. on scotopic illumination). SpeciÞc ethnic groups (Inuit, East Asians) and women suffer more often from angle-closure disease.

Primary angle-closure disease seems to be a complex of mechanisms because of additional dynamic, physiological factors, such as choroidal expansion and/or thickness and iris volume changes when the pupil is dilated.

Fig. 7.2 A chamber angle in an eye with angle closure due to appositions (ITC) before indentation gonioscopy. Only a short line of pigment is visible

Fig. 7.3 During indentation gonioscopy of the same eye as in Fig. 7.2, the scleral spur, the pigmented trabecular meshwork (grade +2 to +3), SchwalbeÕs ring and some pigment anterior to SchwalbeÕs ring have become visible (Courtesy G. Megevand-Sunarevic)

Fig. 7.4 Shallow central anterior chamber in an eye with a thickened lens due to cataract. A pupillary block and subsequent angle closure are highly probable

7.1.2Terminology and Classification of Morphological and Functional Changes

¥Primary angle-closure suspect (PACS): The chamber angle shows appositions or ITC over 270¡ or more. The IOP, the disc/RNFL and the visual Þeld are normal.

¥Primary angle closure (PAC): The chamber angle shows ITC or/and peripheral anterior synechiae. The IOP is >21 mmHg, the disc/ RNFL and the visual Þeld are normal. Appositions usually start in the recess at the iris root (Òcreeping angle closureÓ, ÒB-typeÓ,

mostly superior) or ITCs leave the recess open, but close the angle beyond (ÒS-typeÓ, mostly inferior). This indicates, that the insertion of the inferior iris is more posterior. Two-thirds of patients who have previously experienced an acute angle-closure attack (AAC) show no signs of glaucomatous changes in their disc or visual Þeld, but their iris shows a torque structure and they have pigment depositions on the trabecular meshwork. They are also diagnosed as having PAC.

¥Primary angle-closure glaucoma (PACG): The chamber angle shows ITC or/and peripheral anterior synechiae. The IOP is >21 mmHg, the disc