and the visual Þeld are pathological (increased cup/disc ratio and visual Þeld defect).

¥Acute angle closure (attack) (AAC): Rapid closure of (nearly) the complete circumference of the chamber angle with very high IOP and severe symptoms and signs.

An appropriate diagnosis is only possible by

careful indentation/dynamic gonioscopy with a small and dim slit beam in a dark room. An ITC will open during indentation; a synechia will remain (see Chap. 2, Sect. 2.3).

Note: Only a minority of patients with angle closure (PACS, PAC, PACG) report symptoms such as intermittent pain (differential diagnosis is migraine) or colored rings when looking into a light source. The majority show no symptoms, except in very severe glaucomatous damage.

A system of classiÞcation of angle-closure diseases is shown in Table 7.1.

7.1.3Terms

7.1.3.1“Occludable” Angle?

Per se any angle is occludable. Even a wide-open angle might become occluded over time by the increasing volume of a lens with cataract. However, an a priori narrow angle will become occluded with a much higher probability. A prophylactic iridotomy is generally performed in the second eye of patients with an AAC in the Þrst eye or in eyes with chamber angles graded Shaffer 1 which need regular mydriasis due to diabetic retinopathy or in those with peripheral retinal degeneration.

It is necessary to differentiate between a closed angle (which is either reversibly closed by ITC or irreversible closed by synechiae) and an open angle at the time of examination.

Angles graded 1 (gonioscopically Shaffer or slit lamp van Herick) have a high probability of becoming ÒoccludedÓ or closed in the future, but not necessarily all of them. In fact, the probability

is about 1:10 in those eyes in which the volume of the iris increases instead of decreases with pupillary dilation.

In population survey studies the deÞnition of an ÒoccludableÓ angle is an angle in which only 90¡ or less of the functional, posterior trabecular meshwork is visible.

7.1.3.2“Narrow”-Angle Glaucoma

This term derives from the days before indentation gonioscopy was known, and should be avoided. The angle is either open or closed. ÒNarrowÓ is a qualitative term and does not imply occludable or not occludable. There are conditions of the eyes with primary open-angle glaucoma in which the chambers are narrowed without any ITC or synechiae as a result of an increase in the lens volume. However, such a condition remains an open-angle glaucoma with a chamber angle graded 1 or 2 (Shaffer) and the main outßow resistance is in the cribriform trabecular meshwork. Additional pupillary block may develop, leading to further forward bowing of the iris, ITC or synechiae, and therefore to a ÒsecondaryÓ angle-closure glaucoma.

7.1.3.3“Acute Angle-Closure”

Glaucoma

An acute attack with closure of almost the total circumference of the angle and high IOP not necessarily is leading to an optic neuropathy, i.e. glaucoma per se. The optic disc may sustain no damage in the majority of cases with a single event. A single attack does not lead to progressive disease, and therefore it is Òper deÞnitionÓ no glaucoma.

7.1.4Classification of the Causes of Angle Closure

Four levels may help classify the causes of angleclosure (glaucoma).