Closed angle Glaucoma

Open and closed angles (Image courtesy of Santorio eye institute)

Figure 1. Open and closed angles (Image courtesy of Santorio eye institute)

CLOSED ANGLE GLAUCOMA

Closed angle glaucoma is more commonly seen in South East Asia but also occurs in Australia

In this type of glaucoma, raised pressure within the eye occurs due to mechanical obstruction of the trabecular meshwork by the iris. The iris and posterior surface of the cornea form an angle which is made more acute by the presence of the lens pushing it forward. Hence the term ‘Narrow angle glaucoma’. Largely, the angle configuration is inherited thus this type of glaucoma can run in families. In addition, hyperopes (long sighted individuals) are more prone to this type of glaucoma as their eye is physically smaller leading to less room inside the eye.

As we age, the lens which sits immediately behind the iris tends to grow. As it does so it also pushes the iris forward narrowing the angle. With ongoing growth of the lens, significant narrowing of the angle can occur. This type of narrow angle glaucoma is referred to as phacomorphic glaucoma.

A necessary  requirement to be able to classify this as glaucoma is that there is elevated intraocular pressure with consequent optic nerve damage. Pressure elevation can be sudden as in the entity of Acute Angle Closure Glaucoma or gradual over years.

ACUTE ANGLE CLOSURE

As the iris-corneal angle becomes narrower, a situation can arise where the iris becomes in full contact with the trabecular meshwork. This is called Iridotrabecular contact (ITC). At this point therefore the angle is completely obliterated. This contact may not however create a seal and fluid may still be able to leave the eye. If it does however create a seal, fluid may not be able to exit the eye and the intraocular pressure can rise very quickly to high levels that can quickly damage the optic nerve.

SYMPTOMS OF ANGLE CLOSURE

Most commonly patients can experience halos around lights, pain in the eye or around it and nausea or even vomiting. rarely, if the pressure rises slowly, it can reach very levels with minimal symptoms.

TREATMENT

As a rule, if someone is deemed to be in a high risk category for an attack of angle closure then a peripheral iridotomy is performed.

If after the iridotomy there is ongoing contact between the iris and the trabecular meshwork, then there is a risk of ongoing damage to the meshwork which can with time result in a gradual elevation of pressure to levels that may need medical treatment. Patients with narrow angles should be monitored life long for this reason.

As an alternative to iridotomy, or sometimes as well as an iridotomy, a cataract operation may be required. This is because the removal of the lens will result in a widening of the angle and alleviation of the narrow angle problem.

Patients with narrow angles without cataract but who are long sighted and motivated to reduce their dependence on glasses, can still have their lens removed solving both problems.