Vision Centre

Glaucoma

The eye is made from soft tissue to keep it flexible for fast movements. To focus accurately the eye must maintain its shape, like a ball filled with air to stay firm. Clear fluid (the aqueous) is pumped into the eye via the ciliary body and circulates around the structures of the eye. The aqueous is then drained through the trabecular meshwork to return to the blood stream. Draining of the aqueous is against resistance so the eye pressure is higher than the air pressure but lower than blood pressure.

Glaucoma is a disease in which the optic nerve is damaged.  In most cases this is caused by high  intra-ocular pressure a  result of blockage of the circulation of aqueous or drainage of the aqueous. In other cases the damage may be caused by low blood supply to the optic nerve, weakness of the structure of the optic nerve or another health problem in optic nerve.

Glaucoma is often called the sneak thief of sight as most people with glaucoma do not notice symptoms until they begin to have significant vision loss. As optic nerve fibres are damaged by glaucoma, small blind spots may begin to develop, usually in the peripheral or side vision. If the entire optic nerve is destroyed, blindness results.

Other symptoms usually are related to sudden increases in IOP, particularly with acute angle-closure glaucoma, and may include blurred vision, halos around lights, severe eye pain, headache, abdominal pain, nausea, and vomiting. Intra-ocular pressure or IOP is usually considered normal between 10mmHg and 20mmHg (measured in millimeters of Mercury). High intra-ocular pressure may also be ocular-hypertension, low intra-ocular pressure may not rule out glaucoma as there are forms of normal pressure glaucoma. For this reason more than one test is used to diagnose true glaucoma.

Chronic or Open angle glaucoma is most common and increases in risk with age and family history. In open angle glaucoma the aqueous that normally drains out of the eye cannot get through the eyes filtration system into the drainage canals, causing pressure to build up in the eye. In contrast to angle-closure glaucoma in which the drainage canals themselves are blocked. In angle-closure glaucoma, the iris is pushed or pulled against the drainage channels at the angle of the anterior chamber of the eye. When this occurs, the aqueous that normally drains out of the eye is blocked, elevating the IOP. If this occurs suddenly, immediate treatment is essential to prevent optic nerve damage and vision loss. If closure is gradual it may be mistaken for open angle glaucoma.

Glaucoma is most commonly treated with eye drops. If treatments such as drops fail surgery may be required. In angle-closure glaucoma, Iridotomy surgery may need to be done where a drainage hole is created in the iris to relieve the increased pressure inside the eye. This can be performed using a laser; therefore, an incision in the eye is not needed. Patients may need to have an Iridotomy after an acute episode of angle-closure glaucoma or to prevent an attack of angle-closure glaucoma.

Other types of surgery that are performed to help glaucoma include Trabeculoplasty, and filtering. All of these procedures try to ease drainage of aqueous.