Glaucoma surgery aims to stabilise or reduce the intraocular pressure (IOP). Untreated the increased pressure causes damage to the Optic nerve, resulting in loss of vision.
Surgical options can be laser, non-laser or stent surgery. All procedures aim to achieve a decrease in the production of aqueous humour or increase the outflow (drainage) of this same fluid.
Types of glaucoma
- Open-angle glaucoma - aqueous humour cannot drain properly
- Angle-closure glaucoma - flow of aqueous humour is blocked
- Normal pressure glaucoma - occurs despite average intraocular pressure
- Childhood glaucoma - rare and often hereditary
- Congenital glaucoma - present at birth
- Secondary glaucoma - due to other conditions of the eye.
Involves insertion of a micro-scale device from within the eye’s anterior chamber through a small corneal incision. The device is designed to reduce the intra ocular pressure by restoring the natural outflow pathways for aqueous humour. The procedure may be beneficial for mild to moderate open angle glaucoma patients and is often performed at the time of cataract surgery.
Some devices drain fluid from the anterior chamber into the conventional surgical drainage space, the subconjunctival tissue. Restoring the natural outflow lowers and controls pressure within the eye.
Laser treatment is usually recommended if the use of eye drops does not improve your symptoms. Laser treatment involves using powerful beams of light to improve the flow of fluid out of your eye and reduce the pressure inside the eye.
During the laser surgery, your eye is numbed with anaesthetic eye drops. Then, your doctor will place a special lens in front of your eye. A laser beam is then aimed into your eye and you will see flashes of coloured light.
Types of laser surgery for glaucoma include:
Laser trabeculoplasty: Laser trabeculoplasty is often used to treat open-angle glaucoma. The laser is aimed at the trabecular meshwork, where fluid drains from the eye. This surgery opens the clogged areas and makes it easier for fluid to flow out of the eye.
There are two types of laser trabeculoplasty surgery:
- Argon laser trabeculoplasty (ALT): During ALT surgery, a laser creates burns in the trabecular meshwork.
- Selective laser trabeculoplasty (SLT): During SLT, a laser is used at different frequencies to treat specific cells in the meshwork.
Laser iridotomy is normally performed to treat people with closed angle glaucoma. During iridotomy, the laser creates a small hole through the iris to improve the flow of fluid from the back of the eye to the trabecular meshwork. This opening drains out the fluid and helps lower eye pressure.
Cyclophotocoagulation or laser cyclo-ablation
Laser cyclo-ablation may be helpful in treating people with severe glaucoma, which has not been manageable with medications or previous surgical procedures. In cyclophotocoagulation a laser is used to destroy parts of the ciliary body, a part of the eye that produces eye fluid. This therapy decreases the production of fluid thus reducing the eye pressure.
Trabeculectomy with antimetabolite (Mitomycin C)
A trabeculectomy is the most common type of surgical procedure performed to relieve pressure caused by glaucoma. During the procedure, a new drainage channel is created to ease drainage of fluid from the eye. This new opening allows fluid to drain out of the eye forming a bleb covered by the white outer covering (the conjunctiva) of the eye. Over time the drainage site can scar and therefore close. Scarring is the main reason for failure of trabeculectomy. Antimetabolites can be used to reduce the risk of scarring. Mitomycin C (MMC) is the most commonly used antimetabolite in trabeculectomy surgery. Mitomycin C inhibits the multiplication of cells which produce scar tissue, thus preventing the scar formation.
Trabeculectomy with antimetabolites is generally recommended for reducing intraocular pressure in patients with advanced glaucoma.