Glaucoma surgery has traditionally involved either laser treatment or conventional surgery in which an alternative pathway for fluid drainage is made in the eye to reduce intraocular pressure (IOP) for preventing further vision loss or blindness.
What is glaucoma?
Glaucoma is an eye disease that results in progressive vision loss due to optic nerve damage. The damage to the nerve is pressure sensitive. The optic nerve is a bundle of nerve fibres that carries visual images or signals from the eyes to the brain. A clear fluid called aqueous humour circulates through the eye and then drains out predominantly through a mesh-like channel (trabecular meshwork). In glaucoma this channel does not drain fluid efficiently, leading to increased pressure inside the eye (intraocular pressure/IOP). This increased intraocular pressure causes damage to the optic nerves and blood vessels resulting in loss of vision.
The treatment for glaucoma is to lower the pressure, to a level where the damage to the optic nerve is halted. The existing damage cannot be reversed. Often, early nerve damage is not detectable by the patient, and most glaucoma types have no symptoms. Therefore it is important to have your regular glaucoma testing as recommended by your eye doctor, so early changes can be detected and treatment can be started.
Types of glaucoma
The different types of glaucoma include:
- Primary Open Angle Glaucoma: This is the most common form of glaucoma. This type of glaucoma occurs when the eye's drainage system cannot sufficiently drain the fluid and the pressure inside the eye increases. The angle between the iris and cornea is wide and open. There are no symptoms until the disease is severe, vision is noticeably affected, and cannot be recovered.
- Normal tension (pressure) glaucoma or low-tension glaucoma: In this type of glaucoma the optic nerve is damaged despite normal intraocular pressure.
- Secondary Open Angle Glaucoma: The angle is wide open and there is usually an identifiable underlying cause for a insufficient drainage of the fluid inside the eye:
- Pseudoexfoliation (PXF) Glaucoma
- Pigment Dispersion (PDS) Glaucoma
- Steroid-Induced Glaucoma
- Uvetic Glaucoma
- Closed Angle Glaucoma: This type of glaucoma is less common and can cause a sudden build-up of pressure in the eye, leading to vision loss. The angle between the iris and the cornea is narrow or closed.
- Secondary Closed Angle Glaucoma: The angle is narrowed as a result of a secondary cause, such as:
- Phacomorphic Glaucoma: The cataractous lens pushes forward, closing the drainage angle.
- Neovascular Glaucoma: New abnormal blood vessels grow in the drainage angle, blocking it. The new abnormal vessels form as a result of retinal ischaemia, where there is not enough blood supply to the retina, often secondary to diabetic eye disease or retinal vein occlusion.
- Uveitic Glaucoma: This results directly or indirectly from uveitis, which is a condition characterised by inflammation inside the eye. IOP rises can be acute or chronic.
- Medication-Induced Glaucoma: as a result of medications that shift the position of the structure that makes the aqueous humour, the fluid inside the eye. This results in a narrowing of the drainage angle.
- Benign cysts or malignant tumours affecting the drainage angle.
- Congenital Glaucoma: This type of glaucoma is seen in babies and often runs in families. It is caused by improper development of eye's drainage canals before birth.
- Other types of Glaucoma are traumatic glaucoma, and irido corneal endothelial syndrome (ICE).
What are the treatments of glaucoma?
The aim of the treatment is to reduce the pressure in your eyes (IOP), which involves using special eye drops or medications. Laser treatment (Selective Laser Trabeculoplasty – YAG SLT) is increasingly used as a first line treatment in open angle glaucomas. If cataract surgery is required, newer Minimally Invasive Glaucoma Surgery (MIGS) involves the insertion of microscopic drainage devices. Cataract Surgery itself can also lower the eye pressure. Laser and MIGS surgery can cease or reduce dependence on eye drop medications.
In closed angle glaucomas, laser (YAG PI) may be used to create a new drainage channel. Other treatments will depend on the cause of glaucoma. Treatment may include removing cataract, laser treatment to the retina, or depositing medication into the eye.
In certain cases, glaucoma surgery is performed to prevent further damage.
There are different laser treatments available for treating high intraocular pressure and managing glaucoma, depending on the type.
Types of laser surgery for glaucoma include:
Selective Laser Trabeculoplasty (SLT): Selective Laser Trabeculoplasty is used to treat open-angle glaucoma, and lowers the intraocular pressure. It can be used instead of eye drops, or if multiple eye drops are used for glaucoma treatment, laser treatment can reduce the number of eye drops needed.
The laser is aimed precisely at the trabecular meshwork, where most of the fluid drains from the eye. This surgery opens the clogged areas and makes it easier for fluid to flow out of the eye. Specific cells are targeted by the laser to improve their draining function.
Laser Peripheral Iridotomy (Laser PI): Laser iridotomy is normally performed to treat people with narrow angles or closed angle glaucoma. Some patients have narrow angles that are susceptible to suddenly close off, which can lead to an acute and sudden rise in intraocular pressure, which can in turn lead to irreversible vision loss. In this instance Laser PI is used to prevent an attack of acute angle closure, to protect the eye from such attacks. If the angle has already closed off, Laser PI can be used to break the attack and quickly reduce intraocular pressure back to normal. Often both eyes need to be treated and this is done on separate visits.
During iridiotomy, the laser creates a small hole through the iris in the peripheral region, to improve the flow of fluid around the anterior chamber of the eye. 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 and chronic elevated intraocular pressure, which has not been manageable with medications or surgeries. In cyclophotocoagulation a laser is used to destroy the 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.
What are the risks and complications?
Laser treatment for glaucoma is a painless and quick procedure. Like all procedures there are risks and benefits and Dr Chiu will discuss these with you.
In preparation for laser treatment, your eye is numbed with anaesthetic eye drops. Dr Chiu will then place a special lens in front of your eye, which gently sits on the surface of the eye. During the procedure you will sit upright at the machine much like the slit lamp microscope used to examine your eyes. The laser beam is precisely applied to specific structures in your eye. You may see flashes of coloured light during the procedure. Some people have a slight sensation of discomfort for a short period of time during the laser treatment.
After the procedure the eye may feel irritated and have slightly blurred vision. Rarely a short-term increase or an excessive drop of intraocular pressure can also occur after laser treatment. Dr Chiu or her staff will check your intraocular pressure an hour after your procedure and before you go home. These complications can be manageable with medications. You may also have a slight risk of cataract formation after some type of laser surgeries for glaucoma. After some laser procedures medicated eye drops may be prescibed for use during the post-procedure care period, which is usually one week. You can return to normal activities the same day or day following your procedure.