Glaucoma surgery can be considered when medical treatment alone is not enough to lower the eye pressures to a save level to prevent further damage of the optic nerve. This is usually discussed when there is evidence of deterioration on the visual field. 

There are many types of glaucoma surgeries, ranging from laser treatment that can be carried out in out-patient to complex tube-shunt implant surgery. The choice of procedure depends on the individual patient's condition. Less invasive procedures tend to be less effective in terms of lowering eye pressures and carry lower risks. The more invasive approach may offer better chance of controlling eye pressures for long term especially in complex glaucoma conditions, but these procedures can carry higher risk of complications. The choice of procedure must be discussed carefully with the glaucoma specialists to determine which procedure is most suitable for the patients' condition.

Selective laser trabeculoplasty (SLT) has largely replaced the older Argon laser trabeculoplasty.  The SLT is the commonest out-patient laser procedure for glaucoma. It is a useful adjunt to help lowering eye pressure when medical treatment alone is not enough to bring the pressure down to a safe level. However, about 78% patients respond to the SLT treatment but most patients will need to continue their current glaucoma medical treatments. 

Cyclodiode laser is a procedure that needs to be performed in the theatre under local anaesthetics. This procedure applies a laser probe on the eye surface in order to deliver laser energy to the ciliary body inside the eye, which is the structure that produces water inside the eye and maintain the eye pressure. Therefore, this laser procedure works like turning down the tap inside the eye. This procedure is useful in acute glaucoma condition when there is a very high pressure, e.g. acute angle closure attack. This procedure sometimes can cause excessive inflammation inside the eye and occasionally can cause chronic low pressure in the eyes, therefore this is not normally used for routine glaucoma conditions. 

Endoscopic cyclophotocoagulation is like the cyclodiode laser but instead of applying the laser from outside the eye, this is applied from inside the eyes with an endoscope. This procedure usually combined with cataract operation that the laser probe is inserted inside the eye to deliver the laser energy to burn off the ciliary body epithelium in order to reduce the amount of water production inside the eye. Also, this procedure can cause excessive inflammation but less likely to cause chroinic low pressure problems. 

Trabeculectomy is probably the most commonest drainage procedure performs for glaucoma. It is started in the 1970's but the procedure has gone through major changes over the years to make it safer and more effective in terms of long term eye pressure control. 

This procedure is to create a drainage valve under the upper eye lid to allow water draining from inside the eye into a space that is covered by the conjunctiva, which is the outermost tissue layer of the eye. The risks of this procedure is leakage and overdrainage, but with meticulous techniques, these risks are now much reduced. The use of anti-scarring agent, e.g. mitomycin C,  also increases the sucess rate of this procedure. Therefore this procedure can be used in more complex cases. We generally can expect 70% sucess rate in 5 years. But maintinance procedure may be necessary if there is excessive scarring that slow down the drainage. This procedure is performed with needle pucturing the scar tissues and injection of anti-scarring medicine. 

One pitfall of this procedure is that a subsequent cataract operation tends to cause scarring and reduces the function of this procedure. 

MIGS procedures has become very popular in recent years. The most commonest MIGS proceduren we performed is the iStent implants that is commonly done in combination with cataract operation. 

The iStent is a minature titanium stent that is inserted inside the eye at the drainage angle (trabeculr meshwork) in order to bypass the internal resistance for the water to drain into the cannal that connect the drainage channels to the blood stream. 

The effects of this iStent procedure is quite moderate in terms of eye pressure control. Recent randomised controlled study compared cataract operation alone and cataract operation with iStent implant showed significantly more patients achieving good pressure control with no medication (72% versus 50%). Therefore, patients may be able to reduce the number of glaucoma medications after iStent procedure but most will need to continue with 1-2 medications. 

The advantage of this iStent procedure is that it would not affect further glaucoma procedures if this is become necessary in the future. 

Glaucoma tube-shunt surgery is an important procedure for patients with complex glaucoma condition when other procedures are unlikely to be successful. The commonest tube-shunt that we use is Baerveldt tube implant. 

This procedure is implanting a drainage device with a silicone tube inserted into the eye and the other end of the tube is connected to a plate that allow water dissipating on the surface of the plate, which is covered by the outermost tissue layer, the conjunctiva. This procedure will bypass all the resistance in the natural drainage system and the drainage plate will maintain a reservoir-like system to allow dissipation of water from inside the eye to the surrounding tissue. 

This procedure is very effective in controlling eye pressures. From our previous study, we can expect about 70% sucess in 5 years in both adult and children. However, there are higher risks of complications with this procedure. These include infection, corneal decompensation and chronic low pressure inside the eye.