What are the risks of surgery?

The risks of surgery have to be very carefully balanced against the risk of damage to the vision if the pressure in the eye is not reduced to a satisfactory level.

Hyphaema

This is when a small amount of blood collects in the front chamber of the in front of the iris and pupil. This may cause the vision to be blurred, but it usually clears without any specific treatment, within 1-2 weeks. On rare occasions the bleeding may recur and again no action is normally required other than allowing time for the blood to clear naturally.

Excessive drainage

If the fluid in the eye drains too quickly the pressure may become very low, this is known as hypotony and can result in deterioration of the vision. This problem will often resolve with time but occasionally a large “bandage” contact lens or a firm eyepad may be used to slow down drainage of fluid. If these simple methods are not effective a second operation may be needed to place further stitches in the bleb or trapdoor to slow down fluid drainage.

Very high pressure

This can normally be remedied by reducing the tension in the trap door stitches or by removing them. Your specialist may also gently massage the eye to encourage fluid to pass through the trapdoor into the bleb.

Choroidal Haemorrhage

Bleeding within the layer of blood vessels that nourish the retina is a very rare and unpredictable complication of surgery. If the bleeding is localized the eye may recover but in mores severe cases permanent, severe visual loss may occur.

Endophthalmitis (infection inside the eye)

The risk of developing this sight threatening complication in the initial weeks after surgery is approximately 1 in 1500. However, unlike cataract surgery, there is a very small life-long risk of developing endophthalmitis following drainage surgery. This is because the bacteria which normally live on the eyelids and surface of the eye can, very rarely, penetrate the thin walls of the bleb. Should this occur the first signs and symptoms are increasing pain, redness and deteriorating vision. If these occur you should contact your specialist immediately.

Inflammation, excessive healing or scarring of the drainage site.

This is not uncommon and can result in the drainage site closing and the pressure in the eye becoming too high again. To reduce the risk of this happening your surgeon may use special anti-scarring medications during the surgery. This may be supplemented by injections of the same medicine close to the drainage site, given in the clinic.

Complete loss of vision

Complete loss of vision is normally rare. However, it can be a significant risk following surgery in an eye where there is already advanced loss of vision as a result of glaucoma.