Pressure too low
Bleb leak
This is an early complication which occurs only in about 10% of patients and usually only requires monitoring.  Very occasionally, a small suture needs to be placed to stop the leak.

Choroidal effusions
These occur in about 20% of patients usually when the pressure in the eye following surgery is low.  Although a sign of successful drainage, they tend to result in i) prolonged low pressure (up to 3 months) following surgery and ii) blurring of vision, by causing the crystalline lens in the eye to move forwards.  Choroidal effusions almost always disappear with time and without specific treatment.

Pressure too high
Immediately, after surgery, the pressure may be over 20 mmHg.  This can be dealt with by removing one of the pre-placed sutures in the flap, together with some massage on the top eyelid.
After initial success, the pressure in the eye may start to rise again.  This can be treated by a process of needling which save the operation from having to be repeated.  In this procedure, the scar tissue over the flap is carefully incised with a needle to reopen the drainage pathway. We usually administer anti-scarring drugs under the conjunctiva to reduce the risk of further scarring after this procedure.

Pain
Pain is infrequently reported by patients after trabeculectomy.  On rare occasions when the pressure is low, some bleeding into on of the layers of eye known as the choroid may occur (a choroidal haemorrhage), which stretches one of the nerves going into the eye.
Discomfort may be caused by the elevated “bleb” under the upper lid.

Infection
Endophthalmitis
As in cataract surgery, this may occur one to three days after surgery in about 1:1500 cases.  Symptoms include marked blurring of vision with increasing red eye, swelling of the lids and discharge.  It is vital that you present to either us or the eye casualty at EEMU straightway (within the hour) in these circumstances as early treatment can completely rectify this problem.
Blebitis
This is a localised infection of the drainage bleb under the upper lid, which if left untreated can progress to endophthalmitis.  The risk of blebitis is not limited to just the first few days after surgery, but persists for the rest of the time that the drainage bleb is operational.  If the eye becomes extremely red and the drainage bleb looks white against this red background, then it likely you have developed blebitis.  This problem can usually be successfully treated if dealt with promptly.

Hyphaema
A small amount of blood may collect in the eye and settle to form a horizontal “fluid-level” just behind the cornea.  This is quite common and usually disappears after one to two weeks.

Blurred vision
This is common for 3 months and is caused by temporary changes in the position of the crystalline lens in your eye.  Very occasionally, particularly in quite short sighted people, low pressure can cause the retina to swell (macular hypotony), which blurs the vision.  If the pressure does not increase after a few weeks, we would have to put some more stitches into the scleral flap to reduce drainage of fluid out of the eye.  Finally, blurred vision may be caused by cataracts.  Unfortunately, glaucoma drops and glaucoma surgery both increase the risk of cataract development.

Complete loss of vision
This is extremely rare, but may theoretically occur in patients with very advanced visual field loss who spike a high pressure immediately after surgery.  To prevent this, I will give you two Diamox tablets to take, 2 hours and approximately 8 hours after surgery.

Bleeding
Very, very occasionlly, some blood can appear from the corner of the eye for a few minutes before settling down. This can recur 3-5 times over a period of a month. It is of absolutely no consequence and occurs from some pulling on a blood vessel in the conjunctiva by the expanding drainage bleb. Obviously, this can be distressing, but it always stops and doesn’t interfere with the success of the operation in any way.