Managing elevated postoperative IOP

Answer:

After insertion of a Molteno implant it is normal for the IOP to rise to a peak 4-6 weeks after the onset of drainage (the hypertensive stage of bleb formation) after which it should start to fall.  

Is the patient on topical steroids more than 6 weeks after the onset of drainage?  If so, Stop the Steroids immediately.  The IOP should fall over the next two weeks.

Is the patient is using a steroid based skin cream around the eyes?  If so substitute a non-steroid containing skin preparation such as mycophenylate ointment.

Is the patient on prostaglandin analogues or meiotics?  Both these groups of  hypotensive agents can act as vaso-dilators and may cause anomalous elevation of IOP after glaucoma drainage surgery.  Stop these compounds and substitute oral or topical carbonic anhydrase inhibitors eg. acetazoleamide or equivalent and/or topical beta blocker eg timalol and/or a topical adrenergic agent eg. propine or alphagan.

If these measures reduce the IOP satisfactorily maintain the medication for 6 months and then cautiously reduce dosage of medication according to the response of the IOP.

If none of the above apply or if  the IOP remains elevated two options can be considered

•  'Tap' the bleb. With a 30 gauge needle on an small gauge syringe, tap' about 0.2 ml of aqueous from the bleb to bring the pressure down to about to around 6-7 mm Hg. Monitor the IOP closely on a daily basis and when the pressure rises to around 20 mm Hg repeat the 'tap' taking again around 0.2 ml aqueous from the bleb. Graph your pressure and keep a note of the intervals between the 'taps'. if the interval between taps increases it is a good sign and no more than 5 or 6 taps are likely to be necessary before the pressure stabilises at normal levels.
• Add additional drainage area as described here.