A well-functioning trabeculectomy surgery is a delicate balance between the aqueous production and the additional outflow via the filtering bleb. When it works well and produces an acceptably low intra-ocular pressure, we must be very careful during cataract surgery in order to avoid upsetting this balance.
This patient has a history of advanced glaucoma with a trabeculectomy performed five years ago in another city. The intra-ocular pressure is between 6 and 8 mmHg and has been stable with no further progression of the glaucoma. The patient has since developed a posterior subcapsular cataract which has caused a visual decline.
In performing the cataract surgery we must keep a few key principles in mind:
- do not touch the filtering bleb
- be prepared for fluidic imbalance during phaco since there is an additional outflow channel
- during surgery, viscoelastic can be used to block outflow via the trabeculectomy site
- all viscoelastic must be removed at the end of the surgery
- do not upset the delicate balance of the trabeculectomy — in this case there is some incarceration of the iris at the trab site causing mild corectopia. We will leave this alone and not alter it. Aiming for an improved minor cosmetic benefit could result in worse functioning of the bleb and a loss of control of IOP.
Click below to see how we perform cataract surgery after prior trabeculectomy:
