When Should Trabeculectomy Be Considered?

Determining when it is worth taking the risk of surgery in order to prevent further loss of vision is one of the most challenging aspects of glaucoma treatment.  Intraocular pressure (IOP) measurements as well as visual field defects fluctuate from exam to exam so it’s not always clear to the surgeon whether a patient’s glaucoma is stable or worsening. Sure, IOPs and visual fields can be rechecked but this is not always realistic considering patients’ (and their doctors’) busy schedules and the limitations of insurance coverage. Additionally, time is rarely on the side of the patient with progressing glaucoma so every delay in treatment results in further permanent loss of vision.

Even in those who have documented progression of their vision loss the decision to go ahead with surgery is not always straightforward. After all, surgery has risks – one of which is loss of vision. Choosing to risk loss of vision to save vision is no easy task. That task is made even more difficult by the multiple and frequently encountered risks of trabeculectomy – especially when Mitomycin-C (MMC) is used.

Fortunately, there are now multiple effective surgical options that can be used to treat glaucoma. Trabeculectomy with use of MMC still holds its high school yearbook position as “most likely to lower IOP into the low teens”. However, not every patient with glaucoma needs their IOP that low. Most patients with moderate glaucoma would do just fine with an IOP around 15mmHg.[1] That is a goal attainable by multiple surgical options including canaloplasty, glaucoma drainage devices (tubes or shunts), and even trabeculectomy without MMC.[2]

>> What Is Canaloplasty? I Want To Learn More About It.  << 

So, who should be considering trabeculectomy with or without MMC to treat their glaucoma? Clearly, this surgery should not be offered to someone with well controlled glaucoma who is tolerating her medical treatments. All surgeons and their patients would agree to that.  But what about the patients with documented progressive glaucomatous loss of vision? Are they all candidates for trabeculectomy?

The traditional answer given by most eye surgeons for most patients with open angle glaucoma in whom drops and laser are not working is that trabeculectomy is the surgery of choice. This answer, especially when MMC is used, is worth questioning.[3] If you are facing the prospect of glaucoma surgery I encourage you to ask yourself as well as your surgeon, “Of the available surgical options is this the right one for me?

 

When Should Trabeculectomy Be Considered?

Following are just a few of the reasons why trabeculectomy might be an appropriate surgical option to treat progressing or uncontrolled glaucoma.

Your “Target IOP” is around 10mmHg

If you have advanced or rapidly progressing glaucoma you may need a very low IOP in order to slow the progression of your vision loss. Trabeculectomy with MMC is really the only glaucoma surgery that can on average achieve an IOP in the range of 10mmHg.[4]  Trabeculectomy with MMC was shown in one study to achieve an average IOP of 10mmHg five years after surgery.[5] This came at a high cost, however, as the same study noted a high risk of hypotony, bleb leak, and blebitis.  Indeed, multiple studies have supported this increased complications/lower IOP relationship of MMC.[6]

There is something worth noting for those who can tolerate and afford glaucoma medications.  A target IOP of around 10mmHg can often be achieved with the combination of other safer glaucoma procedures plus the use of topical glaucoma therapy.  Thus, even with a target IOP of around 10mmHg if continued use of glaucoma medications is an acceptable outcome then trabeculectomy with MMC may not be your only surgical option.

You have Normal or Low Tension Glaucoma (NTG or LTG)

In patients with Normal Tension Glaucoma (sometimes called low tension glaucoma) damage to the optic nerve occurs despite IOPs in the “normal” range.  Because the IOP is already in the teens those with NTG need IOPs in the low teens or even single digits (below 10mmHg). Realistically, as with anyone in need of such a low IOP, trabeculectomy with MMC is the only surgery that will achieve this target IOP without also using glaucoma drops.

You cannot tolerate any glaucoma medications and your target IOP is below 15mmHg

Many glaucoma surgeries can get the IOP into the high teens without additional use of glaucoma medications. Some, such as glaucoma drainage devices and canaloplasty can even be expected to get the IOP into the mid-teens.  Trabeculectomy with MMC, however, is really the only option for those patients who absolutely must have a very low IOP without the use of eye drops.

 You have a docile or sedentary lifestyle

Do you spend the majority of your day watching TV, on the computer, or reading?  Although your internist may not be happy with your choice of lifestyle, your glaucoma surgeon might be – at least if trabeculectomy with use of MMC is in your future. Why is that? Because the blebs that form on the surface of the eye after use of MMC are very fragile and easily ruptured. A ruptured bleb could lead to loss of vision.  So taking it easy is desirable after trabeculectomy. That being said, light aerobic activity is fine so this is no excuse to avoid the gym or outdoor walks.

You’re older

No one likes to think of themselves as “older”. Youth, not old age, is what our culture places at a premium. In the case of glaucoma, however, younger is not necessarily a good thing. For one, younger patients have more years of life remaining during which they can lose vision from glaucoma. With regard to trabeculectomy, it is the robust youthful healing response that is undesirable.  This is because scarring increases the risk of surgical failure after trabeculectomy.  As we age our bodies heal less aggressively. Although undesirable in other areas of our health, for those considering trabeculectomy a weaker healing response due to aging is a benefit.

You can take care of yourself

Would you buy a pet if you didn’t have the financial or mental capacity to care for it?  Although we all know people who have done such an irresponsible thing, most of us recognize that certain decisions should be made only after assessing the future costs and expected demands that will be made on us. The decision to have trabeculectomy requires such an assessment.

Those patients who have trabeculectomy will have a new companion for life (or at least until the surgery fails). That companion is neither cute, fluffy, nor lovable.  That companion is the bleb. It must be kept clean, away from trauma, and be taken in for regular check-ups. Inattention could lead to bleb failure and loss of vision.  As such, those considering trabeculectomy should have good hygiene, be responsible enough to show up to regularly scheduled follow-up appointments and testing at the ophthalmologist’s office, as well as avoid those activities that could endanger the bleb.

Summary

Trabeculectomy is often the first glaucoma surgery (after laser) offered to those with progressive loss of vision from glaucoma. Enough is now known about this surgery to recognize that it tends to work better (and carry less risk) for certain groups of people. If you are in one of the above groups then trabeculectomy may not only be the first surgery recommended but the most appropriate option to prevent further loss of vision.

Over the last half century, however, a lot has changed since trabeculectomy was first described in 1961.[7] There are other surgical options available. Many are safer.  Some are as effective as trabeculectomy without MMC. Some of these other treatments may be appropriate for you. Others not. Only you and your surgeon can determine whether trabeculectomy is the most appropriate option for you.

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