Indications for Combined Glaucoma and Cataract Surgery
Chat Highlights
April 20, 2005

On Wednesday, April 20, 2005, Dr. Rick Wilson a glaucoma specialist at Wills, and the glaucoma chat group discussed "Indications for Combined Glaucoma and Cataract Surgery."

Moderator:  Welcome back to chat, Dr. Wilson.  Tonight our topic is "Indications for Combined Glaucoma and Cataract Surgery." In combined glaucoma and cataract surgery, is the glaucoma part of the surgery always a trabeculectomy?

Dr. Rick Wilson:  Rarely, as in neovascular glaucoma, an aqueous shunt might be substituted for a trabeculectomy.

Moderator:  Then combined cataract and glaucoma surgery is almost always cataract surgery and a trabeculectomy?

Dr. Rick Wilson:  Yes, that is correct.

P:  What is the most common reason for combining glaucoma and cataract surgery?

Dr. Rick Wilson:  The most common reason is that patients on multiple glaucoma medications reach the point that the cataract is interfering with their lives.  On the other hand, a patient may have a cataract that is not visually significant, but needs surgery because the intraocular pressure (IOP) is not controlled on maximal tolerated medicines.

P:  Does a trabeculectomy accelerate the growth of a cataract?

Dr. Rick Wilson:  As a rule, a trabeculectomy will speed up the development of cataracts in patients with early cataracts, but not in patients who don't have cataracts.

Moderator:  How do you determine when a cataract is interfering with patients' lives?

Dr. Rick Wilson:  When the cataract is interfering with whatever is important in their lives.  I tell my patients the cataract should not be just a nuisance, but also a hindrance to what they want to do.

P:  Is there ever a danger in postponing cataract surgery?

Dr. Rick Wilson:  If the cataract is white, rarely the capsule can get thin and leak the substance of the cataract into the eye. Waiting in that instance is dangerous.

P:  Are the risks of cataract surgery greater for patients with pseudoexfoliation (PSXF) glaucoma?

Dr.Rick Wilson: Patients with pseudoexfoliation have a weakened support structure that holds the lens (cataract) in place.  That support structure often weakens with time, so in patients with pseudoexfoliation I may be slightly more aggressive in taking care of the cataract earlier, but only slightly.

P:  If a patient needs cataract surgery and the existing bleb is fragile, will the doctor opt to do combined surgery, or wait for the trabeculectomy to fail before doing another trabeculectomy?

Dr. Rick Wilson:  Usually, if the bleb is working well (and most fragile blebs are), the doctor will opt to do just the cataract operation.  Often, after cataract surgery, the added inflammation of the healing will cause the bleb not to work as well.

P:  Doesn't waiting until the cataract is hard make removing it more difficult?

Dr. Rick Wilson:  It used to, but the advances made in phacoemulsification technology usually make the removal of all but the densest lenses safe.

P:  What is phacoemulsification?

Dr. Rick Wilson:  In phacoemulsification, a small hollow needle vibrating extremely fast breaks up the cataract and sucks out the debris.

P:  Why does a trabeculectomy speed up the development of a cataract?

Dr. Rick Wilson:  My supposition, and what I tell my patients, is that the lens is suspended in the middle of the anterior part of the eye without blood supply.  The lens depends upon the flow of aqueous to bring it oxygen and nutrients.  If a good amount of aqueous is drained out during a trabeculectomy, that loss lessens the chance for the aqueous to feed the lens.

P:  Are there any short or long-term effects on IOP from combined cataract and glaucoma surgery?

Dr. Rick Wilson:  Fifteen to twenty-five years ago, when we wanted to get the lowest IOP, we performed an aggressive trabeculectomy, then waited four or more months before performing a cataract extraction.  Now we can combine the operations and achieve the same result as when they are done separately.  In other words, adding the cataract extraction no longer detracts from the success of the trabeculectomy to the extent that low IOPs can't achieved.

P:  Does having an extremely thick cornea, a shallow chamber, or a closed angle increase the difficulty of removing a cataract?

Dr. Rick Wilson:  The cornea is not a problem, but the shallow chamber means that the needle breaking up the cataract is much closer to the cornea.  The fluid waves from the tiny jackhammer and pieces of cataract may hit the cornea and injure it.  Since we are born with all the cells lining the cornea that we will ever have, losing too many of the cells leaves those remaining unable to keep the cornea clear.

P:  What changes in the results of cataract surgery have you seen?

Dr. Rick Wilson:  When I was trained, cataract surgery resulted in approximately 35 to 50% of the cells being lost, and corneas were often swollen for days before they recovered from the surgery.  Now the percentage loss is 3 to 8%, and corneas are rarely swollen and cloudy after cataract surgery.

P:  What additional risks are caused by combining a trabeculectomy with cataract surgery?

Dr. Rick Wilson:  Adding the trabeculectomy increases the risks of bleeding, too low a pressure, and fluid accumulation between the layers of the eye.  These complications, however, are usually less than when only a trabeculectomy is done.  A trabeculectomy usually prevents the pressure rise that can occur in patients who have no excess capacity for fluid outflow.

P:  Would you please elaborate on what you mean by "excess capacity for fluid outflow"?

Dr. Rick Wilson:  What I tell my patients is that there seems to be about 25% or more excess capacity in the normal eye.  When the debris that follows the cataract extraction gets stuck in the eye's drain, there is usually extra capacity to keep the IOP from rising much.  In patients on medication, however, there is no excess capacity, and any additional blockage can cause severe IOP spikes.

P:  Is the incidence of posterior capsular haze (secondary cataract) any higher after a combined procedure?

Dr. Rick Wilson:  Not that I have been able to tell. Capsular opacity is rare these days.  It has been many months since I have had one in my practice.

P:  After cataract surgery, if one eye develops a secondary cataract, does the other eye often develop secondary cataract later?

Dr. Rick Wilson:  It depends upon if the haze in the first eye was caused by leaving a few cells behind on the capsule, or if the capsule was vacuumed clean.  If clean, especially in younger people, a haze could be expected to develop in the other eye.  If the first eye was not vacuumed as much as possible, there may be room for improvement in the second eye.

P:  Does capsular opacity mean the same thing as a cloudy lens?

Dr. Rick Wilson:  The lens has a capsule around the substance of the lens.  It is the substance of the lens that becomes cloudy, resulting in a cataract.  When the cataract is broken up and sucked out, the capsule is left and the intraocular lens is placed into the capsule.  In some people, the capsule turns cloudy with time and forms a haze, or secondary cataract, that is then removed by the Nd:YAG laser.

P:  For the combined surgery, should the patient be looking for an ophthalmologist who is a glaucoma expert or one who is a cataract specialist?

Dr. Rick Wilson:  A glaucoma specialist.  Especially one who does a good number of cataracts.  Usually, they are very good at hard cataract cases, since they usually wait longer to remove cataracts than doctors of patients with more healthy eyes, and the pupils are often small and difficult to work with.

P:  I have had glaucoma for many years and now am developing a cataract. What are the dangers in having the cataract removed in my case?

Dr. Rick Wilson:  If you are on more than one glaucoma medication, and you and your doctor elect to do just the cataract surgery, you should have a medicine in reserve that you know works for you to handle any rises in IOP.

P:  On October 1, 2004, the FDA approved a new form of filtration surgery for open-angle glaucoma called the Singh Filtration or Tranciliary Filtration (TCF) that uses a Fugo Plasma Blade. As I understand it, the Singh Filtration channels pressure-causing fluid into the lymphatic system and seems not to compromise the natural lens. Can you comment on this procedure, both in its relation to glaucoma and to the lens?

Dr. Rick Wilson:  As I remember, the Fugo blade was originally developed to open the anterior capsule, so cataract surgeons could get at the cataract.  Some doctors have been using it to thin the wall of the eye so that fluid can pass more easily through the wall of the eye and lower the IOP.

P:  I read about the use of plasminogen to reactivate a failing bleb. How and when is that used?

Dr. Rick Wilson:  If, in the early period after surgery, there is fibrin (the gluey substance from the clear part of the blood that is holding the trabeculectomy flap down), it can be dissolved by tissue plasminogen activator injected into the eye or under the conjunctiva.

Moderator:  Thank you, Dr. Wilson. Next week we will discuss techniques for combined glaucoma and cataract surgery.

On April 27, Dr. Wilson discussed "Techniques for Combined Glaucoma & Cataract Surgery" in the Chat room. Click here for highlights of that meeting.

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