Techniques for Combined Glaucoma and Cataract Surgery
Chat Highlights
April 27, 2005

On Wednesday, April 27, 2005, Dr. Rick Wilson a glaucoma specialist at Wills, and the glaucoma chat group discussed "Techniques for Combined Glaucoma and Cataract Surgery."

Moderator:  Last week we discussed the indications for combined glaucoma and cataract surgery.  Tonight we will discuss techniques for combined glaucoma and cataract surgery.  Dr. Wilson, what kind of anesthesia is usually used for the combined surgery?

Dr. Rick Wilson:  Combined cataract and glaucoma surgery can be performed with topical liquid anesthesia or topical gel anesthesia, often augmented with an injection or irrigation under the conjunctiva, the top layer of the eye.  Otherwise, it can be done with a shot under and above the eye or one shot just behind the eye.

Moderator:  How long do the shots remain effective?

Dr. Rick Wilson:  The shots usually have a two-hour acting, local anesthetic, but the anesthesia could last more than 12 hours with bupivicaine.

P:  Is the patient sedated when the shots are given?

Dr. Rick Wilson:  The patient is usually put to sleep for a couple of minutes while the shots are being given.  That can be safely done with a push of propofol (Diprivan) up the IV (intravenous) tube.  If topical anesthesia is used, patients can't be too sleepy as they have to cooperate with the surgeon, usually by looking up at the light of the operating microscope.

P:  Do you stop the use of prostaglandins before cataract surgery?

Dr. Rick Wilson:  I usually like to stop prostaglandins up to a week before cataract or glaucoma surgery.  They are a strong class of drug, our strongest, and can cause intraocular inflammation and swelling in the central part of the retina postoperatively. Some surgeons, however, add a non-steroidal, like Acular, to the postoperative steroids to counteract the inflammatory effects of the prostaglandins.

P:  Do you stop the use of Cosopt before cataract surgery?

Dr. Rick Wilson:  I try to stop the Cosopt a day ahead of surgery, so the eye will be making closer to a normal amount of aqueous when I construct the new drain.  I need a near-normal amount of aqueous going through the drain to keep it open.  Since Cosopt cuts down the amount of aqueous made in the eye, it will decrease the fluid going through the new drain.

P:  What do you mean by "construct the new drain?"

Dr. Rick Wilson:  There should be a drawing of a trabeculectomy on the Web site.  Basically, I have to make a flap of conjunctiva for the fluid to flow into, then make a partial thickness flap of sclera, (the white outer coat of the eye, up by the cornea), and then a hole into the eye under the flap. I then remove a small piece of iris directly under the entrance of the hole into the eye to prevent the iris from floating up and blocking the drain. Then the flap is sewn down loosely with multiple sutures, so fluid from the eye has to slowly seep out against resistance under the conjunctiva, which is closed last.

P:  If the visual outcome of the cataract surgery is always the same, does your decision for or against combined surgery hinge on the trabeculectomy portion?

Dr. Rick Wilson:  Yes.  The surgeon opts for a combined procedure if the IOP (intraocular pressure) control is not adequate, or if the patient is already on so many glaucoma medicines that if the IOP increases after surgery, there will be little to add to bring it down.

P:  Do you make one incision or two?

Dr. Rick Wilson:  I make one hole in the eye, rather than two.  I have tried it both ways and found no difference, in my hands.  If there is no difference, why have two wounds?

P:  Are there any exceptions?

Dr. Rick Wilson:  The one exception is in patients with very deep-set eyes or an overhanging brow, either of which make it difficult to take the cataract out from above. Then I use a two-site operation.

P:  Do you ever start topical steroids before a combined procedure?

Dr. Rick Wilson:  Actually, I start topical steroids four to seven days before most glaucoma procedures in patients who have been on glaucoma medications.  The glaucoma medications are irritating to the top layers of the eye and cause a low-grade inflammation that can harm the results of glaucoma surgery.

P:  Which do you do first, the cataract surgery or the trabeculectomy?

Dr. Rick Wilson:  I prepare the site for the trabeculectomy and then soak the surrounding tissue in a dilute solution of mitomycin-C to retard scarring.  Then I do the cataract surgery before doing the rest of the trabeculectomy.

P:  Can sutures be released as needed to keep the pressure under control during the first two weeks after the surgery?

Dr. Rick Wilson:  Yes, I invented one of the first releasable sutures for that purpose.  Now we can also use a lens and the laser to cut the sutures under the conjunctiva.

P:  Are the results of a trabeculectomy better when done alone or when combined with cataract surgery?

Dr. Rick Wilson:  Usually, when done alone, but the use of mitomycin has allowed excellent IOP results with combined cataract and glaucoma surgery.  In fact, I almost never do a staged procedure of bringing the IOP way down first and later doing the cataract.  Back in the 1980s, staged procedures were almost imperative in badly damaged eyes.

P:  Why does a small pupil complicate surgery?

Dr. Rick Wilson:  The surgeon has to gain access to the cataract, which is behind the iris.  The more of the cataract you can see, the easier it is to remove it.

P:  Is the lens removed with a special device?  Does the lens come out whole?

Dr. Rick Wilson:  No, Charles Kelman, an ex-Wills resident, invented phacoemulsification of cataracts.  That involves using a small needle, which vibrates very fast and breaks up the cataract, so it can be sucked out through a less than 3 mm wound.  The eye pressure is maintained by irrigating fluid into the eye.

P:  How can you tell if the IOP rises?

Dr. Rick Wilson:  During the cataract surgery the IOP is maintained by the pressure of the fluid irrigating through the tubing into the eye.  If there is pressure from behind the iris and lens, the front of the eye shallows, alerting the surgeon that there is "positive pressure."  Touching the wall of the eye can tell you what the IOP generally is.

P:  If the intraocular pressure rises during a cataract-only operation, do you do a trabeculectomy?

Dr. Rick Wilson:  No.  If the pressure before the cataract surgery was normal, but goes up during the operation, the cause must be identified.  It could be bleeding from the shot behind the eye, or it could be that a blood vessel has broken between the layers of the eye.  In either case the surgeon would not want to make a hole in the eye when it is being pushed on from outside the retina.

It could also be that fluid from the front of the eye has gotten misdirected into the back of the eye and is building up pressure there quickly.  In that case, the fluid may need to be aspirated from the back of the eye, rather than making a drain.

P:  How long does the entire procedure take?

Dr. Rick Wilson:  The procedure usually takes 40 to 45 minutes, depending upon whether there has been previous surgery with conjunctival scarring.

P:  Does the density of the cataract make a difference?

Dr. Rick Wilson:  With the present advances in cataract surgery, hard cataracts come out almost as rapidly as softer ones.

P:  What causes light sensitivity after cataract surgery, and how long does that sensitivity last?

Dr. Rick Wilson:  Anything that irritates the cornea will cause light sensitivity.  Usually, it only lasts a week or two.

P:  Are any stitches involved in the combined surgery?

Dr. Rick Wilson:  Yes.  The flap is sutured down loosely, so the fluid has to leak slowly out of the eye from under the flap.  The conjunctiva is also closed with sutures to make the wound watertight.

P:  If there are no problems, how quickly after cataract surgery can the patient expect to recover vision?

Dr. Rick Wilson:  After straight cataract extraction, the vision is often quite good by the next day.  After combined surgery, the lower pressure and bigger surgery usually serve to keep vision depressed for three or more weeks.  Because the extensive steroid use slows down the healing of the cataract wound, glasses are prescribed later.

P:  Is the scleral flap always cut in the same direction or can it be cut like the conjunctival flap, at the discretion of the surgeon, limbus or fornix based?

Dr. Rick Wilson:  The limbus is where the conjunctiva meets the cornea.  The fornix is the curve where the conjunctiva on the globe curves up to line the underside of the lid.  It is always based at the limbus, as we want the fluid to be directed posteriorly.

P:  I had epiretinal-membrane surgery last October.  I still have some macular edema and I'm using topical steroids.  My pressure has increased since the operation, and I have developed a cataract.  I plan to have SLT (selective laser trabeculoplasty) soon in the hope of relieving the pressure, and I need to have the cataract removed.  Must the macular edema be cleared up before I have cataract surgery?

Dr. Rick Wilson:  It would be nice, since the cataract surgery serves as another stimulus for retinal swelling.  It would be good to have the retina as near to normal as possible before another stimulus is presented.  That's my opinion only. I am not a retinal expert.

Moderator:  Thank you, Dr. Wilson.

On May 4, Dr. Mark Moster discussed "NTG from a Neuro-Ophthalmologist Point of View" in the Chat room. Click here for highlights of that meeting.

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