Early and Late Complications of Trabeculectomies
Chat Highlights
December 14, 2005

On Wednesday, December 14, 2005, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Early and Late Complications of Trabeculectomies."

Moderator:  Tonight we will continue the discussion with Dr. Rick Wilson that began on November 5, 2005: "Early and Late Complications of Trabeculectomies."

P: What is the reason for doing trabeculectomies?

Dr. Rick Wilson:  Usually a trab (trabeculectomy) is done when the IOP (intraocular pressure) is too high for the continued health of the optic nerve, and eye drops and laser therapy have not helped. At that point, the low risks of the procedure are easily outweighed by the nearly 100% chance of further vision loss from glaucoma.

P:  I lost a lot of vision in my eye after a trab two years ago, and it hasn't improved. My IOP went up to the 50's after the operation. Would that cause vision loss? Is it normal after a trab for the IOP to increase before decreasing?

Dr. Rick Wilson:  Yes, the IOP rise can cause vision loss, if it's in the 50's. After a trab, it's not normal for the pressure go up before going down. However, the hole the surgeon leaves in the eye under the flap is tiny, so that just a small amount of aqueous can leak out slowly at any time. A small clot can block the tiny hole and result in an IOP of 50 mm Hg on the first post-operative day quite easily.

P:  How high an IOP post operatively would be considered too high?

Dr. Rick Wilson:  That depends on the optic nerve. If the eye pressure has been in the mid 30's or above preoperatively for some time, and the optic nerve is not badly damaged, the surgeon might like to have the IOP in the mid 20's for a week postoperatively before cutting a flap suture and lowering the IOP.

Moderator:  Previously you said that the IOP drops to zero during a trab, but filling the anterior chamber with fluid helps it rise. What kind of fluid is used?

Dr. Rick Wilson:  A salt solution with other ingredients is used to approximate the natural fluid.

Moderator:  Earlier we briefly discussed thin blebs as a late complication of trabeculectomy. How are they detected? Does the patient have any symptoms?

Dr. Rick Wilson:  Thin blebs are usually diagnosed by the ophthalmologist looking at the bleb with the slit lamp biomicroscope, the usual apparatus that is used in the office. The patient occasionally has some irritation if the bleb is sensitive. If a hole develops in the thin tissue, the patient is usually aware of the sudden, constant tearing.

P:  What is aqueous misdirection and how early or late can it occur after a trab?

Dr. Rick Wilson:  Aqueous misdirection is a disorder that not all ophthalmologists understand. In patients subject to aqueous misdirection, usually the lens is anteriorly positioned (moved forward) in the eye. A trabeculectomy or injury allows the lens to move even further forward. Aqueous that is made in the ciliary body just behind the iris finds it easier to go posteriorly (backward) into the vitreous cavity, the main space in the back of the eye. The build-up of aqueous in the back pushes the lens and iris forward, blocking the angle (drain). Since aqueous can no longer leave the eye, it continues to build up. Hence, the other name applied to this condition: malignant (highly injurious) glaucoma.

P:  I had a trab one week ago today. My understanding is that most of the redness, discomfort, and occasional sharp pains in the eye are normal responses. Yesterday afternoon and evening, however, now and then when I blinked, my eye made a popping, or clicking, sound. What causes that? Is it normal?

Dr. Rick Wilson:  The sound is unusual, but not that uncommon. The popping sound is usually caused by a build-up of vacuum or suction as the eyelid pulls on the conjunctiva. The fluid coming out of the eye elevates the conjunctiva. When the suction can no longer be sustained as the eye opens further, there's a popping sound when the suction is released.

P:  I have NTG (normal-tension glaucoma). The highest IOPs recorded were 19 mm Hg; the lowest, 12 mm Hg. Four years of being treated with many kinds of eye drops and ALT (argon laser trabeculoplasty) failed to lower the IOP enough. I have lost 90% of the optic nerve in the eye that had a trab, and 85% in the fellow eye, which will also have a trab. Last Thursday, one day after the surgery, my IOP was 15 mm Hg. My doctor said that the pressure "is what it is." Does 15 mm Hg sound okay? I know he used some type of releasable sutures. What can I expect when I see him tomorrow for my first post-op check-up?

Dr. Rick Wilson:  An IOP of 15 mm Hg sounds excellent for the first day. The surgeon probably will need to release a suture or two to get your IOP down to 12 mm Hg or lower for the long term.

P:  I'm 58-years old and have retinal wrinkling after a trabeculectomy. How often does that happen?

Dr. Rick Wilson:  Hypotony maculopathy, retinal wrinkling from too low an IOP, is unusual these days. It happens perhaps two to four times out of a hundred.

P:  If I traveled to Wills to have a trabeculectomy, how long would I need to stay in the area?

Dr. Rick Wilson:  The follow-up for a trab is nearly as important as the trab itself. Therefore, it is usually best to see a glaucoma specialist within driving distance of home. The follow-up period after a trab lasts from 6 to 12 weeks. Sometimes the referring doctor does some of the follow-up if the driving distances are great.

P:  Why does a glaucoma patient lose some vision after a trab?

Dr. Rick Wilson:  If the glaucoma patient has cataracts, the half-line average loss of vision is due to the faster progression of the cataracts.

P:  If a trab fails after seven years, can another trab be performed?

Dr. Rick Wilson:  We can usually perform three trabeculectomies before having to move to an aqueous shunt.

P:  I would like to know if I might be able to stop using Alphagan after a trab. I sleep two hours after each dose. That's a lot of missed hours in a day.

Dr. Rick Wilson:  Most people can stop all, or almost all, of their glaucoma drops post surgery. Certainly surgery is better than sleeping two hours out of your day, assuming you take the second drop at bedtime.

P:  Why is "blood shot" used?

Dr. Rick Wilson:  An autologous blood injection (a shot of your own blood into the bleb) tends to clog up the bleb, cause a little scarring, and raise the IOP 2 to 3 mm Hg.

P:  I had a trab three months ago. Before the trab my vision was 20/25; now it's 20/50. I used atropine for almost two months, and the size of my pupil did not decrease for four weeks, instead of the expected two weeks. I'm wondering if my eye got lazy during the interim on the atropine. Sometimes when I wake up I can see clearly, but then my vision quickly declines during the day. How long does it take after a trab for the vision to be the best it will be?

Dr. Rick Wilson:  Being on atropine that long is quite unusual. Did you have a shallow chamber, fluid buildup between the layers of the eye, too low an IOP post-operatively? Any of those could blur your vision.

P:  My IOP was 5 mm Hg after two months; now, after three months, it is 7 mm Hg. The last suture was removed last week. I was on the atropine about six weeks. I didn't have a shallow chamber or build-up of fluid. I have ICE (irido-corneal syndrome), and sometimes I see large halos at night. They are usually worse when I exercise, and I see some wrinkling in the corner of my eye.

Dr. Rick Wilson:  You would see better if your IOP was at least a couple of points higher. Perhaps the cornea is not doing so well due to the ICE Syndrome, and that may be the cause of the blurred vision.

P:  Should an ICE patient be seen by both a cornea specialist and a glaucoma specialist?

Dr. Rick Wilson:  Yes, when the cornea starts to be swollen, i.e., decompensate. Seeing a corneal specialist early, before there are symptoms, does not help the final prognosis.

P:  I have permanent halos in the eye with ICE eye. Is that a symptom? Will the glaucoma specialist be the one to tell me when it's time to see a corneal specialist?

Dr. Rick Wilson:  Yes, halos can be a symptom of swelling of the cornea due to ICE or any other cause. The glaucoma specialist will tell you when it's time to see a cornea specialist.

P:  Do you see any point in my doing focusing exercises or patching the good eye to make the eye with the trabeculectomy work harder?

Dr. Rick Wilson:  Focusing exercises or patching at a mature adult age does no good. Whether the vision will return depends upon the cause of the vision loss, e.g., cataract, retinal wrinkling, vein occlusion, etc.

P:  Does Imetrex have any effect on the eye after a trab?

Dr. Rick Wilson:  I don't know of any deleterious effect.

P:  My son had a trab in his left eye ten months ago. Since July his pressure has been going down and is now between 0 and 2 mm Hg. Is it possible that the pressure will rise after a revision of the trabeculectomy?

Dr. Rick Wilson:  The pressure can rise again, with at least a partial return of vision.

P:  My mother had a combined trabeculectomy and cataract removal. I wouldn't say her eye watered a lot afterward, but her eye was always wet and glassy looking. Was that normal?

Dr. Rick Wilson:  When the fluid comes out of the trabeculectomy under the conjunctiva, it lifts up the conjunctiva and often gives the glassy-eye look.

P:  I am 49-years old. Two ALT's (argon laser trabeculoplasty) and a SLT (selective laser trabeculoplasty) in the last six months, failed to lower my IOP. I see a trab in my near future. Are the risks and complications greater at my age? The probability of success for the lasers was so high I thought for sure they would work. Now I question the 80% probability of success I was given for a trab.

Dr. Rick Wilson:  At age 49, the probability of any long-term success with an ALT or SLT is remote, unless you have pigmentary glaucoma or a lot of pigment in the trabecular meshwork. On the other hand, the probability of success with a trab is in the high 80's percentile.

P:  I don't have a lot of pigment in the trabecular meshwork, but thought I was told that SLT could be used by altering the frequency of the laser. Did I misunderstand something?

Dr. Rick Wilson:  One study suggested that SLT might be more effective than ALT in patients with little pigment in the meshwork. I have not found a noticeable difference between ALT and SLT in the reduction of IOP.

P:  Is it common for a glaucoma patient's visual acuity to vary from day to day? Does that have anything to do with the stage of the disease?

Dr. Rick Wilson:  It is common in those patients with advanced glaucoma, and may depend upon the quality of the lighting. It is also common in those with low IOPs, as every blink or squeeze of the eye can push too much fluid out and lower the IOP till it is not high enough for the eye to be the best visual apparatus.

P:  Why does the visual acuity of a patient with advanced glaucoma vary from day to day with the same lighting conditions?

Dr. Rick Wilson:  We suspect it is related to systemic factors, such as circulation, more than ocular factors, such as the size of the pupil.

P:  Thank you, Dr. Wilson. I respect you and the moderators so much for providing this valuable service to the world through the Internet. The archives of the chat highlights keep growing.

On December 21, Dr. Wilson discussed "Training Non-Physicians to Recognize Signs of Glaucoma" in the Chat room. Click here for highlights of that meeting.

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