Controlling Eye Pressure after a Trabeculectomy

Controlling Eye Pressure after a Trabeculectomy

Chat Highlights – January 16, 2013
Guest Speaker – Dr.  Anand Mantravadi
Lorraine Miller, Editor, Chat Topic Researcher

 

Moderator:  Good evening!  Dr. Anand Mantravadi is with us tonight to discuss, “Controlling Eye Pressure after a Trabeculectomy.”

P: After a trabeculectomy, what percentage of patients requires manipulation of the eye to reach their target pressure?

Dr. Mantravadi:  Every patient’s postoperative plan of care is individualized. Many patients will need suture lysis to further open the drain, and some may need additional medications.

P:  Is controlling eye pressure different with a mini express shunt and trabeculectomy combined surgery versus just a trabeculectomy?

Dr. Mantravadi:  The ExPress is a device designed to standardize a part of the traditional trabeculectomy. The ExPress has not been shown to be superior to a standard trabeculectomy, but it does eliminate a few steps.   It has advantages and disadvantages.

Success rates after a combined cataract and trabeculectomy have shown a lower long-term success rate compared to a trabeculectomy alone.  It is very hard to generalize because different patient populations, techniques, and definitions of success affect success rates reported in the literature.

P:  What office visit schedule are most patients on following the three months post surgery?

Dr. Mantravadi:  If the patient is stable from a pressure and disease progress standpoint, the follow-up is determined based on the stage of the disease.  The more advanced the case, the more closely one should be monitored.

P:  Dr Mantravadi, how do different trabeculectomy techniques influence intraocular pressure (IOP) control postoperatively? Does the fornix approach achieve better control?

Dr. Mantravadi: A fornix compared to a limbus-based approach refers to the location of the conjunctival incision, and both are successful. Studies have not demonstrated a significant difference in success rates between the two. There are advantages and disadvantages to each approach from a surgical standpoint. In recent years, more emphasis has been placed on a broad diffuse application of antimetabolites to discourage bleb morphologies that may lead to problems.

P: Some patients experience blurriness after the surgery. Why does this occur?

Dr. Mantravadi: There are many reasons.  I will list the reasons from the front of the eye to the back.  There can be a refractive change since the eye shape can change.  The most common causes are due to astigmatism or a slight tendency of hyperopia.   Some people can have mild inflammation or self-limited bleeding that can affect vision.  There may be transient swelling in the back of the eye related to a period of lower pressures that may cause blurry vision. There can also be multifactorial reasons for the blurriness.

P: If blurriness occurs, how long does it take to dissipate?

Dr. Mantravadi: The majority of people are within one line of their original vision on the Snellen chart within two months of their trabeculectomy.   Many experience clear vision much sooner.

P: The day after a trabeculectomy, some patients have a stitch lasered. Why is this done?

Dr. Mantravadi: It is not common to laser a stitch the first day after a trabeculectomy.  We would like to wait one to two weeks if suture lysis is required. The fundamental mechanism of a trabeculectomy is to create a scleral flap that allows aqueous fluid to percolate from the anterior chamber out of the eye, under the flap, and collect under the conjunctiva to form a filtering bleb. If one starts healing and the pressure rises above goal, then a suture placed in the scleral flap can be released either manually or with a laser. This enables greater flow resulting in a lower pressure.

P: Is lasering a stitch painful to the patient? Does the eye need to be numbed?

Dr. Mantravadi: It is not a painful procedure and is well tolerated by most. The eye is temporarily anesthetized with a topical drop, which is sufficient.

P: How quickly do you see results from lasering the stitch?

Dr. Mantravadi: Typically, the result is immediate.

P: What is the timing schedule and decision-making process involved in the removal of the stitches?

Dr. Mantravadi: The timing is dependent on the goal pressure for the individual based on the stage of disease and the body’s individualized healing response. We would like to wait roughly a week before suture removal. Suture removal may be done earlier in patients exhibiting an aggressive healing response, characterized by forming scar tissue and a decrease in flow through the trabeculectomy site. In patients who are healing normally, suture removal may not be needed at all. Some people require removal of one stitch, others require removal of them all, and some patients don’t require any of their stitches to be removed.

P: Why are fluorouracil (5-FU) injections used after a trabeculectomy?

Dr. Mantravadi: 5-FU injections are used to reduce the healing response that may negatively affect a trabeculectomy’s function.

P: What is a shallow chamber?

Dr. Mantravadi: A shallow chamber refers to the front of the eye having less volume due to excessive aqueous flow. This is usually temporary as the eye equilibrates following surgery.

P: Why is a contact lens inserted in the eye after surgery?

Dr. Mantravadi: A contact lens is used by some practitioners to help facilitate healing of the incision site or to reduce filtration if it is excessive.

P: How long can the contact lens remain in the eye? How does a patient take care of it?

Dr. Mantravadi: A contact is placed postoperatively after a trabeculectomy to facilitate healing.  It can be left in short term and taken out by the physician during the follow-up visit. Keeping your hands clean before touching the eye during this period is a good idea.

P: Is laser suture lysis more effective than the manual releasable sutures?

Dr. Mantravadi: No, the concept is the same.   Access to a laser for laser suture lysis is required while manual releasable sutures can be released in the office.

P: How is target pressure determined?

Dr. Mantravadi: Developing a goal or target pressure is a process individualized for each patient.  It is determined based on the individual’s stage of disease, their perceived tempo of disease progression, and projected life span.  Information gleaned from randomized controlled trials demonstrates the extent of pressure lowering and the relationship to glaucoma progression.

P: Could some antimetabolites cause a steep rise or drop in IOP independent of the trabeculectomy?  I have heard MMC is involved in cataract formation.

Dr. Mantravadi: A trabeculectomy enables pressure to be lowered. If an antimetabolite is applied, and no trabeculectomy performed, pressure will remain elevated. Antimetabolites have enhanced the success rate of the surgery. There are studies that demonstrate a greater rate of cataract formation in eyes that have had a trabeculectomy.

Intraocular mitomycin can be toxic. It is typically applied to the surface of the sclera during surgery.

P: How long does the Carlo E. Traverso maneuver control IOP?

Dr. Mantravadi: It is effective in the early postoperative period. Some physicians advocate digital massage long-term.

P: When would an amniotic membrane patch graft be used to close a postoperative leak?

Dr. Mantravadi: An amniotic membrane is used in select refractory or in recurrent cases, and when the conjunctiva is not healthy enough to be mobilized to cover the leak.

P: When is viscoelastic gel added to the eye? Why is this procedure done?

Dr. Mantravadi: It is used temporarily to elevate the eye pressure, slow down filtration if excessive, to reform the anterior chamber if too shallow, and to allow time for the body and Mother Nature to catch up and heal.

P: Is balanced salt solution (BSS) used to reform the anterior chamber (AC)?

Dr. Mantravadi: Yes, BSS is used intraoperatively. Postoperatively it can be used but viscoelastic is far more commonly used to reform the AC.

P: If cataract surgery is performed three months post-trabeculectomy, is there more pain or a longer healing period?

Dr. Mantravadi: Cataract surgery performed greater than three months postoperatively is not associated with any greater pain or healing period than if it is performed without a prior trabeculectomy.

P: Why do some patients require cataract surgery following a trabeculectomy?

Dr. Mantravadi: If a cataract is visually significant, then it can be removed. Patients who have had a trabeculectomy may develop a cataract at a slightly faster rate.

P: How does cataract surgery affect the success of a recent trabeculectomy?

Dr. Mantravadi: Cataract surgery can lead to a rise in pressure with a reduction in the function of the trabeculectomy. Patients may retain function of the trabeculectomy following cataract surgery.

P: Why do patients suffer from glare problems after a trabeculectomy?

Dr. Mantravadi: Glare after a trabeculectomy can occur if the eye is dilated pharmacologically with atropine.  This may be recommended for a short period of time after surgery. Glare and light sensitivity can result from normal or abnormal postoperative inflammation. Dry eye or the surface of the eye being dry may result in glare-related symptoms which can improve with lubrication.

P: When can a patient drive again following a trabeculectomy? Can a patient drive after the eye is manipulated during post surgery office visits?

Dr. Mantravadi: One can drive depending on the condition of the other eye.  Depth perception may not be accurate since the eyes are not working together.  This should improve when healing is a bit more underway.

P: How is the eye numbed for a trabeculectomy?

Dr. Mantravadi: A trabeculectomy is performed under monitored anesthesia care such as IV relaxing medication.  The eye is locally numbed in a few different ways. Anesthetic can be applied locally underneath the lining of the eye which should be sufficient. Anesthetic can also be administered around the eyeball both retrobulbar and peribulbar which is also effective. This is individualized for each patient.

Moderator: Thank you, Doctor, for joining us this evening.  It is always a pleasure to have you with us.

Dr. Mantravadi: Thanks everyone.  Good night.

 

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About the Author:

The Glaucoma Service Foundation’s mission is to preserve or enhance the health of all people with glaucoma and to provide a model of medical care by supporting the educational and research efforts of the physicians on the Wills Eye Institute Glaucoma Service, the largest glaucoma diagnosis and treatment center in the country.

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