What to Say to Patients With Glaucoma Prior to Filtration Surgery


What to Say to Patients With Glaucoma Prior to Filtration Surgery

Mahmoud A. Khaimi, MD

Patients who face glaucoma filtering surgery often have a variety of questions regarding the need for surgery, goals of the operation, and likely outcome (Table 59-1). Because the main goal of filtering surgery is to reduce intraocular pressure (IOP) and preserve vision rather than improve vision, this should be carefully discussed preoperatively. Not infrequently, it may be necessary to briefly review the pathophysiology of glaucoma and how it causes vision loss. New therapies and the use of adjunctive antimetabolites, such as mitomycin C, should be discussed comprehensively, including their indications, use, risks, and benefits. An additional point of discussion, if indicated, is whether cataract surgery should be performed as a staged procedure or as a combined operation.

What follows is a stylized exchange between a patient and her ophthalmologist regarding planned glaucoma filtering surgery. Although it is not practical to address all of the questions raised in this discussion with each patient prior to filtering surgery, we strongly feel that it is in the best interests of all concerned to have a well-informed and prepared patient prior to embarking on the surgical management of glaucoma.

Mrs. Smith is a 65-year-old Black woman with primary open-angle glaucoma in both eyes, diagnosed approximately 4 to 5 years previously. Despite maximally tolerated medical and laser therapy, the patient’s IOP is 30 mm Hg in the right eye. The left eye pressure is 18 mm Hg and is currently being treated with a prostaglandin analog. The patient’s visual acuity is 20/60 in the right eye with correction of –1.75 + 0.75 X 165 and 20/30–2 in the left eye with correction of –1.00 + 1.00 X 10. Relevant family history includes a sister who has undergone laser trabeculoplasty treatment and a glaucoma filtering procedure for glaucoma, and Mrs. Smith’s mother was on drops for glaucoma in the 2 years just prior to her death at 74 years of age. Mrs. Smith is also being treated for mild essential hypertension, which is presently controlled with one drug therapy.

Dr. Khaimi: “Mrs. Smith, as we have discussed on many occasions, glaucoma is a very serious and chronic condition, which is a leading cause of blindness.”

Mrs. Smith: “Yes, Dr. Khaimi, I have been so afraid of losing my vision. I have tried very hard to use the medicines as you have prescribed, and I still can see to sew, to drive, and to do most things.”

Dr. Khaimi: “Fortunately, glaucoma does not affect the central vision until the very end stages of the disease; yet, you do appear to have damage in both eyes. Actually, from the time of diagnosis, the right eye has evidenced rather significant damage from the appearance of the optic nerve and as well from the visual field, which we have previously discussed is the test that evaluates the function of the optic nerve.”

Mrs. Smith: “Is my left eye also damaged?”

Dr. Khaimi: “At least from the appearance of the optic nerve and a suggestion of early changes on the visual field, it also evidences damage. Fortunately, however, there have been no advanced changes or threatening findings on the visual field. The concern presently is with the pressure being too high in the right eye.”

Mrs. Smith: “But I thought that the pressures had come down significantly! How low does the pressure need to be?”

Dr. Khaimi: “Actually, your pressure had responded and initially, for a year or so, was adequately reduced. We don’t really know exactly what the safe pressure level is for people in general. It is a very individual consideration with the pressure goal for each patient’s glaucoma being different and perhaps even different for each eye of each patient. Because the damage in your right eye is significantly greater than would appear in the left eye, it would be reasonable to understand that the right eye pressure must be reduced to a much lower level than the left eye pressure. In some patients with pressures at even 20 to 22 mm Hg or lower, which previously was considered in the normal range, glaucoma-type damage to the optic nerves has still occurred. Such patients are felt to have normal or low-pressure glaucoma in that the optic nerve has some peculiar sensitivity to even ‘normal’ levels of pressure. It would seem that we need your pressures at a very low level in the right eye, perhaps high single digits or low teens on a continuous basis, and at 18 mm Hg or so in the left eye.”

Mrs. Smith: “But I thought that we had gotten the pressure to a safe level! The pressure in the right eye had been in the teens after the laser. Has the laser stopped working again? We seem to have gotten a really good effect from the original laser and some help from the one retreatment 2 years later. Can’t we try the laser again?”

Dr. Khaimi: “Often, laser will work very well, especially in certain types of glaucoma. We have talked many times about your glaucoma and have also discussed that laser trabeculoplasty can be highly effective, especially initially and even with a retreatment. However, over time, primary open-angle glaucoma tends to be progressive, and ultimately there will be little to gain from repeated treatments with the laser.”

Mrs. Smith: “Well, is there any alternative other than surgery?”

Dr. Khaimi: “As you know, we have had to use oral Diamox in an effort to obtain better control of your eye pressures. Unfortunately, despite initiating systemic therapy, your right eye’s pressure is still uncontrolled.”

Mrs. Smith: “By the way, I felt awful on the 2 tablets twice a day and still seem to have no energy. I just don’t feel like myself.”

Dr. Khaimi: “Well, I am sure it is difficult to get through the day feeling that you have no energy, and this is one more reason why we have evolved to the point of needing to discuss surgery. You will likely not be able to tolerate the oral medications for much longer, and stopping this medication will lead to a further increase in your pressure. Glaucoma filtering surgery is designed to create a new pathway for the fluid in your eye, which is not effectively draining through your eye’s natural drain system.”

Mrs. Smith: “Yes, we have talked about surgery in the past. But, what exactly is involved with glaucoma filtering surgery? Do you place a tube in my eye? It seems that I have heard or read about drainage devices being placed in an eye.”

Dr. Khaimi: “There are glaucoma drainage devices that are used and inserted in some eyes that have glaucoma. Typically, however, glaucoma drainage devices are used in patients with more advanced forms of glaucoma, in patients who have not responded to conventional filtering surgery, or in those who have certain significant risk factors, such as inflammation in the eye or significant scar tissue formation from previous eye surgery.”

Mrs. Smith: “What actually do you do? Do you put me to sleep? Will the surgery be painful?”

Dr. Khaimi: “Actually, the surgery is performed under local anesthesia. You will be given preoperative sedation so that you are relaxed, and you will be kept sedated and comfortable for the procedure. A member of the anesthesia staff will be monitoring your vital systems, and it is unlikely that you will have any life-threatening problems. It will be necessary to use a local anesthetic to inject medicine around your eye to put the pain and motor fibers to sleep so that your eye will not move and you will have no discomfort during the surgery. The method for using local anesthesia to put the eye to sleep is quite similar to that which is performed for a dental procedure.

“The surgery is very delicate and involves creating a controlled opening, which will allow fluid to escape from the eye. It is somewhat like creating a manhole cover with stitches around the edges of the cover so that fluid can flow out around the edges of the cover. A medication called mitomycin C is placed on certain parts of the eye at the time of surgery, and this medication has been shown to have local effects in preventing scar formation and enhancing the drainage of fluid from the eye. An additional outer layer of tissue known as the conjunctiva will then be sewn over the draining fluid, which will help allow the fluid to spread out and away from the inside of the eye.”

Mrs. Smith: “Will I feel this filter or be able to see it?”

Dr. Khaimi: “Yes, often, there will be a small, raised, localized area of tissue, like a little bubble or bleb, which will be hidden under the upper lid. It is likely that you could see it in a mirror with the lid elevated, and it may be that you will have an awareness or sensation of a raised area under your lid with blinking and lid movement.”

Mrs. Smith: “How long will the surgery take?”

Dr. Khaimi: “The time required for the surgery will vary with each patient. Sometimes, the tissue dissection can be more difficult due to the conjunctiva being thinner, or there can be prominent blood vessels and a bit more localized bleeding in certain patients, thus requiring more time for the surgery. So, do not let the time be a concern, although usually the surgery lasts approximately 30 to 45 minutes once we start.”

Mrs. Smith: “Will I see better or differently after the surgery?”

Dr. Khaimi: “It’s good that you asked about your vision, as there are several important considerations. As you have commented on several occasions, your vision has been variable and at times somewhat blurred.”

Mrs. Smith: “Yes, and my night vision has been poor for some time. I have even stopped driving at all after sunset because things are so dark. I also have had difficulty reading, and I seem to need more light to be able to read the newspaper.”

Dr. Khaimi: “These symptoms, as we have discussed before, are related to both the maturing cataract and the worsening of your glaucoma in your right eye. The goal of filtering surgery is to lower your eye pressure in efforts to halt the progression of your glaucoma. Glaucoma surgery is not done to improve your vision but is needed to keep your present vision from progressively getting worse. Remember that loss of vision due to glaucoma is irreversible, and hopefully, glaucoma surgery will lower your eye pressure to a safe and protective range, whereby you will no longer have further loss of vision.”

Mrs. Smith: “Is the surgery reasonably safe? Could my vision be worse or even possibly could I go blind?”

Dr. Khaimi: “In every way, I want to reassure you that the chances are very minimal that you would have any major problem that would affect your vision significantly. Patients who undergo any type of intraocular surgery can experience some degree of accelerated cataract formation. Because you already have a cataract related to your age, it is likely that your cataract could significantly progress over time, requiring removal of the cataract. And, one must acknowledge that, however small the risk, you could develop an infection or have a hemorrhage that could result in loss of some or all vision in your eye and possibly even have to have the eye removed. Because glaucoma patients typically have variable eye pressure, which affects the vessels in the retina and back of the eye, they are at greater risk for developing spontaneous bleeds than are patients who do not have glaucoma and are merely undergoing cataract surgery. While complications are not likely during the surgery, they can still happen, and it is important to realize that before deciding on the surgery.”

Mrs. Smith: “Are there any other complications or problems that may occur and that I need to know about?”

Dr. Khaimi: “During the early postoperative period, your filtering site can drain too much fluid from the eye, which can result in the front part of the eye shallowing and subsequently in the lens moving forward and possibly even touching the back surface of the cornea. Occasionally, if too much fluid is draining from the eye, you can get swelling in the back of the eye that leads to some loss of vision. If the process does not respond to tight patching of the eye or certain medications that we use in these circumstances, then an additional surgical procedure may be required.”

Mrs. Smith: “What type of surgical procedure, and would it be very risky to have this surgery?”

Dr. Khaimi: “Yes, unfortunately there is rather moderate risk with each additional surgical intervention; yet, the procedure is usually able to be performed without significant additional complications. Should there be excess fluid drainage from the eye in the early postoperative period that warrants correction, then we would need to return to surgery again under local anesthesia to perform a procedure in which the fluid is drained from the choroid and the chamber is deepened. A small incision will have been placed into the anterior chamber through the cornea, and this incision site will be used for filling the chamber with fluid, which will allow deepening of the chamber and thus normalizing the distance between the cornea and the lens. At the same time, a small incision will be made just back from the edge of the cornea over the site of fluid accumulation, which will allow drainage of the fluid from the choroid and thus will also assist with deepening the chamber and reducing the excessive filtration of fluid. It can happen that the incision in the tissue overlying the choroid could result in a significant hemorrhage or possibly even a tear of the retina. There could also be more accelerated cataract formation, which develops over several days or perhaps over several months, thus necessitating removal of the cataract.”

Mrs. Smith: “Well, you have indicated that I already have a cataract. Why aren’t we removing the cataract at the same time I’m to undergo the glaucoma surgery so that all is done at one time?”

Dr. Khaimi: “I am glad that you mentioned this, Mrs. Smith. It certainly is possible that a combined cataract-glaucoma procedure could be performed with insertion of an implant, and often this type of combined procedure is performed very successfully. Your cataract is mature enough to seriously consider this option. Often, glaucoma filtering surgery is combined with cataract surgery and lens implant because glaucoma surgery can cause the cataract to progress. If this were the case, one would have to go back to the operating room to take out the cataract at a later point. Therefore, if a patient has moderate cataract formation, I typically suggest proceeding with a combined procedure in order to avoid another surgical procedure later on and to address the cataract that is currently present.”

Mrs. Smith: “That makes sense. I really don’t think I would want to go through a second operation if it could be avoided. Earlier, while describing the glaucoma filtering procedure, you mentioned the use of mitomycin C to prevent scarring.”

Dr. Khaimi: “Yes, numerous studies have indicated a significant benefit in using certain types of adjunctive medications know as antimetabolite agents, such as mitomycin C or 5-fluorouracil, during glaucoma filtering surgery. Mitomycin C is applied at the time of surgery to a very localized area, which can, as I had mentioned, have local effects in preventing scar formation and enhancing filtration.”

Mrs. Smith: “Are there any dangers with using these drugs? Are both drugs considered to be safe to use in the eye?”

Dr. Khaimi: “Both drugs are very powerful agents that interfere with the activity of cells that cause scar tissue formation. Yet, these drugs can also result in defective healing with resultant separation of the wound, defects in the filter site itself with leakage and flattening of the bleb, and can be dangerous to the internal aspects of the eye if they inadvertently get into the interior of the eye. Yet, much information has been gathered about these drugs, and we have become very skilled at using them in appropriate doses for our desired effect. It also must be mentioned that a very thin filtering bleb may develop after use of these drugs, and with time the eye can overfilter with the pressure becoming too low. The filtering bleb itself can become too thin, resulting in leakage and prompting the need to have the area resutured and possibly revised. If indeed the pressure becomes too low on an extended basis, then the eye can become soft with stretch marks developing in the central retina or the macular area with some damaging effect from the hypotony. If the pressure is not adequately reduced or is too high in the early postoperative period, whether a primary filtering procedure is done or a combined cataract-filtering procedure, then the laser can be used to cut one of the stitches in the edge of the “manhole cover” to allow more fluid to be released from the eye, thus lowering the pressure. Usually, there are no problems with performing the laser. One must be aware that the laser being performed through the conjunctiva or outer layer of tissue could result in a hole being created, which would leak and thus require suturing or patching. I must also mention that adjunctive antimetabolites have been shown to increase the lifetime risk of eye infection and that any potential signs of infection, such as eye redness, pain, or discharge, must be addressed immediately.”

Mrs. Smith: “Well, it seems that we have decided what to do about the right eye. Do you feel comfortable that my left eye is in a stable situation?”

Dr. Khaimi: “Actually, I have some concern that there has been damage of the optic nerve. There also are early changes in the visual field, and the pressure is at a borderline level even now while on an oral medication, which we will need to discontinue for the filtering surgery. It is our usual practice to discontinue the oral Diamox because it affects both eyes, and the effect is that of reducing flow in the eye, which results in lower pressures. Once the filter is created, it is necessary that fluid flow through the opening in order to maintain the patency and to assist with the filter becoming established and reducing the eye pressure. Thus, it would be potentially harmful to the success of the surgery to be on the oral medication.”

Mrs. Smith: “But, what about the pressure in my left eye?”

Dr. Khaimi: “It is likely that the pressure will increase once you are off of the Diamox, and the pressure would then be at a level that would be unsafe. We can add a second pressure-lowering drop to hopefully avoid this problem. Another consideration would be to keep you on your topical pressure-lowering drop and to perform laser trabeculoplasty to reduce the pressure to a safer level in the left eye by the time of the surgery for the right eye, which is to be done in the next few weeks. We will definitely pay close attention to your left eye while we are following the postoperative course of your right eye.”

Mrs. Smith: “After surgery on my right eye, will I still have to use my glaucoma drops?”

Dr. Khaimi: “No. You will immediately stop taking your glaucoma drops that you were on in your right eye prior to surgery and start postoperative drops the day after your surgery. On your postoperative day 1 visit, I will take the patch and shield off your operated eye and check your vision and pressure. I will also carefully examine your eye. You will then be instructed on how to properly take your postoperative drops. You will be placed on a topical steroid on a somewhat frequent basis in the right eye in order to quiet the inflammation from the surgery to prevent scarring of the filter. You will use a topical antibiotic drop to prevent infection. You will also be placed on a combination antibiotic and steroid ointment to be used at bedtime. In some cases, you might need a drop that dilates your pupil and helps in cases where the eye pressure might be too low early on. This drop can cause your vision to be blurry early on but is helpful in specific situations.”

Mrs. Smith: “Are there any restrictions after surgery?”

Dr. Khaimi: “Yes. I ask all my patients to avoid bending, lifting, and any strenuous activity for several weeks after surgery. I also instruct all my patients to protect the operated eye by wearing their original glasses or the protective eyewear we give out in the postoperative kit. Finally, I instruct all my patients to wear a shield over the operated eye at bedtime for at least 2 weeks postoperatively.”

Mrs. Smith: “Dr. Khaimi, I want to thank you for discussing this surgery and my various options and the risks of this procedure as I have had great concern about my vision. Actually, I should tell you that my mother was nearly completely blinded by her glaucoma because she avoided glaucoma surgery at all costs because she was terrified of surgery.”

Dr. Khaimi: “Mrs. Smith, there is risk with everything that we do. The greatest risk in glaucoma is not controlling the pressure and not being appropriately aggressive, because untreated glaucoma and inadequately reduced pressure results in loss of all vision as it did with your mother. What I would want you and your family to know and to understand is that we are partners in this process and that no matter what may occur, we will deal with problems and situations as they come up. Meanwhile, we will be confident that things will go well and that we can achieve control of your pressure and preserve your vision.”

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Mar 7, 2021 | Posted by in OPHTHALMOLOGY | Comments Off on What to Say to Patients With Glaucoma Prior to Filtration Surgery

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