CATARACT + GLAUCOMA
Managing Cataract Patients With Coexisting Glaucoma
Despite improvements in technology, managing patients with coincident conditions requires careful planning and consideration. Here are some guidelines to help you.
By Desiree Ifft, Contributing Editor
Thanks to a steady stream of improvements in technology and technique, performing cataract surgery for patients with glaucoma isn't what it used to be. Phaco and small-incision procedures are less traumatic for the eye. New medications render glaucoma much more controllable from the start. As a result, you won't have to perform as many risky phacotrabeculectomies as the cataract surgeons who came before you. And you're likely to achieve better outcomes.
Even so, you have to be ready. Cataract surgery for a glaucoma patient involves more variables than a routine case. New Ophthalmologist recently spoke with Thomas W. Samuelson, M.D., of Minnesota Eye Consultants in Minneapolis, about cataract surgery in patients with coincident glaucoma. He suggests that you keep the following points in mind as you hone your skills in this area.
Make Sure Patients Understand the Situation
As a cataract surgeon, you'll face a full spectrum of patients who also have glaucoma. Some patients will have very early and easily controlled glaucoma. In these patients, the glaucoma won't influence your cataract procedure much, if at all.
But other patients will have more severe disease. It's important that you explain to them that some of their vision deficit is due to the cataract and some is due to the glaucoma. Even when the cataract is successfully removed, the glaucoma still may limit the quality of their vision. Patients should be aware of this, so they don't assume that cataract surgery will be a cure for all of their vision problems.
Choose the IOL to Maximize Post-op Vision
As you know, glaucoma reduces contrast sensitivity, sometimes even in its earliest stages. Therefore, it makes sense to avoid implanting an IOL that could reduce it more, further compromising the patient's vision. Monofocal IOLs that add to the positive spherical aberration of the cornea and multifocal IOLs could be culprits in this situation.
"I'm not opposed to using a multifocal design in a glaucoma patient with early disease, but I am much more cautious," Dr. Samuelson explains. (See "Are Multifocal or Accommodating IOLs a Good Idea for Glaucoma Patients?") "In general, I prefer an aspheric IOL, which can potentially improve contrast sensitivity, for my patients with glaucoma. I also can use aspheric IOLs and a monovision strategy for glaucoma patients who desire a greater degree of spectacle independence."
While several quality aspheric models are available, Dr. Samuelson is most likely to choose the Tecnis CL (AMO, Santa Ana, Calif.). Because of its effect on spherical aberration and thus contrast sensitivity, it was the first IOL with claims approved by the FDA for reduced spherical aberration, improved functional vision and improved night-driving simulator performance.
The Tecnis CL targets zero ocular spherical aberration for the average patient. It was designed based on the finding, via wavefront analysis, that the average human cornea has +0.27 microns of spherical aberration throughout life. The IOL corrects for –0.27 microns of spherical aberration, just like the average crystalline lens does between the ages of 19 and 25. More "youthful" vision is the result, according to the manufacturer.
The lens also has other features that contribute to the patient's ocular health and quality of vision, Dr. Samuelson says. Its rounded anterior edge scatters light, which can reduce internal reflections. A sloping side edge minimizes the potential for glare. A squared posterior edge facilitates 360-degree contact with the capsule, which helps to prevent posterior capsule opacification (PCO). The Tecnis CL optic is made from current-generation silicone, which has proven to be as biocompatible as acrylic, according to the manufacturer.
| "In general, I prefer an aspheric IOL, which can potentially improve contrast sensitivity, for my patients with glaucoma. I also can use aspheric IOLs and a monovision strategy for glaucoma patients who desire a greater degree of spectacle independence." —Thomas W. Samuelson, M.D. |
Be Prepared for Perioperative Challenges
When you're performing cataract surgery for a glaucoma patient, you must also be aware of the potential for intraoperative challenges, such as small pupils and zonular instability. In addition, perioperative spikes in IOPs are a concern.
According to Dr. Samuelson, certain glaucoma subtypes can cause posterior synechiae or bound-down pupils and make dilation more difficult. These circumstances are less frequent than in the past due to decreased use of cholinergic medications for the treatment of glaucoma. However, you can expect to encounter some difficult-to-manage pupils related to previous iridotomy or exfoliation syndrome.
"Often, stretching is sufficient for handling hard-to-dilate pupils, but it helps to be proficient with using hooks for times when they are necessary to ensure a safe procedure," Dr. Samuelson says. He also utilizes viscoelastic materials for some extra help. "You also can take advantage of viscodynamics. A dispersive, retentive viscoelastic has a stronger tendency to stay in the eye, which maximizes anterior chamber pressure, pushing down on the lens-iris diaphragm, which in turn leads to better dilation."
Exfoliation syndrome, and other glaucoma-related lens issues, also can lead to loose zonules. To combat the accompanying safety risks, Dr. Samuelson recommends making sure you're familiar with using a capsular tension ring, either a standard model or a modified model that is sutured in place.
Minimizing postoperative IOP spikes is another key aspect in performing cataract surgery for glaucoma patients. One way to do this is to diligently remove all of the viscoelastic at the end of the procedure. This is especially important when you're using cohesive viscoelastics. They are composed of longer molecular chains, which give them a greater propensity to cause pressure spikes. Retained cortex is sometimes hidden in patients with poorly dilating pupils and also can lead to a postoperative pressure spike. Therefore, you must inspect the entire operative field at the end of the procedure. As part of that process, Dr. Samuelson uses a Kuglen hook to check the capsular bag fornices for cortical material.
Dr. Samuelson also prefers a chop technique for cataract surgeries in glaucoma patients. "In my experience, chopping keeps the surgical action in the center of the bag, which makes for a more controlled and thus safer procedure."
Plan for More Frequent Post-op Monitoring
Your goal of controlling IOP in these patients, who are most susceptible to the damaging effects of an increase, should carry over into the postoperative period. "Bring them in for follow-up, particularly tonometry, more frequently than your cataract patients who don't have glaucoma," Dr. Samuelson advises.
"Moreover, in some cases, you may want to check pressure on surgery day, approximately 4 or 5 hours after the procedure," he says. "At the very least, you should see glaucoma patients on postoperative day one, as usual, and perhaps again after 1 week instead of the usual 2 or 3."
| Are Multifocal or Accommodating IOLs a Good Idea for Glaucoma Patients? As word spreads about today's presbyopia-correcting IOLs, an increasing number of patients with cataracts are drawn to the idea of less reliance on eyeglasses and contact lenses. In every practice, a certain percentage of these patients also have glaucoma. Given the coexisting conditions, your first instinct might be to avoid these types of lenses altogether. But is that really an acceptable decision? According to Thomas W. Samuelson, M.D., of Minnesota Eye Consultants in Minneapolis, your goal for every cataract surgery patient should be the same: to provide the best possible range of vision. Therefore, in his practice, when a patient who has glaucoma and cataract is interested in a presbyopia-correcting IOL, he explores that option along with the others. "As long as a patient's vision isn't compromised by the glaucoma, or is only mildly compromised, I'm not opposed to implanting a refractive or diffractive multifocal IOL or an accommodating IOL," he says. "Those who are highly motivated for spectacle independence and have no well-defined visual field defects on perimetry can do very well. This can be the case, for example, when glaucoma has caused a generalized loss of retinal sensitivity but no large visual field cuts. On the other hand, I'm not inclined to implant a presbyopia-correcting IOL, especially one with a multifocal design, in the presence of significant contrast sensitivity loss or significant visual field loss, such as an altitudinal or substantial arcuate defect close to fixation." According to Dr. Samuelson, all of the presbyopia-correcting IOLs involve some type of visual trade-off for patients. Some patients won't perceive their vision to be exactly what they'd like it to be at all viewing distances. Furthermore, multifocal IOLs have the potential to cause a decrease in contrast sensitivity as well as unwanted glare and halos at night. Therefore, Dr. Samuelson avoids adding these potential visual trade-offs to eyes already compromised by glaucoma. Instead, as explained in the accompanying article, he generally opts for one of the aspheric IOLs currently available. In deciding whether a presbyopia-correcting IOL is a viable option for a glaucoma patient, Dr. Samuelson also considers his or her overall visual prognosis. " 'Yes' is the likely decision if we've been able to keep intraocular pressure under control and field loss at bay," he explains. " 'No' is the likely decision if glaucoma has been difficult to control in the cataractous eye and has caused severe vision loss in the fellow eye." Dr. Samuelson says that, as with any cataract surgery patient, he is particularly cautious about implanting a multifocal IOL in a glaucoma patient who frequently drives at night. "Arguably, the accommodating IOL may be a better option in these cases because by virtue of its design, it's less likely to induce night vision problems," he says. "Or, if the patient is older, he or she may no longer drive, which allows us to be less concerned about the night vision issue in the first place." As long as we put their ocular health and visual functioning first, patients with glaucoma can take advantage of the benefits that our most advanced IOLs have to offer." |
Determine the New Baseline IOP
In general, cataract surgery lowers IOP. Therefore, in order to appropriately treat the glaucoma patient from cataract surgery forward, you need to determine what the new baseline IOP is. According to Dr. Samuelson, a common mistake to avoid is trying to determine the new baseline too soon. Instead, keep in mind what he calls the "three phases of pressure management."
During phase one, which extends from the day of surgery to perhaps a week after surgery, retained viscoelastic and inflammation can raise IOP temporarily. During phase two, which lasts 3 or 4 weeks while the patient remains on steroid therapy, IOP may increase in response to the postoperative cortisone. During this phase, you can taper the steroid if the inflammation isn't too severe. Or you can add a topical beta-blocker, alpha-2 agonist or carbonic anhydrase inhibitor. Phase three is the correct time to determine the new baseline IOP. It's approximately 6 weeks after cataract surgery, when inflammation is resolved and the steroid and any supplemental glaucoma medications have been discontinued for approximately 1 week.
Different But the Same
Even though you have many advanced tools at your disposal, none can substitute for knowing what to expect and being prepared for the special circumstances of cataract surgery for glaucoma patients. Also, keep your eyes on the same prize — the best possible postoperative vision — and you and your patients should be fine. nMD
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