Ike Ahmed, MD: Improving your view of the angle can be done in many ways. My colleagues and I practice this firsthand by incorporating the use of multiple technologies into our practice that enhance our ability to best manage our glaucoma patients. We gathered together to take a closer look at new technology that is designed to enhance glaucoma detection and progression, which is still a relevant aspect of assessing glaucoma. However, there is something that is more important than diagnosing glaucoma or treating it, and that is monitoring and managing its progression. In this insightful dialogue, my colleagues and fellow glaucoma thought leaders identify the ways in which we use technologies to our fullest potential to track glaucoma progression.

What is your typical monitoring strategy for a glaucoma patient?

Richard A. Lewis, MD: I perform a combination of diagnostic testing, including visual field testing, OCT, and fundus photography. I also obtain all baseline data, including IOP, disc examination, and gonioscopy. I rely on my visual field analyzer a great deal for progression analysis because we can never fully trust our patients to adhere to their medications. The visual field analyzer becomes the report card that shows whether a patient is compliant. Its glaucoma progression analysis is helpful because it differentiates statistically significant progression of visual field loss from random variability. The analysis is based on detailed empirical knowledge of the variability found at various stages of glaucomatous visual field loss, all through information acquired in extensive multi-center clinical trials worldwide. I also rely on OCT for progression analysis, so these two modalities serve as the backbone of my glaucoma strategy.

Beyond the baseline, I have patients return for assessments depending on the severity of their disease. I see early to mild patients every 4 to 6 months, and I see patients with ocular hypertension every year. However, I see typical glaucoma patients every 4 months for IOP measurements, and for yearly visual field analysis and OCT. I perform fundus photography every 1 to 2 years, depending on the patient’s risk factors (i.e., family history, pachymetry, or hysteresis). Imaging the nerve is essential in early glaucoma before the disease is pre-parametric.

Dr. Ahmed: Some literature suggests that in the first few years of diagnosis, frequent visual field testing helps establish a baseline and, more importantly, establishes the rate of progression, which would mean performing four to six visual field tests in the first couple of years.

Tom Samuelson, MD: I administer visual field testing and analysis with greater frequency for those patients who have marginal IOP or are progressing. I ensure that I have an adequate sampling to have a baseline, but for me, that might be two in the first 6 months. The reality is that it depends on the stage of the disease. Patients often get too hung up on IOP, which, obviously, is important, but there’s nothing better than showing sequential OCT images of the nerve fiber layer directly to the patient. Sequential OCT images can reveal how stable a patient has been or may reveal that a patient has gotten worse. Quality sequential images can really drive the point home. I’m constantly telling patients IOP is like a weather forecast. The forecast isn’t the weather, but a predictor of the weather. IOP is like the forecast, whereas OCT scans of the nerve fiber layer are the actual weather.

Is there anything on OCT that you specifically look for and rely on during a glaucoma evaluation?

Cathleen McCabe, MD: I like to evaluate the OCT retinal nerve fiber layer (RNFL) thickness in conjunction with the visual field test. If the visual field test is reliable and the OCT RNFL loss confirms structural changes in the corresponding areas where there is a functional defect on the VF, this gives me confidence that the changes are real. This is helpful in determining the progression of the disease, as well. If the structure and functional tests do not match, I repeat the visual field test.

Dr. Ahmed: It’s always nice to pair up structure and function. For a patient who has a visual field defect and RNFL loss, I monitor the patient more frequently early. I want to get a sense of whether he or she will progress quickly.

Inder Paul Singh, MD: There are many useful parameters on my OCT (Cirrus HD-OCT, Carl Zeiss Meditec) print out. One parameter I look for, that some doctors don’t feel quite as comfortable looking for clinically, is the size of the nerve. The larger the disc size, the less worried I am in the context of a larger cup, especially if the RNFL and rim look good.

The OCT provides me with an objective view of the disc size. This has often helped me decide that a patient is a glaucoma suspect rather than a glaucoma patient, by using the size of the disc size, along with the rim, cup, and RNFL measurements. It is also helpful to show a patient the nerve and the RNFL when educating them about their condition and the decision to treat or not treat.

How confident are you that you can adequately detect progression with visual field and OCT separately, and what value do you add when you bring them together?

Dr. Lewis: We don’t typically see visual field loss until there is more advanced optic nerve damage. The OCT may show significant nerve fiber layer loss before visual field loss occurs. If I’m monitoring progression, I often lose the value of the OCT imaging if there is significant nerve fiber layer loss. The visual field analysis gives us some incremental change that is valuable. The other answer to that question depends on the patient’s baseline IOP. If someone consistently has low IOP measurements (low-tension glaucoma), I want more regular control, so I think there is much more to the story than either visual field or OCT. We should consider the whole clinical picture of the patient.

Dr. Ahmed: Sometimes I see a patient that has some variability on the visual field test, and I can determine whether it is progression or variable testing. If I see that same progression on OCT, it gives me confidence.

Dr. Singh: I agree. When I see a field, I question whether it is fluctuation or the patient’s subjectivity. We must look at all the indices, such as fixation losses, false positive, and false negatives to address the test-taking skills of the patient that day. Also, when I can obtain an objective measurement, such as OCT, demonstrating progression (i.e., inferior thinning that corresponds to a superior paracentral VF defect), I feel more confident in initiating treatment because of the combination of both imaging modalities. It is always reassuring to see structure and function correlate.

How valuable is it to be able to view a combined printout to correlate structure and function on a map?

Dr. McCabe: A picture is worth a thousand words. When you view a combined printout, it confirms that the structure and function correlate.

Dr. Lewis: The issue with some patients is that the functional part of the imaging hasn’t caught up to the structural part when we see significant NFL loss. The visual field is going to catch up, but it’s always frustrating clinically when we have patients whose fields are fine and we’re misled into thinking we have control. Then one day the patient shows up and they have lost the top half of the original field. It’s because we weren’t aggressive at the earlier stage to prevent it.

Dr. Samuelson: That is a great point. I suspect if you did a frequency doubling test on those individuals, it would show a significant superior loss.

Dr. Ahmed: We often underestimate the severity of glaucoma. Someone who has moderate to mild glaucoma has advanced nerve disease when you think about the amount of RNFL loss that has occurred. The ability to put it all together and follow these patients and structurally look at the progression of their disease is very important.

Can you describe to me how important your scope is and how you utilize that to perform minimally invasive glaucoma surgery (MIGS) procedures?

Dr. McCabe: It is important to achieve an excellent view of the angle when inserting MIGS devices and there are a few steps that can improve the quality of the view and the flow of the surgery. For example, I keep my surgical microscope tilted at an appropriate angle for gonioscopy (~20-30 degrees toward me) and then tilt the patient’s head at least 45 degrees away from me.

I also have the patient look away from me. This gives an excellent view of the angle structures and, because I keep the scope at this angle all the time now, the flow of the surgery isn’t interrupted by having to reposition the microscope. An added benefit has been less stress on my back and neck by having the scope in this position for all of my cataract surgeries.

Dr. Singh: Visualization of all the angle structures is a key part of the success of a MIGS surgery and one aspect many new doctors struggle with at first. My surgical microscope (OPMI Lumera, Carl Zeiss Meditec) has truly enhanced my ability to view the smallest details of the trabecular meshwork (TM) and the rest of the angle structures. This has been an advantage in many difficult cases, such as those with light TM, hazy corneas, or those where the anatomy is not quite normal. Having a binocular teaching scope, coaxial illumination, a red reflex, and other features, truly gives me the best view for my MIGS cases and has helped me become more decisive when performing each of the surgical steps. Incorporating image-guided technology (Callisto Eye, Carl Zeiss Meditec) helps me to better align my toric lenses at the end of a MIGS case when, often, manual markings may have come off.

How often do you incorporate MIGS in cataract patients with glaucoma?

Dr. McCabe: I talk to any patient who has mild to moderate glaucoma about MIGS procedures if the patient is on even a single glaucoma medication. Having MIGS in my toolbox allows me to avoid having to go to the next surgical step and even allows me to avoid additional medication that may have side effects. It is my responsibility to treat glaucoma patients during their cataract surgery, if possible.

Dr. Ahmed: MIGS is to phacoemulsification what toric IOLs are to IOLs. It is a necessity to have MIGS. We wouldn’t consider not treating astigmatism with a toric IOL. It should at least be considered. I think we should take the same approach with MIGS. If someone has glaucoma and is undergoing cataract surgery, MIGS should be at the top of the list.

How has MIGS affected your workflow in the clinic or in the operating room (OR)? Has it changed it at all?

Dr. McCabe: Initially, you should build in extra time for MIGS cases so you don’t feel rushed with a new procedure. However, we don’t currently allow any extra time for our MIGS cases over what we traditionally do. It takes a little time to get adjusted, but I think MIGS can be very efficient in the OR. One of the things that has been helpful for me is to insert a trabecular microbypass stent (iStent, Glaukos) at the beginning of the combined cataract and MIGS procedure, just after the capsulorhexis when the view is ideal and before any other surgical steps have begun. When I use a supraciliary stent (CyPass Micro-Stent, Alcon), I place it after the IOL is implanted, because there is a little more likelihood of bleeding.

Dr. Lewis: It is important that everyone become comfortable with MIGS because the bar has been set high and patients expect it. They have read about it, and they’re walking into practices demanding it. And I don’t think it’s necessarily in the purview of only glaucoma doctors. As we discussed, MIGS is a straightforward procedure that we should all be willing to perform by getting comfortable with positioning during gonioscopy and utilizing the microscope. In other words, the key to the procedure is comfortably visualizing the angle before you enter with instruments.

Dr. Singh: To customize surgery for each individual patient, I truly believe it is important for surgeons to gain experience with multiple MIGS devices and procedures. The common thread with all MIGS devices is feeling comfortable working in the angle and, therefore, being able to efficiently manage the scope, patient’s head tilt, and lens position and pressure. Once surgeons gain experience with those steps, the overall procedure, regardless of type of MIGS, starts to become more efficient as well. Postoperative flow is improved compared to standard glaucoma surgery. Patients often need fewer medications, which means technicians spend less time verifying drops, and patients tend to be happier, as well. GP

Dr. Ahmed is an assistant professor at the University of Toronto and a clinical assistant professor at the University of Utah in Salt Lake City. Dr. Ahmed has no financial interest in the products or companies mentioned.

Dr. Lewis is in private practice at Sacramento Eye Consultants in Sacramento, California. He is a consultant and member of the speakers bureau for Carl Zeiss Meditec.

Dr. McCabe practices at The Eye Associates in Bradenton, FL. She is a member of the Carl Zeiss Meditec speakers bureau.

Dr. Samuelson is an attending surgeon at Minnesota Eye Consultants in Minneapolis and an adjunct professor at the University of Minnesota in Minneapolis. He is a consultant to Carl Zeiss Meditec.

Dr. Singh practices at The Eye Centers of Racine and Kenosha in Wisconsin. He has no financial interest in the products or companies mentioned.