Glaucoma detection key to MIGS success
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I am a comprehensive ophthalmologist practicing at the Center for Excellence in Eye Care, a subspecialty ophthalmology group in Miami. Given our location, we see a high proportion of minority patients from the Caribbean.
Minorities, overall, experience a higher incidence of visual impairment from glaucoma than non-minorities. There are many potential reasons for health care disparities among minority populations, including income and language barriers, medication costs and other factors. The Ocular Hypertension Treatment Study showed a correlation between glaucoma and corneal thickness, and African Americans tend to have thinner corneas. So, we know there are physiological factors, in addition to socioeconomics, that disproportionately affect minorities. Because of the high incidence of glaucoma in my practice, I am acutely aware of the potential for advanced visual loss and the importance of reducing the treatment burden on patients through the expanded use of MIGS procedures.
Source: Carlos Buznego, MD
Putting glaucoma on the radar screen
When I talk with cataract surgeons, I often hear them say they do not see much glaucoma in their practice. According to Market Scope, nearly one in five patients undergoing cataract surgery has coexisting glaucoma. In addition, studies consistently show that about half of those with glaucoma are unaware they have the disease. Cataract surgeons may question the need for MIGS intervention at the time of cataract surgery if the patient can be controlled on just one medication. However, improving pressure control is highly beneficial because noncompliance is a well-known issue with eye drop therapy.
As ophthalmologists, our goal should be to remove the burden of care from the patient whenever possible. Unlike medication, a MIGS intervention works 24/7, eliminating the noncompliance issue. In our practice, we have implemented an efficient glaucoma screening into the cataract workup to find previously undetected glaucoma and address it at the time of surgery with the goal to minimize late-stage disease and vision loss.
Glaucoma workflow in a cataract practice
The role of the technician: Because glaucoma is closely tied to family history, we train our technicians to ask focused health and family history questions during the cataract evaluation.
- Have you ever been told you have glaucoma or high pressure?
- Were you ever tested for glaucoma?
- Does anyone in your family have glaucoma?
- Are any of your relatives blind?
These questions will direct the diagnostic workup and allow technicians to begin the education process. “We need to do some additional testing to rule out glaucoma. If you have glaucoma, there are some procedures that we can perform during your cataract surgery to help control the disease.”
Clinical exam: In busy practices, the Tono-Pen (Reichert Technologies) will often replace applanation tonometry; however, the results can be inconsistent. The gold standard is applanation tonometry, which will obtain more accurate readings. In addition, corneal pachymetry is important to determine if the cornea is thin. These findings will indicate the need for additional diagnostic tests, such as visual field testing and OCT.
Optic nerve analysis: Careful examination of the optic nerve during the fundus examination can provide clues to early glaucoma, such as optic cup size, notching, nerve fiber layer defects or asymmetry between the two nerves. Often, abnormal findings can be found in patients with normal IOP values, which can be indicative of normal-tension glaucoma.
Patient counseling
When I diagnose a cataract patient with glaucoma, I explain that we can provide interventions, which are usually covered by insurance with no out-of-pocket costs, at the time of cataract surgery to help control the disease. In my experience, about 80% to 90% of the time, we can either reduce or eliminate the need for medications. Given the choice, patients will almost always opt for MIGS at the time of cataract surgery. I also stress that MIGS procedures have a low incidence of complications compared with performing cataract surgery alone.
At the time of diagnosis, I prescribe pressure-lowering drops until the patient returns for cataract surgery. In case the patient disappears, I feel better knowing I have provided an immediate intervention.
MIGS options
Cataract surgeons may be concerned about increased surgical risks, particularly if they have little MIGS experience. Based on the well-known iStent (Glaukos) FDA clinical trial, adding MIGS to cataract surgery did not increase complication rates or patient morbidity as compared with cataract surgery alone. Hypotony, infection or other sight-threatening complications that can occur with traditional glaucoma surgery are almost never seen with MIGS procedures. I have also found the learning curve with MIGS to be quite low as it takes only a handful of cases to gain a high comfort level.
In open-angle glaucoma, we have no diagnostic tool available to show us where the obstruction is located. The resistance to flow can be in the trabecular meshwork, Schlemm’s canal or the distal collector channels. I typically perform canaloplasty using the Omni surgical system from Sight Sciences because this technology allows me to achieve physical dilation of the canal and viscodilation of the distal collector channels to address all levels of obstruction along the conventional outflow pathway (Figure 1). As I retract the Omni device, I utilize the catheter to perform goniotomy to remove several clock hours of diseased trabecular meshwork. I will often implant trabecular bypass stents as another modality to maximize long-term reduction in outflow resistance.
A large percentage of the 4 million cataract patients treated nationwide can benefit from MIGS, and the cataract evaluation is an ideal time to assess eligibility. Minority patients, in particular, are more likely to have undetected glaucoma and are at higher risk for losing vision due to glaucoma disease, so MIGS intervention at the time of cataract surgery may be optimal. Whether we are treating mild or moderate glaucoma, the goal is to get the pressure down as low as possible, control the progression of the disease, and help our patients by reducing or eliminating their dependence on daily medications.
- References:
- Friedman DS, et al. Arch Ophthalmol. 2004;doi:10.1001/archopht.122.4.532.
- Kass MA, et al. Arch Ophthalmol. 2002;doi:10.1001/archopht.120.6.701.
- Schmier JK, et al. Curr Med Res Opin. 2009;doi:10.1185/03007990902791132.
- 2022 glaucoma surgical device market report: Global analysis for 2021 to 2027. https://www.market-scope.com/pages/reports/337/2022-glaucoma-surgical-device-market-report. Published August 2022. Accessed May 1, 2023.
- Varma R, et al. Ophthalmology. 2004;doi:10.1016/j.ophtha.2004.02.001.
- For more information:
- Carlos Buznego, MD, of the Center for Excellence in Eye Care in Miami, can be reached at cbuznego19@gmail.com.
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