October 2018

GLAUCOMA

Presentation spotlight
Management of refractory glaucoma


by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer


Refractory glaucoma in siliconic and buckled eye following vitreoretinal surgery
Source: Sidi Mohammed Ezzouhairi, MD

 

Recognizing the signs of refractory glaucoma and how to manage it

Refractory glaucoma is defined as uncontrolled intraocular pressure with evidence of optic nerve and/or visual field deterioration despite maximally tolerated topical and/or systemic anti-glaucoma medications, failed surgical treatment or a combination of surgery and medicines, or a high risk of failure of trabeculectomy.1 It is a progressive complication associated with almost all types of glaucoma, according to Sidi Mohammed Ezzouhairi, MD, Mohammedia, Morocco, who spoke about it at the 2018 World Ophthalmology Congress, saying that although the management of refractory glaucoma patients is exceedingly challenging, it is the specialist’s job to preserve residual visual function in these patients and never give up.
“The criterion that best defines refractory glaucoma is the loss of regulation of IOP and the resultant inability to control optic neuropathy progression using the maximum tolerated medical therapy,” Dr. Ezzouhairi said. “Depending on the systemic status of the patient, the status of the patient’s eye, and the grade of glaucoma, one or more criteria are added to this constant one. There are many other clinical cases that make the situation critical and lead to refractory glaucoma. The commonly accepted and used criterion is the failure of traditional filtering surgery.”
Dr. Ezzouhairi explained that all types of glaucoma can become refractory to treatment. However, several specific case scenarios are more likely to do so and demand the glaucoma specialist’s attention, such as primary angle closure glaucoma (PACG), which has been shown statistically to cause more blindness than primary open angle glaucoma (POAG). Also, damaged conjunctiva, for example, by caustic burns and pemphigoid, secondary glaucoma (e.g., neovascular glaucoma, pseudoexfoliative glaucoma, post-uveitic glaucoma, etc.) can be responsible for a higher incidence of refractory glaucoma than the primary ones. In POAG, the more glaucoma risk factors there are, the greater the likelihood that the glaucoma will evolve rapidly to refractory glaucoma.

Management

The best management is always prevention. To prevent refractory glaucoma, the ophthalmologist needs to perform a thorough assessment of the patient, which requires monitoring and management of all types of glaucoma. “These are challenging cases,” he said. “A particular awareness of the ocular surface during the initial patient evaluation is important, and it should be assessed at each follow-up examination. Patient management should be adapted to the status of the ocular surface. Ocular surface disease increases the rate of unsuccessful filtration surgery.”
The available options for the management of refractory glaucoma include microinvasive glaucoma surgery (MIGS), glaucoma drainage devices, ultrasound ciliary plasty, and cyclophotocoagulation laser diode, continuous or micropulse waves.
Dr. Ezzouhairi considers conventional surgery when maximum tolerated medical therapy and laser become ineffective. Surgery should be well prepared, and the follow-up period is equally important to achieve good outcomes. The post-surgery failure rate is closely correlated with the standard of postoperative care.
The most well-known glaucoma drainage devices are the Ahmed (New World Medical, Rancho Cucamonga, California), Baerveldt (Johnson & Johnson Vision, Santa Ana, California), and Molteno (Katena, Denville, New Jersey). With all three of these devices, the long-term IOP seems to depend on the surface area of the implant, which determines bleb size, tissue response to the implant, and thickness of the fibrous capsule controlling percolation of aqueous humor through the bleb wall.2 “The aim of the glaucoma drainage devices is to drive the aqueous humor posteriorly, to an area where the scarring is less important,” Dr. Ezzouhairi said.
The Ahmed device is a valved silicone or polypropylene, single- or double-plated implant made in various sizes. Valved devices offer more immediate IOP control and a lower rate of hypotony. The Baerveldt implant is a non-valved silicone implant, and the Molteno consists of a non-valved polypropylene device, both available in various sizes and number of plates. Non-valved devices are often occluded with a stent or a ligature suture, leaving the postoperative IOP unchanged and requiring the continuation of the medications until the fibrous capsule forms.2
A study that reviewed the 5-year outcomes of the Ahmed versus Baerveldt implants in refractory patients showed that most of the failures happened in the first 2 years after surgery. However, the reason for failure was different in the two groups; the cause of failure from high IOP was higher in the Ahmed valve group (80% failure in this group) compared to the Baerveldt group (53% failure) (P=.003). The reverse was true as well with the Baerveldt group showing a higher risk for persistent hypotony (47% of failures) compared to the Ahmed group (20% of failures).3 The success rate of the Ahmed valve decreases by 10% per year, and success after 5 years is below 50%, Dr. Ezzouhairi said.
Dr. Ezzouhairi said that although some studies that examined the use of sequential glaucoma drainage devices seem to have revealed lower success rates, he thinks that the results of the initial implant studies may not be accurately extrapolated to additional shunts.
Experiencing initial success with a glaucoma drainage device does not necessarily mean that the patient is out of the woods. According to Dr. Ezzouhairi, complications include early or delayed hypotony sometimes associated with athalamy, choroidal detachment, and hemorrhage. There can also be early or delayed ocular hypertension caused by tube obstruction, tube retraction, and an inflammatory scarring membrane around the reservoir. Further complications include corneal touch and edema, cataract, and endophthalmitis.
Some specialists turn to cyclodestruction as a means of alleviating refractory glaucoma. It avoids complications linked to blebs and is easy to perform. The procedure performed in a closed eye method avoids complications linked to blebs such as infection. It’s easy to perform, is not time consuming, can be repeated if it fails, and is inexpensive. “The limitation of cyclodestruction is the location on the ciliary body. In order to focus the energy accurately on the ciliary body, we have to use systematic transillumination. This must be maintained during the whole procedure and the tip placement carefully controlled at each impact. This allows better targeting of the ciliary body, higher efficacy, and less side effects and complications,” he explained.
In his own experience with transillumination in 168 eyes with refractory glaucoma, Dr. Ezzouhairi applied the transscleral cyclodiode along the entire circumference of the ciliary body avoiding 3 and 9 o’clock as usual in one row in one group and along three parallel rows perpendicular to the circumference in a second group of eyes. The energies used were in a soft mode and without “pop” (1.2 watts maximum for 2 seconds). He found that the second group achieved a better IOP reduction of 57% while the first group achieved 40% IOP reduction. Visual acuity, however, was not significantly different in the two groups. His main complication using cyclodestruction was hypotony of less than 5 mm Hg in both groups, but significantly lower in eyes treated in a three rows mode than those treated in a one row mode.
“Hypotony is the main risk factor for cyclodiode therapy. The rate of hypotony is influenced more by higher energy applied at each application than the total energy delivered or the number of applications used. Furthermore, there is a higher risk for hypotony and worse overall outcomes in patients who undergo multiple sessions. It occurs mainly in complicated or complex refractory glaucoma,” Dr. Ezzouhairi said.

References

1. Nassiri N, et al. Ahmed glaucoma valve and single-plate Molteno implants in treatment of refractory glaucoma: a comparative study. Am J Ophthalmol. 2010;149:893–902.
2. Sarwat S, et al. Glaucoma drainage devices. American Academy of Ophthalmology. EyeWiki. Last updated May 2015.
3. Koh V, et al. Review of the Ahmed versus Baerveldt study–5-year treatment outcomes. Ann Eye Sci. 2017;2:18.

Editors’ note: Dr. Ezzouhairi has no financial interests related to his comments.

Contact information

Ezzouhairi
: ezzouhairis@hotmail.com

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