Pre-existing glaucoma poses considerations for corneal procedures

Patients with pre-existing glaucoma require special consideration before performing a corneal procedure.

Reviewed by Peter A. Netland, MD, PhD

Charlottesville, VA-Patients with pre-existing glaucoma are at high-risk for elevated IOP after a corneal surgery and require special considerations preoperatively to avoid potential disasters.

Peter A. Netland, MD, PhD, presented various surgical options and the optimal order in which they should be performed to achieve the maximal visual outcomes for these patients.

He described the case of a patient who had pre-existing glaucoma and who developed elevated IOP and lost vision after Descemets stripping endothelial keratoplasty (DSEK) performed in the left eye. The treatment was implantation of a glaucoma filtration device (EX-PRESS, Alcon Surgical) under a partial-thickness scleral flap. The patient then needed corneal surgery in the right eye and planning glaucoma therapy in that eye was important to avoid decreased vision as occurred in the fellow eye.

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Pre-existing glaucoma is a risk factor for elevated IOP and secondary glaucoma after both penetrating keratoplasty (PK) and DSEK.

“In patients who do not have pre-existing glaucoma, about 20% develop increased IOP,” said Dr. Netland, the Vernah Scott Moyston Professor and Chair, Department of Ophthalmology, University of Virginia School of Medicine, Charlottesville, VA.

“However, in patients who have pre-existing glaucoma, 55% develop increased IOP.”

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A number of factors can be involved in the elevated IOP after PK, according to Dr. Netland. These include peripheral anterior synechiae formation and angle closure, a distorted anterior chamber angle and trabecular meshwork, pupillary block, a steroid response, iritis, and malignant glaucoma.

However, the major factor in elevated IOP after DSEK is likely to be a steroid response.

“These patients generally develop an open-angle glaucoma usually 1 to 3 months after DSEK is performed,” he said. “Most patients are treated medically, but some need surgery, especially those with pre-existing glaucoma.”

Glaucoma surgical procedures

When planning glaucoma surgical procedures in patients undergoing a cornea procedure, the literature shows that most patients are treated with trabeculectomy with mitomycin C (MMC) or an EX-PRESS device is implanted under a partial-thickness scleral flap with MMC. Glaucoma drainage implants are another option.

However, the placement of the tube has come under increased scrutiny, with discussions of placement in the anterior chamber, ciliary sulcus, or pars plana. Cyclophotocoagulation had been used as an early treatment option, but compared with trabeculectomy and drainage implants, the procedure is associated with early graft failure, poor IOP control, and visual loss, Dr. Netland commented.

Surgeons have the option of performing staged surgeries, that is, a corneal procedure followed by a glaucoma procedure or vice versa, or combined simultaneous surgeries.

“Staged surgery is commonly performed with the corneal surgery first followed by the glaucoma surgery, which may be an option in patients with early-stage glaucoma,” he said. “In the case under discussion, however, visual loss had occurred in the fellow eye when that approach was used.”

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When the glaucoma surgery is performed first and DSEK or PK follows, trabeculectomy or implantation of the EX-PRESS device under a scleral flap is a good surgical choice in a high-risk patient with pre-existing glaucoma when a low target IOP is desired.

Glaucoma drainage devices are also suitable options, especially if the patient is considering wearing contact lenses and a bleb is not an option.

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“When these surgeries are performed with DSEK, there is very little or no increased risk of intraoperative or early postoperative complications,” Dr. Netland said.

Combined surgery is rarely performed with DSEK because of issues associated with the air bubble in DSEK, but combined surgery has been reported, although uncommonly, for deep sclerectomy with DSEK.

Combined surgery with PK

Combined surgery with PK is an option.

“The outcomes for IOP control and maintaining a clear graft are as good or better after glaucoma surgery and PK combined compared with staged procedures,” Dr. Netland commented.

However, he also pointed out that the long-term IOP control after a combined PK and glaucoma surgery may not be comparable to that after trabeculectomy alone but compared with staged surgery, it can be a good choice.

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Dr. Netland concluded that high-risk patients, those with pre-existing glaucoma, may require surgical glaucoma treatment in many cases before the corneal surgery. This usually includes a trabeculectomy or an EX-PRESS implant with MMC, or a glaucoma drainage device.

A staged surgery may be performed with Descemets membrane endothelial keratoplasty, DSEK, or PK. A combined procedure may be performed with glaucoma surgery and PK, and perhaps in the future also with MIGS and the other corneal procedures. The management is affected by the individual patient factors.

In the case under discussion, in which the patient had vision loss after DSEK in the left eye, a staged surgery with trabeculectomy or an EX-PRESS implant under a partial-thickness scleral flap in the right eye would be the recommendation before the corneal surgery.

He also advised consultant with a corneal specialist before undertaking any high-risk patients.

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Peter A. Netland, MD, PhD

E: pnetland@gmail.com

Dr. Netland has no financial interest in the subject matter.