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Glaucoma specialists discuss the use of laser peripheral iridotomy and lens extraction as surgical intervention for chronic angle closure.
Glaucoma experts discuss the use of laser peripheral iridotomy and lens extraction as surgical intervention for chronic angle closure.
By Cheryl Guttman Krader; Reviewed by H. George Tanaka, MD, and Steven D. Vold, MD
However, lens extraction can also open the drainage angle-and depending on individual circumstances-it may be considered as the first-line of surgical intervention whether or not the patient has a significant cataract, according to H. George Tanaka, MD, and Steven D. Vold, MD.
Both glaucoma specialists considered lens extraction a good choice for a patient with an occludable angle who has a visually significant cataract. However, it can also be appropriate for an angle closure patient with minimal to no lens changes who has good visual acuity, but may be a candidate for a presbyopia-correcting IOL in a refractive lens exchange procedure.
“In light of recent advances in cataract surgery, I find myself performing fewer iridotomies for angle closure now than in the past,” said Dr. Vold, private practice, Fayetteville, AR. “These patients are often good candidates for multifocal lenses. Removing the lens may help prevent the development of angle-closure glaucoma and simultaneously correct the patient’s refractive error and improve quality of vision.”
“In a patient who is a presbyopic hyperope with astigmatism and a narrow angle, laser-assisted cataract surgery with corneal arcuate incisions can kill five birds with one stone,” said Dr. Tanaka, private practice, California Pacific Medical Center, Oakland and San Francisco. “It will deepen the angle and improve the patient’s vision by removing their cataract and correcting their spherical error, cylinder, and presbyopia.”
Dr. Vold said he will also consider lens extraction over LPI in patients with brown or relatively thick irides as those patients are prone to a more robust inflammatory reaction after LPI that will increase the risk for peripheral anterior synechiae (PAS) formation.
“To avoid these issues, I might be inclined to perform cataract surgery first in these patients, especially if there is any evidence of cataract,” he said.
Dr. Vold said LPI should generally be avoided if the patient has more than 180° of PAS. Due to a reduced incidence of LPI closure postoperatively, Nd:YAG laser is preferred for the procedure over an argon laser. Although the iridotomy is classically placed between 11 and 1 o’clock, Dr. Vold said he commonly places it temporally since use of a superior site can lead to visual symptoms if the lid bisects the iridotomy.
He recommended treating more peripherally at a site beyond the lens equator, and Dr. Vold emphasized the need to make sure the iridotomy is large enough so that it remains patent.
“The traditional LPI size is 150 to 200 µm, but I personally prefer LPIs of at least 300 µm,” he said.
When performing LPI in a patient with suspected angle closure, he recommended checking IOP several weeks after the procedure and obtaining measurements both before and after dilation to make sure that IOP does not increase after dilation. If the IOP rises, iris plateau syndrome should be considered, Dr. Vold said.
Dr. Tanaka pointed out that there is no good evidence from randomized clinical trials to guide decisions on treatment of patients with angle closure, both in terms of identifying who should be treated and how.
The Effectiveness in Angle Closure Glaucoma of Lens Extraction (EAGLE) study, a prospective, randomized clinical trial now under way in the United Kingdom and Asia, will compare the relative safety and effectiveness of LPI to lens extraction for patients with newly diagnosed primary angle closure glaucoma (PACG).
However, there remains a need for a narrow angle equivalent of the Ocular Hypertension Treatment Study (OHTS) to help inform management decisions on patients who only have narrow angles, Dr. Tanaka said.
“Prior to OHTS, any patient with elevated IOP would be started on topical treatment,” he said. “However, that probably represented overtreatment since only a small minority of patients with ocular hypertension goes on to develop glaucoma. Based on the findings of OHTS and other studies, we can now target patients who should be treated based on individual risk.
“Similarly, we know that not everyone with narrow angles gets into trouble, and there are risks associated with our surgical interventions for angle closure,” Dr. Tanaka continued. “On the other hand, we also know that angle closure is a progressive process that becomes irreversible at a certain point.”
Therefore, clinicians need some method to identify people at significant risk for progression so that they can be appropriately treated and hopefully prevented from developing glaucoma and even blindness from glaucoma, he said.
In deciding about management for patients with angle closure, Dr. Tanaka encouraged clinicians to use the current staging system for angle-closure disease that divides the condition into primary angle-closure suspect (PACS), primary angle closure (PAC), and primary angle-closure glaucoma (PACG).
PACS is defined by presence of an anatomically narrow angle with a normal IOP and optic disc. With PAC there is evidence of trabecular meshwork compromise. This abnormality can be structural in the form of peripheral anterior synechiae (PAS) and/or functional as manifested by elevated IOP. PACG is diagnosed if patients have developed glaucomatous cupping of the optic nerve.
Dr. Tanaka said he feels comfortable with observing a patient with PACS who has no positive family history of glaucoma blindness. However, he will perform LPI if the patient has any symptoms consistent with intermittent angle closure, has elevated IOP, or has suspicious optic nerve changes.
If the angle remains narrow after LPI, he would not perform lens extraction in a patient with no or minimal cataract unless the patient has evidence of trabecular meshwork dysfunction, a history of symptoms suggestive of intermittent angle closure, a history of systemic medications that can precipitate angle closure, or a need for routine dilated eye examination (e.g., because the patient has diabetes or has existing retinal disease), or does not have reliable access to eye care.
“In those special circumstances, it is reasonable to take out the lens,” Dr. Tanaka said. “However, we will have better answers on the role of lens extraction based on the results of the EAGLE trial.”
H. George Tanaka, MD
Dr. Tanaka is a speaker for Alcon Laboratories, Allergan, and Merck.
Steven D. Vold, MD
Dr. Vold is a consultant for Alcon Laboratories, Carl Zeiss Meditec, and TrueVision Systems, and receives research support from Calhoun Vision.
This article was adapted from a presentation by Dr. Tanaka and Dr. Volk during Glaucoma Day at the 2014 meeting of the American Society of Cataract and Refractive Surgery.