Q: A patient presented to an optometric referral center with a diagnosis of open-angle glaucoma, which was being treated with a prostaglandin and a beta-blocker. But because the IOP had not improved, the patient was referred for selective laser trabeculoplasty (SLT). Is anything amiss about this approach? Should any other tests be done?
A: “Yes, there is something wrong with this picture,” says Howell Findley, O.D., of Commonwealth Eye Surgery, a comanagement and ocular surgery center in Lexington, Ky. “Further evaluation is necessary before subjecting the patient to surgery. Specifically, why is the IOP not responding to conventional therapy?”
The answer: Take a look at the angle.
“Appropriate treatment of glaucoma requires accurate assessment of the anterior chamber angle,” Dr. Findley says. “Gonioscopy is an essential, but often overlooked, part of glaucoma management. I’ll bet you that this patient has a closed angle, but did not have gonioscopy performed.”
In acute angle closure, the classic symptoms—steamy vision with halos around lights, a red, painful eye, mid-dilated pupil, markedly elevated IOP, and sometimes nausea and vomiting—are easy to identify, Dr. Findley says.
“However, if the angle closes gradually, your patient may remain asymptomatic. Intermittent angle closure and chronic angle closure are not uncommon conditions. These patients may even present with IOP in the normal range and a clear cornea,” he says.
Slit lamp estimation may or may not reveal a narrow angle, so you can’t rely on it alone. “The only way to know the status of the drainage system is to visualize it directly, which requires gonioscopy,” Dr. Findley says.
Slit lamp exam (left)
shows a narrow angle, which should prompt you to perform gonioscopy.
However, subsequent gonioscopy (right) revealed a nearly closed angle
with only a small area of trabecular meshwork visible on either side.
Gonioscopy is an easily learned procedure, he says. “I recommend a four-mirror lens that uses the tear film as an interface (e.g., Zeiss, Posner or Sussman). Have adequate support for the gonio lens on the patient’s eye—hold the handle or the body of the gonio lens with the thumb and forefinger, while the ring finger and pinkie anchor onto the slit lamp or touch the patient’s cheek. Support for the elbow is also very helpful in maintaining steady contact with the eye,” Dr. Findley says.
Unlike an acute angle-closure attack, which is first treated medically, chronic angle-closure glaucoma is treated primarily by laser peripheral iridotomy (LPI).
“But if treatment is delayed, the angle may remain permanently closed and require a filtering procedure. Post-LPI, some patients may still require continued use of glaucoma medications,” he says.
If the patient has a visually-significant cataract, removal of the crystalline lens may achieve the dual purpose of improving vision and deepening the angle. “Consider this option rather than LPI if the angle does not appear to be in imminent danger of closure,” Dr. Findley says.
In this patient’s case, the slit lamp exam showed what appeared to be a narrow angle, and gonioscopy confirmed that the angle was actually closed 360°. The angle remained closed after LPI.
The patient was scheduled for a surgical consult with a glaucoma subspecialist.
