A National Eye Institute-supported clinical trial reported today that surgery for a potentially blinding condition was ineffective and may be harmful to a person’s vision. Researchers also found that nearly half of those who received no treatment had substantial improvement in their eyesight after just six months.
Based on these results, published today in the Journal of the American Medical Association, the researchers recommended that doctors stop performing the procedure for nonarteritic ischemic optic neuropathy (NAION). It is estimated that doctors perform well over a thousand of these operations, called optic nerve decompression surgery, for NAION each year in the United States.
“These findings indicate that decompression surgery is not an appropriate treatment for NAION,” said Shalom Kelman, M.D., a neuro-ophthalmologist at the University of Maryland at Baltimore and chairman of this study. “It was neither safe nor effective in the study.”
Today’s findings could save between 30 and 60 million dollars annually in reduced health care costs. “These results highlight the necessity of conducting clinical investigations on currently available treatments, such as decompression surgery, that have not been adequately evaluated,” said Carl Kupfer, M.D., National Eye Institute director.
NAION is thought to be the most common cause of sudden visual loss in older Americans. It is estimated to affect as many as 6,000 people annually. The condition results from a painless swelling of the optic disc (where the retina and optic nerve meet) that causes a rapid reduction in vision.
NAION had been long considered an untreatable condition. But in 1989, a small study suggested that relieving pressure on the optic nerve, called decompression surgery, helped to improve vision in those whose sight was progressively worsening. A few small followup studies seemed to support this hypothesis.
As decompression surgery became more popular for NAION, many practitioners said that the procedure needed more scientifically rigorous testing. In 1992, the National Eye Institute launched the Ischemic Optic Neuropathy Decompression Trial (IONDT), a randomized controlled clinical trial to compare the safety and efficacy of decompression surgery plus careful followup versus careful followup alone.
Although the IONDT was designed to run for several more years, its preliminary results showed that decompression surgery was clearly not beneficial for patients:
- At six months of followup, 43 percent of careful followup patients improved three or more lines of vision (using the New York Lighthouse chart). In the surgery group, 33 percent had a three-line improvement in their vision over the same followup period. Thus, surgery has no positive effect on outcome compared to careful followup.
- Twelve percent of eyes in careful followup lost three or more lines of vision at six months, compared to 24 percent in the surgical group. This suggests that decompression surgery may be harmful.
- The IONDT’s finding that 43 percent of careful followup patients had spontaneous improvement of three or more lines in their vision (See Bullet 1) is much higher than previously reported. Most of the earlier studies had indicated a spontaneous improvement rate of ten percent or less.
- No beneficial surgical effect on visual acuity was seen in patients with progressive visual loss.
Optic nerve decompression surgery is also performed for some other conditions such as pseudotumor cerebri, a condition of increased pressure on the brain that may lead to visual loss. But Dr. Kelman stressed that today’s results apply only for NAION.
Because of these early findings, the study’s Data and Safety Monitoring Committee recommended in October 1994 that the treatment protocol be suspended, and that study investigators be notified of the findings. The Data and Safety Monitoring Committee is an independent advisory group comprised of physicians, biostatisticians, and ethicists that oversees the conduct of the clinical trial.
The National Eye Institute also issued a clinical alert to more than 25,000 ophthalmologists and neurologists nationwide prior to journal publication of the findings.
The National Eye Institute, part of the National Institutes of Health, is the Federal government’s lead agency for vision research, and supports more than 75 percent of vision research conducted in the United States.
The Ischemic Optic Neuropathy Decompression Trial (IONDT) is a randomized, controlled clinical trial to assess the safety and effectiveness of optic nerve decompression surgery for non-arteritic ischemic optic neuropathy (NAION). The study is headquartered at the University of Maryland at Baltimore and is being conducted at 25 clinics nationwide.
As of September 1994, the study had outcome data from 244 patients. These patients had: (1) been diagnosed as having NAION by IONDT neuro-ophthalmologists, (2) best corrected visual acuity of 20/64 or worse in affected eye, (3) swelling of the optic disc, where the retina and optic nerve meet, and (4) a loss of side vision typical of NAION.
Patients were randomly assigned to one of two groups:
- Surgery: There were 119 patients assigned to optic nerve decompression surgery and followed at least 6 months.
- Careful Followup: There were 125 people assigned to have periodic followup examinations and followed at least 6 months. No treatment was given.
After randomization, patients in both groups received followup examinations at one week, one month, three months, six months, and one year.
Decompression surgery was standardized in the study to provide the most reliable data on the procedure. It consists of making two or more slits in the membrane that surrounds the optic nerve allowing the escape of cerebrospinal fluid. This reduces pressure on the nerve.
All surgeons were required to have previously performed 10 or more decompression surgeries to participate in the study. Each doctor’s surgical ability was also carefully reviewed by the IONDT’s Surgical Quality Assurance Committee.
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- Optic Nerve Decompression Surgery for Nonarteritic Anterior Ischemic Optic Neuropathy (NAION) Is Not Effective and May Be Harmful. The Ischemic Optic Neuropathy Decompression Trial Research Group. JAMA. 1995 Feb 22. PubMed