Vitreous traction release considered as treatment for NAION

Tehran, Iran-Hypothesizing that vitreous traction on the optic nerve head may have a role in the pathogenesis of nonarteritic anterior ischemic optic neuropathy (NAION), physicians in Iran performed a small, preliminary study of a new treatment in which vitrectomy was performed to release the traction.

Mehdi Modarres, MD, professor of ophthalmology, Iran University of Medical Sciences, Tehran, reported that postoperative visual acuity significantly improved in 13 of 16 eyes in which this procedure was performed.

The specific mechanisms of optic nerve injury in NAION remain unclear, Dr. Modarres said. Suggested mechanisms include atherosclerosis, which is often accompanied by hypertension, diabetes, or hyperlipidemia; hypercoagulability; hypotension; cupless disc; or crowded disc.

"None of these treatment modalities has been conclusively proven to be effective, so there is no proven treatment for this problem," he added.

In addition to his university position, Dr. Modarres is a solo practitioner specializing in retina/vitreous surgery.

The rationale for the hypothesis on epipapillary vitreous traction as a causative agent and vitrectomy as a treatment stemmed from a literature search, which found several reports indicating that vitreous traction on the optic disc may cause vitreous elevation, blurring of disc margins, disc hemorrhages, and decreased visual acuity or various combinations of these problems.

While most of the reports involved only one or two patients, a study from Germany included 17 diabetic patients in whom visual acuity decreased and vitreous traction occurred on the disc.

After vitrectomy and the removal of the traction, visual acuity improved in the majority of patients, he said.

"This was a kind of tractional papillopathy, not diabetic papillopathy," Dr. Modarres continued.

Based on these observations, he and his colleagues designed a noncomparative, interventional case series in which 34 patients with NAION were studied. Five already had optic atrophy from NAION in the other eye. Exclusion criteria were the presence of any other concomitant pathology in the optic nerve, optic disc, vitreous, or retina.

Patients underwent a detailed vitreous exam and ocular coherence tomography (OCT-2, Carl Zeiss Meditec).

"There are more advanced versions of this instrument, but this is what we had available," Dr. Modarres commented.

In 17 of 34 eyes, vitreous was separated from the retina but attached to the optic nerve head, meeting the definition of partial posterior vitreous detachment (PVD).

"Partial PVD was presumed to have caused vitreous traction on the disc, compromising the optic nerve function," Dr. Modarres said. "So if such a hypothesis is true and we do vitrectomy and remove the traction, we may be able to improve the vision in these patients."

This course of action was suggested to the 17 patients with partial PVD, and 16 consented, resulting in 16 procedures performed on 16 eyes. During surgery, in all of the cases, formed vitreous was found to be attached to optic nerve head and was removed using suction and surgical instruments.

With at least 3 months of follow-up completed on all patients, visual acuity improved in 13 of 16 eyes (81%). Mean preoperative visual acuity was 20/160, compared with 20/70 postoperatively. This corresponds to four lines of improvement in Snellen acuity, which Dr. Modarres termed "quite encouraging."

Improvements were also noted in visual fields and color perception.

"We conclude that vitreous traction on the optic nerve head may have a causative role in some cases of NAION, and vitreous traction may cause optic nerve swelling and decreased visual acuity by compromising optic nerve circulation and exoplasmic flow," Dr. Modarres said.