Surgery to improve vision in people with nonarteritic anterior ischemic optic neuropathy (NAION)

Review question
This review looked at the evidence about the safety and effectiveness of surgery (optic nerve decompression surgery) compared with no treatment on the vision of people with nonarteritic anterior ischemic optic neuropathy (NAION).

Background
NAION is a sudden and painless loss of vision in the eye attributed to swelling of the area inside the eye where the optic nerve connects to it. The swelling of the tissue puts pressure on the optic nerve, and it is believed that this pressure interrupts the blood supply to the optic nerve, causing loss of vision. The cause of NAION is not known. No treatment has been proven to help.

A proposed treatment for NAION is called optic nerve decompression surgery. This surgery makes two slits or a window in the swollen eye tissue surrounding the optic nerve. These slits allow fluid building up around the optic nerve to escape. The hope is that this would reduce the pressure on the optic nerve and vision would improve.

Study characteristics
The search for studies was done on 23 October 2014. One study (a randomized controlled trial) was found. There were 258 participants in the trial. These 258 people were randomly divided into two groups. One group received the optic nerve decompression surgery along with careful follow-up. The other group received careful follow-up alone. Careful follow-up included an ophthalmologic examination at each study visit and visual field testing at 12 months and as needed. The technician performing the follow-up tests did not know to which group the participants belonged (surgery or no surgery). Funding for this trial was provided by National Eye Institute, USA.

Key results
The trial was stopped early because the surgery was not helping the participants more than careful follow-up alone. The trial found no evidence of benefit from the surgery, but there were several harms caused by the surgery, such as further vision loss. Pain and double vision were harms experienced by some participants in the surgery group at one week after the surgery. The trial investigators reported that continued enrollment would be unlikely to produce results in favor of surgery.

Quality of the evidence
The quality of evidence in this one trial is considered high.

Authors' conclusions: 

The only eligible trial provided no evidence of a beneficial effect of optic nerve decompression surgery for NAION. Future research should focus on increasing our understanding of the etiology and prognosis of NAION. New treatment options should be examined in the context of randomized clinical trials.

Read the full abstract...
Background: 

Nonarteritic anterior ischemic optic neuropathy (NAION) is characterized by sudden and painless loss of vision in the eye, accompanied by pallid swelling of the optic disc. Its etiology is unknown and no medical therapy has been proven effective in treating this condition. Optic nerve decompression surgery, a proposed treatment for NAION, involves making two or more slits or a window in the tissue surrounding the optic nerve, thereby allowing cerebrospinal fluid to escape, and theoretically reducing the pressure surrounding the optic nerve.

Objectives: 

The objective of this review was to assess the safety and efficacy of surgery compared with other treatment or no treatment in people with NAION.

Search strategy: 

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2014, Issue 10), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to October 2014), EMBASE (January 1980 to October 2014), PubMed (1948 to October 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). There were no date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 23 October 2014.

Selection criteria: 

All randomized trials of surgical treatment of NAION were eligible for inclusion in this review.

Data collection and analysis: 

From full-text copies of all reports from relevant trials, one author extracted data which were verified by another author. No data synthesis was required.

Main results: 

The one included trial, in which 258 participants were randomized, was stopped early for futility. At the time of the 24-month report the follow-up rate was 95.3% for six months and 67.4% for 24 months (174 participants; 89 careful follow-up and 85 surgery). There was no evidence of a benefit of surgery on visual acuity. Measurements of visual acuity and visual fields were performed by a technician masked to the treatment received. At six months 32.0% of the surgery group had improved visual acuity by 3 or more lines compared with 42.6% of the careful follow-up group (unadjusted risk ratio (RR) 0.75, 95% confidence interval (CI) 0.54 to 1.04). At 24 months 29.4% of the surgery group had improved compared with 31.0% of the careful follow-up group (unadjusted RR 0.95, 95% CI 0.60 to 1.49). Participants who underwent surgery more often lost 3 or more lines of visual acuity in the study eye, although the increased risk was not statistically significant. At six months 18.9% in the surgery group had worsened visual acuity in the study eye compared with 14.8% in the careful follow-up group (RR 1.28; 95% CI 0.73 to 2.24). At 24 months 20.0% in the surgery group had worsened visual acuity in the study eye compared with 21.8% in the careful follow-up group (RR 0.92; 95% CI 0.51 to 1.64). Participants who received surgery experienced both intraoperative and postoperative adverse events, including central retinal artery occlusion during surgery and light perception vision at six months (one participant); and immediate loss of light perception following surgery and loss of vision that persisted to the 12-month visit (two participants). In the careful follow-up group, two participants had no light perception at the six-month follow-up visit; one of these had improved to light perception at 12 months. Pain was the most common adverse event in the surgery group (17% in surgery group versus 3% in the careful follow-up group at one week). Diplopia (double vision) was the next most common complication (8% in the surgery group versus 1% in the careful follow-up group at one week); at three months there was no statistically significant difference in proportion of participants with diplopia between the two groups.

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