Objective: To describe visual acuity outcomes of patients in the Ischemic O
ptic Neuropathy Decompression Trial (IONDT) after 24 months of follow-up.
Design: The IONDT is a single-masked, multicenter, randomized clinical tria
Settings: Patients were evaluated and followed up at 25 clinical centers lo
cated throughout the United States. Data were sent to and analyzed at a cen
tral coordinating center.
Patients: Two hundred fifty-eight patients SO years or older with nonarteri
tic anterior ischemic optic neuropathy and visual acuity of 20/64 or worse,
but better than no light perception, were randomized to either a careful f
ollow-up group (n=131) or an optic nerve decompression surgery (ONDS) group
(n=127). Of these, 174 continued participation for at least 24 months, 89
in the careful follow-up group and 85 in the ONDS group.
Methods: Randomized patients underwent a standard visual acuity examination
at 3, 6, 12, 18, and 24 months of follow-up. The primary outcome was a cha
nge of 3 lines or more of visual acuity, defined as a difference of 0.3 in
logMAR scores, between baseline and 6 months of followup. A secondary outco
me was mean change in visual acuity (in logMAR units) at 3, 6, 12, 18, and
24 months following baseline. These changes were estimated using available
data from all randomized patients for whom we had data.
Results: Of the 258 patients randomized, 143 (55.4%) were male, and 169 (65
.5%) were 65 years or older. Mean visual acuity was statistically significa
ntly improved from baseline value at all study visits and for both treatmen
t groups, although visual acuity declined gradually in both groups after th
e 3-month visit. There were no significant differences between careful foll
ow-up and ONDS in mean change in vision from the baseline and any follow-up
time point. At 24 months of follow-up, 31.0% of patients in the careful fo
llow-up group and 29.4% of patients in the ONDS group experienced an increa
se of 3 or more lines of vision compared with baseline acuity; 21.8% of pat
ients in the careful follow-up group and 20.0% of patients in the ONDS grou
p experienced a decrease of 3 or more lines. In patients who could read at
least 1 letter on the Lighthouse chart, there wets a gradual decline in mea
n visual acuity noted over time for both treatment groups, although acuity
remained significantly better than at baseline.
Conclusion: Analysis of visual acuity data from patients enrolled in the IO
NDT at 24 months of follow-up confirms that there is no benefit of ONDS com
pared with careful follow-up in patients with nonarteritic anterior ischemi
c optic neuropathy.