Table 3. Summary of studies evaluating secondary prevention of NAION in the fellow eye.

Author, year (reference)	§ Level of evidence	Number of patients	Type of study	Treatment (dose)	Frequency of NAION in the fellow eye	p value
Beck, 1997 (7)	III	153 treated 278 untreated	Retrospective	Aspirin	At 2 years: 7% of treated,15% of untreated At 5 years: 17% of treated, 20% of untreated	p=0.22
Kupersmith, 1997 (57)	III	57 treated 43 untreated	Retrospective	Aspirin (65-1300 mg)	At 2 years: 17.5% of 57 treated, 53.5% of 16 untreated	p=0.01
Salomon, 1999 (76)	III	36 treated 16 untreated	Retrospective	Aspirin (100 - 325 mg)	22.2% of 36 treated, 50% of 16 untreated	N/A
IONDT, 2002 (70)	III	At baseline: 87 treated 237 untreated After baseline: 86 treated 131 untreated	Retrospective*	Aspirin	** Aspirin at baseline: 20% of 87 treated, 13% of 237 untreated *** Aspirin after baseline:15% of 86 treated, 15% of 131 untreated	p=0.25 p=0.65

^*Although the IONDT was a prospective trial to evaluate optic nerve sheath decompression, it was not a prospective trial to evaluate aspirin therapy. Aspirin data are observational only.

^**Reported starting regular aspirin use at least 1 month before onset of symptoms at baseline visit.

^***Responded positively to ‘started regular use’ of aspirin on at least one study visit after baseline.