A comparison of risk factors for postoperative and spontaneous nonarteritic anterior ischemic optic neuropathy

Background: Whether postoperative non-arteritic ischemic optic neuropathy (NAION) is caused by surgery is unsettled. To provide further evidence on this issue, it is useful to compare the characteristics of patients who develop NAION following intraocular surgery to those who develop NAION spontaneously. Methods: In a retrospective review of patients diagnosed with NAION between January 1, 1993 and December 31, 1999, 12 cases of NAION in 11 subjects were identified as occurring within 30 days of cataract extraction or intraocular lens exchange (postoperative NAION group). Using Fisher exact test, the prevalence of NAION risk factors (hypertension, diabetes mellitus, hypercholesterolemia, smoking, small cup-to-disc ratios) was compared with that of a similarly aged control group of 37 subjects diagnosed with spontaneous NAION (spontaneous NAION group). Results: Patients with postoperative NAION had a lower prevalence of hypertension than did those with spontaneous NAION (27% versus 68%, P = 0.034) and a lower prevalence of cup-to-disc ratios of less than or equal to 0.2 (55% vs. 94%, P = 0.006). The prevalence of elevated cholesterol, diabetes mellitus, and tobacco use was similar in the two groups. Conclusions: The prevalence of hypertension and low cup-to-disc ratios is significantly lower in subjects with NAION following lens-related intraocular surgery than in those with spontaneous NAION, indicating that risk factors for NAION in these settings may be different.