Incipient nonarteritic anterior ischemic optic neuropathy.

OBJECTIVE To describe the clinical entity of incipient nonarteritic anterior ischemic optic neuropathy (NAION). DESIGN Cohort study. PARTICIPANTS Fifty-four patients (60 eyes) seen in our clinic from 1973 through 2000. METHODS At their first visit to our clinic, all patients gave a detailed ophthalmic and medical history and underwent a comprehensive ophthalmic evaluation, color fundus photography, and fluorescein fundus angiography. At each follow-up visit (of 49 patients [55 eyes]), the same ophthalmic evaluation was performed, except for fluorescein fundus angiography. MAIN OUTCOME MEASURES Clinical features of incipient NAION. RESULTS Mean age (+/- standard deviation) of the patients was 58.7+/-15.9 years. Median follow-up time was 6.3 years (interquartile range [IQR], 2.1-8.5). At initial visit, all had optic disc edema (ODE) without any visual loss attributable to NAION. In 55%, the fellow eye had classic NAION; in 25%, incipient progressed to classic NAION (after a median time of 5.8 weeks [IQR, 3.2-10.1]); and in 20%, classic NAION developed after resolution of the first episode of incipient NAION. Patients with incipient, compared with classic, NAION had a greater prevalence of diabetes mellitus (P<0.0001) and lower prevalence of ischemic heart disease (P = 0.046). Patients who progressed to classic NAION versus those who did not were significantly younger (P = 0.025), and their visual acuity worsened in 31% and 0%, respectively, and remained stable in 62% and 98%, respectively; in the eyes with progression, central (in 31%) and peripheral (in 77%) visual fields worsened compared with only 1 eye and 2 eyes, respectively, that did not (P = 0.01 and P<0.0001, respectively); and median time to resolution of ODE in the progressed group was 5.8 weeks (IQR, 4.6-8.7) versus 9.6 weeks (IQR, 6.0-17.7) in those who did not progress. CONCLUSIONS The results show that incipient NAION is a distinct clinical entity, with asymptomatic ODE and no visual loss attributable to NAION. When a patient seeks treatment with asymptomatic ODE, incipient NAION must be borne in mind as a strong possibility in those who have had classic NAION in the fellow eye, in diabetics of all ages, and in those with high risk factors for NAION; this can avoid unnecessary and expensive investigations.