VISUAL-FIELD DEFECTS IN OPTIC NEURITIS AND ANTERIOR ISCHEMIC OPTIC NEUROPATHY - DISTINCTIVE FEATURES

Background: We analyzed the value of visual field defects in the diffe rential diagnosis of optic neuritis (ON) and non-arteritic anterior is chemic optic neuropathy (AION). Methods: Ninety-nine consecutive patie nts with acute-onset optic neuropathy formed the basis for this study. Compressive and vasculitic neuropathies were excluded. Eighty-six pat ients fulfilled the criteria for either ON (50 patients): less than or equal to 35 years, normal disk, recovery of visual function, or AION (36 patients): greater than or equal to 60 years, swelling of the disk , no recovery of visual function. Without knowledge of other clinical data, visual fields obtained by Goldmann perimetry were classified int o five types of defects (forced choice). With the correct diagnosis at hand, fields were reviewed for characteristic features. Results: Forc ed-choice classification into defect types [%]: Central scotoma ON 68, AION 18; superior altitudinal defect ON 13, AION 7; inferior altitudi nal defect ON 8, AION 52; peripheral defect ON 1, AION 5; diffuse defe ct ON 10, AION 18. Search for pathognomonic defects: a scotoma centere d on the fixation point with a sloping border occurred exclusively in ON (25 of 50 patients). An inferior altitudinal defect with a sharp bo rder along the horizontal meridian, particularly in the nasal peripher y, occurred only in AION (10 of 36 patients). A steep centrocecal scot oma occurred in 3 of the 36 AION cases and not at all in the ON cases. Scotomas in the center breaking through to the periphery, superior al titudinal defects (with a sloping border along the horizontal meridian ) and diffuse depressions verging on blindness occurred in both ON and AION. Conclusion: A scotoma centered on the fixation point with a slo ping border is highly characteristic of ON, while an inferior altitudi nal defect with a sharp border along the horizontal meridian, particul arly in the nasal periphery, is highly characteristic of AION. To iden tify these diagnostic criteria, it can be necessary to examine full fi elds. With restriction of perimetry to 30 degrees a large central scot oma can be mistaken for a diffuse defect and the border in the nasal p eriphery can be missed.