Optic nerve head drusen associated with abnormally small optic discs.

Using Littmann's method for correcting the magnification of central fundus photographs we evaluated the absolute optic disc size in 26 eyes with visible optic nerve head drusen. The optic nerve head area in these eyes (1.79 + -0.50 mm2) was significantly smaller (p less than 0.001) than normal standard values previously determined (2.89 + -0.76 mm2). The drusen were most commonly located and most densely packed at the upper and lower optic disc border. The coefficients of variation of the method's reproducibility were 0.06 for intraobserver and 0.11 for interobserver determination. The abnormally small optic disc indicating an abnormally small optic nerve scleral canal may inhibit by mechanical compression the axonal flow within the optic nerve fibers. This may ultimately lead to drusen formation. Pseudoneuritis also associated with an abnormally small optic disc may be a preceder of acquired optic nerve head drusen.