Optic nerve head drusen associated with abnormally small optic discs

Abstract

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.

Racial and Ethnic Differences in Ocular Anatomy

“…Also, a smaller optic disc in whites may have some bearing on their higher prevalence of nonarteritic ischemic optic neuropathy and optic disc drusen. 60,61 Mansour 58 also reported very similar neuroretinal rim areas between black and white children. There were no differences between these races.…”

Anterior ischemic optic neuropathy: Nonarteritic form in small and giant cell arteritis in normal sized optic discs

“…They were significantly larger than optic nerve heads with drusen [17] and with pseudopapiUedema [18]. They belong to a spectrum of optic nerve head anomalies and diseases the prevalence of which is correlated to the optic disc size.…”

“…They were significantly smaller (p<0.001) than 457 unselected normal optic discs (2.69 + -0.70mm 2) [13], smaller than 17 so called 'congenital asymptomatic macrodiscs' (4.91+ -0.34ram 2) [10], smaller than 15 optic nerve heads with pits (4.84 + -1.42 mm 2) [11], and smaller than 17 optic discs with 'Morning-GlorySyndrome' (7.47+ -2.63mm 2) [16]. They were significantly larger (p<0.001) than 26 optic nerve heads with drusen (1.79 + -0.50mm 2) [17], and larger than 35 unselected optic discs with pseudopapilledema (1.95 + -0.33 mm 2) [18] ( Table 2). The optic cup and the cup/disc ratios could not be measured due to the optic disc swelling.…”

Racial Variation of Optic Disc Size

“…Still the racial variation should be accounted for in studying the optic nerve head. We anticipate a lower prevalence of optic disc drusen and a lower incidence of nonarteritic ischemic optic neuropathy in blacks as these two enti ties are associated with small optic disc size [25][26][27][28].…”