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Y.–N. Cheng, G.V. Jirawuthiworavong, F.N. Ross–Cisneros, L. Richine, K.P. Kolostyak, J. Sebag, A.A. Sadun; Anatomical Origins of Blind Spot Enlargement in Pseudopapilledema Associated With Optic Disc Drusen as Determined by OCT . Invest. Ophthalmol. Vis. Sci. 2006;47(13):744.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize the anatomical basis for blind spot enlargement on visual field testing in pseudopapilledema due to optic disc drusen, using optical coherence tomography (OCT).
Radial OCT scans centered on the optic disc were made in 16 eyes of eight subjects with bilateral optic disc drusen visible on red–free fundus photography and confirmed by ancillary testing. Average optic disc diameters were derived from OCT evaluations of the optic discs without compensation for refractive error, axial length, or corneal curvature. Five of the eight participants also underwent automated threshold visual field testing. Optic disc diameters were correlated with visual field defects, specifically blind spot enlargement.
Average optic disc diameter was 2.28 ± 0.29 mm (range, 1.91–2.80 mm), which is 40 % greater than normal (∼ 1.6 mm). This difference cannot be explained by refractive error, axial length, or corneal curvature, since the refractive error of five out of eight participants only ranged from 0 to –1.50 D (mean –0.38 D, s.d.= 0.50 D). The OCT images of the optic disc demonstrated triangular (base against the optic canal) spaces in the peripapillary subretinal areas, which is also seen on histopathology. The amount of blind spot enlargement seemed to correlate with these optic disc extensions.
These results suggest that in pseudopapilledema due to optic disc drusen, blind spot enlargement is due to peripapillary retinal traction resulting from anterior displacement of the optic nerve head by the drusen and lateral displacement of the RPE, which also results in OCT measurement of a wider optic nerve.
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