Friday, October 31, 2008

Neuroopthalmology testing-- bedside pearls

Riddoch's phenomenon-- patient won't see an object in a damaged field unless it is moved.

shading of a visual field-- if larger objects are seen in a damaged field where smaller objects are missed, , suggests defect is partly caused by edema or pressure phenomenon.

Bjerrum screen (tangent screen) enlarges central meridian to 30 degrees and is most helpful for measuring central scotomata and the blind spot.

Graying of vision (finger does not appear flesh colored) or red desaturation (eg. red pin ) is appreciated before a quantifiable field defect.

Notes bitemporal upper quadrantic defect suggests chiasmal compression from above, but bitemporal lower field defect suggests compression from below.

Arcuate defect- optic nerve lesion prechiasmatic.

Bitemporal scotomata-- early bitemporal field defect or consider bilateral optic nerve lesions eg in kids.

Fundoscopic exam
Venous pulsations are seen only in the middle and not the margins of the disk unless there is a large pulse pressure such as in aortic insufficiency. severe hyperthyroidism or arteriovenous fistula.

Miscellaneous findings include commotio retina, an intense light streak seen with acute head injury of Kohlmeyer-Degos disease (arteritis with atrophic skin lesions).

Hemorrhages from papilledema occur off the disk margin (slit hemorrhages) whereas those from venous occlusion occur in the central retina and macula.

Torsten's syndrome is a hemorrhage that moves with head position following a burst aneurysm, also called preretinal or subhyaloid hemorrhage. Often can identify side of hemorrhage based on.

Lupus patients may have "grains of rice" or cytoid bodies in peripheral retina.

Renal patients may have a macular star (edema outlining the nerve sheath layer).

Hollenhorst plaque or branch point occlusion of cholesterol emboli are larger than occluded vessel birefringent and yellow.

Platelet fibrin emboli from HIT are white and multiple.

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