Bjerrum Method

Bjerrum Method (Bjerrum), represents an improved method for examining the visual field on a plane—kinetic perimetry; applied for central and paracentral visual field defects. The examination is performed on a black curtain from a distance of 1 or 2 m using small objects—white ivory balls with a diameter of ^x/g ^mm > 1, 2 and 5 mm. The use of such small objects and the increased distance from the object to the examined eye leads to an extreme reduction in the visual angle at which the object is perceived. The ordinary method of perimetry consists of examining the visual field with an object visible at an angle of 3°48'37" (an object 20 sq. mm from a distance of 35 cm); when using the Bjerrum method, however, the visual angle of the moving object is reduced to 1'45" (an object 1 sq. mm from a distance of 2 m), which achieves greater precision in the examination. At present, the original Bjerrum method is not usually used, but the modification introduced by Seidel, which consists of performing the examination not on a curtain but on a matte black board, on which the boundaries of the detected visual field defect are marked with chalk. To transfer the obtained results to a card, the method proposed by Samoylov for outlining the boundaries of visual field defects in a tenfold reduced form on the matte glass of a photographic apparatus is applied.