. A treatise on diseases of the eye . zontalmeridian of the field of vision, and as in normal eyes the angle betweenthe plane which passes through the fovea centralis and the nodal Fig. los point of the eye and a similarplane which passes through thecentre of the optic disk is 15 degrees,the centre of the physiologicalblind spot is situated 15 degreesto the temporal side of the verti-cal meridian of the field of blind spot is usually circularand measures about cm. at30 cm. from the cornea. In somecases the outline of the blind spotis slightly oval. The contour ofthe blind sj)ot
. A treatise on diseases of the eye . zontalmeridian of the field of vision, and as in normal eyes the angle betweenthe plane which passes through the fovea centralis and the nodal Fig. los point of the eye and a similarplane which passes through thecentre of the optic disk is 15 degrees,the centre of the physiologicalblind spot is situated 15 degreesto the temporal side of the verti-cal meridian of the field of blind spot is usually circularand measures about cm. at30 cm. from the cornea. In somecases the outline of the blind spotis slightly oval. The contour ofthe blind sj)ot in moderate illumi-nation is not regular; two or threeshort projections marking the pro-longations of the large branches ofthe arteria centralis retina may be determined. The field of vision of the liyjXM-opic eye is greater llian inthe normal eye, and that of the myopic eye is less. With a dilated pupil the field is larger (about 2 degrees) (han i( is witha small pupil. The extent of the field of vision is recorded on charts bearing. -Bine ? Ret Normal extent of color fields. 142 EXAMINATION meridional lines at angles of 15 or 30 degrees and coneentrie lines incircles placed at regular intervals, conventionally marked to representinterval of 10 degrees. Field of Vision for Color.—The visual fields for colors are tested byusing test objects of the approjjriate color. The test object is eithera colored ball 1 cm. in diameter or a colored s(juare of 1 cm. Smalldefects in the color fields are detei mined by the use of a ball or squaremeasuring 5 mm. The mean normal color fields, when determined witha test object of 1 cm. in diameter or of 1 cm. square, are: Outward. Inward. Downward. Upward. For blue 80 45 58 40 For red 05 30 45 33 For green 50 25 30 27 The field for yellow is very similar to that for blue. Although theextent of the fields for color are as represented above when examinedas indicated, it is well known that the fields for the different colors extendalmost, if not
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