Text-book of ophthalmology . [Fig. 398.—Keratoscopic Images in a case of Regular Inverse Javal (from Norris and Oliver). C. reflex, from center of cornea. The reflex is an ellipse with the vertical diameter the , D, H, G, reflexes from outlying portions of the cornea where the astigmatism is more marked andis also slightly irregular.—D.]. [Fig. 399.—Keratoscopic Images in a Case of Irregular Javal (from Norris and Oliver).—D.] 57 898 TEXT-BOOK OF OPHTHALMOLOGY The determination of the corneal astigmatism with the ophthalmometer facili-tates very grea
Text-book of ophthalmology . [Fig. 398.—Keratoscopic Images in a case of Regular Inverse Javal (from Norris and Oliver). C. reflex, from center of cornea. The reflex is an ellipse with the vertical diameter the , D, H, G, reflexes from outlying portions of the cornea where the astigmatism is more marked andis also slightly irregular.—D.]. [Fig. 399.—Keratoscopic Images in a Case of Irregular Javal (from Norris and Oliver).—D.] 57 898 TEXT-BOOK OF OPHTHALMOLOGY The determination of the corneal astigmatism with the ophthalmometer facili-tates very greatly the determination of the total astigmatism present, but does notalone suffice for this purpose; in every case the examination of the eye with glassesmust also be made. For in the first place the ophthalmometer gives only the differencein refraction between the two principal meridians, but not their absolute refraction;it does not tell us whether either one of these meridians is hypermetropic or myopicor to what extent they are so. In the second place the astigmatism that is determinedwith the ophthalmometer does not agree precisely with that which is found with testsby glasses, for the ophthalmometer shows only the astigmatism of the cornea, butthe glasses give the astigmatism of the whole eye (functional As). Yet the differencebetween one kind of
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