Ocular refraction and the shadow test . ye is myopic this may be done without interposing anylenses whatever. If the eye is not myopic, the myopic condition maybe created by interposing the necessary lens or lenses, to locate theartificial far point at a definite distance. TJiis definite distance from the eye under observation, ivhich theoperator selects, is called the working distance. The proper working distance in retinoscopy has been the subjectof much discussion and diversitv of opinion, which tends to confusethe student. If the meaning of the term is thoroughly understood itneed not be p
Ocular refraction and the shadow test . ye is myopic this may be done without interposing anylenses whatever. If the eye is not myopic, the myopic condition maybe created by interposing the necessary lens or lenses, to locate theartificial far point at a definite distance. TJiis definite distance from the eye under observation, ivhich theoperator selects, is called the working distance. The proper working distance in retinoscopy has been the subjectof much discussion and diversitv of opinion, which tends to confusethe student. If the meaning of the term is thoroughly understood itneed not be perplexing. In the majority of cases it will be found that a working distanceof forty inches, which is equal to one metre, will be most convenientIt will simplify the matter of making allowance for the working dis-tance because forty inches is equal to the focus of a one dioptre is conveniently near to the patient, so that lenses may be chang-ed in the trial frame by the operator without leaving his position. OCULAR A C T I O Figure It is sufficiently far away to enable the operator to note the slight-changes in the appearance of the reflex as the reversal point is neared. R E T I N O S C O P Y. I6i If the pupil is small, as frequently occurs with elderly people; orthe reflex is dull and indistinct, which may be due to a high degree oferror of refraction or a dense retinal pigment, a nearer point thanforty inches may have to be selected, for the working distance. These points will be more fully explained in describing actualpractice. Fortunately the introduction of the luminous retinoscope, seefigure 128, carrying its own source of light, simplifies the workingconditions and affords the refractionist ample freedom to choose anyworking distance best suited to the case in hand. The position ofthe light source may be ignored because it is always under intensity of the light may be regulated, and increased to suchbrilliancy that a reflex may be obtained under
Size: 970px × 2577px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookidocularrefrac, bookyear1903
