Ocular refraction and the shadow test . ight are brought to a focus upon the retina. The pupil is contracted. pil is also contracted, an action that occurs with accotnmodation. A simple experiment to detect the act of accommodation in onesown eye inay be made by anyone. Stand before a window having alace curtain before it, let the eyes be eight or ten inches from thecurtain. Look across the street and the mesh of the lace will disap-pear. Without any movement of the head now look at the threads ofthe curtain; when they appear distinctly, the object across the streetwill have becotne so blurred
Ocular refraction and the shadow test . ight are brought to a focus upon the retina. The pupil is contracted. pil is also contracted, an action that occurs with accotnmodation. A simple experiment to detect the act of accommodation in onesown eye inay be made by anyone. Stand before a window having alace curtain before it, let the eyes be eight or ten inches from thecurtain. Look across the street and the mesh of the lace will disap-pear. Without any movement of the head now look at the threads ofthe curtain; when they appear distinctly, the object across the streetwill have becotne so blurred as to be indistinguishable. Why is it that the distant object disappeared when looking at thecurtain, and the mesh of the curtain disapipeared when looking at adistance ? The rays of light from both objects enter the eyes all thetime. Let figure 97 represent the emmetropic eye adjusted for distance,the parallel rays focus upon the retina. The divergent rays from thepoint P, represented by the dotted lines, do not focus upon the retina. An emmetropic eye adapted for distance, the divergent rays represented by dotted lines,form circles of diffusion upon the retina their focus being behind the retina. but at the point P back of it. The rays from the object at P formcircles of diffusion upon the retina and the object does not appeardistinctly.
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Keywords: ., bookcentury1900, bookdecade1900, bookidocularrefrac, bookyear1903
