The home medical adviser, a popular work on the treatment of disease . ndthe Retina at f. A Convex Glass (1) is Required to Converge the Rays (Dot-ted Line) so that They Will Focus Exactly on the Retina at r. The retina is the sensitive area for receiving light impressions in theback of the eyeball. Sight is really a brain function; one sees withthe brain, since the optic nerve endings in the back of the eye (retina)merely carry light impressions to the brain where they are properlyinterpreted. In order that vision be clear and perfect, it is essential that therays of light enter-ing the eye b
The home medical adviser, a popular work on the treatment of disease . ndthe Retina at f. A Convex Glass (1) is Required to Converge the Rays (Dot-ted Line) so that They Will Focus Exactly on the Retina at r. The retina is the sensitive area for receiving light impressions in theback of the eyeball. Sight is really a brain function; one sees withthe brain, since the optic nerve endings in the back of the eye (retina)merely carry light impressions to the brain where they are properlyinterpreted. In order that vision be clear and perfect, it is essential that therays of light enter-ing the eye be bentso that they strikethe retina as a singlepoint (Fig. 67). Inthe farsighted orhyperopic eye, theeyeball is usually tooshort for the rays tobe properly focused on the sensitive nerve area in the back of theeye. A farsighted eye is one smaller than it should be—an undevel-oped eye. Parallel rays from distant objections are focused betterthan converging rays from near objects as shown in Figure 68,where h. h. are the parallel rays, and N rays from a near Fig. 67. -Focusing of Light Rays in a Normal(Emmetropic) Eye. 694 THE EYE AND EAE This defect in vision is, however, overcome by the act of accom-modation. There is a beautiful transparent, double-convex body, N-~V
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishernewyorkandlondonda
