Transactions . t an infinite distance from the eye. When they reachit, they are practically parallel. Let O represent the dioptricsystem of three eyes, one hyperopic. one emmetropic and onemyopic. Let R, R, and R represent the positions of theretinas of the respective eyes. The focus falling on R, therewill be no circle in the emmetropic eye, but there will be onR and R, and if they are at the same distance in front ofand behind R respectively, the circles formed will have thesame diameter. But in the hyperopic eye there will be an ef-fort of accommodation, whereas in the myopic eye there will
Transactions . t an infinite distance from the eye. When they reachit, they are practically parallel. Let O represent the dioptricsystem of three eyes, one hyperopic. one emmetropic and onemyopic. Let R, R, and R represent the positions of theretinas of the respective eyes. The focus falling on R, therewill be no circle in the emmetropic eye, but there will be onR and R, and if they are at the same distance in front ofand behind R respectively, the circles formed will have thesame diameter. But in the hyperopic eye there will be an ef-fort of accommodation, whereas in the myopic eye there willbe none. Of course, these circles are very small, but theyexist in the nonaccommodating eye, and may be graphicallyrepresented by connecting the various points formed by theintersection of the retina by the rays coming from any onepoint on the surface of the object. At the same time theseintersected rays impinge upon and stimulate a certain numberof retinal nervous elements, as shown by the following Fig. 4 Let BT and DT be two refracted rays from a point on anobject situated at an infinite distance from a hyperopic eye,whose retina, R R is intersected at the points L and L. LetBM and DM be two refracted ravs from an object at an infinite 117 distance from a myo|)ic eye, whose retina, S S, is intersectedat the points M and M, after the rays have passed beyond thefocal point of tlie dioptric system of the eye. Let L L equalM M. Let G and G be respectively the retinal elementstraversed by the rays of the respective eyes. If these dia-grams are compared, it will be seen that there are two distinctdifferences in the relation of the rays to the retinal elementsin the two eyes. In the first place the number of elementstraversed by the rays in the hyperopic eye is apparentlygreater than that in the myopic eye. If the object were veryclose to the hyperopic eye, or if the myopia were verylow, this factor might enter into the problem. But as a matter of fact, the numbers of e
Size: 2794px × 894px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectophthalmology, bookye
