. Refraction and motility of the eye, with chapters on color blindness and the field of vision . strength to2D., though the patient says he can see a trifle clearer with+ As the strength of the cylinder increases, thepatient becomes more intolerant of any deviation from theaxis 90°. The use of this cylinder corrects a large part ofthe astigmatism and enables him by accommodating about3 D. to focus both the horizontal and vertical strokes sonearly together on his retina as to improve his vision up to ASTIGMATISM. 187 possibly 20/30. If now we place in front of the cylindera convex spheric
. Refraction and motility of the eye, with chapters on color blindness and the field of vision . strength to2D., though the patient says he can see a trifle clearer with+ As the strength of the cylinder increases, thepatient becomes more intolerant of any deviation from theaxis 90°. The use of this cylinder corrects a large part ofthe astigmatism and enables him by accommodating about3 D. to focus both the horizontal and vertical strokes sonearly together on his retina as to improve his vision up to ASTIGMATISM. 187 possibly 20/30. If now we place in front of the cylindera convex spherical lens, we do not necessarily improve hisvision, but give him the same vision without compellinghim to accommodate, and we increase the sphere till itbegins to reduce his acuity. Probably he will not be ableto relax so as to accept over + We have then got himto accept a + 1-50 C + axis 90° in each eye alone,while we feel confident that, if he could relax completely,it should be nearly +3 + 3 axis 90°. By using both eyestogether we can certainly increase the sphere and possibly. the cylinder without reducing his vision and can get him towear a combination of + 2 + 2 axis 90° in each, = V20/30. If he consults us because of headache or tiredeyes, we prescribe the strongest possible combination, con-fident that it will be more of a comfort for near work thanfor far. But if the glass is for the improvement of distantsight, he will be much better pleased, if the sphericalelement is reduced a little so as to let him exercise his veryefficient accommodation a little. If it seems best toexamine the patient under atropin, if our retinoscopy isaccurate, he ought to obtain his maximum vision with— + 3 axis 90 in each eye. When we test his visionwithout glasses, we find it greatly reduced, since he nolonger has the asistance of his accommodation perhaps20/200 in each eye. For the same reason neither the 188 REFRACTION AND MOTILITY OF THE EYE. cylinders nor spheres alo
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