State Board Examinations Questions and Answers

by Christian Henry Brown

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1919 Excerpt: ...As explained above, if this should be 5 inches, then 8 D. is the measure of the amplitude of accommodation; if at 4 inches, then 10 D. of accommodation. (b) The degree of convergence is measured by the angle through which each eye must turn from parallelism of the visual lines in order to converge to the near point of ... Read More

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1919 Excerpt: ...As explained above, if this should be 5 inches, then 8 D. is the measure of the amplitude of accommodation; if at 4 inches, then 10 D. of accommodation. (b) The degree of convergence is measured by the angle through which each eye must turn from parallelism of the visual lines in order to converge to the near point of fixation. The amplitude of convergence is the distance from the far point to the near point of convergence, and is expressed by the greatest number of meter angles which the eyes can exert, the meter angle being that angle through which the eyes must turn from parallelism to converge at a point one meter away. At 20 inches (% meter) there would be 2 meter angles of convergence; at 10 (% meter) 4 meter angles, and so on. In emmetropia the convergence and accommodation are equal; for instance, at 10 inches there are 4 meter angles of convergence and 4 D. of accommodation. The convergence can also be measured by the strongest prisms, bases out, which the eyes are able to overcome and maintain single vision. Give reasons for and against full correction of myopia (a) in orthophoria, (b) in heterophoria. (a) When orthoporia exists in connection with myopia, the indications would be against the full correction of the refractive error, all other things being equal, because the normal relation between accommodation and convergence has not been maintained. (b) If esophoria exists in connection with myopia, the indications are still stronger against the full correction of the refractive error, because the relations between it and the muscle balance are just the reverse of what they should be. When exophoria exists in connection with myopia, full correction of the latter is indicated, because the relations are normal, and the concave lens also corrects th... Read Less