. Annals of medical history. detrodclalunaclluvjeicdclmifmo t:jminoi otradc la. S .cjue Ic vepordctueradc la mil ma luna,enronces fc note en cl pahllo el lugar donde citu vierolos ancojos,mo(lrado la igual daddelo^ quicadoslosantojos,apli c]ucrcclpaIil!oaJalinea,dcrdeeI puiito de la mircie qiic num:ro muclba clpuiico fcnaladocn el gradosfe- raa los fi palTarcn di diczgtados^cn clla fegun- da mcdi ia. B. H. Ic lia- Jlaiaii !os dc i mas, hafla tieynta. Y c(la mif- ina mcdiJa fcpocdtn ta biclaber los gva.^os dc qjjlefquicr aurojoscon
. Annals of medical history. detrodclalunaclluvjeicdclmifmo t:jminoi otradc la. S .cjue Ic vepordctueradc la mil ma luna,enronces fc note en cl pahllo el lugar donde citu vierolos ancojos,mo(lrado la igual daddelo^ quicadoslosantojos,apli c]ucrcclpaIil!oaJalinea,dcrdeeI puiito de la mircie qiic num:ro muclba clpuiico fcnaladocn el gradosfe- raa los fi palTarcn di diczgtados^cn clla fegun- da mcdi ia. B. H. Ic lia- Jlaiaii !os dc i mas, hafla tieynta. Y c(la mif- ina mcdiJa fcpocdtn ta biclaber los gva.^os dc qjjlefquicr aurojoscon lifc dc uicz gradoSjalfe- tan. A chart for determining the strength of lenses.{From Daca de Valdezs essay on spcelacles, i6.»j) bring divergent rays to a focus, whileconcave lenses scatter (aparlan) them. In a subsequent and important chapterthe numeration of lenses is considered, andit is this portion of the work that mostlyinterests the ophthalmologist. Chapter \idiscusses—and what a practical subject!—. the size of the prescribed lenses, and (helped(Hit by diagrams) the means by which onemay recognize the strength of both concaveand convex glasses. This latter processis mainly that of testing the focal distanceof each lens by a person with perfectsight. An account of the chief nictliods ofdetermining the refraction now follows,in which a decided difference is notedbetween congenital and acquired \isualdefects. Ordering glasses for the relief of presby-opia in the Spain of 1622 was quite as satis-factory and eflicient a process as thatadopted nowadays by jewelers shops anddepartment stores. If the patient was notat hand the following rules obtained: fora man between 30 and 40 years of age aconvex glass of two degrees is required;between 40 and 50, two and one-halfdegrees; between 50 and 60, three degrees;60 and 70 three and one-half degrees; 70and 80, four degrees; after that period fiveor even six degrees. The degree (rara) of Valdez closelyapproximated our diopter.
Size: 1338px × 1868px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookidannal, booksubjectmedicine
