How widely the prisoptometer was used is unclear but the Standard Optical Company later patented a new model, The Standard Prisoptometer, on June 21, 1904. Edward Jackson's crossed cylinder technique of determining astigmatism was first detailed in the Transactions of the American Ophthalmological Society (1887)4:595-598. The convenience of Jackson's crossed cylinder lenses over the prisoptometer in weight, cost, portability and reliability meant that they were soon almost universally adopted.This is a rare item as few are known world wide.This instrument is an optometer, that is, a device to measure the refractive error of an eye. It is made of cast iron, steel, brass and glass. It contains a prism which could be rotated, and was used to view a disc or an object circle. The prism caused monocular doubling of the object circle and the separation of the two images varied as the prism rotated, depending on the astigmatism present. The axis of the astigmatism was indicated by the prisoptometer and trial lenses were used to determine the the magnitude of the spherical and cylindrical refractive errorImprinted:"DR CULBERTSON'S PRISOPTOMETER/ GENEVA OPTICAL COMPANY MAKERS, GENEVA, N.Y./ PATENTED SEPT, 21, 1886". Stamped "853" on eyepiece and lens mounting.optometry, prisoptometer, optometer, astigmatism, refractive error, refraction, culbertson

This is the 1854 fourth edition of a book on diseases of the eye by William MacKenzie (1791-1868) first published in 1830. William MacKenzie was surgeon oculist in Scotland to Her Majesty (Queen Victoria), lecturer in the University of Glasgow and a surgeon in the Glasgow Eye Infirmary. This fourth edition appeared just after Helmholtz's invention of the ophthalmoscope, but Mackenzie did not at this stage have much understanding of the internal diseases of the eye. Nor did he properly understand refractive errors which were soon to be elucidated by the work of Donders. MacKenzie did however recognise the hardness of the eye as being an essential sign of glaucoma.This book is significant historically as it shows contemporary understanding of eye disease in the early nineteenth century. It is not rare as copies still turn up at book markets and also are held in other Australian institutions.This book, bound in full calf leather (probably later 19th Century) with 1107 pages including an index and is followed by a publisher's catalogue. It is the 1854 fourth edition of William MacKenzie's 'A practical treatise on the diseases of the eye' first published in 1830. It has a long (32 pages) introductory section on the anatomy of the eye by Thomas Wharton Jones, FRS. There are 27 chapters on eye disease. Chapter 24 is on refractive errors and presbyopia.eye, ocular anatomy, ocular disease