A contribution to ophthalmoscopy / by W. Laidlaw Purves.

  • Purves, William Laidlaw, -1917.
Date:
1873
Catalogue details

Licence: Public Domain Mark

Credit: A contribution to ophthalmoscopy / by W. Laidlaw Purves. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    duated handle and motion of the disks, after the same method as Stokes lens, as constructed by Cretes. It would consist of two disks having each eight apertures, one without any lens, the other seven having in the one disk concave 2, 4, 6, 8, 12, 18, 24, and the other convex 4, 6, 8, 12, 18, 24, 48, or any other combination that may be thought more suitable—(vide Schulek’s Ophthal- moscope in Zehenders Archives for 1871.) Each disk would be rotated by a button on the handle, and the action of each lens marked on the corresponding side there- of, thus obviating the necessity of moving the eye once from the examination—^should it be desired to determine the refraction by such,—and the usual un- pleasant change of disks or glasses. Should none of the lenses mentioned give the proper correction, the other disk has only to be revolved on the first to obtain most of the intermediate numbers, by acting on the concave glasses with the convex, or on the convex with the concave. A half-ring placed in front of the disks can receive any mirror preferred. The iniriT ■, disks, and lenses ought to be made as thin as possible, and the aperture of the mirror—if a metal mirror is used—and the two apertures in the disks should have knife edges. The disks ought to be small in diameter, so as to allow of a near approach to the eye. Utrecht, 12th February, 1873. W. LAIDLAW PURYES. Robert Hardwicke, Printer, 192, Piccadilly.