To the Editor.
—Donaldsen4 claimed several new features for his keratograph, but none of these is novel. He stated that no previous keratographic instrument had used an electronic, flash-light source, but keratographs with electronic flash have been widely used in the last decade.2-8 Donaldson claimed that previous instruments, at best, record little more than the central half of the cornea and that his instrument covers about 80% of the cornea. Many previous curved-target keratographs have done at least as well as this.2,9-12 Curved targets were introduced by Berg13 in 1929 and Stimson and Weeks12 in 1940. The hemispherical target form used by Donaldson is not optimum in any case as the target virtual image formed by the cornea is not flat and therefore is not everywhere in focus on the film.7 An ellipsoidal form of target is superior,9 even when account is
Clark BAJ. Comments on Donaldson's New Instrument for Keratography. Arch Ophthalmol. 1973;90(4):345-346. doi:10.1001/archopht.1973.01000050347030