To the Editor.
—We read the interesting article by Shin et al1 in the November 1989 issue of the Archives on the reversal of glaucomatous optic disc cupping. Though their findings are of significance, we feel that an important issue has been overlooked while interpreting the computerized topographic measurements of the optic nerve head.It is essential to distinguish random variability associated with the technique of computerized topographic measurements from actual changes in the optic nerve head over time. Based on repeated measurements on the same eyes, previous studies have reported confidence levels for the variability of optic nerve head topographic measurements with different computerized image analyzers.2,3 Shin et al1 used the Rodenstock analyzer. For this instrument, Bishop et al2 calculated that two measurements on the same glaucomatous eye would have to differ by at least 0.138, 0.273 mm,2 and 0.189 mm3 for the
Dandona L, Quigley HA. Changes in Glaucomatous Optic Disc Cupping or Variability of Computerized Topographic Measurements?. Arch Ophthalmol. 1990;108(5):635. doi:10.1001/archopht.1990.01070070021006