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May 1990

Changes in Glaucomatous Optic Disc Cupping or Variability of Computerized Topographic Measurements?-Reply

Author Affiliations

Detroit, Mich

Arch Ophthalmol. 1990;108(5):635-636. doi:10.1001/archopht.1990.01070070021007

In Reply.  —We are pleased to acknowledge the special attention given to our report by Drs Dandona and Quigley as well as the accompanying editorial by Dr Spaeth.1 In our study, of great concern to us was the possibility of type 2 error; that is, the optic disc cup reversal and its correlation with intraocular pressure (IOP) reduction, even if present, might not be great enough to be demonstrable because of the expected variability2 associated with the computerized measurements with the Rodenstock optic nerve head analyzer (RONA) (G. Rodenstock Instrumente GMBH, Munich, West Germany). We were able to reject the null hypothesis. Thus, the cup reversal following IOP reduction and its correlation with percent IOP reduction must have been great enough to be demonstrable despite the variability associated with the measurements. Furthermore, according to the nature of the relationship between the reversal of each optic disc parameter and the

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