A comparison of cupola-free perimetry with conventional perimetry: preliminary results.

In the comparison of ten normal and two pathological visual fields, excellent agreement was found between examinations made with Octopus perimeters (types 201 and 500) and a prototype version of a new cupola-free perimeter (CFPP). The examination of a single glaucomatous visual field, however, exhibited an elevated mean defect value with the prototype instrument in comparison with Octopus 201 examinations of the same visual field. Although this difference may be easily explained by long-term fluctuation effects, further investigations based on a broader empirical basis will be required. Based on the results of this preliminary work the following remarks can be made with respect to the cupola-free perimeter: provided that the zero point of the dB scale is chosen appropriately, ie, with a stimulus luminance of about 4,000 asb used as the 0 dB level, the same differential light sensitivity (DLS) values for normal visual fields can be obtained with the CFPP as with all Octopus models (201, 500, 2000). Within the limits of measurement error, the same decrease of DLS was found with the CFPP as obtained using the other perimeters for test locations (of the G1 program), ranging from the center out to an eccentricity of 30 degrees. Thus it appears that the normal values as used in the other Octopus perimeters can also be utilized in this cupola-free instrument within this range.