Use of a blue filter in visual field analysis.

One hundred and twenty seven eyes of 127 patients were studied by means of a Kodak 47B Wratten blue gelatin filter in conjunction with the Friedmann Mark 1 visual field analyser. There were 49 patients in the normal group, 50 patients in the ocular hypertension group, and 28 patients in a group with early glaucoma. A simple scoring system did not show a useful difference between these three groups. However, use of a derived threshold value for each target group designated by the letters B to P (giving selective blue field scores) differentiated between normal subjects and those with early glaucomatous field loss. When used with a calculated upper limit of normal to give a specificity of 96%, this test had a sensitivity of 64%. Of the ocular hypertension group 22% gave abnormal results in comparison with normal persons. This simple adaptation to the Friedmann protocol may aid the ophthalmologist in the detection and confirmation of early glaucoma.