To the Editor.
—Enoch and co-workers recently demonstrated (Archives 97:76-78,1979) that patients with optic neuritis suffered a dramatic loss of visual acuity while looking into an interferometric acuity testing device, whereas normal subjects were able to maintain good visual acuity. We have since heard from Dr Enoch that the instrument used was putting out more light than anyone suspected, in the neighborhood of 100,000 trolands. We have been using an interferometric acuity device1 set at a retinal luminance of 800 trolands (its maximum output) and we have found that even at this intensity there is a slight tendency for vision to fade in eyes with optic neuritis. The Figure showsComparison of vision loss between patients with optic neuritis and normal subjects. the percentage of vision (Snell-Sterling scale) lost in a group of patients with optic neuritis compared with a group of normal subjects. Visual acuity of most of
RUTGARD JJ, Snyder J, Thompson HS. Interferometric Acuity Testing Devices and Loss of Visual Acuity. Arch Ophthalmol. 1980;98(1):187. doi:10.1001/archopht.1980.01020030189027