Distinct patterns of spatial frequency response by normal, recovered optic neuritis, and normal fellow eyes to a new linearly variable neutral density device.

Upon apparent recovery from optic neuropathy, structural damage to the optic nerve may remain while usual measures of visual function appear normal. To test for such damage, the logarithm of optical density to cause a pattern to disappear is read directly on the scale of our device. Patients in the first study observed the disappearance of a red Amsler grid; this Threshold Amsler Score, used jointly with acuity scores, separates normal eyes from eyes with optic neuropathies. Patients in the second study used the device to measure the disappearance of the highest contrast Vistech patterns to show that this device, used over a range of spatial frequencies, differentiates "subclinical" neuropathies (recovered optic neuritis eye; never symptomatic fellow eye to a diagnosed eye) from normal eyes. This device may measure the functional photopic brightness of the stimulus pattern; when the score from our device is higher, the range of photopic brightness for the stimulus is wider, and the retina is more sensitive to contrast.