We thank Drs. Wall and Schiefer for the comment on our article. [1] While we agree that
Humphrey visual fields (HVFs) are not perfect tests, they remain the clinical gold
standard for measuring visual defects in hemianopia. There are several problems with Drs.
Wall and Schiefer's statements. First, a shift in attention does not automatically cause a
shift in fixation, as addressed in the extensive literature on covert visual attention,
[2] and whose manipulation we are pursuing actively in NIH-funded work to enhance visual
recovery in hemianopic fields. Second, while 24-2 HVFs have a resolution of 6 degrees, the
10-2 HVFs have a resolution of 2 degrees. As stated in our paper, [1] we combined and
interpolated these two tests and the two eyes algorithmically, creating maps with a
resolution of 0.1 degrees squared. Because these maps were formed from the averaging and
interpolation of 4 separate fields, any small spontaneous fixation shift would have had to
occur consistently 4 separate times for locations within the inner 10 degrees, and twice
for locations greater than 10 degrees from fixation. Moreover, we excluded patients with
abnormal false positive, false negative, and fixation loss rates and our 10-2 short-term
fluctuations were approximately 2dB. [1] Ultimately, our inclusion of untrained patients
provided the best evidence that recovery seen in trained patients was not due to test-
retest variability or learning to perform better on the test. Only subjects with improved
HVFs had improved psychophysical performance under strict fixation-controlled conditions
enforced binocularly using an Eyelink1000 eye tracker with superior spatial and temporal
resolution. [1] It was precisely to address the types of criticisms raised by Drs. Wall and Schiefer that we proposed a new approach to collecting and analyzing HVFs, while
rigorously controlling for drifts in fixation, whether attention-induced or otherwise.
1. Cavanaugh MR, Huxlin KR. Visual discrimination training improves Humphrey
perimetry in chronic cortically induced blindness. Neurology 2017;88:1856-1864.
2. Carrasco M. Visual attention: the past 25 years. Vision Res 2011;51:1484-1525.
For disclosures, please contact the editorial office at journal@neurology.org.
We thank Drs. Wall and Schiefer for the comment on our article. [1] While we agree that Humphrey visual fields (HVFs) are not perfect tests, they remain the clinical gold standard for measuring visual defects in hemianopia. There are several problems with Drs. Wall and Schiefer's statements. First, a shift in attention does not automatically cause a shift in fixation, as addressed in the extensive literature on covert visual attention, [2] and whose manipulation we are pursuing actively in NIH-funded work to enhance visual recovery in hemianopic fields. Second, while 24-2 HVFs have a resolution of 6 degrees, the 10-2 HVFs have a resolution of 2 degrees. As stated in our paper, [1] we combined and interpolated these two tests and the two eyes algorithmically, creating maps with a resolution of 0.1 degrees squared. Because these maps were formed from the averaging and interpolation of 4 separate fields, any small spontaneous fixation shift would have had to occur consistently 4 separate times for locations within the inner 10 degrees, and twice for locations greater than 10 degrees from fixation. Moreover, we excluded patients with abnormal false positive, false negative, and fixation loss rates and our 10-2 short-term fluctuations were approximately 2dB. [1] Ultimately, our inclusion of untrained patients provided the best evidence that recovery seen in trained patients was not due to test- retest variability or learning to perform better on the test. Only subjects with improved HVFs had improved psychophysical performance under strict fixation-controlled conditions enforced binocularly using an Eyelink1000 eye tracker with superior spatial and temporal resolution. [1] It was precisely to address the types of criticisms raised by Drs. Wall and Schiefer that we proposed a new approach to collecting and analyzing HVFs, while rigorously controlling for drifts in fixation, whether attention-induced or otherwise.
1. Cavanaugh MR, Huxlin KR. Visual discrimination training improves Humphrey perimetry in chronic cortically induced blindness. Neurology 2017;88:1856-1864.
2. Carrasco M. Visual attention: the past 25 years. Vision Res 2011;51:1484-1525.
For disclosures, please contact the editorial office at journal@neurology.org.