Transient tritanopia in migraine: evidence for a large-field retinal abnormality in blue-yellow opponent pathways.

Purpose: To determine whether the magnitude of transient tritanopia (TT) differs between migraine and control groups. TT is a retinal phenomenon characterized by a paradoxical reduction in sensitivity to short-wavelength (purple) stimuli after extinction of long-wavelength (yellow) adapting displays. A group difference in the magnitude of TT would provide evidence for a retinal contribution to the S-cone-specific color-processing abnormalities that have been reported in migraine.
Methods: Thirty-two migraineurs and 32 age- and sex-matched control participants were tested with a four-alternative, forced-choice procedure to determine S-cone increment and decrement detection thresholds before and after adaptation to a long-wavelength (yellow) display and a neutral (white) display. Migraine history, migraine triggers, and pattern sensitivity were also assessed.
Results: Both groups' detection thresholds for increment (purple) S-cone stimuli were increased after extinction of the long-wavelength adapting display compared with the neutral display, demonstrating TT. This loss of sensitivity was significantly greater in the migraine group. In contrast, loss of sensitivity to decrement (yellow) S-cone stimuli was less marked and did not differ between the groups. The magnitude of TT correlated positively with indices of pattern sensitivity and susceptibility to visually triggered migraines but not with migraine history.
Conclusions: These results demonstrate that abnormalities in a specific retinal circuit contribute to decreased short-wavelength sensitivity after adaptation in migraine. As thresholds did not correlate with indices of migraine history, it is unlikely that this finding reflects cumulative damage induced by repeated migraine episodes.