knee-jerk reaction. Fig. an automatic or reflex reaction; an immediate reaction made without examining causes or facts. With one of his typical knee-jerk reactions, he said no immediately, citing some moral argument that no one understood. See also: reaction.
What did you see when the patients head was rolled to the opposite side? In horizontal canal BPPV, you should have seen a direction change. When the horizontal nystagmus is geotropic, the BPPV is suspected to be canalithiasis, occurring on the side with the more intense nystagmus.
Against-the-rule astigmatism â the horizontal meridian is steepest (a rugby ball or American football standing on its end). Oblique astigmatism â the steepest curve lies in between 120 and 150 degrees and 30 and 60 degrees. Irregular astigmatism â principal meridians are not perpendicular.