In reply
In response to Dr Kushner, a binocularly viewed point of light is converted in 1 eye into a line of light by a Maddox rod, which disrupts the fusion reflex and uncovers a heterophoria. The line of light does not provide a stable fixation point for the eye. It is formed optically and is not physiologically equivalent to an afterimage.1 Head roll is frequently accompanied by a degree of yaw and pitch. Dr Kushner's method does not allow the control, observation, or recording of fixation of how the eye and head are moving. There is no proof that the eye maintains a constant orbital position during the head tilt. His method relies on a subjective sensory phenomenon. The decrease in vision after head tilt that is associated with high astigmatism can be explained by lack of synchrony between the head and eye. The visual environment does not tilt with the subject. Biological equilibrium is the rule.