Frederick W. Brock, born in Switzerland, was an optometrist, a major contributions to vision therapy, and the inventor of various vision therapy devices including the Brock string. Brock's approach to treating eye disorders has been crucial in paving the way to overcome an erroneous but long-standing medical consensus that stereopsis could not be acquired in adulthood but only during a critical period early in life: neuroscientist Susan R. Barry, the first person to have received widespread media attention for having acquired stereo vision in adulthood, attributes him a central role in her recovery of stereopsis, a discovery which in turn influenced the prevalent scientific conceptions with regard to the neuroplasticity of the visual system.
Frederick Brock made many contributions to vision therapy, and his work focussed mainly on the application of vision training to the diagnosis and therapy of binocular dysfunction.
Brock trained his patients with rich stereo images which closely resembled the natural environment, and favored these over the use of (simplified) stereographs. In a first session with a client, Brock would invest great time into finding a point at which the client already performed binocular fusion, and Brock would refer to this point as his "point of attack" from which he would try to expand the range of positions in which fusion was achieved. He made use of the peripheral vision of his patients to lock binocular fusion, using his so-called "stereomotivator" to project large red/green anaglyphic stereo images onto a wall such as to stimulate very large receptive fields in the patients. He spoke against the use of an amblyoscope during training, because in his view the patient needed to take the correct binocular posture (aiming the two eyes such that they simultaneously look at the same target in space) when fusing, otherwise the training would not be likely to succeed.