Syntonics, also known as optometric phototherapy or photic stimulation, is a type of vision therapy that involves the use of specific visual light frequencies to help improve visual function and alleviate certain visual problems. The theory behind syntonics is based on the idea that light can have a therapeutic effect on the visual system by stimulating specific parts of the brain and the visual pathways. Here's how syntonics works in vision therapy:

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1. Light Selection: In syntonics, specific colored lights, often in the form of a light box or goggles, are used. These lights emit different wavelengths of light, typically in the blue and green spectrum. The selection of light color and wavelength depends on the individual's visual condition and the goals of therapy.

2. Light Exposure: The patient is exposed to the selected colored lights for a predetermined amount of time during each session. The lights may be directed into the eyes, and the patient may be asked to focus on them.

3. Visual Stimulation: The light exposure is intended to stimulate the visual system and specific neural pathways associated with vision. It is believed that this stimulation can help improve visual processing, reduce visual stress, and enhance the coordination of the eyes.

4. Individualized Treatment: Syntonics is often individualized based on the patient's specific visual problems. It is used as part of a broader vision therapy program prescribed by an optometrist or vision therapist. The treatment plan may vary in terms of the duration and frequency of sessions.

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Syntonics is sometimes used as a complementary therapy for various vision-related issues, including strabismus (eye turns), amblyopia (lazy eye), focusing and convergence problems, learning disorders, and in the treatment of brain injuries and emotional disorders.