Larissa S. Almeida, B. Optom

Fellow – BV & VT, Vasai Blind Relief Association, Maharashtra , India


What is syntonic therapy?

The application of syntonic through the visual pathway was experimented with and clinically valid in 1933 by H. Riley spitler. The device used for the therapy is known as a syntonizer. Syntonic therapy is primarily neurologic in action and neurobehavioral in effect. (1) The light entering the eyes creates images as well as travels throughout the brain entering the pineal gland and hypothalamus, these parts affect one’s vision as they are responsible for the body’s hormones and chemical balances. Many studies found that the body’s nervous system could be restored if the brain is stimulated with light which can indirectly improve one’s vision. The state of “restored balance in the body” is known as syntony hence the name syntonic.

How does syntonic phototherapy work?

The traditional syntonizer is incorporated with a white light source which is placed behind coloured absorption filter focused by a frosted collimating lens (Figure 1). The patient is instructed to look down through a 50 cm tube with 50 mm diameter frosted lens for 20 minutes. Specific filters are prescribed for conditions. (3) There are 13 different filters available. The syntonic filter prescription mainly depends on the patient’s medical history, symptoms, and clinical findings.


Figure 1: A patient taking a syntonics treatment.
(Figure courtesy: Gottlieb, R.L. (2010) Syntonic Phototherapy: Mechanisms for Low Light Therapy)

Applications of syntonic phototherapy:

Syntonic therapy can be prescribed in various vision disorders such as Binocularity, accommodative facility, visual discrimination, functional field loss, deficits in ocular motor skills and information processing. It has shown drastic results in restoring functional vision. Being neurobehavioral in effect it has shown positive outcomes on a broad spectrum of visual, cognitive, academic, and emotional areas. (1)(2) Below are some evidence-based parameters.

Functional field loss – A condition where nerve tissue is not destroyed but damaged due to poor oxygen, oedema, metabolic or toxic imbalance. It has shown significant expansion in the visual field in a patient having strabismus (Figure 2) in a study done in 2010 (1)

Figure 2: The Visual field being plotted on a Lloyds Campimeter with photos of a young, cross-eyed girl and her visual fields before (eyes crossed) and after (eyes straight) following 20 syntonic phototherapy treatments. The initial visual field measured just 6 degrees and expanded to a full 60 degrees after. The small oval plotted in the After field is the ‘‘normal physiological blind spot.’’

(Figure courtesy: Gottlieb, R.L. (2010). Syntonic phototherapy: mechanisms for low light therapy.)

Visual memory: A study done in 1986 by Jack Liberman evaluated the effect of syntonic in three types of memory i.e. (2) 

  • Visual memory  
  • Visual motor memory 
  • Auditory verbal memory has boosted receptivity and integration between all three aspects resulting in improvement in an individual’s memory and ability to recall. 

Treatment of amblyopia: Syntonic phototherapy in a multi-modality approach has played a vital role in improving binocularity, oculomotor skills, and expanding a constricted visual field. (4-6)

Traumatic brain injury: Along with prism spectacles or vision therapy syntonic phototherapy has shown great results in colour visual field expansion with improvement in binocularity and symptomatology in paediatric patients having traumatic brain injury whose visual field is affected. (7)

Rod-cone dystrophy: An irreversible condition where peripheral vision is affected by night blindness, Syntonic phototherapy combined with vision therapy has restored visual acuity for distance and near (Snellen’s acuity) by two lines, expansion in the functional visual field and oculomotor abilities in Rod-cone dystrophy patients in a case series report. (8)



  1. Gottlieb, R. L., & Wallace, L. B. (2010). Syntonic phototherapy. Photomedicine and Laser Surgery28(4), 449-452.
  2. Liberman, J. I. (1986). The effect of syntonic (colored light) stimulation on certain visual and cognitive functions. International Journal of Biosocial Research.
  3. Wallace, L. B. (2009). The Theory and Practice of Syntonic Phototherapy: A Review. Optometry & Vision Development40(2).
  6. Suttle, C. M. (2010). Active treatments for amblyopia: a review of the methods and evidence base. Clinical and Experimental Optometry93(5), 287-299.
  7. phototherapy-restoring-visual-function-and-balance-through-light/