Protocol Study for a Randomized Controlled Trial of the Effects of Transcranial Direct Current Stimulation (tDCS) Associated With Proprioceptive Training in Blind People

Ethical Aspects The study will be conducted in compliance with the principles of the Declaration of Helsinki as well as the guidelines for research involving human subjects stipulated by the National Board of Health of the Brazilian Health Ministry. Eligible individuals will receive clarifications regarding the objectives and procedures and those who agree to participate will sign a informed consentment.

Sample and recruitment The study will be conducted in three phases. First: to determine differences in postural control and gait between individuals with congenital and acquired blindness with and without a guide stick when wearing shoes and while barefoot. Second: will involve the characterization of differences in the effects of anodal tDCS on postural control and gait when stimulation is administered to different areas of the brain: primary motor cortex; somatosensory cortex; and visual cortex. Third: will involve a treatment protocol in which the participants will be randomly allocated in four groups: Group 1 - active tDCS + dynamic proprioceptive exercises; Group 2 - sham tDCS + dynamic proprioceptive exercises; Group 3 - active tDCS + static proprioceptive exercises; and Group 4 - sham tDCS + static proprioceptive exercises. Randomization will be performed with the use of sealed opaque envelopes containing a card stipulating to which group the volunteer will be allocated.

Individuals with a diagnosis of complete congenital or acquired blindness will be recruited from the community and associations that offer assistance to individuals with visual impairment. The characterization of blindness will be based on the classification of the degree of visual impairment proposed by the International Statistical Classification of Disease and the 10th Edition of the International Classification of Disease, in which visual acuity <20/400 or <20/200 in the better eye is classified as blindness.

With regard to the inclusion criteria: abnormalities of the optic nerve, retina disorders, glaucoma, Stargardt disease, macular degeneration, retinitis pigmentosa, congenital toxoplasmosis, congenital cataracts, congenital Leber's amaurosis, detached retina and astrocytoma. The exclusion criteria: medical diagnosis of injury affecting balance in the previous three years; use of medication affecting the central nervous system, coordination or balance; current symptoms of vertigo or dizziness; medical neurological diagnosis or symptoms suggestive of vestibular disorder; and past surgery or clinical condition of lower limbs or spinal column that can affect balance and gait. The subjects will be defined as independent if capable of locomotion without the assistance of others in all environments with or without the use of a guide stick.

Evaluation procedures Quantitative assessment of the gait The space-time gait parameters will be obtained with a wireless inertial detection (G-Sensor®, BTS Bioengineering SpA, Italy), previously validated in the gait assessment (Bugané et al., 2012; Pau et al., 2015).