Here is the design of a clinical trial:

Official Title: Assessment of the Rehabilitation of Postural Imbalance After Chronic Right Supratensorial Stroke by Prismatic Adaptation: Multicentric Randomised Sham-controlled Trial

Included conditions:
- Chronic Right Supratensorial Stroke Patients

Study Armgroups:
- {'label': 'Prismatic adaptation (PA) group', 'type': 'EXPERIMENTAL', 'description': 'Patients in the experimental group will benefit from 10 sessions of adaptation prismatic (PA) by means of one daily session of 20 minutes (5 times by week; 2 weeks), performed by an experienced physical therapist or occupational therapist. All patients will also benefit from conventional rehabilitation (Standard physical therapy, standard occupational therapy, standard speech therapy ...) according to the needs of the patients.', 'interventionNames': ['Device: The prismatic adaptation (PA)']}
- {'label': 'Sham group', 'type': 'PLACEBO_COMPARATOR', 'description': 'Patients in the sham group will benefit from 10 sessions of sham adaptation prismatic (S-PA) by means of one daily session of 20 minutes (5 times by week; 2 weeks), performed by an experienced physical therapist or occupational therapist. All patients will also benefit from conventional rehabilitation (Standard physical therapy, standard occupational therapy, standard speech therapy ...) according to the needs of the patients.', 'interventionNames': ['Device: The sham prismatic adaptation (S-PA)']}

Interventions:
- {'type': 'DEVICE', 'name': 'The prismatic adaptation (PA)', 'description': 'Prismatic adaptation (PA) is based on the wearing of a pair of glasses producing a visual field deviation of 10° to rightward. While wearing theses glasses, the patient is asked to perform fast pointing movements towards targets by the right hand. Targets are symmetrical located at 10° in the right and left side in front of the patient. The order of pointing between these two targets is pseudo-randomly by the therapist. At the beginning of the exposure, the patient performs pointing movements with a shift toward the right side (initial errors consecutive to the prism deviation). Taking into account theses errors, the patient then compensates the optical deviation. After removing the prismatic glasses, the asked pointing movement to the targets is once again shifted but to the left side this time (after-effects attesting the prismatic adaptation)', 'armGroupLabels': ['Prismatic adaptation (PA) group']}
- {'type': 'DEVICE', 'name': 'The sham prismatic adaptation (S-PA)', 'description': 'The sham prismatic adaptation (S-PA) is based on the wearing of a pair of glasses producing no visual field deviation. Theses sham glasses is identical with theses used in PA group without the optical deviation. The conditions are similar with theses in the PA group.\n\nThe procedure with the sham glasses are similar with these one used in the PA group: While wearing the sham glasses, the patient is asked to perform fast pointing movements towards targets by the right hand. Targets are symmetrical located at 10° in the right and left side in front of the patient. The support with targets are the same as these one used in the PA group. The order of pointing between these two targets is pseudo-randomly by the therapist. At the beginning of the exposure, the patient performs pointing movements without shift. No compensation of movement is observed. After removing the prismatic glasses, the asked pointing movement to the targets is not shifted (No after-effects observed)', 'armGroupLabels': ['Sham group']}

Primary Outcomes:
- {'measure': 'Balance: The inter-group difference of within-group changes for the Berg Balance Scale (BBS)', 'description': 'Balance : The inter-group difference of within-group changes for the Berg Balance Scale (BBS) Score between 0 and 56 points', 'timeFrame': 'Change from baseline (mean of the 2 pre-tests) at 7 days after the end of treatment (3 weeks about after the baseline)'}

Please estimate the sample size based on the assumption: 
Alpha risk of 0.05, statistical power of 95%, bilateral test, and consideration of potential lost to follow-up or dropping out.
Sample size
        According to the pilot study,62 we could postulate a within-group difference at D+7 of 4.83 points on BBS for the experimental group and of 2 points for the control group, with a pooled SD of change of 2. To our best knowledge, in patients after stroke at chronic stage, the minimal clinically important difference for BBS was never assessed while the minimal detectable change was estimated between 2.5 and 4.7 points.83â86 On the basis of these hypotheses, considering alpha risk of 0.05, a statistical power of 95%, and a bilateral test, we have to include 13 participants per group. To take into account potential lost to follow-up or dropping out before the primary outcome, one additional participant by group could be included. We could therefore include 28 participants.