The Effect of Oral Administration of 9-cis Rich Powder of the Alga Dunaliella Bardawil on Visual Functions in Adolescent Patients With Retinitis Pigmentosa

Inclusion Criteria: * Written informed consent to participate in the study. * Adolescent 12-18 years old. * Electroretinogram (ERG) responses compatible with the diagnosis of Retinitis Pigmentosa Exclusion Criteria: * Currently a smoker * Current use of vitamin A/ β-carotene supplements * Active arterial disease within 3 months prior to enrolment in the study, e.g. unstable angina, myocardial infarction, transient ischemic attack, stroke, coronary artery bypass graft surgery * History of malignancy, excepting basal or squamous cell skin carcinoma * Females who are pregnant, or breast feeding, or are premenopausal but not using chemical or mechanical contraception * Uncontrolled hypertension, defined either as resting diastolic blood pressure \>95 mmHg (taken from the mean of 3 readings) or as resting systolic blood pressure \>180 mmHg * History of alcohol abuse or drug abuse or both * Intention to engage in vigorous exercise or an aggressive diet regimen * Uncontrolled endocrine or metabolic disease * Participation in another investigational drug study within 4 weeks prior to enrolment * Serious or unstable medical or psychological condition which, in the opinion of the PI, would compromise the subject's safety or successful participation in the study * Initiation of hormone replacement therapy or oral contraceptive therapy within 3 months prior to enrolment