A young adults presents with night blindness and tubular vision. On examination, IntraocularPressure was observed to be 18mm and the anterior segment was unremarkable. Fundoscopyshowed attenuation of aerioles and waxy pallor of the optic disc with bony corpuscles like spicules of pigmentation in mid peripheral retina. Ring scotomas were observed on perimetry. Which of thefollowing is the most likely diagnosis -