How does retinitis pigmentosa cause night blindness and tunnel vision?

Retinitis pigmentosa is a group of hereditary eye diseases characterized by the progressive degeneration of the retina. The pathology behind its primary symptoms involves the following processes:1

• Night Blindness: This occurs because the disease causes the early destruction of rod cells. Rods are the specialized photoreceptors responsible for vision in dim light, containing the pigment rhodopsin which is essential for low-light sensitivity. As these cells degenerate, the eye loses its ability to adapt to darkness, leading to night blindness in youth.2341
• Tunnel Vision: As the disease progresses, further atrophy of the retina and changes in the supporting pigment epithelium occur. This leads to a gradual constriction of the visual field, eventually causing the affected individual to perceive the world as if looking through a tunnel.1

While the course of the disease is typically slow, it represents a significant impairment of the visual system.1