A 20-year-old male has a history of severe nyctalopia since his early teens. Approximately two months ago, he became concerned that he was frequently bumping into people in the streets. The patient is otherwise healthy. Family history is negative for eye diseases, with the exception that his mother reports prolonged dark adaptation when going to the theatre, and his deceased maternal grandfather had a long history of “night blindness and poor vision”. The patient’s examination shows best-corrected visual acuity of 20/20 OU, normal IOP and slit-lamp examination. Fundus examination showed 3+ retinal vessel attenuation, bone-spicule pigment clumping for 360-degrees in the mid-periphery with a preserved central retina. OCT reveals thin retinal layers with an absent ellipsoid zone layer, except for sub-foveally. Fundus autofluorescence reveals hypo-autofluorescent patches surrounding the vascular arcades and a peri-macular hyper-autofluorescent ring. Full-field and multi-focal electroretinogram (ERG) were extinguished. Visual fields were constricted to the central 10 degrees. What could be happening?