How do I reduce my games render distance (for all players not just my own pc)?

I have a world with 2 different islands on which both have lots of parts and meshes. It gets kind of laggy when i look in different directions and need help. I need a way to make it so the game only renders in 1 island at a time. A.K.A How the hell do i reduce my games render distance so it doesn't load in everything at once. thx