Blank corners?

When i turn around sometimes on 1.8 up to 1.8.9 it might still be at 1.9 but i dont play it since servers are still 1.8. So i was playing in a server EVEN when i was playing singleplayer, I turned a certian angle and a edge of a screen appeared black, i turn on a different angle its gone. Just strange... I got i pic of something SIMILAR but its really on the bottom left corner in a slight triangle shape