Bad frame rate since 1.6.1 release

Since the 1.6.1 update I have had low frame rate (20fps Max) on Normal render distance and low settings. Before the update, I would get at least 30FPS on far render distance.

I have a high spec laptop with a 2.3Ghz i5 processor, NVIDIA GT 540M Graphics card and 8Gb of RAM so that rules out my laptop being the problem.

Is this a bug and will it be fixed soon as I find the game unplayable and much less fun with a shorter render distance.