If you are encountering low FPS or drops when you play, please try/check the following:
- Update your graphics drivers.
- Make sure that your CPU/GPU are not spiking to 100%. If it is, you should be closing background applications that you are not currently using.
- Disable Optifine and see if this is still an issue. If you are no longer having issues, you should reset your Optifine configuration or find and fix the bad setting.