Reading from Arduino via USB Serial seems too slow

Hello, It seems that I have a problem with the reading speed from arduino. I only get the half of the values sent to Matlab and I have no idea why this is happening. I am getting the information with an infinitive while loop and reading line by line. I have an idea to save all the information in the buffer and then to try reading it all at once, but I don`t know how to implement it. Can sombody give me a suggestion how to solve the problem. Thanks in advance!