Arduino and Matlab communication

Hi everyone, I am doing a project using both Matlab and Arduino and Computer Vision. I want to send Arduino only one signal that can just have 3 values depending of the image(frame) processed. So in each frame I have only a value and this value will change eventually with the change of the frame. Can I read the value of this variable through the serial communication? (If so any link that can help me) Or I have to use the Arduino Support Package and upload my Matlab code on it? (that I think it cannot be possible cause I would also be loading the image processing code and that would be too much for Arduino)

Does anyone have any suggestions?

Thanks in advance!