what is the method of testing vision acuity called?!

My former doctor never used the snellen chart with me. He used this method involving different color lights. If I remeber correctly, the colors were red and green. From my understanding, it look liked he would start the light with extremely dim and ask if I could see certain numbers, which I wouldn't be able to see until he gradually increase the light power to proper strength. I need to know because I'm seeing a new doctor for eye exam. I'm terrible at the eye snellen chart