Hello, I just got my 1st class medical re-issued yesterday, and the doctor told me I'd be getting a letter from the FAA about needing to go to an optometrist to get my eyes checked. I didn't fail any test relating to near vision, far vision, or color, and I've always had "needs corrective lenses" on my medical. However, there was a test I've never seen before (hah) done yesterday. The doctor used one of those lights that checks your pupil dilation (also used to look in ears, nose, mouth - thin pointy-tipped light), and he had some sort of hand-held diffuser with a red lense, that when held over one eye made the white light appear as a thin red line. He asked, when this object was in front of my eye, if the light touched the line. Could have lied and said yes, but I didn't, and so he twisted a dial on it to make it get closer. Well apparantly the limit is "6" and I was at "8" to get the line to match the light. I have no idea what this test was supposed to measure, only that he said I'd get a letter, and that I didn't "fail", I just needed to get my eyes checked. My vision hasn't changed in my last two or three yearly visits to the opt, but the only thing I can think of is something that the opt tried last year on me. There was some test where he tried to get me to have double-vision, and while it started off for my eyes as double-vision they quickly corrected to make an image. Opt said that my eyes were very strong.... and said it wasn't bad. So I guess my question is, what was the test, what might be "wrong" with my eyes, and how am I supposed to prevent this from pretty much derailing my flying career. Like I said, I was issued a medical with nothing else except the same "must wear corrective lenses" and told I didn't fail the test.