From whom I should get my eyes checked: opthamologist or optometrist?

I’m 18 and one of my eyes is 20/440 as of my last optometrist visit almost a year ago and getting worse every year. This has been going on since I was in elementary school. The other is only 20/40. What could have caused so much vision lost in just the one eye? A good friend of mine has glaucoma and has lost sight in one eye because of it. He says that I should go to an ophthalmologist to see what’s up. Not sure what to do please help.