Hello, I’m Dr. Croley and welcome to Case of the Day. Today we’re gonna talk about something I get asked about a lot, and that is “what is a refraction.” A refraction is actually a method in which we determine your glass prescription.
This instrument is called a phoropter. And it has always lenses inside the phoropter. That way we can offer a patient essentially an unlimited, almost, amount of choices, as far as, what glass prescription or what glass they think they see the best with.
Some of the lenses in here when we cut this dial, these are spherical lenses. That is, they’re just round, normal lenses like a magnifying lens. So someone who’s nearsighted or farsighted, and they have no astigmatism, then these spherical lenses then correct the vision. So we’re gonna ask some patient, “Is this lens better, the first glass or the second one?” And we change the glass and we give you an option of which glass you see better with.
Then people who have astigmatism, that is, their eye is shaped more like a football than a basketball. So therefore a round eye, or without astigmatism, the cornea is totally round like a basketball. When light goes through it, all the light points are focused to one point.
If your eye is shaped like a football, then it’s steeper on one side, flatter on the other. So when light goes through, the light doesn’t get bit at the same amount. So therefore, that light is focused toward the line inside the eye. So when people have astigmatism, and they look at the light at night and they don’t have their glasses on, they see a streak coming out of the light because that’s how the light is being focused in their eye.
So these other lenses, then have the astigmatism in it. Then we have what’s called a Jackson cross cylinder that has astigmatism lenses exactly at 90 degrees opposite of each other. Then we ask people which glass is better so we know the axes, that is, how many degrees; where are the axes; where do they like the astigmatism to be located. Then we flip the lens, cross cylinder in the other direction and then we start asking again how strong of those astigmatism lens do they want in that number of degrees. That is, a hundred and eighty degrees or whatever that amount of degrees is. Then we come back and fine-tune the cylinder. That’s how you choose a glass prescription.
There is obviously some expertise on the part of the person doing the refraction who give you options. But still as a patient, you are the one who’s sort of choosing that lens. So it’s sort of a cooperative effort on trying to get the right glass prescription for a patient.
The other thing that is always asked about very commonly is that a refraction is considered by most insurance companies and Medicare as a non-medical part of the eye exam. That is, they do not cover the cost of doing this part, the refraction, of an eye exam. I disagree with that but that’s what Medicare says and most insurance companies. They’ve done that because they don’t wanna pay for it, basically.
But a refraction is very important. It really is a medical, does give medical information. Anytime we make decisions on someone’s health of their eye, a major factor in deciding what’s going on with someone’s vision or the health of their eye is what is their best correctible vision. That is, what is the best vision you have. We find out through the glasses that with your refraction, you can see 20/20, or sometimes better than 20/20, but we need to know what that number is because all decisions are pretty much based on that best correctible vision.
So if you came here and your vision is 20/20 the year before or two years before, and now you come in as 20/25 or 20/30, a little worse. I wanna know if you’re just now developing some astigmatism; you’ve become a little nearsighted, farsighted. I wanna know whether you still can see the 20/20 or not, or it’s just 20/25 or 20/30 because you have an eye disease.
So you can see it’s important for us to know what someone’s best correctible vision is because then if you’re not correctible to 20/20 anymore then I have to find out why. Sometimes it’s not always obvious in an eye exam, but if there is a vision problem, and we can’t correct you to your 20/20 vision, then we have to get to the bottom of why you don’t see 20/20. So it’s extremely important to know what’s your best correctible vision is. So it’s too bad insurance companies and Medicare have chosen not to cover them on those cases because it really gives us valuable information about the health of your eye. So a refraction is not just to determine your glass prescriptions, though it’s a part of it. Also a refraction is a medical part of your eye exam in determining your best correctible vision so we can follow the health of your eye.
So if you have any questions about what a refraction is, or any other questions about your eyes, you can always contact us at the website, we’d be happy to try to answer your questions. If not, may God bless you with healthy eyes and great vision.