BC question

[RMortis]

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Hey ODs,
I'm a medical student on an ENT rotation now, they do a lot of surgery involving the orbit and often have bad vision problems, they ask us about it and we don't get the education that an OD gets to answer them so we send them to see one of our ODs.

I've found I also have a rather simple question (I think): how do you measure the Base Curve in contact lenses? What does a higher or lower number mean and how is it used? Thanks for expanding my education!

 

[KHE]

Hey ODs,
I'm a medical student on an ENT rotation now, they do a lot of surgery involving the orbit and often have bad vision problems, they ask us about it and we don't get the education that an OD gets to answer them so we send them to see one of our ODs.

I've found I also have a rather simple question (I think): how do you measure the Base Curve in contact lenses? What does a higher or lower number mean and how is it used? Thanks for expanding my education!

If you're asking how to you measure the patient to determine what the base curve needed is, there are a number of devices that do this. A common one is something called a keratometer.

If you're asking how to determine what the base curve is of a contact lens you are holding in your hand, if it's a soft lens, there's no really good way to get an accurate reading. They do sell these devices that you can "mount" a soft lens on and measure it but they aren't particularly accurate and most of the time it's faster to just throw a lens on the patient and see how it fits. Most soft contact lenses come in only one or base curves anyways.

If it's a rigid lens that the patient is happy with and you're trying to duplicate it, there is a tool that can be used to determine what the base curve is.

BC is a measure of the radius of the back surfact of the lens. So the higher the number, the longer the radius and therefore, the "flatter" the lens is.