Why do I Need an “A” Scan?

What is “A” Scan Biometry?

An “A” Scan is a highly precise measurement of the eye used to help us choose the correct lens implant power before cataract surgery. Our office uses state of the art technology with the Zeiss IOL Master, a totally noncontact instrument. This “A” Scan device measures the length of the eye in addition to the shape of the surface of the eye, and the dimensions of other structures in the eye. It then runs calculations using multiple different formulas to help us predict which intraocular lens implant power will provide the best outcome for the patient. At the same visit, our staff will perform a corneal scan (corneal topography) to map your corneal surface. A macular scan will also be performed to look for abnormalities of the macular region.

How is an “A” Scan performed?

The patient places his/her chin on a chinrest and is asked to look at a small target. No anesthetic is needed as nothing touches the eye. The IOL Master, the instrument that performs the “A” Scan, is then focused on the eye and several measurements are taken. The IOL Master uses a process called interferometry, where a single light source is split into two wavelengths with mirrors, then directed into the eye and the pattern generated is used by a computer to provide measurements of the eye. This is a completely noninvasive test that poses no risk to the patient. Corneal and macular scans are all done at the same visit and are similarly noninvasive, painless and do not touch the eye.

Will I feel anything?

No. These measurements do not touch the eye and are completely painless.

Is an “A” Scan required for a Premium Lens Implant?

When cataract surgery is performed, the natural lens in the eye is removed and replaced with a man-made intraocular lens implant (IOL). Regardless of the type of lens implant used, standard or Premium, measurements of the eye are needed before surgery. These measurements are highly precise, and combined with special computerized calculations, allow the surgeon to choose the lens implant power that is appropriate for each eye. Because each eye has a different size and shape, the power in the lens implant needed is different depending upon the many measurements of that eye. For this reason, an “A” Scan is always required prior to cataract surgery.

How reliable are the measurements?

Is the “A” Scan covered by insurance?

Yes, an “A” Scan is always needed before cataract surgery, so it is covered by insurance. When we feel a repeat scan is needed, we do not bill the patient or the insurance.