This is a non-invasive test. Dilation is not necessary but it does not affect the test if the patient is dilated.
The IOL Master uses a non-invasive light beam in order to measure the eye for cataract surgery. During the test the patient places his or her chin in a chinrest while pressing their forehead to the forehead rest for several minutes each eye. Blinking is allowed but the patient must remain as still as possible for the best and quickest measurements to be captured.
The IOL Master is able to read measurements of the central corner, anterior chamber, axial length of the eye and white-to-white measurements. These measurements help your physician to calculate the lens implant that will best fit the eye when the cataract is removed.
ASCAN (Axial length scan)
If the patient has a cataract that is too dense for the IOL Master or additional confirmation of the measurements are needed, an Ascan ultrasound will be performed. Some physicians also just prefer the accuracy of Ascan measurements over the use of the IOL Master.
An immersion Ascan does not require dilation but if the patient is dilated it will not affect the results.
A patient can expect to be brought to the ultrasound bed and lay in a comfortable position. Occasionally measurements will be taken upright depending on each patient specific needs. Drops will be put into the eye which anesthetizes, or numbs, the eye. A small, contact lens-like cup, will be placed onto the eye for a few moments with a bath of sterile water. This test only takes a few moments and takes a thorough reading of each chamber of the eye.
The process is quick and does not cause pain to the eye although there will be slight pressure applied.
K readings, or readings of the corneal curvature of the eye, will also be taken non-invasively in order to give your physician the proper calculations needed to choose the lens that will be used in your surgery.
Bscan (Brightness scan)
Bscan is an ultrasound of the back of the eye, which is known as the posterior chamber.
This test is ordered when the physician is unable to get a clear view of the inside of the eye, which may be due to a dense cataract, hemorrhage or corneal edema. The Bscan can also rule out a retinal detachment or swollen optic nerves.
Typically performed while the patient is laying down, a probe with clear gel is applied to the eye, usually on the closed lid. This is a very easy test however the Bscan occasionally needs to be done on the globe of the eye. For this the eye is anesthetized and the probe scans the open eye if the lid is blocking the necessary view.
UBM (Ultrasound biomicroscopy)
A UBM is an ultrasound of the front of the eye, which is also known as the anterior chamber.
During this test the patient lays down and the eye is anesthetized. A contact lens cup is placed on the open eye and a sterile water bath is added. A small probe is placed into the water bath which scans the eye. The probe does not directly touch the eye. The test lasts only a few minutes and is able to show the cornea, the anterior chamber, placement of the lens, ciliary body and the iris.