Intraoperative Aberrometry: Measuring the Eye During Surgery

ORA at our practice

ORA is available for cataract and refractive lens exchange (RLE) procedures when appropriate. These procedures are performed at the outpatient surgery centers we use, and your surgeon discusses whether it would help in your case.

The problem it solves

The power of a lens implant is calculated before surgery from the eye's length and the cornea's curvature. In most eyes the calculation is accurate. In eyes that have had laser vision correction or radial keratotomy, the cornea's curvature has been changed in a way the standard formulas do not fully capture, and the calculated power can be off by enough to leave a noticeable prescription. Toric lenses add a second variable: the axis at which they must be placed, which is estimated from corneal measurements taken with the cataract still in the eye.

How the measurement is taken

With the cataract removed, the eye has no lens and its optics are those of the cornea alone, a state called aphakia. An aberrometer mounted on the operating microscope sends a beam through the eye and measures the wavefront that returns, in real time, in a few seconds. From that measurement it calculates the lens power the eye needs and, for a toric lens, the axis of the cornea's astigmatism as it actually is on the table. The surgeon compares this with the pre-operative plan and chooses the lens accordingly. After the lens is placed, a second reading confirms its alignment.

Who benefits

• Patients who have had LASIK, PRK or RK, where aberrometry can add a useful check on the lens power
• Patients receiving toric lenses, where confirming the axis reduces residual astigmatism
• Eyes with unusual measurements, such as very long or very short eyes, where formulas are less certain
• Patients choosing multifocal or extended depth of focus lenses, whose result depends on hitting the target closely

Aberrometry and the Light Adjustable Lens

The two technologies approach the same problem from opposite ends. Aberrometry improves the choice of lens during surgery; the Light Adjustable Lens corrects whatever error remains after surgery. For eyes with previous laser surgery, your surgeon discusses which approach, where available and appropriate, suits your eye.