Wavefront Technology in Eye Exams

Wavefront technology revolutionizes eye examinations to the extent that, some day, familiar eye charts and instruments traditionally used for diagnosis of vision errors may become obsolete.

Most of us have undergone eye examinations with a device known as a phoropter, fitted with various lenses of different powers. An ophthalmologist or optometrist changes out the lenses and quizzes us about which lens produces the best image.

But with this conventional approach, information we give the eye care practitioner can be very subjective, based more on what we think we see instead of what we actually see. A wavefront analysis instead is objective, because vision errors can be automatically identified by the way light waves travel through the eye.

Wavefront eye analysis also potentially could replace conventional eyeglass or contact lens prescriptions, which describe visual problems in terms of the eye's roundness (sphere), irregular curvature (cylinder), and orientation needed for the corrective artificial lenses (axis). This information helps identify the type and severity of vision errors we may have. [Read more about interpreting your contact lens prescription and wavefront lenses.]

But compared with conventional methods, wavefront analysis can provide much more detail about vision errors. Wavefront analysis also has been incorporated into vision correction surgeries such as LASIK.

We now see the term "wavefront" increasingly associated with descriptions of processes used to create artificial lenses for vision correction. Lasers used in LASIK and other vision correction procedures also may be identified as wavefront-guided or wavefront-optimized.

So exactly what does wavefront mean in terms of vision correction?

In the simplest terminology, a wavefront can be explained by picturing light traveling as a bundle of rays. If you draw lines perpendicular to the tips of a bundle of light rays, you obtain what is called a wavefront map. In an eye with perfect vision, the wavefront is perfectly flat. The wavefront of an imperfect eye is irregular.

Types of distortions this wavefront acquires as it travels through the eye provide valuable information about vision errors and how to correct them.

Aberrometry measures the way a wavefront of light passes through various refractive or focusing components of the eye, such as the eye's clear front surface (cornea) and crystalline lens. Different distortions that occur as light travels through the eye are known as monochromatic aberrations, representing specific vision errors. [Read more about how the eye bends or refracts light to achieve focus.]

Wavefront technology, or aberrometry, diagnoses both lower- and higher-order vision errors represented by the way the eye refracts or focuses light. Higher-order aberrations are more complex vision errors, whereas lower-order aberrations are more common vision errors such as nearsightedness, farsightedness, and astigmatism.

Previously, with conventional methods of eye examinations, only lower-order vision errors could be diagnosed and treated. Higher-order aberrations such as coma, trefoil, and spherical aberration were largely ignored by eye care professionals because their impact on vision was believed at the time to be slight and because no feasible means existed to precisely identify or correct them. [Read more details about higher-order aberrations.]

Now that higher-order aberrations can be accurately defined by wavefront technology and corrected by new kinds of spectacles, contact lenses, intraocular lenses, and refractive surgery (adaptive optics), they have become more important factors in eye examinations.

In the past, these higher-order aberrations received even more attention because they were identified as sometimes serious side effects of refractive surgery, showing up as halos, ghosts, and a host of other debilitating vision symptoms. Newer wavefront-guided lasers used in vision correction surgery, however, now have been shown to have the ability to reduce certain higher-order aberrations, which potentially can improve low light image quality during activities such as driving at night.

Page 2 of 2: How a Wavefront Diagnosis Is Performed