Signs and Symptoms:
The eye often has several different higher-order aberrations working together. It is sometimes hard to single-out individual symptoms that may point to another diagnosis. Some higher-order aberations can, however, produce patient complaints such as these:
- Glare
- Halos
- Starburst effect
- Ghost images
- Blurring
Causes:
The human eye sometimes produces distortions of an image. These distortions are called aberrations. As a ray of light passes through an optical system, it has a wavefront. In a perfect eye, the wavefront is undisturbed and smooth. In an eye with imperfections, the wavefront becomes distorted and has a characteristic three-dimensional shape. Higher-order aberrations may be caused by irregular curvatures in the cornea and lens, trauma, scarring, dry eyes and very large pupils.
Diagnosis:
Higher-order aberrations are measured most commonly by a "Shack-Hartmann aberrometer." This device measures the wavefront of the eye and compares it to an eye that has no aberrations. This aberration map is referred to as the eye's "optical finger print" because it is unique and unlike any other person’s optical system. Unlike traditional vision measurements, which require subjective input from the patient, an aberrometer takes only seconds to obtain measurements and requires no patient input.
Treatment:
Knowledge of higher-order aberrations has been available for many years. Only in the last few years has wavefront technology been advanced enough, however, to produce accurate measurements and diagnoses. Certain types of new wavefront desinged glasses, contact lenses, intraocular lens implants and wavefront-guided laser vision correction can correct higher-order aberrations. Much more will be heard about treatment of higher-order aberrations in the next few years, as wavefront technology appears to have many applications in vision correction.
