What are higher order aberrations? (Posted: jan 2005)

Wavefront aberrations are imperfections in the cornea that prevent light from focusing perfectly on the retina, resulting in defects in the visual image. There are two kinds of aberrations - "lower order" (myopia, hyperopia, astigmatism) which are the kind that can be corrected with glasses, contacts or refractive surgery, and "higher order" aberrations (such as spherical aberration or coma) which cannot be corrected by any reliable means with today's technology.

Laser eye surgery increases higher order aberrations and if they increase enough they will cause problems with vision quality. The most common problems associated with higher order aberrations after laser eye surgery are reduced contrast sensitivity, starbursts, haloes and ghosting.

What causes higher order aberrations? (posted: jan 2005)

In laser eye surgery, simply having the surgery done will increase the higher order aberrations, however, not always enough to be perceptible to the patient. The specific cause (in patients with excessive amounts of aberrations) depends on the type of aberration. Spherical aberration (associated with night vision problems) is often blamed on excessive flattening of the cornea as a result of laser eye surgery or on too small a treatment zone relative to the patient's pupil size. Coma (associated with double vision) is often caused by an off centre laser treatment (decentration).

What symptoms are associated with higher order aberrations? (posted: jan 2005)

Low to moderate aberrations are mostly associated with vision quality defects such as starbursts, haloes, and ghosting. Larger amounts of aberrations may cause a loss of best-corrected visual acuity.

How are higher order aberrations diagnosed? (posted: jan 2005)

With a wavefront aberrometer.

How can higher order aberrations be treated? (posted: jan 2005)

The most effective and least risky treatment for higher order aberrations is gas permeable contact lenses. The potential for successful treatment depends on the topographical features of the cornea, the amount and type of the aberrations, the patient's ocular surface condition and other factors affecting contact lens tolerance.

In terms of surgical treatments, in some patients higher order aberrations can be reduced using a wavefront-guided laser surgery (LASIK or surface ablation), however, these techniques are far from reliable as yet and patients need to be thoroughly aware of the risks of undertaking such treatment.

There are several other potential techniques for managing symptoms, the efficacy of which depends on the individual patient's condition. For example, in some patients, a miotic eyedrop such as Alphagan can produce temporary constriction of the pupil and improve vision quality.

Where can I get more information about higher order aberrations?

Click here for Encyclopedia entry for higher order aberrations, which may have additional articles and links.