Higher-Order Aberrations - Causes, Symptoms, Diagnosis & Treatment
Higher-order aberrations are complex deviations from normal vision, much severe than astigmatism or nearsightedness and manifested as distortions acquired by wavefronts of light passing through the various refractive components in ocular globes – the tear film, cornea, the aqueous humor, the lens and vitreous humor.
Although these aberrations are thought to be present in all eyes to some degree, they’re asymptomatic most of the times and cause no problems. However, in certain cases these disorders lead to blurry vision, difficulties in seeing at night, double vision, glare, starburst patterns and halos.
According to statistics, ten to fifteen percent of people suffer from higher-order visual aberrations. The most common forms this disorder can take are spherical aberration, diffraction, chromatic aberration, quadrafoils and curvature of field.
Causes and symptoms of higher-order aberrations
When the condition manifests through night vision problems, it’s called spherical aberration and its trigger is most probably the excessive flattening of the cornea after laser surgery. Another form this ailment can take is called coma and it’s associated with double vision. This time, the trigger is most often an off-center laser treatment or decentration.
Generally, low to mild aberrations manifest through starbursts, ghosting and haloes, symptoms that interfere with the quality of vision, while more serious aberrations cause a loss in visual acuity.
Scars on the cornea from surgery, eye diseases or trauma, a very large pupil as well as an abnormal curvature of the cornea can favor the onset on these vision impairments. Also, the clouding of the lens due to cataracts and eye dryness resulting from an altered tear production can lead to aberrations in light perception, manifested as loss of contrast and other similar symptoms.
The severity of these manifestations is higher in people with larger pupils, especially when exposed to low light but people with smaller pupils can suffer from significant vision problems caused by aberrations as well.
Diagnosis and treatment of higher-order vision
Higher-order aberrations can be diagnosed using a wavefront aberrometer or Shack-Hartmann aberrometer, device which measures the wavefront of the patient’s eye and compares the value with the one obtained for a healthy eye. The process is very quick, it’s completely painless and offers a map of eyes aberrations, often referred to as the eye’s optical finger print.
Once the type of aberration is identified, treatment can be applied for correcting the visual impairment. A very effective and risk-free solution for this eye problem is represented by gas permeable contact lenses, which are comfortable and custom made to fit the shape and size of each patient’s cornea.
Wavefront computerized technologies and laser technologies can be used for reducing these sight problems, the wavefront-guided Lasik surgery being known as one of the most effective treatments for higher-order visual aberrations. This technique was proven to bring better results than eyeglasses, contact lenses and classic Lasik surgery, the last alternative being actually linked with the worsening of symptoms in some patients.
Wavefront glasses, intraocular lens implants as well as miotic eye drops can improve vision’s quality for short intervals of time as they work directly on the pupil, forcing it to constrict or enlarge in order to allow the proper amount of light to enter the ocular globe. Refractive surgery, which works by modifying the shape of the cornea, is also listed as a valuable treatment alternative for patients with higher-order aberrations.