An aberrometer is an instrument that identifies and measures structural anomalies in the eyeball, which affect the ability of the eye to perceive images. It detects refractive aberration or visual error, which is the distortion caused by the imperfections in the cornea and the lens of the eye as light travels to the retina. Most refractive aberrations create conventional (lower- order) visual disorders such as nearsightedness, farsightedness, and astigmatism, which may be corrected with prescription lenses or traditional laser eye surgery. However, close to 10% of the population have complex (higher-order) visual errors which are unique, much like fingerprints. It is necessary to make a customized map of the patient's eye to treat these complex disorders.
Aberrometry is a modern technique of measuring visual aberration that enables doctors to differentiate between conventional and complex refractive errors. Aberrometry analyzes the way a wavefront of light goes through the patient's cornea and the eye lens. Light travels as a bundle of lines or rays. If a line is drawn connecting the tips of the rays in the light bundle, the resulting graph or map is called a wavefront. An aberrometer measures the wavefront as it goes through the eyes.
The conventional eye tests provide subjective information while wavefront measurements are objective because refractive aberration can be identified automatically. Aberrometry or wavefront technology can diagnose both conventional and complex visual errors represented by the way the eye focuses or refracts light. The types of distortions the wavefront gets as it flows through the eye offer valuable information about a patient's visual errors and how to correct them.
Also Known As
- Wavefront technology
- Wavefront aberrometer
An aberrometry test can be conducted at the doctor's office or eye clinic by:
- A technician
- An optometrist
- An ophthalmologist
An aberrometer is primarily used as a component of a custom laser surgery (LASIK) procedure. The aberrometer projects a beam of laser light into the patient's eye to detect the visual error. The beam travels through the cornea and the eye lens and is reflected by the retina. The reflected beam is then analyzed by the aberrometer to detect lower and higher-order aberrations, which are shown on a computer screen in 3-D images.
The wavefront map is an accurate description of all the aberrations affecting the patient's eye. The doctor uses it as a blueprint for customizing the patient's vision correction therapy. The information is interfaced with the laser for the vision correction surgery. It directs the delivery of laser light for a precise reshaping of the patient's cornea. It can also be used for customizing intraocular lenses, contact lenses, or glasses.
An aberrometer may also help the doctor to diagnose and treat eye ailments. He/she can use it to identify the causes of visual disturbances, such as halos, glare and night visual disorders, and screen patients whose sight may be compromised by these conditions. Furthermore, the device enables the doctor to assess highly distorted eyes.
Wavefront technology is a digital technique that is revolutionizing the way eye ailments are diagnosed and treated. It makes it possible for doctors to detect eye abnormalities early on and handle them more efficiently. Many doctors are now incorporating aberrometer into routine eye examinations to get the most accurate measurement of a patient's visual errors.
Preparation & Expectation
There is no special preparation required for an aberrometry test. However, if a patient uses contact lenses, they will have to remove them before the test.
- Tscherning Aberrometer
- Hartmann-Shack Aberrometer
Most aberrometers employ Hartmann-Shack wavefront sensors. They transform the feedback from the patient's eyes into a set of spots or data points on a digital camera. The data points are produced when microlenses focus the reflected beam onto the camera.
Tscherning aberrometer analyzes the light as it enters the eye. The gadget shoots red laser beams into the patient's eye. It creates a laser grid pattern on the retina. As the rays travel to the retina, they are distorted by the aberrations in the cornea and the lens. A picture of the pattern on the retina is caught by a video camera.
With most aberrometers, the patient places their chin on chin support. Then, the doctor asks the patient to peer into the aberrometer and focus their eyes on a target of light. The device projects a low-level laser beam into the patient's eye and analyses the reflection. The test takes a few seconds, and the wavefront map is produced after several minutes.
The wavefront map is like a fingerprint and is unique to each patient. In a person with perfect vision, the eye has no aberrations, and the wavefront will be perfectly flat. In a patient with visual imperfections, the wavefront is irregular, bent and distorted. Anomalies in the cornea and lens can affect the path of the laser beam by causing it to slow down, speed up, or refract (incorrectly bend).
Abnormal results could be due to lower-order or higher-order aberrations.
- Lower-order irregularities are common disorders such as astigmatism, nearsightedness and farsightedness, etc. Most people with vision disorders suffer from lower-order aberrations.
- Higher-order aberrations are rare abnormalities that cause visual disorders such as double vision or blurry vision. Until the introduction of aberrometry, higher-order aberrations were often left undiagnosed.
Wavefront technology has made it easier for doctors to diagnose and treat both higher- and lower-order aberrations. Furthermore, some higher-order aberrations can be permanently corrected by using a wavefront map in refractive surgeries such as LASIK.
Risks & Complications
Wavefront technology has no risks or complications.