Customized Laser Vision Correction
Personalized Vision Correction
Wavefront LVC , uses 3-dimensional measurements of how your eye processes images to guide the laser in re-shaping the front part of the eye.
With a wavefront measurement system, some extremely precise, individualized vision correction outcomes may be achieved that would be impossible with traditional methods.
With customized IVC, your eye’s ability to focus light rays is measured, and a 3-D map is created that demonstrates irregularities in the way your eye processes images. Information contained in the map guides the laser in customizing the treatment to reshape your eye’s corneal surface so that these irregularities can be corrected.
Standard prescriptions for glasses, contact lens, or traditional LVC procedures can correct ordinary vision defects such as myopia, hyperopia, and astigmatism. But other irregularities associated with the eye’s optical system could not be addressed until the advent of wavefront and related technology used in customized LVC.
Potential Benefits of Wavefront-Guided LVC
Wavefront technology is groundbreaking because it has the potential to improve not only how much you can see, visual acuity measured by the standard 20/20 eye chart, but also how well you can see, in terms of contrast sensitivity and fine detail. This translates into a reduced risk of post-LVC complications, such as glare, halos, and difficulty with night vision.
Why we need wavefront- guided refractive surgery ?
Measurement of the wave front error of the eye provides an accurate method to:
Assess the optical properties of the eye beyond sphere and cylinder
Evaluate the optical properties of the eye
Provide the necessary information to design optical prescriptions for the eye to minimized all refractive errors
Conventional Laser Refractive Surgery:
May reduce contrast acuity.
Increase higher order aberrarions.
Increasing with the magnitude of refractive correction.
High refractive corrections, both myopic (>6.00 D) and hyperopic (>5.00 D), can lead to very high levels of corneal higher order aberrations.
Decrease night-driving visual performance.
Higher order aberrations can cause:
Night vision disturbances such as starbursts, halos, glare.
Low contrast acuity.
Wavefront-guided Laser Refractive Surgery provides:
Better contrast sensitivity.
Induces fewer higher order aberrations.
More effective than Plano scan in the correction of total, high order and 3rd order aberrations.
The most important advantage of the wavefront-guided technology is it saves tissue ablation depth in the range of 20% or 25%.
Clinically the most useful methods of evaluating the success of wavefront-guided repairs.
Subjective improvement
Contrast sensitivity
The pre operative evaluation consisted of:
- Measurement of uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA).
- Manifest,Subjective and Cycloplegic refractions.
- Slit lamp biomicroscopy,
- Tonometry.
- Indirect ophthalmoscopy ,
- Corneal topography ,
- Ultrasound pachymetry ,
- Orbscan II 0r Pentacam
- Aberrometry (Zyoptix evaluation).
- Pupillometry
Exclusion criteria are history of:
Previous refractive procedures.
Keratoconus
Cataract surgery
Diabetes
Glaucoma
Connective tissue disorders
Retinal disease
Pregnant or nursing period
How much you see depends on vision defects known as lower-order aberrations associated with common refractive errors including myopia, hyperopia, and astigmatism, which traditional Laser Surgeries can treat.
How well you see can depend on presence of the type and numbers of visual distortions known as Higher Order Aberrations which can include irregularities other than common refractive errors. These higher-order aberrations can create problems such as decreased contrast sensitivity or night vision, glare, shadows, and halos. However, higher-order aberrations do not always affect vision. Unlike traditional Laser Surgeries, customized Laser Surgeries treats both lower- and higher-order aberrations.
Wavefront LVC creates a highly individualized laser correction of your eye’s surface, guided by precise analysis of vision errors that occur as light rays travel through your eye.
Customized laser correction advantage lies in the area of quality of vision:
Greater chance of achieving 20/20 vision
Greater chance of achieving better than 20/20 vision
Reduced chance of losing best corrected visual acuity
Reduced chance of losing visual quality or contrast sensitivity
Reduced chance of night-vision disturbances and glare
Potential also exists for customized LVC to treat those people who have lost best-corrected vision from any past refractive surgery; LASIK,LASEK.PRK,RK
“Prior to the advent of wavefront measurements, there wasn’t anything we could do to measure or treat higher-order aberrations .link that information to the laser, and actually correct higher-order aberrations that diminish contrast sensitivity. Wavefront technology enables the surgeon to improve overall vision quality better than in the past.”
Not all refractive surgeons agree that wavefront-guided LVC can treat higher order aberrations. In fact, some surgeons argue that both wavefront LVC and conventional LVC can sometimes cause these aberrations because of artificial changes made to the natural shape of the eye’s surface. However, wavefront-guided LVC may be less likely to induce higher order aberrations than conventional LVC.
A 2005 survey revealed that most refractive eye surgeons now use wavefront-guided LVC in their practices.
Wavefront-Guided LVC & Contrast Sensitivity
Refractive eye surgeons appear overwhelmingly to favor customized or wavefront LVC as evidenced by results of a 2005 American Society of Cataract and Refractive Surgery (ASCRS) survey of 4,645 U.S. members (16 percent responded). About 74 percent of refractive surgeons now use wavefront-guided LVC in their practice, compared with fewer than 10 percent in 2003.
In certain cases, outcomes such as improved night vision with use of wavefront-guided LVC appear to surpass results that can be achieved with conventional LVC.
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FDA-Approved Custom LASIK Systems |
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| Laser System and Manufacturer | FDA-Approved Indications | Features |
| LADARVision 4000 with CustomCornea & LADAR6000 with CustomCornea (Alcon) |
Myopia: up to -8 D with or without myopic astigmatism up to -4 D
Hyperopia and hyperopic astigmatism: up to +5 D (near vision problems) and astigmatism causing distance vision problems up to -3 D |
Eye tracking, integrated wavefront, small spot system for precise laser application, no pupil dilation needed for treating larger optical zones in LADAR6000 system |
| Technolas 217z Zyoptix System (Bausch & Lomb) |
Myopia: up to -7 D with or without up to -3 D myopic astigmatism and total refractive error equal to or less than 7.5 D | Integrated wavefront and “flying spot,” meaning fast, uniform application of laser beam with each pulse for smooth corneal surface |
| Star S4 Active Trak with CustomVue (Visx) | Myopia: up to -6 D, with or without up to -3 D myopic astigmatism
Hyperopia: up to +3 D with or without up to +2 D for hyperopic astigmatism |
Eye tracking, integrated wavefront, no pupil dilation required, which speeds up procedure, unique wavefront analysis system known as Fourier for increased resolution |
| Star S4 IR with CustomVue (Visx) | Myopia: up to -6 D with or without up to -3 D of myopic astigmatism
Hyperopia: up to +3 D with or without up to +2 D of hyperopic astigmatism Mixed astigmatism: up to 5 D |
Same as S4 Active Trak |
| Allegretto Wave with Allegro Analyzer (WaveLight) |
Myopia: up to -7 D with or without up to 3 D of astigmatism | Scanning spot system, eye tracking, integrated wavefront, algorithm (mathematical measurement) based on population studies that helps minimize possibility that a vision error known as spherical aberration might be induced during vision correction |
Customized LVC Technique:
The surgeon in one popular method will begin by using the wavefront device to transmit a safe ray of light into your eye. The light is then reflected back off the retina out through the pupil and into the device, where the reflected wave of light is received and arranged into a unique pattern that captures your lower- and higher-order aberrations.
All of these visual irregularities are then displayed as a 3-D map, referred to as a wavefront map. This information is then electronically transferred to the laser (in wavefront-guided systems), and computer-matched to the eye’s position, enabling the surgeon to customize the LVC procedure to your unique visual requirements.
Customized LVC usually costs significantly more than traditional LVC, partly because a fee is paid to the device manufacturer for each procedure. Research is continuing into expanding the degree of vision errors (such as high myopia) that can be corrected with customized LVC. Investigations also are underway for use of custom LVC to create multifocal corrections, which would enable older eyes that have developed presbyopia to see at near, middle, and distant ranges at the same time.
Like conventional LVC, customized LVC won’t cure all vision-related problems, so it’s important to discuss its applications with your eye doctor or surgeon to determine if you are a good candidate.