Wavefront Technology and CustomVue Wavefront guided Laser Vision Correction, VISX STAR S4 IR laser.

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Introduction

Chances are, several of your friends or family members are experiencing the joys of living without glasses or contact lenses as a result of laser vision correction. You have heard the excitement in their voices, noticed the boost in their confidence, and watched the quality of their lives improve with new- found freedoms from contacts and glasses. It's very probable that they had conventional LASIK or PRK and achieved superb results. Something has changed in the field of laser vision correction that makes the procedure safer and with even better visual results. We at Grendahl Eye Associates are very excited about this. Now, people undergoing the new procedure (CustomVue) are experiencing less problems with night vision and a greater number of people are achieving 20/20 vision. The changes have come with new technological advances in the instrument that gathers the information that drives the laser correction, and with advances in the laser. The new technological advancement in the instrument that gathers the information is called a wavefront analyzer (WaveScan). The new technological advancement in the laser is called the VISX STAR S4 IR laser. The new procedure utilizing these two new technological advancements is called customized laser vision correction, or CustomVue. Customized LASIK or PRK can be done, and is collectively called CustomVue. It is called CustomVue because the procedure corrects not only myopia, hyperopia, and astigmatism as we previously did, but it now corrects the other 100% unique imperfections of your eye.

As you read you will notice there are a total of eight sections. In the first four sections that follow, we will explore very generally the WaveScan system, how the CustomVue laser vision correction proceeds, what the benefits and results are, and the VISX STAR S4 IR laser. In the last four sections we will describe in much more detail how wavefront errors affect your vision, the details of the WaveScan system and wavefront errors, centering and orientating the wavefront information on the eye undergoing CustomVue treatment, and how the CustomVue procedure works. While the first four sections focus on more general information, the last four sections are written for the technologically curious person. The following is a list of glossary terms that you will find useful when navigating through the web pages.

Glossary of terms:

1. Conventional LASIK and PRK- Non-customized laser vision correction procedure. Can be done with the VISX STAR S4 IR excimer laser or older lasers.

2. Customized LASIK and PRK (CustomVue) - Customized laser vision correction procedure. Individualized for each eye utilizing a wavefront analyzer (WaveScan). Corrects the eye's 100% unique vision imperfections.

3. CustomVue- The trade mark name for the customized laser vision correction procedure developed by VISX. Can be either LASIK or PRK. Information is gathered with the WaveScan about the 100% unique imperfections of the eye and is transferred to the VISX STAR S4 IR excimer laser for the procedure.

4. Wavefront analyzer- a device that is used to collect information about the 100% unique vision imperfections of the human eye. It is used in the customized laser vision correction procedure. A sophisticated measurement device, which passes a narrow ray of eye-safe light through the optical system of the human eye and measures the optical distortions (aberrations) of the light as it passes out of the eye.

5. WaveScan- the trade mark name for the wavefront analyzer manufactured by the VISX Company. Other companies manufacture wavefront analyzers. Alcon manufactures LADERWave. We at Grendahl Eye Associates have chosen the WaveScan.

6. VISX STAR S4 IR- This is the trademark name of the excimer laser manufactured by VISX used for customized or non- customized laser vision correction. Other companies manufacture excimer lasers used for customized LASIK and PRK. Alcon manufactures LADARVision 4000. We at Grendahl Eye Associates have chosen the VISX STAR S4 IR.

7. Wavefront map - A sophisticated way to represent the 100% unique vision imperfections of the human eye. These maps are created by passing a narrow ray of eye-safe light through the optical system of the human eye and printing out the resultant measurements of the optical distortions (aberrations) of the light as it passes out of the eye.

8. Aberration- An irregularity or departure from the norm. In this context, it is a departure of the wavefront from a normal planar surface. In this context, an imperfection in the human eye affecting vision. For example vision can be blurry, point light sources like street lights have hallows around them or star burst effect.

9. Wavefront- Describes how light travels out or propagates in space from a light source. In this context first a narrow ray of eye-safe light is made to pass through the optical system of the human eye and forms a point light source on the retina. The light propagates or travels back out of the eye in the form of a surface called a wavefront .

10. Low order aberration- A collective term for a series of common vision imperfections including myopia, hyperopia, and astigmatism. These are the vision imperfections corrected in conventional or non- custom LASIK and PRK.

11. Higher order aberration- A collective term for a series of imperfections in the eye's optical system that may result in vision problems experts believe to be responsible for low-light vision difficulties. A combination and varying amount of these aberrations is what makes the eye's imperfections 100% unique just like your fingerprints or DNA. These and lower order aberrations are the vision imperfections corrected in custom LASIK and PRK (CustomVue).

12. Wavefront guided treatments- The CustomVue procedure utilizing the WaveScan derived information to drive the STAR S4 IR excimer laser in customized LASIK and PRK.

Wavefront Technology and CustomVue

Individualized Laser Vision Correction is now a possibility so that you can achieve your Personal Best Vision. CustomVue Individualized Laser Vision Correction was developed by VISX, the company recognized for bringing innovation and breakthrough technology to laser vision correction. With CustomVue, a new standard in laser vision correction is established, providing a precise level of measurement and correction never before possible.

Using Wavescan based digital technology, originally developed for astrophysics to reduce atmospheric distortions when viewing distance objects in space through high-powered telescopes, eye surgeons can now identify, measure, and correct imperfections in your eyes 25 times more precisely than with standard methods used for contacts, glasses and conventional LASIK or PRK. This information is transferred to the laser by a floppy disk and directs the laser to correct the unique imperfections, providing a new level of precision and accuracy never before possible.

Just like a fingerprint, each person's visual imperfections (optical aberrations) are 100% unique to each of there eyes. Before the recent advancements in technology, eye surgeons were only able to use standard equipment (phoropter and trial lenses) and measurements to correct vision by the Excimer laser.

Phoropter		trial lenses

This meant that prescriptions ( -6.00 -2.25 x 90 ) could only provide a certain level of laser vision correction regardless of an individual's unique vision imperfections called optical aberrations. In the past, the eye surgeon typed in the prescriptions into the laser computer and this drove the laser vision correction.

Now, the VISX CustomVue procedure utilizes the WaveScan and the STAR S4 IR and can measure and correct the unique visual imperfections (optical aberrations) so that you can achieve your Personal Best Vision.

How does CustomVue Wavefront guided treatment proceed

The laser vision correction process begins with a consultation with your eye surgeon, where you can learn about the technology and the procedure. You will first sit in front of the WaveScan System and look at a light through an opening in the system while it scans your eye. We may take more than one measurement and then choose the most appropriate one to use as a basis for the CustomVue PRK or LASIK treatment. You will go through a comprehensive eye examination. This includes the standard and cycloplegic refraction, corneal topography, corneal thickness measurements, a check for cataracts and glaucoma, and assessment of eyelid and orbit anatomy to see what microkeratome will be used if you decide to have LASIK. The doctor will also take other routine measurements of your vision to help design your treatment. Then you will go through a risk and benefits discussion about refractive surgery, and you will be counseled as to whether you are a candidate for CustomVue or conventional laser vision correction. Once it's confirmed that you are a good candidate for laser vision correction the procedure can be scheduled.

If you are a candidate for CustomVue Wavefront guided laser vision correction the process is capture, match and treat. The captured wavefront information is used to calculate the unique laser treatment (algorithm) to correct your 100% unique vision imperfections (aberrations). The special software in the WaveScan computer calculates how much tissue is to be removed in the center of the cornea to achieve the desired amount of myopic and astigmatic correction, how much and where the tissue is to be removed to correct higher order aberrations, the size and number of the variable spots scanned across the cornea to achieve this and a smooth transition out to the periphery from the treatment zone. Simultaneously it constructs the treatment algorithm to minimize the amount of corneal tissue removed and minimize treatment times. All of this is called the treatment algorithm. The treatment algorithm is then dumped onto a floppy disk.

On the day of the procedure, anesthetic drops are placed into the eyes. The patient's unique correction information is transferred from the WaveScan to the laser. This is done by placing the floppy disk is into the computer of the VISX STAR S4 IR excimer laser, for each eye to be treated. Then we match the wavefront information (the treatment algorithm) to the eye (orientation - registration and centration). After this is achieved we proceed with the treatment. The laser correction works by gently reshaping the cornea with the cool beam to remove microscopic amounts of tissue - less than the thickness of the human hair - to create the new unique shape. The laser typically takes 20 to 30 seconds and the majority of individuals feel no discomfort. Many people notice immediate results after CustomVue and vision continues to improve over several days. Routine follow-up visits complete the process.

Benefits And Results

One year after the CustomVue procedure, patients in a clinical study reported:

1. 98% could see 20/20 or better 2. 70% could see 20/16 or better 3. 23% could see 20/12.5 or better 4. 100% could pass a drivers test

The results are shown in graphic form in the above figure on the left for wavefront guided treatments (CustomVue procedure). The bell shaped curve above right demonstrates the shift to the left when compared to conventional procedures below right. As a comparison, Conventional LASIK resulted in 76% of people achieving 20/20 or better, while 98% CustomVue LASIK patients achieved 20/20 or better. See the figure below left. The circled portion of the graph below is the same group of people with myopia in a similar range ( 0-6.00) compared to the CustomVue procedure results above left.

In the clinical study, most patients got an improvement in night vision and overall quality of vision compared to wearing glasses or contacts (pre-op). Four times as many people were very satisfied with their night vision after the CustomVue procedure as compared to their night vision before with contacts or glasses. In the figures below pre-op refers to glasses or contacts and 6 months refers to 6 months after Custom Vue Wavefront guided Ablation. Of the 85% of people who reported that they were very satisfied or satisfied, 44% were very satisfied.

One year after the CustomVue procedure, patients in a clinical study reported that there was an over all improvement in quality of vision:

1. Sharpness and clarity improved 2. Over all vision comfort improved 3. Consistency of vision improved 4. Less people were dissatisfied 5. More likely night vision will be improved 6. Less glare at night

In the clinical study, four times as many people were very satisfied with their night vision after the procedure as compared to their night vision before with glasses or contacts lenses. The photos on the left represent vision before the CustomVue procedure while in glasses and contacts and the photos on the on the right after the CustomVue procedure. The same vision quality differences can be represented for conventional LASIK and PRK (left) and after the CustomVue procedure (right).

Currently CustomVue PRK and LASIK treatment can correct up to -11.00 diopters of nearsightedness with up to -3.00 diopters of astigmatism. Treatments can correct up to +3.00 diopters of hyperopia with up to -3.00 diopters of astigmatism. Mixed astigatism can also be corrected. When the magnitude of the astigmatism (from 1.00 to 5.00) is grater is grater than the magnitude of the sphere. If you have nearsightedness, hyperopia and /or astigmatism within this range, CustomVue PRK or LASIK treatment may help you see distant objects clearly and become less dependent on eyeglasses or contact lenses.

The VISX Star S4 IR Excimer Laser

VISX laser systems have been used to perform millions of laser vision correction procedures in the U.S. and around the world. Every year, more doctors use VISX lasers to perform laser vision correction surgery than any other system. The VISX STAR S4 IR can be used in combination with the VISX CustomVue wavefront device to correct the unique imperfections of each individual's eye. This is called wavefront-guided treatments (CustomVue). The VISX STAR S4 IR can all so be used for conventional LASIK and PRK treatments. The excimer laser produces a beam of cool ultraviolet light. The eye surgeon programs your information into a computer that controls the laser. The laser produces a series of rapid pulses that remove small and precise amounts of corneal tissue. Excimer laser light does not penetrate into the eye and leaves other structures (iris, lens, retina) undisturbed.

The VISX STAR S4 IR is one of the most advanced systems on the market today. This technologically advanced laser offers faster treatments and corneal tissue sparing using variable spot scanning beam technology, resulting in smoother treatments and an eye tracking system that track eye movements in all three dimensions.

The VISX STAR S4 IR variable beam technology allows the eye surgeon to treat patients with different laser beam sizes and shapes, determined by each person's unique visual imperfections. The variable spot scanning (VSS) is used in Custom Vue Wavefront guided treatments during the entire procedure and in conventional treatments to create just the blend zone. During Custom Vue Wavefront guided treatments spot sizes varying between .65 to 6.5 mm are used to remove the corneal tissue. These varying spot sizes first create the central optic zones, correcting the myopia and astigmatism as well as correcting the higher order aberrations, followed by blending this out into the periphery. The VISX STAR S4 IR Smart Beam technology variable spot scanning (VSS) adjusts beam size and number of pulses of a given beam size according to the 100% unique treatment plan for your eye, minimizing the amount of corneal tissue that needs to be removed and minimizing treatment times.

The VISX STAR S4 IR excimer laser system produces an extremely smooth treatment surface on the cornea after the procedure. Smoother treatments promote faster healing and result in better visual outcomes. Unlike other laser systems with eye tracking technology the VISX STAR S4 IR with Active Track requires no pupil dilatation, leading to an even quicker visual recovery time.

The laser also contains an auto-centering eye tracking system, which will automatically compensate for any of your eye movements during the CustomVue treatment or conventional LASIK and PRK. The infrared cameras detect and compensates for any small eye movements by guiding the laser beam to keep it centered precisely over the treatment area. This is the only system that allows the eye surgeon to track eye movements in all three dimensions. Having the laser beam centered correctly on the eye at all times helps ensure precise results.