This process is called stimulated emission. The bombarding photon and the emitted photon may then each strike other excited atoms, stimulating further emission of photons, all of the same frequency and phase. This process produces a sudden burst of coherent radiation as all the atoms discharge in a rapid chain reaction.
What are the types of Lasers?
There are many different types of Lasers. The Laser medium can be a solid, gas, liquid or . Lasers are commonly designated by the type of lasing material employed:
- Solid-state Lasers
- Gas Lasers
- Excimer Lasers
- Dye Lasers
-
Semiconductor Lasers
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Here are some typical lasers and their emission wavelengths:
What are the Uses of Lasers?
First built in 1960, lasers now range in size from semiconductor lasers as small as a grain of salt to solid-state and gas lasers as large as a storage building. The light beam produced by most lasers is pencil-thin and maintains its size and direction over very large distances.
Lasers are widely used in industry for cutting and boring metals and other materials, in medicine for surgery, and in communications, scientific research, and holography. They
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are an integral part of such familiar devices as bar-code scanners used in supermarkets, scanners, laser printers, and compact disk players.
Laser eye treatment works by using an excimer laser to gently reshape the cornea, which is the clear domed front surface of the eye. This helps light images to focus on or near to the retina improving vision.
WHAT IS LASIK SURGERY?
LASIK being performed in the operation theatre
Laser Assisted In-situ Keratomileusis (LASIK) is similar to PRK, but does not treat or alter the very front surface of the cornea. A liquid anesthetic is dropped into the patient's eye, numbing it for surgery. The surgeon then props the eyelids open and marks the cornea with water soluble ink to guide in the later repositioning of the flap. A suction ring
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is placed on the eye to secure the eye and maintain pressure within the eye while the cornea is drawn outward. Simultaneously, a microkeratome (a small, automated scalpel) is placed in the track of the suction ring. The blade of the microkeratome then moves across the cornea, creating a flap of corneal tissue some 30-40% deep into the total corneal thickness. This layer is not cut away completely, but remains attached at one side and is then opened like a door on a hinge to reveal the stromal bed beneath. . The flap is then gently lifted up and the excimer laser is used to remove a precalculated microscopic amount of tissue underneath it. The flap is then repositioned for a quick and natural recovery.
Patients can experience the results of LASIK almost immediately, with most experiencing a marked improvement within 24 hours.
What is PRK or Photorefractive Keratectomy?
In PRK, the Laser was used on the surface of the cornea. But this procedure has been largely superseded by the Lasik method in which the Laser treatment is applied under a protective corneal flap.
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What is the Excimer Laser?
Excimer Laser being used
This is a modern adaptation, using the Excimer Laser which was originally developed for the manufacture of computer microchips to etch the circuits. However, its extreme accuracy resulted in it being developed as an eye laser. The LASIK technique leaves the original surface of the cornea virtually intact, the mild healing process results in minimal regression and no scarring. The LASIK procedure is now regarded as the most advanced refractive surgery technique.
This method of using the Excimer Laser to correct refractive errors is a breakthrough which can benefit millions of patients who are shortsighted or have other refractive errors. The technique has advanced to a point where we can reliably predict that Excimer Laser treatment will, in suitable patients, provide good vision without glasses or contact lenses. For people who undergo Excimer Laser procedures, less dependency upon corrective lenses is a major benefit.
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The Excimer Eye Laser is extremely accurate and removes only 0.25 microns (1/4000 th millimetre) of tissue per pulse. During the re-sculpturing the Laser gently "evaporates" tissue; there is no burning or cutting involved. In most cases the Laser treatment takes only 20 to 45 seconds depending on how severe your refractive error is. The Excimer Laser accurately re-sculptures the cornea to make the curve of the cornea balance the length of the eye; light rays are then focused normally on the retina.
Before Treatment After Treatment
In myopia the cornea is flattened (as shown above), whereas in hyperopia the cornea is made more curved. With astigmatism the surface of the cornea is re-sculptured to a regular curvature.
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WHAT DOES LASIK ACTUALLY DO?
The intent of (refractive) eye surgery is to change the natural curvature of the cornea in order to alter the eye's focusing power.
According to the FDA, this treatment may improve distance vision in far-sighted people who have difficulty seeing clearly at a distance. Although some patients may retain some or all of the correction achieved during the surgery, for most people the amount of farsightedness correction achieved will decrease over time. The amount of correction remaining at 24 months is typically about half of the correction observed at 6 months. Some patients will regress completely but correction depends on the amount of correction attempted and age.
IS LASEK BETTER THAN LASIK?
Laser Epithelial Keratomileusis (LASEK). This new procedure resembles LASIK but still has significant differences. In the LASEK surgery the surgeon cuts an ultra-thin flap of the outermost part of the cornea, the epithelium and applies an alcohol solution to loosen it up and make it easily manipulable. It must be noted that there are serious questions as to the impact this alcohol has as it permeates various structures in the eye.
The surgeon then lift the flap he has just created and then uses the same laser used in a LASIK procedure to ablate (vaporize) the corneal tissue at a layer closer to the outer
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surface than the way it's done in LASIK. The epithelial flap is then replaced and the patient is given a contact lens to wear for a few days as the eye heals.
The procedure is in clinical trials. Some think LASEK may turn out to be an alternative to LASIK for those with low to moderate myopia. It has also been tested for those with hyperopia. LASEK is being considered as an alternative to LASEK because it may eliminate some of the flap related complication currently experienced in LASIK.
Who is a suitable candidate for LASIK?
Almost all patients with myopia, astigmatism, and hyperopia are suitable for Excimer Laser treatment. Patients with presbyopia alone cannot be treated by the Excimer Laser but may be suitable for Presby implants.
During the free screening test, one can get a good idea as to whether you are a possible candidate. However, before proceeding with treatment, a full eye examination is needed to exclude any diseases and contraindications.
The following tests are performed: -
- How much myopia, or other refractive error, is present?
- A measurement of cornea is made by computerized corneal topography
- What is the thickness of your cornea?
- The size of pupils in the dark is measured.
- Is your refractive error stable?
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- Personal information about allergies and other medical conditions that may effect the laser treatment will be requested.
A computerized corneal topography unit being used to measure corneal curvature
What are the chances of success?
The decision to undergo LASIK refractive surgery seems to be based most often on a vocational or psychological reason, which makes it an elective procedure rather than a medical necessity. Primarily, the decision to have the surgery is the patient's, unless the surgeon determines that the patient, for medical or other reasons, would not be a good candidate.
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Medical studies and scientific data may provide compelling evidence in support of having LASIK vision correction surgery performed. Nevertheless, the most convincing testimonies praising the outcomes of surgery come from the many patients who provide firsthand accounts of their successful operations that resulted in much improved vision and a better quality of life.
I have read the various opinions and comments of patients who have undergone LASIK correction and on the basis of their personal experiences, it is apparent that the correction surgery is not as easy nor as successful and the rosy picture portrayed by surgeons is evidently false. The treatment like any other surgery is laden with risks and sometimes unexpected failures.
Sally Mathews of Washington narrates the nightmare she suffered and her torture continues till date. “I had PRK 7 months ago. Went in -7 and -8 and came out +6.5 and +3.50 respectively. Experienced severe pain for a week, and was out of work for 3
months. Developed severe haze in both eyes. Had PTK in the right eye 3 months after PRK to "begin to address the problem." Experienced another week of hell (with multiple daily trips to the doc for pain med injections around the treated eye). Still have haze (both eyes). Glasses do little to help and it feels like I'm constantly looking through plastic wrap covering a fishbowl over my head. Night vision is even worse (much worse).
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After 4 "second opinions" (none with good news), I'm heading to a major West Coast medical center next week for a work up. Pretty nervous as to what I might hear.”
Shadet of Indiana has a similar story to tell. “I am writing my story with the hope that I might help someone else to not jump lightly into LASIK surgery, which can cause more complications than doctors let on. My “windows to the world” have been damaged and my doctor doesn’t seem to care. I want to thank all of you who have posted on this site, telling your stories and sharing your souls. Because of you, I’ve learned so much: I’ve read, searched, listened. If it weren’t for your posts, I would still think I’m the only one in this situation. Several days after the surgery, my vision was only up to four feet, I was so stressed out I couldn’t concentrate on anything—I called again. I was told to come in that day. My left eye was bulging (it actually was bulging immediately after surgery, but I couldn’t see it!). The surgeon said he didn’t know why and suggested I should have my thyroid checked. The blood tests came out normal and an MRI was recommended—nothing was found. At this point I knew I was in trouble. I was stressing my right eye to compensate for not having good vision in my left. I was worried about my retina (seeing flashing lights) so I went to see a retina specialist who told me my vitreous was very cloudy.
My surgeon then sent me to an ophthalmic plastic orbital surgeon. He then suggested I have plastic surgery to make my eyelids smaller to stop the bulging!”
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May 2002 Article in says: "Laser in-situ keratomileusis vision correction surgery malpractice lawsuits are on the rise, due in part to a growing number of web sites that encourage dissatisfied patients to sue surgeons.”
Dr. Gerald Horn's board says, “Bad LASIK results are so devastating that you will likely end up in therapy for depression or Post-Traumatic Stress Disorder if your vision is damaged. I am posting the letter below because the world needs to know that people ARE committing suicide because of poor LASIK outcomes.”
What are the risks involved?
Most patients are very pleased with the results of their refractive surgery. However, like any other medical procedure, there are risks involved. That's why it is important to understand the limitations and possible complications of refractive surgery.
Before undergoing a refractive procedure, the risks and benefits should be carefully weighed based one’s own personal value system, and one should not be influenced by friends that have had the procedure or doctors encouraging you to do so.
- Some patients lose vision that cannot be corrected with glasses, contact lenses, or surgery as a result of treatment.
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- Some patients develop debilitating visual symptoms such as glare, halos, and/or double vision that can seriously affect nighttime vision.
- Only a certain percent of patients achieve 20/20 vision without glasses or contacts and glasses or contact lenses maybe needed after surgery.
- Some patients may develop severe dry eye syndrome – the patient’s eyes may not be able to produce enough tears to keep the eye moist and comfortable and this may lead to blurring and other visual symptoms.
- Results are generally not as good in patients with very large refractive errors of any type and glasses may still be needed.
- For some farsighted patients, results may diminish with age.
- Long-term data is not available. LASIK is a relatively new technology. The first laser was approved for LASIK eye surgery in 1998. Therefore, the long-term safety and effectiveness of LASIK surgery is not known.
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Even the best screened patients under the care of most skilled surgeons can experience serious complications.
- During surgery. Malfunction of a device or other error, such as cutting a flap of cornea through and through instead of making a hinge during LASIK surgery, may lead to discontinuation of the procedure or irreversible damage to the eye.
- After surgery. Some complications, such as migration of the flap, inflammation or infection, may require another procedure and/or intensive treatment with drops.
Even with aggressive therapy, such complications may lead to temporary loss of vision or even irreversible blindness.
Under the care of an experienced doctor, carefully screened candidates with reasonable expectations and a clear understanding of the risks and alternatives are likely to be happy with the results of their refractive procedure.
What are the benefits of LASIK eye surgery?
LASIK eye surgery is safe and mostly successful, with complications affecting fewer than 5 percent of patients. The advantages of LASIK are as follows: -
- LASIK heals more predictably.
- It has a wider range of correction, from +4 to -12 dioptres.
- There is a quicker restoration of vision.
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- There is minimal discomfort.
- There is usually no permanent haze.
- Eye drops are needed for usually 2 weeks following treatment.
- Any enhancement to treatment can be performed by simply lifting the flap.
How successful has LASIK been?
Beverley Doohan (above) is a member of the nursing team at Drayton House Clinic, where she had LASIK surgery in March 2000 to correct her short-sightedness. Beverley had worn glasses from the age of l2. Beverley says, "Having LASIK surgery is the best decision I have ever made, both with regard to my sporting life and my confidence. I love to run and swim and both of these activities were very much hindered by having to wear glasses."
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Miss Fiona Looker (above) says "I wake up in the morning and can see clearly straight away without reaching for my glasses and I don't have to worry about dust blowing into my contact lenses."
The Results
LASIK can reduce or eliminate your dependence on contacts or glasses. Patients, who have worn corrective eyewear all of their lives, are thrilled with the results. For the first time, they're able to see the alarm clock in the morning. Even watching television becomes easier. Without corrective lenses, you'll be able to pursue hobbies and sports activities. You may also be able to pursue your career-of-choice more freely.
Corrected Vision on the Human Eye
Sports Lovers - Reducing your need for contacts or glasses will improve safety, and even increase your performance.
Readers - LASIK can reduce or eliminate your dependence on corrective lenses or glasses which is a boon for voracious readers.
Travelers - LASIK makes your traveling more streamlined as glasses and contacts are not required anymore.
Seasonal Difficulties - Cold weather causes fogging, while allergies and dust make contact lenses impossible to handle and LASIK prevents such situations.
Career Choices - For pilots, firefighters, or police officers, good vision can be extremely important and LASIK provides this.
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What has been my Personal Experience of LASIK?
My personal experience of the LASIK treatment is based on my father’s decision to undergo correction of his myopia. He has been wearing glasses since the age of 15 and although his prescription is not very high (1.5 and 2.5) he wanted to get rid of glasses as he is an ardent Golfer!
The reputation of Dr. Mann of Mann-Berkeley eye-institute based at Houston, Texas influenced our decision and after fixing an appointment, we visited the institute at Houston in July 2002. A 15 minute video demonstration of the entire surgical process was the beginning of our session. This was followed by a question-answer session with a doctor. We were very reluctant to fix the date without proper information but on the other hand, the doctor insisted on fixing the surgery the very next day. The American style of marketing wherein “A Discount” could be offered on the surgery if the decision was taken on the spot was very amusing and at the same time appalling. The doctors seemed very commercial, in a rush and insensitive to the patient’s queries - especially on the
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possible side-effects. We refused to be bulldozed by their persistence and instead bombarded them with queries to satisfy our doubts and enable us to take a decision. No statistics or figures on successes and failures were being revealed and all questions on side-effects were being evaded. Unsatisfied due to the possible side effects and realizing that although the chances of complications and failure is only 30 %, vision being restored and correction of side effects in failure cases is impossible, we left without opting for the treatment. Hopefully in the near future, the technology would improve and the chances of failure would decrease and we decided to wait till then.
What are the factors which might cause failure?
- A doctor needs only a medical license, and no special certification, to perform LASIK. Although most surgeons are ophthalmologists, they don't to have be, and their training in the procedure can range from a weekend seminar to a fellowship in corneal surgery.
- Some doctors are willing to perform Lasik surgery even on high-risk patients, who can suffer serious damage to their vision as a result.
- Some patients are not suitable candidates such as: -
- Under 18
- Pregnant
- Having a history of eye disease, from optic nerve damage, to cataracts or to problems with the cornea or corneal thinning
- Extremely large pupils
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- Very thin corneas
- Very strong prescriptions
CONCLUSION
With over 98% of patients treated achieving legal driving standard vision or better without the assistance of glasses or contact lenses, it's easy to understand why millions of people world-wide are already enjoying the benefits of laser sight correction. Although there are varying opinions on LASIK and it is not possible to draw any conclusions based on the evidences, I am of the opinion that LASIK should definitely not be taken lightly.
It is an established fact that although the success rate of such treatments has improved since the usage of the EXCIMER LASER over the PRK technique, the fact still remains that once the surgery fails due to any of the factors mentioned above, it is IMPOSSIBLE to restore vision or get rid of the side – effects and the patient may have to live with Headaches, blurred vision, dry eyes all throughout the life. The decision to opt for the treatment should be taken after evaluating all the pros and cons and having obtained consultations with one or more doctors. The side-effects and risks involved should not be overlooked and the corrective surgery should not be done for purely cosmetic reasons. Only if it is a necessity or a demand made by the profession should such an option be considered. However New Technologies are continuously being developed and I am positive that in the near future, we will be having a better Laser technique which promises 100% success rate and eradicates all the side effects and traumas involved with
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failure such as headaches and blurriness. For people whose profession or career demands it, the correction treatment should be performed but for others, I would suggest – Have patience for a few months or a couple of years and you will be able to say GOODBYE to your Glasses and contact lenses and also have guaranteed 20/20 vision restored.
Surgical Eyes - http://www.surgicaleyes.org – Patient Stories
Surgical Eyes - http://www.surgicaleyes.org – Patient Stories
Eye World Medical Journal Published in USA, Issue date May 2002 - Article on LASIK disasters
Eye World Medical Journal Published in USA, Issue date May 2002 - Article on LASIK disasters
LASIK at Drayton House Clinic – Patient Testimonials - http://www.draytonhouseclinic.com
LASIK at Drayton House Clinic – Patient Testimonials - http://www.draytonhouseclinic.com
