What is an Excimer Laser Procedure?
The Excimer Laser shapes the front surface of the eye with a very short wavelength of light energy. This is called Photorefractive Keratectomy, or PRK. It is a safe, non-invasive out-patient treatment which corrects nearsightedness and astigmatism. The Excimer Laser utilizing the multi-pass/multi-zone technique is by far the most technologically advanced method of correcting nearsightedness, farsightedness and astigmatism.
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How do I know if I am a candidate for this surgery?
PRK can be performed on almost anyone who has myopia (nearsightedness) and/or astigmatism or hyperopia (farsightedness). A myopic eye is one which can focus on objects close up, but objects in the distance appear blurry. A myopic eye is either too long for its focusing power or the cornea (the clear 'window' in front of the eye) is too steep. Astigmatism occurs when there is an irregular curvature of the cornea. A hyperopic eye is one for which objects at close or intermediate distances are blurry. It is either too short for its focusing power or the cornea is too flat. A highly specialized device is used to make a detailed map of the surface of the eye prior to surgery. This topographical map is interpreted by the surgeon to determine how the Laser can best correct the patient's vision.
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How does the Laser correct my vision?
As stated before, there are two reasons why people are nearsighted. The cornea is responsible for more than 60% of our focusing and it is easily modified. The Excimer Laser flattens the cornea by essentially vaporizing a minute portion of tissue from the top surface of the eye to change the curvature of the cornea. The laser affects 20-80 microns (1 micron = 1 thousandths of a millimetre) of tissue, or 4 to 15% of the cornea, without disturbing any surrounding tissue or weakening the structure of the eye.
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Is this a painful procedure?
The procedure itself is virtually painless. Prior to surgery, the patient has drops applied to the surface of the eye to numb it. During the procedure, the surgeon uses the laser to remove the outer layer of 'skin' (the epithelium) on the cornea to prepare the surface for treatment. This layer usually grows back within 3-5 days. During this time patients may feel a slight irritation or scratchy feeling. The patient will use a combination of drops as well as a bandage contact lens which makes the eye more comfortable.
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How long does the procedure take?
The initial consultation and examination prior to surgery take approximately 1 hour. If you are a contact lens wearer, your lenses will need to be out for 1-3 weeks prior to this exam. During the exam your pupils will need to be dilated with drops which may distort vision and make you light sensitive for several hours. On the day of surgery, the eye is numbed with drops prior to the treatment. The procedure takes approximately 15 seconds to 3 - 4 minutes, with the laser time being only 15-120 seconds, depending on the amount of correction required.
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Do I need to take time off work?
Patients are advised to take at least three days off work and avoid strenuous activity after surgery. This period of time is critical to the healing and stability of the eye. Time off work will vary on the individual and occupation. Individual assessment is required to determine the time needed for recovery.
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What kind of vision can I expect with PRK?
This depends largely on the amount of correction required. Very high degrees of myopia may not achieve the full desired correction with a single treatment. Most others can expect a high degree of predictability. The majority of people can expect vision very similar to what they had with glasses or contact lenses. Vision is typically quite blurry in the first week or two following surgery, with the lower prescriptions gaining better vision more rapidly. Most patients with lower prescriptions (-1 to 6 diopters) should be able to legally drive without correction after about 1 week. Please ask one of our technicians about visual options if you are wearing bifocals.
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What are the risks?
Data gathered from follow-up studies indicate few complications with the Laser procedure. However, as with all medical procedures there are always risk factors to be considered. The three main concerns with PRK are infection, corneal haze and under or over correction. Patients are given a prescription for an antibiotic drop following surgery. If the drop is used as directed while the epithelium is healing, the risk of infection is rare. A superficial, transient corneal haze can be detected on some patients following surgery. This does not usually affect visual acuity. In most cases, the haze disappears within 6-8 weeks. Rare cases of persistent haze have been successfully removed with the Laser. Under corrections can be retreated with a retreatment procedure. Patients are initially over corrected as the normal healing process allows for regression to the desired correction. Permanent over corrections are extremely rare.
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What are the benefits?
Freedom from glasses or contact lenses! Participating in sports and leisure activities without the hassle of corrective lenses; occupational options (eg. Police Dept., Fire fighters, etc.); being able to see the alarm clock in the morning and numerous other benefits!
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Excimer Laser Corneal Surgery
There are several types of Excimer Laser corneal surgeries available.
Photorefractive Keratectomy (PRK) . The technique combines the use of a surgical blade and the excimer laser to remove tissue from the surface of the cornea to correct a refractive problem. Removal of tissue is precise and does not weaken the cornea.
Laser Assisted In-Situ Keratomileusis (LASIK). LASIK combines the older method of splitting the cornea with a blade called a microkeratome to form a flap. The inside of the cornea is then treated with the excimer laser. This type of surgery is known for having quicker initial healing and less discomfort than Standard PRK but is more invasive and carries increased risk.
'no touch' T laser vision correction. This technique evolved from PRK. It also treats the surface of the cornea, but unlike Standard PRK or LASIK, requires no assistance from manual surgical instruments. It is the only technique to use exclusively the excimer laser from start to finish.
Phototherapeutic Keratectomy (PTK). This procedure uses the laser to remove tissue from the cornea to correct a medical problem with the cornea such as recurrent erosions or a dystrophy.
top of page Who Qualifies For Laser Vision Correction?
It is essential for anyone interested in laser vision correction to have a full eye examination to determine if they are a suitable candidate or not. However, the following list of conditions can be used as a general guideline.
The patient should:
- be 18 years of age or older
- have stable vision for at least one year prior to surgery
- have healthy eyes, free from ocular disease (some general health and eye problems could affect healing)
- have realistic expectations for surgical outcome
- accept that due to natural aging conditions, will likely need some reading magnification as they reach their 40's and 50's
Candidates for
'no touch' T laser vision correction.
Presently, patients with virtually any degree of myopia (nearsightedness); hyperopia (farsightedness) or astigmatism can be treated. Results show an extremely high predictability with excellent visual outcomes.
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The 'no touch' T Procedure : Myopia and Astigmatism
The majority of surgical time is spent preparing both the laser and the patient's eye for the operation. The eye is prepared by anaesthetizing it with drops. Laser preparation involves programming the laser's computer to the eye's individual characteristics.
During the procedure the laser sculpts (ablates) the tissue of the cornea. With our 'no touch' T technique, no instrumentation beyond the laser, is in contact with the cornea. Flattening of the eye is achieved by removing more tissue from its centre than its periphery. The sculpting usually lasts between 30 seconds and 3 minutes (however, the total time in the operating room is approximately 5 minutes per eye). The sculpting produces the desired curvature by a computer controlled aperture opening in a circular or linear manner. This allows a different time exposure to the laser pulses to vary throughout the treated area in relation to the required curvature. The patient feels nothing during this process. The eye is held open with a retainer so the patient doesn't have to worry about blinking or closing their eye.
Immediately after surgery the eye is fit with a bandage contact lens, usually for two or three days. The patient normally has little pain or discomfort post-operatively. The patient is however, advised to rest for the remainder of the day following treatment.
Vision is relatively good once the epithelium has grown back and the corneal surface has smoothed itself (usually two or three days). Within the next three weeks, predictable changes occur as healing stabilizes the end result. The vision is quite functional during this period. Stable vision should be accomplished between one to six months after the surgery. Results vary with different degrees of near and farsightedness and astigmatism, and individual healing rates.
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Pain
Pain is not a significant problem with 'no touch'T laser vision correction. Approximately 40% of our patients report no pain. The majority have grittiness or burning, some watering and light sensitivity lasting less than 12 - 24 hours, and very few state that they had extremely disruptive pain. Virtually everyone is comfortable the next day. For control of pain, a bandage contact lens is used to shield the treated area. This is accompanied with analgesic drops and anti-inflammatory / antibiotic drops that are given to all patients. The average patient may take between two and four Tylenol 3 tablets during the healing time and possibly one relaxant tablet the first night.
Pain should not be a reason to consider more complicated, higher risk or invasive procedures such as LASIK.
Recovery Time
Time is a most valuable commodity. The amount of downtime (time away from work or relative duties) is an important consideration in having treatment. The vast majority of patients choose bilateral (both eyes) surgery which in turn means quicker return of binocular vision. 'no touch' T has also sped up recovery time due to faster healing.
Patients are functional the day of surgery meaning that they are mobile and are able to manage routine tasks on their own. However, we do recommend that patients have someone close at hand for assistance. Legal driving vision is usually attained between day three to day five. Statistics show the majority of patients are able to drive by at least day four. Depending on age, "over the counter" reading glasses may be necessary for the early recovery days. Return to work depends on occupation. Two days to one week is normal. The eye is not weakened structurally with 'no touch' T, so activity is generally not a problem.
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The Surgical Procedure : Hyperopia and Hyperopic Astigmatism
Myopia was the first refractive error to be corrected with laser vision correction. Subsequent to this, astigmatism correction was developed and more recently, hyperopic or farsighted correction and farsighted astigmatism. Considerable research and development of the hardware and software components was required for each of the above refractive error corrections.
At Total Vision Eye Care we use two different lasers for farsighted correction:
1. Hyperopic Excimer Laser Correction
At present, Total Vision Eye Care is performing hyperopic correction over two diopters with the Excimer laser. This is done with a slight variation of our 'no touch' T procedure. For hyperopia, the periphery of the cornea must be treated and therefore a larger area of surface epithelium is removed. In most cases, this is dissolved by placing a liquid solution on the intended area. No surgical instruments or incisions are required.
Recovery after the Hyperopic Excimer Procedure
Healing and recovery time is longer with hyperopic treatment than with myopic treatment because the zone treated is larger (9mm). It is for this reason that some farsighted patients are treated one eye at a time or suggested to allow for additional time from work. Most farsighted patients will become temporarily nearsighted during initial healing leaving good near vision during the first few days, but causing some distance frustration. Temporary distance correction may be needed in some cases.
2. Hyperopic Holmium Laser Correction
The Holmium laser has been used at the clinic since 1993. The value of the Holmium laser is its safety and very short downtime required post treatment. The Holmium laser uses an infrared wavelength to tighten the tissue around the edges of the cornea. This results in the steepening of the cornea. No removal of the outer skin layer (epithelium) is required. being minimally invasive, this procedure has little risk and requires less follow up care. The procedure is called Laser Thermal Keratoplasty (LTK).
The Holmium is limited in its treatment potential. Selected patients of two diopters or less of hyperopia do very well with this procedure. It is also the treatment of choice if over correction occurred with excimer laser treatment of nearsightedness. LTK is also used to reduce dependency on reading glasses due to aging changes (presbyopia). See monovision below.
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What is Monovision / Will I Need Reading Glasses?
Some patients who choose to have refractive eye surgery may already be aware of a condition called presbyopia. This condition is the requirement for reading glasses. Not to be confused with hyperopia (farsightedness), patients who have to wear reading glasses do so because the lens inside the eye has become rigid with age.
A common solution to this is either bi-focal or progressive glasses or specially fitted contact lenses. With contact lenses one lens can be adjusted to intentionally leave you slightly nearsighted. This difference (usually about 1 diopter) is enough to aid your vision and your brain to "accommodate" and lessens the reading glasses requirement. This is known as monovision.
Therefore, just as contact lenses can have different amounts of correction to lessen your dependence on reading glasses, so can laser vision correction. If you presently are presbyopic, wearing bi-focals or monovision contact lenses, our technical team can advise you on how to lessen your dependency on reading glasses presbyopia by intentionally under correcting your non-dominant eye. This, in effect, will give you monovision. This concept should not be decided until discussed and demonstrated at time of examination.
If all you require is reading glasses, monovision can be a solution for you, using holmium laser on only one eye.
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