The Excimer Laser is one of the greatest inventions in ophthalmology. The Excimer Laser is the device that physically corrects your glass prescription during surgery.
LASIK is Laser Assisted in SItu Keratomileusis.
It is kind of Laser eye surgery for correcting various kinds of refractive errors or eye powers like Myopia(-power), Hypermetropia(+power) or Astigmatism(cylindrical power).
Many people choose Lasik instead of wearing Glasses or Contact lenses.
Let us see what the refractive errors are all about? |
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What is Myopia?
Myopia or nearsightedness is a defect of the eye in which the person is able to see near objects clearly but distant objects appear blurred.
3 types:
Axial myopia: the axial length of the eye is large
Curvature myopia: the myopia is due to increased curvature of Cornea
Index myopia: the myopia is due to cataract formation
The usual treatment for myopia is Glasses, Contact lenses or LASIK Lasik is not suitable for Index myopes. |
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What is Hypermetropia?
Just opposite to myopia if the eyeball is short or the cornea is flat the patient is unable to see objects especially for near. Hypermetropia is often confused with Presbyopia which is a defect usually appears at the age of 40 years due to a loss of accommodation of the lens causing a similar problem of not being able to see near objects.
These Refractive errors usually become stable by the age of 18 years. |
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 What is Astigmatism ?
Astigmatism causes difficulties in seeing fine detail. In some cases vertical lines and objects such as walls may appear to the patient to be leaning over like the Tower of Pisa. Astigmatism can be often corrected by glasses with a lens that has different radii of curvature in different planes (a cylindrical lens), contact lenses, or refractive surgery. |
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| Spectacles (most common) |
| Contact Lenses (Soft lens, Soft Toric lens, RGP lens) |
| Excimer Laser treatment: |
LASIK(90% of the procedures) |
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PRK |
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LASEK |
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Epi-LASIK (currently we are not doing it) |
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| Implantable collamer lens |
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Laser eye surgery is a treatment that reshapes your cornea in order to produce clear vision. The Laser refractive eye surgery procedure can treat myopia (nearsightedness), hyperopia (farsightedness), and astigmatism, and reduce your dependency on contact lenses or glasses.
After successfully undergoing Laser eye surgery, the benefits you will be most excited about is your new-found freedom from corrective eyeglasses and contact lenses. New career opportunities will open up. |
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| However you are not a good LASIK candidate if one or more of the following conditions apply to you: |
- Your age is under 18. In this case your growth phase has not been fully completed. This means that your eyes can still change. In that case LASIK is not a good option.
- You are pregnant or nursing. Pregnancy causes changes to your hormone system. This can also cause your vision to change. It is therefore better to wait until your child is born and you have finished nursing.
- You have glaucoma
- Keratoconus a corneal irregularity
- Inflammation of the eye (uveitis, blepharitis or iritis)
- Herpes simplex infection of your eye
- Previous severe injuries on the eye
- Corneal scars or infections
- Certain medications: Isotretenoin for Acne & Amiodarone for cardiac reasons.
- Unstable refraction.
- If your visual loss is attributable to AMD, diabetic retinopathy, cataract or others
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| If any of the indications listed above apply to you, make sure to consult our ophthalmologist prior to considering LASIK. |
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| LASIK is also not recommended for patients with: |
- Very large pupils
- Thin corneas
- Dry eye
- Unstable refractive errors
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If any of these apply, the right technology or surgery technique can still be suggested by your attending ophthalmologist who will provide you with an appropriate treatment plan. But make sure you discuss the risks in detail with your doctor.
At DISHA we offer you the ALLEGRETTO WAVE Excimer Laser with the ALLEGRETTO OCULYZER providing the most safe and advanced laser vision technology available to date. |
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Why is our LASIK so safe?
OCULYZER
Based on the proven Pentacam technology, the ALLEGRO Oculyzer adds a new dimension to customized surgery, providing the most extensive diagnostic information about the anterior segment of the eye before LASIK.
Used in conjunction with the integrated Oculink software and a WaveLight laser system, the Oculyzer enables us to perform advanced topography-guided treatments across the entire cornea.
The ALLEGRO Oculyzer is the solution for difficult cases, in which standard wavefront and regular topography measurements would not prove clinically efficient. |
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| SURGICAL PROCEDURE |
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| Following are the basic steps of a typical LASIK procedure: |
- You will be positioned under the laser and directed to look at a specific Green light.
- Anesthetic drops will be used to numb your eyes so there will be no pain.
- Eyelids and lashes are then cleaned, covered and held open with drapes and a gentle eyelid holder so that they are out of the surgical field.
- Cornea is marked to assist the surgeon in realigning the flap at the end of the procedure.
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| 2 Step Procedure |
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| STEP 1 |
- A suction ring is placed on the eye, giving a little squeezing sensation to hold the eye steady; lights usually disappear for a few seconds.
- MORIA Microkeratome "flapmaker," (much like a carpenter's plane) is used to make the flap.
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| STEP 2 |
- Surgeon centers the laser.
- Laser is activated, the surgeon carefully watches patient’s eye to be sure it remains in position while the eye tracker is constantly adjusts for micro movements and proper pulse placement with utmost accuracy.
- Flap is repositioned so surface is smooth; inner surface is rinsed.
- Drapes and eyelid holder are removed.
- Antibiotic and anti-inflammatory drops are started.
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| SOMETHING ABOUT OUR TECHNOLOGY |
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| FLAP MAKING |
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The LASIK vision correction procedure begins with the creation of a hinged corneal flap. After the eye is anesthetized with topical eye drops, the LASIK eye surgeon will create the flap on the outer surface of your cornea to expose the underlying cornea. The flap will be created with a microkeratome (a hand-held device).
The MORIA M2 microkeratome which will be used is driven directly and independently by 2 independent motors ensuring highest reliability.
At this point of time you may feel some pressure in your eyes due to the suction ring and the light perception will be lost temporarily for few seconds till the flap making is over. |
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| SPEED |
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With a repetition rate of 200 Hz, the ALLEGRETTO WAVE treats one diopter in only four seconds. When having your eyes treated, the speed of each laser pulse that is applied to the cornea is very important. If the laser is too slow and you have a high power, the exposed flap may shrink because of the time it takes to correct your vision. Older lasers only apply 10 to 60 pulses of the laser per second. The ALLEGRETTO WAVE Excimer Laser applies 200 individual laser pulses per second ensuring the fastest treatment for optimal results.
An example of this would be a car that only goes 10 km/h. If you were trying to go 20 kilometers it would take you 2 hours to get there but if you were driving 200 km/h it would only take you 6 minutes. In this case, the longer it takes you to have your eye treated, the higher the risk of an adverse result.
Only the ALLEGRETTO WAVE Excimer Laser has the ability to provide fast and precise treatments increasing your likelihood for a successful procedure and decreasing your chances for complications due to dehydration of the flap and corneal surface.
This means that the average low myopic treatment takes only about 10 seconds or less…the time it takes you to pour yourself a cup of coffee. |
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| EYE TRACKER |
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The best example of the relationship between the eyetracker and the laser is to try and imagine throwing a ball at a moving object that is going 200 miles an hour. Although you can see the moving object, your reflexes are too slow to adjust to the constant changes of the moving object. As a result, every time you throw the ball you are missing the moving object.
The ALLEGRETTO WAVE Excimer Laser encompasses both a 250 Hz eyetracker with the ability to react between 4 to 8 ms. The human eye has a maximum twitch rate of 60 Hz. This optimizes the ability of each pulse being placed on the appropriate spot on the cornea.
So there will be no erroneous or misplaced pulses contrary to the older laser technology. |
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| Beam size and profile |
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A small diameter laser beam or also known as spot size is very important for both accuracy and smoothness. An ideal beam size is approximately 1mm or less. If the size of the laser beam is larger the result is that the beam is too large to make fine adjustments throughout the cornea.
Imagine filling a fishbowl with marbles compared to filling is with sand. The marbles allow gaps while the sand contours and fills the fishbowl exactly.
While beam size is critical so is the type of laser beam that is being used. A Gaussian beam allows for the smoothest corneal surface as compared to non-Gaussian beams. The result is that with a small beam less than 1 mm with a Gaussian profile allows for the proper and accurate treatment of the smallest curvatures of the cornea and also allowing for a smooth corneal surface. |
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| OPTICAL ZONES |
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Optical Zone is the term used to describe the size of the treated area of the laser that will be applied to the surface of the cornea. Older generation lasers typically can only treat pupils no larger than 6.5mm since the largest optical zone they can use is 6.5 mm. If your pupils are larger than 6.5 mm then your chances for night vision problems increase significantly if your eyes are not treated with a laser that can provided larger optical zone ranges. Only the ALLEGRETTO WAVE Excimer Laser combines optical zones from 5.5mm to 8mm. This allows the physician to customize your treatment to maximize your desired outcome and reduce or eliminate night vision problems.
The ALLEGRETTO WAVE Excimer Laser allows each patient to receive a truly customized treatment for pupil sizes up to 8mm. This not only increases your quality of vision during the day but also reduces or eliminates night vision. |
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| LASEK (Laser Epithelial Keratomileusis) |
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LASEK corrects nearsightedness, farsightedness, and astigmatism. It is similar to PRK except that the surface layer (the epithelium) is replaced after surgery. Both PRK and LASEK are similar to LASIK in that they use the excimer laser to shape the cornea, but unlike LASIK neither procedure preserves the surface layers. PRK and LASEK are sometimes recommended instead of LASIK for people with thin corneas because they do not penetrate as deeply into the eye's surface.
In LASEK, the epithelium is loosened and peeled back to expose the cornea. The excimer laser then reshapes the cornea, the epithelium is placed back into position and a bandage contact lens is placed on the eye to facilitate healing. Like LASIK, recovery time is rapid but discomfort is somewhat increased compared to LASIK. |
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| SIDE EFFECTS |
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Night vision disturbances : are often described as ghosting, haloes or glare. Night vision disturbances resulting from laser eye surgery can occur from laser treatment areas that are smaller than the actual pupil size. This is because in dim or low lighting conditions, such as at night, the pupil dilates (gets larger).
These disturbances were more common with previous generation lasers (pre-1997). They had the potential to cause night vision disturbances because they were only able to treat a small area of the corneal surface; an area smaller than the dilated pupil. |
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| Adverse Events |
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| Adverse Event |
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| Corneal infiltrate or ulcer requiring treatement |
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| Lost, misplaced or misaligned flap, or any flap/cap problems requiring surgical intervention beyond 1 month |
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| Corneaal edema at 1 month or later visible in the slit lamp exam |
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| Any comlication leading to intraocular surgery |
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| Melting of the flap of >1mm sq |
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| Epithelium of > 1mm2 in the interface with loss of 2 lines or more of BSCVA |
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| Uncontrolled IOP rise with increase of > 5 mm Hg or any reading above 25 mm Hg |
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| Retinal detachment or retinal vascular accident |
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| Decrease in BSCVA of > 10 letters not due to irregular astigmatism as shown by hard contact lens refraction |
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| Complications Summary table |
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| Adverse Event |
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| Corneal edema between 1 week and 1 month after the procedure |
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| Corneal epithlial defect at 1 month or later |
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| Any epithclium in the interface |
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| Foreign body sensations at 1 month or later |
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| pain at 1 month or later |
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| Ghosting or double images in the operative eye at stability or beyond |
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| Need for lifting and / or reseating of the flap / cap prior to 1 month |
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