A life without glasses -The different laser treatment options
Laser surgery techniques for refractive vision correction were well established, both scientifically and clinically, by the mid-80s. The basic principle behind all the methods is using a laser to model the outer corneal layer so that the focal point of the bundled incidental light is on the surface of the retina itself and not in front of or behind it.
The original treatment methods, PRK and LASEK, manually removed the outer protective layer (epithelium) of the cornea before the laser surgery. The consequences often included post-operative pain and very slow recovery of visual acuity. As a consequence, laser surgery techniques which involved preparing a corneal flap (LASIK and Femto-LASIK) were then developed. Here, a mechanical cutting tool (microkeratome) or a femtosecond laser is used to create a thin flap of cornea which is just 120 micrometers thick. Almost a complete circle (270°) is cut in the upper layers of the cornea. The flap is then folded back like the cover of a book. Subsequently, the exposed corneal tissue is then ablated using an excimer laser in a separate stage of treatment. The greater the level of vision defect, the more tissue needs to be removed. In the final stage of treatment, the corneal flap is then folded back into its original position.
It then adheres in the original place over the coming weeks and months. The disadvantage is that the flap can shift or even tear off (flap displacement) as the result of rubbing or other physical contact after the operation.
The SMILE principle: The high-precision VisuMax® femtosecond laser creates a small lens (lenticule) inside the intact cornea, the volume and form of which are determined by the degree of vision defect to be corrected. This lenticule is then removed in a minimally invasive procedure from the interior of the cornea through a small access measuring just a few millimetres. In contrast to earlier techniques, it is no longer necessary to fold back the cornea. There is no flap incision, the area of the incision is reduced to a minimum and the outer corneal layers remain more or less intact. All of which is made possible by a sensitive, precise and convenient treatment method.
The treatment steps
The benefits of SMILE
In recent years minimally invasive diagnostic and treatment methods have set new standards in modern medicine. This is because minimally invasive very often means minimum discomfort for the patient. In its smile method Carl Zeiss has developed a new technique for the minimally invasive laser correction of vision defects. This innovative treatment technique yields a whole range of benefits:
- No folding back of a corneal flap
- Lenticule preparation in the intact cornea
- Minimally invasive access measuring just a few millimeters (80 % less lateral incision than in LASIK and Femto-LASIK)
- Almost complete preservation of protective corneal layer (epithelium) and stabilizing outer corneal layers (Bowman’s membrane)
- Maximum number of corneal nerves responsible for tear regulation remain intact
- Practically painless during and after the procedure
Entire treatment carried out using femtosecond laser (all-femto)
- Use of high-precision femtosecond technology
- Outstanding predictability of results, even in cases of severe myopia (> -7.00 D)
- Anatomically shaped contact glass avoids unnecessary compression of the cornea
- No loss of vision during treatment
- Noiseless and odorless treatment
- Stabilization of visual acuity typically within 14 days
- Entire laser correction in a single treatment step
- No device change during the operation
- Short procedure
Precise and sensitive treatment “VisuMax femtosecond laser”
The specially developed laser system used for the SMILE procedure is the Carl Zeiss VisuMax® femtosecond laser. In Femto-LASIK surgery it has already impressed patients and physicians alike with its sophisticated technology, its precision and its reliability. SMILE now permits accuracy down to nearest micrometer precision in the preparation of the lenticule within the intact cornea.
The high-precision femtosecond laser provides targeted correction of the vision defect while leaving the surrounding corneal tissue virtually unaffected.
A contact glass specially designed to match the individual anatomy of the cornea permits customized treatment in which the corneal tissue does not need to be unnecessarily compressed. This helps avoid temporary loss of vision caused by excessive intraocular pressure.
An ergonomically designed and functionally versatile patient supporting system provides extra comfort and relaxation during treatment. The position of the patient is continuously monitored during the laser procedure and automatically adjusted and corrected, if necessary.
Frequently asked questions on SMILE
What makes SMILE so special?
Unlike in all other laser eye surgery procedures, the corneal tissue is not ablated using an excimer laser. In ReLEx, proven femtosecond laser technology is the only technology used. A small lenticule is prepared inside the intact cornea using the femtosecond laser. This lenticule is removed through an access point just a few millimeters across. In fact, the cornea does not have to be opened at all – unlike with LASIK and Femto-LASIK. The technique is made possible by the unique precision and performance of the VisuMax® femtosecond laser made by Carl Zeiss.
There is no flap in PRK or LASEK either
How do these procedures differ from SMILE?
In PRK and LASEK procedures, the top layer of the cornea (epithelium) is removed manually. The exposed deeper layers of the cornea are then ablated using an excimer laser. The disadvantages: there is significantly greater pain after the operation, and the healing process and the stabilization of visual acuity take a relatively long time. PRK and LASEK are not recommended for the treatment of severe nearsightedness. The risk of scarring (haze) is significantly higher. Smile combines the benefits of PRK and LASEK (no flap incision) with those of LASIK and Femto-LASIK (minimum discomfort and rapid restoration of visual acuity) – but without any of their disadvantages.
How much experience has gone into SMILE?
The name Carl Zeiss has stood for quality and precision in optics since 1846. In 1986 Carl Zeiss unveiled the first excimer laser for refractive correction of the eye. Over the last 25 years the company has been at the forefront of advances in the laser correction of vision defects. Femtosecond technology has been extensively trialed and has proven its clinical value over many years. Refractive lenticule extraction has been performed in controlled clinical studies since 2006. The first patients have already undergone 5 years of post-treatment monitoring. ReLEx smile is now being deployed in many countries worldwide as a standard treatment method.
How can I find out if I am suitable for SMILE?
As with all other vision correction methods, you will have to undergo a detailed eye examination. The nature and degree of ametropia, the curvature and thickness of the cornea, as well as many other factors play a role. Your ophthalmologist will advise you personally after conducting a detailed examination.
After SMILE, how long will it be before I can see properly without glasses or contact lenses and return to my normal routine?
Every healing process is different. In most cases visual acuity is very good one or two days after the operation and stabilizes within two to three weeks. Following PRK or LASEK, by comparison, full recovery can take up to three months. After SMILE, you will generally be able to drive, work and do sports without glasses or contact lenses just a few days following treatment.