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All-in-one femtosecond laser refractive surgery
A specialist outlines two procedures for correcting refractive errors using a single laser.
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 Thomas John |
Corneal refractive surgery continues to advance, and patients’ quality of vision has continued to improve in recent decades. While a microkeratome has been used to create the corneal flap for LASIK, that method has now been bypassed in many centers in favor of femtosecond laser technology. Such a directional change in LASIK has the added advantage of largely decreasing or even eliminating most of the known flap-related complications of LASIK. However, this setup requires the purchase of two lasers, a femtosecond and an excimer. This twin-laser setup adds to the overall cost and maintenance and requires additional floor space in the laser suite. Further, the patient needs to be moved on the same bed from one laser to the other to complete the procedure, adding to the overall surgical time. It would be beneficial if an all-laser LASIK (without a microkeratome) could be performed with a single laser.
In this column, Dr. Rupal Shah describes the use of a single laser to perform the FLEx and SMILE procedures to correct refractive errors. It should be noted that the new VisuMax femtosecond laser (Carl Zeiss Meditec) used in these procedures is not currently approved by the U.S. Food and Drug Administration. Further studies and close monitoring of these newer procedures are needed to evaluate the overall success and long-term safety.
– Thomas John, MD
OSN Surgical Maneuvers
Editor
Carl Zeiss Meditec recently introduced a new femtosecond laser, the VisuMax, into the non-U.S. ophthalmic market. Unlike other popular femtosecond lasers, the VisuMax has a curved, rather than planar, contact glass. It has special optics to create a precise spot focused in the cornea with extremely high accuracy. The scanning and focusing optics of the VisuMax make it capable of placing the laser spot at a specified three-dimensional position almost anywhere in the cornea. It is already a popular instrument for making LASIK flaps.
Surgical techniques
The VisuMax can also be used to perform all-in-one femtosecond laser refractive surgery in two procedures called FLEx and SMILE. In these procedures, the VisuMax is first used to remove a precise refractive lenticule from the cornea by laying down pulses that separate the posterior part of the lenticule from the stroma (Figure 1). In the second step, the VisuMax is used to lay down pulses that separate the anterior surface, or upper cut, of the lenticule from the stroma. The upper cut of the lenticule is extended a fraction of a millimeter beyond the edge required for the lenticule, thus serving as the flap. In a further step, the flap side cut is then created to make a hinged flap. The flap is lifted and the lenticule is extracted from the stroma. The flap is then replaced. The tissue that otherwise would have been ablated by the excimer laser is removed physically and intact in the FLEx procedure, which entails lenticule extraction rather than tissue ablation. Thus, there is no need for an excimer laser for the refractive correction. FLEx represents the first all-in-one procedure that uses only the femtosecond laser to complete all steps in LASIK.
 Figure 1. Schematic representation of FLEx procedure. Images: Shah R |
 Figure 2. Schematic representation of SMILE procedure. |
SMILE takes this whole process a step further. Instead of making a complete flap side cut, only a small incision is created (Figure 2), and the flap is never lifted. Instead, the lenticule is extracted from within the cornea from a small incision. This virtually eliminates flap displacement in SMILE procedures, and there is little risk of the flap dislocating with trauma to the eye at a later point. Additional benefits may include reduction of dry eye problems and improvements in corneal biomechanical stability.
All-in-one femtosecond laser refractive surgery promises to change the way eye surgeons perform LASIK. It requires investing in only one laser, and therefore paying for only one laser’s consumables and maintenance. It also simplifies workflow within the laser suite. There is less total energy applied to the cornea, and there are none of the limitations of excimer lasers, such as the dependence on corneal hydration levels and environmental humidity. Thus, it appears to represent a paradigm shift in the way laser vision correction is carried out.
References:
- Blum M, Kunert K, Gille A, Sekundo W. LASIK for myopia using the Zeiss VisuMax femtosecond laser and MEL 80 excimer laser. J Refract Surg. 2009;25(4):350-356.
- Sekundo W, Kunert K, Russmann C, et al. First efficacy and safety study of femtosecond lenticule extraction for the correction of myopia: six-month results. J Cataract Refract Surg. 2008;34(9):1513-1520. Erratum in: J Cataract Refract Surg. 2008;34(11):1819.
- Thomas John, MD, OSN Cornea/External Disease Board Member, is a clinical associate professor at Loyola University Chicago and is in private practice in Tinley Park and Oak Lawn, Ill. He can be reached at 708-429-2223; fax: 708-429-2226; e-mail: tjcornea@gmail.com.
- Rupal Shah, MD, can be reached at 91-265-305-8603; fax: 91-265-305-8600; e-mail: rupal@newvisionindia.com. Dr. Shah is a consultant to Carl Zeiss Meditec.
