IntraLASIK

IntraLASIK, also known as Femto-LASIK or All-Laser LASIK, is a form of refractive eye surgery similar to LASIK that creates a corneal flap with a femtosecond laser microkeratome rather than with a mechanical microkeratome, which uses a steel blade. The only difference between LASIK and IntraLASIK is the method by which the LASIK flap is created. The actual refractive correction by corneal ablation can then be performed with any excimer laser that is able to perform LASIK, including conventional, wavefront-optimized, or wavefront-guided ablation. IntraLASIK can be used to surgically create monovision to enhance the ability to see objects both distant and near for those affected by presbyopia.[1]

History

Intelligence Surgical Laser (ISL) approached Arturo S. Chayet M.D. (Mexico) in 1994 with the idea of using a picosecond laser as an alternative to the excimer laser for the correction of refractive errors. Soon enough, however, after a series of clinical trials, Chayet concluded that the picosecond laser was not well suited for refractive corrections, but rather for the creation of corneal flaps, which at the time were created with the mechanical microkeratome (Chayet is credited with the conception of Intralasik). The creation of the corneal flap with the picosecond laser, in conjunction with the use of the excimer laser for the corneal ablation, was the first step to creating a spin-off of LASIK. Researchers at the University of Michigan, however, realized that the picosecond laser was inadequate for Chayet's idea and discovered that the femtosecond laser would work more effectively. After 1999 Nobel Prize in Chemistry was awarded to Ahmed Hassan Zewail, an Egyptian-American Scientist, who is the "Father of Femtochemistry", for his pioneer research work on studying the chemical reactions in a very short time. He developed a technique called "Ultrafast Imaging" shining "ultrashort laser flashes" across "Femtoseconds" for studying the "transition states" of the chemical reactions. Zewail needed a laser capable of emitting ultra-short femtosecond pulses of laser light. His research group at Caltech was among the first to acquire such a laser. In 2000 the Father of a corneal flap created by the femtosecond laser along with a refractive error corrected by the excimer laser was conducted on a patient for the first time, in which case Intralasik or All Laser LASIK was conducted for the first time.

The term IntraLASIK is derived from IntraLase, the name of the first manufacturer to achieve Food and Drug Administration approval of a femtosecond laser for use in the United States,[2] and the surgical procedure 'LASIK'. Although additional femtosecond laser manufacturers have entered the US market,[3] the name IntraLASIK is commonly used.

Procedure

The computer-guided infrared femtosecond laser is focused just below the surface of the cornea. Each laser pulse creates a tiny bubble there. A pattern of many overlapping bubbles is created, allowing to lift off a flap off the cornea. The procedure then continues as in traditional LASIK, with an excimer laser removing material from the exposed surface beneath the flap.

Claimed advantages

A LASIK flap created with a femtosecond laser is regarded by many ophthalmologists as an improvement over traditional LASIK because of a greater accuracy in flap size, shape, and thickness.

Contradictory information exists as to whether the use of femtosecond lasers in LASIK achieves statistically better visual acuity and refractive outcomes than with microkeratomes.[4][5]

Although the final long-term clinical outcome of LASIK with a mechanical microkeratome and IntraLASIK with a femtosecond laser may be similar, the increased accuracy of the flap with the femtosecond laser provides an added margin of safety. LASIK with a flap that is thinner has been shown to provide outcomes superior than a thicker LASIK flap.[6] A thinner LASIK flap requires greater accuracy and predictability.

Complications

A small percentage of IntraLASIK patients develop Transient Light Sensitivity (TLS), "Although there is no loss of uncorrected visual acuity, symptoms can be prolonged, especially without prompt steroid therapy."[7] TLS causes severe photophobia for a period of weeks, however normally resolves with healing and treatment.

Alternatives

An alternative to IntraLasik, femtosecond laser intrastromal vision correction, is a laser eye surgery technology that is one of several possible alternatives to LASIK now under investigation. Lower-energy femtosecond lasers may improve upon the traditional excimer laser by reducing disruption of ocular structures, with intrastromal ablation obviating the need for the damaging epithelial incision and ablation currently employed in LASIK and PRK procedures.

First clinical results were obtained in 2003,[8] and several different techniques are now under investigation, including both ISPRK (intrastromal PRK), and more ambitious wavefront variants. It is believed that intrastromal techniques may eventually increase predictability and repeatability of wavefront ablation. Both 20/10 PERFECT VISION and IntraLase are known to be sponsoring FLIVC studies using their respective lasers.

References

  1. ↑ "Monovision Lasik". Usaeyes.org. 2010-04-12. Retrieved 2011-12-10.
  2. ↑ "Ophthalmic Devices Panel" (PDF). U.S. FDA. 2000-11-08.
  3. ↑ "510(k) Summary for the Femtosecond Laser Microkeratome". U.S. FDA. 2006-03-11.
  4. ↑ Durrie DS, Kezirian GM (January 2005). "Femtosecond laser versus mechanical keratome flaps in wavefront-guided laser in situ keratomileusis: prospective contralateral eye study". J Cataract Refract Surg 31 (1): 120–6. doi:10.1016/j.jcrs.2004.09.046. PMID 15721704.
  5. ↑ Lim T, Yang S, Kim M, Tchah H (May 2006). "Comparison of the IntraLase femtosecond laser and mechanical microkeratome for laser in situ keratomileusis". Am. J. Ophthalmol. 141 (5): 833–9. doi:10.1016/j.ajo.2005.12.032. PMID 16678504.
  6. ↑ He TG, Shi XR (June 2006). "[Clinical study of ultrathin flap LASIK and LASEK for the treatment of high myopia with thin cornea]". Zhonghua Yan Ke Za Zhi (in Chinese) 42 (6): 517–21. PMID 16857131.
  7. ↑ Stonecipher KG, Dishler JG, Ignacio TS, Binder PS (January 2006). "Transient light sensitivity after femtosecond laser flap creation: clinical findings and management". J Cataract Refract Surg 32 (1): 91–4. doi:10.1016/j.jcrs.2005.11.015. PMID 16516785.
  8. ↑ Ratkay-Traub I, Ferincz IE, Juhasz T, Kurtz RM, Krueger RR (2003). "First clinical results with the femtosecond neodynium-glass laser in refractive surgery". J Refract Surg 19 (2): 94–103. PMID 12701713.