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Cornea Arcuate Incisions in Corneal Surgery Christopher L Blanton, MD Director, Corneal and Refractive Surgery Service, Inland Eye Institute, Colton Abstract This article describes the current status of the femtosecond generated arcuate incision to correct corneal steepening. It covers the history of the surgical correction of astigmatism and describes the entrance of the femtosecond laser into modern corneal and cataract surgery. The process of photodisruption is explained as are the current indications for use of the femtosecond laser to make corneal incisions. A detailed narrative for programming the laser to perform arcuate incisions is included. Nomograms are referenced, and advantages over bladed incisions are described. A case is presented to show the use of these incisions in clinical practice. Finally, future developments are contemplated. Keywords Arcuate, incision, femtosecond, astigmatism, cornea, nomogram Disclosure: Christopher Blanton serves as a Medical advisor/Monitor at Abbott Medical Optics. Received: November 27, 2012 Accepted: December 10, 2012 Citation: US Ophthalmic Review, 2013;6(1):26–8 Correspondence: Christopher Blanton, MD, 3257 E. Guasti Rd, Suite 210, Ontario, CA, US, 91761. E: Blanton007@aol.com History The first recorded case of the surgical reduction of astigmatism was published in 1885 by the Norwegian ophthalmologist, Schiotz. 1 Much later, Richard Troutman proposed the concept of making arcuate corneal incisions for the reduction of post-keratoplasty astigmatism in a landmark article entitled ‘Relaxing incision for control of postoperative astigmatism following keratoplasty’. This article was published in the journal Ophthalmic Surgery in 1980. 2 In 1986, Lee Nordan proposed a system to quantify the correction of astigmatism at lower levels using transverse incisions. 3 Richard Lindstrom, also developed a nomogram to quantify the effects of corneal incisions to reduce astigmatism, 4 eventually leading to a clinical trial known as the ARC-T study group. These results were published by Price et al. in 1995. 5 All of these systems, of course, relied on the use of a physical blade. The methods were efficacious but imprecise. These techniques remained the state of the art until very recently. Advent of the Femtosecond Laser for Corneal Surgery In 2001, the Intralase corporation obtained clearance for the use of a femtosecond laser for the creation of a corneal flap to be used in the Laser-assisted in Situ keratomileusis (LASIK) procedure. This was the genesis of a revolution; the dawn of the laser scalpel for creating corneal incisions. The acceptance of the femtosecond laser was slow. There were two primary reasons; first, the predicate device, a micro- keratome had a reasonably good safety and efficacy record. Second, economic factors created a barrier for many surgeons. Gradually, surgeons recognized the superior safety profile and improved results when using a femtosecond laser to create the flap. Today, the femtosecond laser has become the dominant device for creating 26 flaps during LASIK surgery. During these last eleven years while the femtosecond laser was slowly overtaking the microkeratome, engineers and scientists were developing this tool for other applications in the field of ophthalmology; specifically, cataract surgery. Advent of the Femtosecond Laser for Cataract Surgery In 2012, it was well known that the femtosecond laser could make a very precise cut into corneal tissue. The fact that corneal incisions had become a routine part of the cataract procedure, made for a likely entrance of this device into the arena of cataract surgery. The femtosecond cataract procedure of today involves a clear corneal incision for entry into the anterior chamber, an arcuate incision for the correction of astigmatism (if warranted), a capsulotomy and finally some level of fragmentation of the nucleus. This article is focused on the arcuate incision portion for the correction of astigmatism. Capabilities of the Infrared Fiber System The device uses an infrared laser beam to achieve its surgical effect by means of a process known as photodisruption. A laser pulse of ultra-short duration (one quadrillionth of a second, also known as a femtosecond) is focused and creates a plasma. As the plasma expands it forms a cavitation bubble and vaporizes tissue. The tissue disruption is on the order of one micron. The bubble is composed of water and carbon dioxide and is easily dissipated by the normal physiology of the cornea. By placing these pulses in an appropriately spaced pattern and by utilizing a proper energy level; a cleavage plane held together by tiny tissue bridges is created. These microscopic tissue bridges are easily transected with a blunt instrument. This process can be applied to make an infinite number of incisions in the cornea. © Tou c h ME dical MEdia 2013