**1. Introduction**

Techniques in cataract surgery have been dramatically progressing over the past half-century with associated improvements in outcomes and safety [1, 2]. Manual phacoemulsification remains the most popular technique in developed countries, representing about 90% of procedures [3]. Although a number of recent developments have occurred in intraocular lens technology, the basic phacoemulsification procedure has remained unchanged over the past 20 years [4, 5].

"Femto" is a prefix of the International System of Units that stands for 10−15, a millionth of a billionth. The femtosecond laser consists of a solid-state laser source that emits impulses of a wavelength close to the infrared spectrum with a duration measurement in femtoseconds. Its emission frequency is 10,000 pulses per second of monochromatic light. Corneal flap creation during laser in situ keratomileusis (LASIK) is the most common use of this laser [6, 7]. The latest innovation is its use in cataract surgery, called FLACS (femto laser-assisted cataract surgery) [8, 9]. The recent introduction of femtosecond laser to cataract surgery, by Nagy et al. in 2008, and its Food and Drug Administration (FDA) approval in 2010 represents a potentially significant advancement in cataract technology, with expectations of greater safety and better visual outcomes [10–12].

### **2. Femtosecond laser principles**

The femtosecond laser has a similar action to the *Nd:YAG* laser used in pseudophakic capsulotomies. The Nd:YAG laser and the femtosecond laser have nearly identical wavelengths, respectively 1.064 and 1.053 nm. The femtosecond laser light pulses are shorter than the impulse of the Nd: YAG laser, which is on the order of nanoseconds (**Table 1**).

Photodisruption starts with a process called laser induced optical break-down (LIOB), which occurs when conditions of high frequency laser pulses are highly focused with short duration and applied through a small beam laser diameter [13]. The LIOB generates a high-intensity electrical field. The laser pulses cause ionization, meaning the breaking of the bonds between electrons and atomic nuclei, which is responsible for a cavitation bubble phenomenon, related to the expansion of this plasma consisting of ions [14]. This plasma complex will tend to expand at supersonic speed, separating tissue in its path, rapidly losing energy and vaporizing tiny quantities of corneal tissue. The cavitation bubble consists of CO2, N2 and H2O molecules, which are absorbed by the corneal pump mechanism or eliminated when the corneal flap is raised or the eye opened [15]. These ultrafast pulses are too brief to transfer heat and generate inflammation to the tissue, and therefore are considered particularly adapted to cleave tissue. Hundreds of thousands of adjacent pulses can shape uniform horizontal, vertical or oblique cut surfaces. The pulses are always emitted from the deepest targeted layers of the cornea toward the most superficial ones, to avoid the generated cavitation bubbles from stopping laser pulses focused on the underlying layers. One of fundamental requirement for femtolaser intervention is corneal transparency, allowing precise focus of the laser spots and energy delivery.

The femtosecond laser used in cataract surgery has been specifically developed for the following surgical steps: main and accessory corneal incisions, capsulorhexis, lens fragmentation, and optional arcuate incisions for intraoperative correction of astigmatism. The depth of treatment can reach 8 mm, from the corneal epithelium to lens posterior capsule. The pulsed energy used by a femtosecond laser for cataract surgery is on a scale of microjoules (μJ) and 15 μJ is the maximum energy of pulses.


**19**

**Table 2.**

and 3 m3

Room size (m)

Laser size (h × l × p, m)

Included bed

Corneal refractive procedure

*FLACS platforms available.*

Docking Curved

Screen: 1.22 × 0.76 × 0.61; laser: 0.51 × 0.58 × 0.20

applanation lens

Imaging HD-OCT HD-OCT +

*Femto Laser-Assisted Cataract Surgery*

*DOI: http://dx.doi.org/10.5772/intechopen.88821*

**3. Platforms available and procedure**

Five FLACS devices are currently available:

• LenSx (Alcon LenSx, Inc., Aliso Viejo, CA, USA)

• LensAR (LENSAR, Inc., Winter Park, FL, USA)

• Catalys (OptiMedica, Abbott Medical Optics, Santa Clara, CA, USA)

• LDV Z8 (Ziemer Ophthalmic Systems AG, Port, Switzerland)

the phacoemulsifier. **Table 3** summarizes these requirements.

3.4 × 4.3 4.57 × 4.57 3.04 ×

1.65 × 1.97 × 0.8

Fluid-fill suction ring

Scheimpflug camera

• Victus (Technolas Perfect Vision and Bausch and Lomb, Rochester, NY, USA)

The laser programming consists in individual steps: (1) customize the treatment with the graphic user interface, (2) dock with patient interface, (3) image via OCT scan, (4) analyze the image and (5) treat with the femtosecond laser. These functions are clustered on a computer supplied with the femtosecond laser (and the patient bed, depending on the device). The association of the femtosecond laser, the graphic user interface, the docking system, and the OCT scan constitutes the femtolaser platform. Femtolaser platforms are quite similar to each other and are fitted either with an optical coherence tomography (OCT) imaging system or a Scheimpflug camera to guide the laser beam to the target. Recording of patient data and customized profiles are made through the touchscreen monitor. Platforms differ in step order, docking interface, lens fragmentation patterns and speed of action (**Table 2**). The environmental needs for the laser system are crucial to provide reproducible procedures. The space in the operative room must be considered as the devices occupies between 2

(except the LDV Z8, which is a smaller portable device) and must be near to

**LenSx LensAR Catalys Victus LDV Z8**

3.35

1.15 × 1.64 × 0.84

Fluid-fill suction ring

No No Yes Yes No

Yes No No Yes Yes

**Technolas**

Curved applanation lens

HD-OCT HD-OCT HD-OCT

**Ziemer**

needs

Fluid-fill suction ring + curved applanation lens

3.4 × 3.7 No specific

1.67 × 2.1 × 0.82 1.4 × 1 × 0.6

**Alcon LensAR AMO Bausch & Lomb,** 

**Table 1.** *Use of lasers in ophthalmology.* *Eyesight and Imaging - Advances and New Perspectives*

safety and better visual outcomes [10–12].

**2. Femtosecond laser principles**

nanoseconds (**Table 1**).

in cataract surgery, called FLACS (femto laser-assisted cataract surgery) [8, 9]. The recent introduction of femtosecond laser to cataract surgery, by Nagy et al. in 2008, and its Food and Drug Administration (FDA) approval in 2010 represents a potentially significant advancement in cataract technology, with expectations of greater

The femtosecond laser has a similar action to the *Nd:YAG* laser used in pseudophakic capsulotomies. The Nd:YAG laser and the femtosecond laser have nearly identical wavelengths, respectively 1.064 and 1.053 nm. The femtosecond laser light pulses are shorter than the impulse of the Nd: YAG laser, which is on the order of

Photodisruption starts with a process called laser induced optical break-down (LIOB), which occurs when conditions of high frequency laser pulses are highly focused with short duration and applied through a small beam laser diameter [13]. The LIOB generates a high-intensity electrical field. The laser pulses cause ionization, meaning the breaking of the bonds between electrons and atomic nuclei, which is responsible for a cavitation bubble phenomenon, related to the expansion of this plasma consisting of ions [14]. This plasma complex will tend to expand at supersonic speed, separating tissue in its path, rapidly losing energy and vaporizing tiny quantities of corneal tissue. The cavitation bubble consists of CO2, N2 and H2O molecules, which are absorbed by the corneal pump mechanism or eliminated when the corneal flap is raised or the eye opened [15]. These ultrafast pulses are too brief to transfer heat and generate inflammation to the tissue, and therefore are considered particularly adapted to cleave tissue. Hundreds of thousands of adjacent pulses can shape uniform horizontal, vertical or oblique cut surfaces. The pulses are always emitted from the deepest targeted layers of the cornea toward the most superficial ones, to avoid the generated cavitation bubbles from stopping laser pulses focused on the underlying layers. One of fundamental requirement for femtolaser intervention is corneal transparency, allowing precise focus of the laser spots and energy

The femtosecond laser used in cataract surgery has been specifically developed

for the following surgical steps: main and accessory corneal incisions, capsulorhexis, lens fragmentation, and optional arcuate incisions for intraoperative correction of astigmatism. The depth of treatment can reach 8 mm, from the corneal epithelium to lens posterior capsule. The pulsed energy used by a femtosecond laser for cataract surgery is on a scale of microjoules (μJ) and 15 μJ is the maximum

**Laser Wavelength (nm) Effect on tissue** Carbon dioxide 10600, far infrared Photothermal Nd:YAG 1064, near infrared Photodisruption Femtosecond 1053, near infrared Photodisruption

Excimer 193, far ultraviolet Photoablation

Krypton 647-531, visible light Photochemical coagulation Argon 614-488, visible light Photochemical coagulation

**18**

**Table 1.**

*Use of lasers in ophthalmology.*

delivery.

energy of pulses.
