The first and one of the most important steps of femtosecond laser assisted cataract surgery is the docking procedure with any types of femtosecond lasers. The Alcon-LenSx femtosecond laser (Fig. 7.1) operates with a curved soft contact lens which is integrated with a sterile limbal suction ring (SoftFit Patient Interface = PI). The tubing uses vacuum with a 16–20 mm Hg suction force to fixate the treated eye. The patient interface should be docked centrally then the rest of the procedure seems easier [12]. In case of decentered docking, incisions might be incomplete, due to paralaxis and geometrically attenuated femtolaser beam. Otherwise it is simple to dock and it provides a large viewing for the surgeon, which allows performing the peripheral corneal incisions and arcuate keratotomy incisions. Due to the low suction force, ocular perfusion and visual perception is usually not disturbed during the femtolaser pretreatment. With the new PI and soft contact lens use, there are no corneal folds, which allows using lower energy and the rate of free floating capsulotomy increased to 98 % [12]. Other femtosecond lasers also operate with a special PI, some of them using coupling fluid to avoid corneal folds. All femtosecond lasers at the moment using moderate suction force to stabilize the eye during femtolaser pretreatment.

The femtolaser has an in-built HD (high definition) optical coherence tomography (HD-OCT) system and a live video with a separate screen to assist the surgeon and to provide total control for the surgeon during the docking procedure and surgical pattern determination [12]. The OCT uses the same optical path as the laser beam. Therefore the surgeon knows by micrometer precision where the laser beam will incise within the ophthalmic tissues. The high-definition OCT (HD-OCT) covers the complete anterior segment of the eye up to the posterior capsule with dilated pupil and is also able to assess the clinical density of the crystalline lens. The surgical pattern is offered automatically and performed by the LenSx femtosecond laser. However, the surgeon should check and alter treatment parameters if necessary prior starting the treatment. The femtosecond laser produces approximately a 100 μm acoustic shock wave (very small); therefore a minimum of 500 μm safety distance from the posterior capsule is recommended (Fig. 7.2).

Due to the technical development a new preoperative assessment tool has been created, which is called the Verion system. It allows a complete preoperative assessment and postoperative follow-ups as well. Meanwhile with data transfer it helps the surgeon in the OR to perform the surgery with the greatest exactness. The Verion pre-operative assessment system identifies the conjunctival, scleral vessels and iris characteristics. In the OR all structures are recognized automatically and information is provided where to perform corneal incisions, shows the diameter and localization of the capsulotomy and helps implanting the intraocular lenses in the best available position, which is especially useful during toric lens implantation.

The first human femtolaser assisted cataract surgery was performed in 2008 by Zoltan Z. Nagy at Semmelweis University in Budapest, Hungary [5]. Since then the United States Food and Drug Administration (FDA) has granted approval and the European Conformité Européene (CE) mark has granted for femtosecond lasers, and femtolasers became available for the public. There are currently four international companies producing and providing this new technology for cataract surgery. The number of peer-reviewed publications is increasing on femtosecond laser assisted cataract surgery and it is foreseen that within a decade the method could be spread generally in the largest ophthalmic centers in the world.

During the first study the accuracy of the diameter of the anterior capsulotomies have been evaluated and compared to standard manual capsulotomies targeting also the same diameter of 5 mm and found that using the manual technique the diameter was 5.88 (±0.73) but it was 5.02 (±0.04) mm using the Alcon LenSx femtosecond laser. During the surgery of human crystalline lenses, the Alcon LenSx FSL was able to perform all capsulotomies within ±0.25 mm accuracy, whereas with the manual technique it was only achieved in 10 % of the eyes [15].

The in-the bag position with an 0.25–0.5 mm coverage of the posterior chamber lens by the anterior capsule, so the effective lens position (ELPo) is a very important parameter in predictability of postoperative achieved refraction against the planned one. Therefore exact IOL calculation especially with multifocal IOLs [10, 21] and the accuracy of the size and position of rhexis is very important regarding ELPo [14, 15] A recent study by Packer et al. reported that planning and achieving the capsulotomy centred on the optical axis of the lens with a diameter of 5.25 mm optimizes the consistency of final ELPo-s [20].

The size and central location of capsulorhexis is one of the most important factors to achieve the targeted accurate final post-operative refraction (Figs 7.3 and 7.4). In the literature there not too much about the accuracy of the standard manual technique because for more than two decades it has been the only method available, little attention has been paid to the effect of capsulotomy diameter and localization on the refractive outcome. A larger or smaller than intended rhexis may cause anterior or posterior shift of the IOL, respectively or IOL tilt [15–17]. In that cases myopic or hyperopic shift or increase in the higher order aberrations and possibly in the final ocular astigmatism may be the consequences. Irregular capsulotomies cannot provide enough defence against remaining epithelial cells so the incidence of posterior capsular opacification also may increase.

In a study of our team, it was found that Femto Second Laser (FSL) capsulotomies were not stronger compared to manual capsulotomies, but due to perfect circularity and central location, the predictability of tearing was much better than in manual capsulotomies [18, 19]. A capsule strength study found that capsulotomies performed by the OptiMedica FSL required two to three times more force to tear compared with the manual capsulotomies [17, 20].

So the real strength of FSL created capsulotomies is still debated in the literature and it is depending what method was used for force testing, but it is questionable that a less regular edge capsulotomy tested by the electron microscopy would be 3 times stronger than manual ones. Femtosecond laser creates small circular shape irregularities (“saw teeth shape”) within the capsule, the lower the energy, the more regular is the edge of the capsulotomies and the stronger the capsule against tearing forces [18].

Authors performed two studies at Semmelweis University in Budapest in an assessed the accuracy of the circularity of the femtosecond laser created rhexis with the Alcon LenSx and the effect on IOL centration postoperatively. They found that the LenSx performed anterior capsulotomy was more regular and circular shaped and provided better centration and capsule/IOL overlap compared with the manual capsulorhexis. Vertical and horizontal IOL decentration following the standard manually created rhexis was found to be statistically higher than the LenSx [15] even if capsulorhexis was performed by the same experienced surgeon.

In another anterior comparative study, anterior capsulotomy was created by the Alcon LenSx femtosecond laser (Figs. 7.3 and 7.4). The circularity was statistically significantly better in the FSL group (p = 0.032) and there was significantly less incomplete overlap of capsulotomies with the manual rhexis (28 % of eyes versus 11 %; p = 0.033). In highly myopic eyes the capsulotomy tended to be larger in the manual group than in normal eyes. The possible cause is the larger size of myopic eyes, the larger dilated pupil, which may deceive the surgeon assessing the relation to anatomy [16]. The letter one is very important in ELPo and predictability, so in high myopic eyes the size and centration of capsulotomies have a higher importance than in eyes with normal axial length and less or no preoperative refractive error.

The various femtosecond laser platforms offer different types of lens fragmentation. With soft lenses, LOCS grading less than 2.0, a central 0.25 mm central liquefaction is typically used. This technique is especially important in clear lens extraction, in patients with high myopia or high hyperopia or in presbyopic subjects who are seeking a refractive solution for the refractive error and not for cataract. During lens liquefaction concentric rings (cylindrical pattern) are created within the nucleus of the crystalline lens, rings elevate from the bottom toward the anterior part of the crystalline lens. With LOCS grading greater than 2.0, lens fragmentation is typically recommended and used. This can be a cross pattern (two perpendicular incisions within the lens), or can be customized with an increased number of cuts. Typically six cuts are performed and called “cake” or “pizza” pattern by the surgeons on the LenSx platform. The surgeon might decide to choose a hybrid pattern which means a central 3.0 mm diameter of liquefaction and a six lines fragmentation especially at the peripheral part of the crystalline lens [6]. This allows a quick nuclear removal and a help to fragment the remaining part of the crystalline lens. The final aim is to increase the safety of the method. The fragmentation length area should not be greater than 1–2.0 mm of the capsulorhexis diameter, due to the concave shape of the back of the lens surface. With longer fragmentation lines, the risk of trauma to the posterior capsule might be above acceptable risks.

Cubicle pattern was introduced first by another platform (Catalys), by now it is available in most types of the femtosecond lasers. The author found that using the cubicle pattern, two main planes are still required in order to chop the crystalline lens and to avoid the epinuclear ‘bowl’ phenomenon that can make the rest of the surgery really difficult to remove due to limited accessibility either to phaco or to irrigation-aspiration hand-pieces [13].

The use of the cross pattern and ‘quick chop’ surgical technique with the LenSx femtosecond laser compared to standard phacoemulsification resulted in a 43 % reduction in cumulative dissipative energy (CDE) and a 51 % reduction in effective phacoemulsification time (EPT) using the Infiniti (Alcon, Forth Worth, Texas, USA) phacoemulsification device already at the early phase of femtosecond laser use [5]. Since a decrease of more than 90 % is reported in the literature using FSL technology. Of course this result is depending what type of cataract is being pre-treated by the FSL.

Manually created incisions with a blade usually require stromal hydration at the conclusion of cataract surgery due to irregular, sometimes imprecise tunnel structure. If the wound is smaller than required a tear during phacoemulsification or lens implantation might be the consequence, therefore wound hydration is a must. If wound leaks during the postoperative period a lower intraocular pressure might cause the manual wound to open with free entering of bacteria from the conjunctival sac, leading possibly to endophthalmitis [22]. Precise wound position, geometry and architecture are very important in controlling postoperative infection and also to minimize surgically induced astigmatism (SIA) [22, 23]. FSL offers a new horizon due to precise wound geometry and architecture resulting in a better wound closure and no need for stromal hydration at the end of the surgery [22]. The consistency of wound structure is of utmost importance also important, especially implanting toric and multifocal IOLs [22]. Femtosecond laser created corneal incisions should be as peripheral as possible. Conjunctiva must be avoided, because if laser incision hits the conjunctiva the wound usually cannot be opened with the special blunt spatula. The reason is different laser absorption in conjunctiva and possible hemorrhage from peripheral conjunctival vessels may cause loss of laser absorption. In order to control preoperative corneal astigmatism corneal incisions can be arcuate or limbal relaxing and case reports with the LenSx and Catalys OptiMedica FSLs indicate successful correction of large amounts of corneal astigmatism [24].