First experience with a new high-frequency FLACS system

Take-home message: In this article, Dr Pajic presents an observational case series illustrating his initial experiences with the new Z8 laser system for cataract surgery in terms of both performance and safety. 

By Dr Bojan Pajic, MD, PhD, FEBO

Femtosecond laser-assisted cataract surgery (FLACS) provides excellent clinical outcomes and a low overall complication rate means it is generally regarded as a safe procedure. Indeed, FLACS has numerous proven advantages over manual capsulorhexis. For example, available data have demonstrated that femtosecond laser capsulotomies are more accurate in size than those created by manual continuous curvilinear capsulorhexis, and that laser lens fragmentation is accompanied by significantly decreased phacoemulsification power.^1-5 Corneal laser-created incisions have also demonstrated superiority over conventional corneal incisions, in terms of tunnel morphology and tissue damage. Furthermore, they do not significantly increase postoperative high-order aberrations.^6-8

Enabling cataract and corneal-refractive surgery

The Femto LDV Z8 (Ziemer Ophthalmic Systems AG, Port, Switzerland) (Figure 1) is a new high-frequency femtosecond laser system. The system was designed to enable the whole spectrum of corneal-refractive surgery, in addition to cataract surgery.

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The Femto LDV Z8’s powerful laser source permits resection of a larger target volume with adjustable pulse energy (nJ) according to cataract grade, and a very high repetition rate in the MHz range with overlapping spots which leads to a cut without tissue bridges. The system uses a new liquid-patient interface that prevents posterior corneal folds. Preventing such folds has the benefit of guaranteeing good laser beam transmission, with only minimal intraoperative intraocular pressure increase. Integrated high-definition optical coherence tomography (OCT) allows the surgeon to identify the precise location of the ocular surfaces during surgery. The system has received CE accreditation and is pending approval from the US Food and Drug Administration.  

Next: First experiences

First experiences with the Femto LDV Z8

In a recent observational case series, we reported our experiences with the prototype Z8 laser system for FLACS. System safety and performance (as perceived by the operating surgeon) were assessed following surgery to 14 eyes (14 patients; 4 males and 10 females with a mean age of 73.5±10.6 years). Only grade 2 and 3 cataracts (Lens Opacities Classification System III) were included in the study, which provided the first published prospective results for the system.⁹

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All procedures were performed by myself (Dr Pajic) at the Orasis Eye Clinic (Reinach AG, Switzerland) in May 2014 as follows:

• Pupils were dilated using a combination of phenylephrine and tropicamide eye drops

• A disposable suction ring was applied to the eye, with careful centration over the limbus

• After the suction ring was filled with balanced salt solution (to create a fluid-filled interface), the mobile arm of the system was docked over the corneal apex

• The integrated OCT system imaged ocular structures, and custom treatment parameters were determined with the laser platform settings wizard

• Laser lens fragmentation (an eight-piece pie-cut pattern) was carried out, followed by an anterior capsulotomy (5.0 mm diameter) (Figure 2)

• Following anterior capsule removal, hydrodissection and nuclear splitting, bimanual phacoemulsification was performed using the Catharex 3 system (Oertli Instrumente AG, Berneck, Switzerland) (Figure 3)

• Bimanual irrigation/aspiration of the residual cortex was performed

• Posterior capsule polishing concluded the procedure

Next: Complications explored

All intraocular lenses were placed in the capsular bag without complications and patients were scheduled for postoperative examination at 1 day; 2 weeks; and 1, 2, and 3 months after surgery. The main measures evaluated were:

• Preparation time for femtosecond laser (minutes)

• Effective phacoemulsification time (EPT, seconds)

• Total duration of surgery (minutes)

• Ease of phacoemulsification (on a 4-point scale)

• Completeness of capsulotomy and ease of capsule button removal (on a 10-point scale)

• Complications

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Table 1. Results from the case series

No major complications, such as anterior capsule tears, posterior capsule tears, or dropped nuclei occurred during the study and no patients developed subconjunctival haemorrhage postoperatively. Forty-two percent of patients (6/14) showed Descemet's folds directly postoperatively.

Next: Effectiveness of safety

Effective with a high level of safety

One of the key reasons that lens fragmentation by femtosecond laser offers potential advantages over manual surgery, is that pretreatment may allow for reduced instrumentation, movement, and EPT during cataract removal, which presumably translates to an increase in safety. Lower EPT can also improve clinical outcomes as it is associated with less vacuum, fluid, and intraocular manipulation during surgery, thus lowering risk of injury to the capsule, iris, and corneal endothelium, as well as reducing endothelial cell loss, postoperative inflammation, and corneal oedema.

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The high frequency femtosecond LDV Z8 laser system facilitates anterior corneal surface and posterior lens capsule visualisation, regardless of cataract grade. In addition, uninterrupted laser treatment is made possible as the fluid-filled interface does not lead to formation of marked corneal folds.¹⁰ In this case series these features allowed precise and complete removal of the capsule button; 13 of 14 capsule buttons were free floating (score 10) and one required only minimum effort for removal (score 9). Ease of fragmentation as perceived by the surgeon was excellent (3.9). EPT was low, as expected, since with femtosecond laser segmentation and fragmentation, the required phacoemulsification power decreases markedly.^3,5,11 Total duration of surgery decreased significantly during the learning curve period (all P< 0.05).

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Radial anterior capsule tears, posterior capsule tears, and dropped nuclei have all been reported as major complications of FLACS.¹² However, no major complications were observed during this case series, possibly due to meticulous preparation of the laser settings, which can provide high levels of procedural safety. Investigators reported that the incidence of postoperative Descemet's folds (seen in 42% of patients) were most likely due to the learning curve surgeons unavoidably undergo when operating with a new technology and a change in operation method.

In this small sample case series, FLACS with the Z8 system facilitated complete and precise capsulotomy, as well as highly effective and reproducible lens fragmentation. The safety level of the procedure was very good, and the time-consuming adjustments on the femtosecond-laser setting wizard, although relatively high in the early period, were markedly improved during the learning curve for this method. Larger studies should now be conducted to further investigate efficiency and safety, and to assess the cost-benefit ratio of the emerging FLACS.

“Since the first publication of the above study, we have performed 357 cataract procedures with the LDV Z8 and have achieved very similar results to those previously described,” Dr Pajic explained. “The EPTs were 1.44 ± 1.92 sec for cataract grades 1-4. We have however noted one difference to the initial study, in the occurrence of Descemet folds. Since changing the Xylocain anaesthetic drops, we have see a significant decrease in the rate of Descemet folds. Postoperatively we have observed Descemet folds in 9.5% of patients, which suggests that their presence was related not to the femtosecond laser, but to the anaesthetic drops instead.”

Next: Advantages of FLACS

Advantages of FLACS with the Z8

One of the key advantages to conducting FLACS with the Z8 is that the workflow remains the same as in the conventional procedure (Figure 4). “Thanks to high frequency and overlapping spots we are able to obtain a very smooth cut, especially in the clear cornea (Figure 5). In my experiences, there have been no tissue bridges,” explained Dr Pajic.

“The main advantages of the Femtosecond laser can be witnessed in difficult cataract cases. For example, in eyes with a floppy iris, whereby the pupil diameter is quite narrow from the beginning and continues to get smaller and smaller during surgery. In these cases the surgeon can rely on the good capsulorhexis and lens fragmentation that is made possible with the Z8, enabling safer surgery.” (Figures 6-10)

“Another example of a difficult case that may benefit from the use of the Z8 is that of a patient with lentodonesis and cataract grade 4. With the Z8 it is possible to adjust/recline the laser head and adapt it to the patient’s eyes. During the lens fragmentation and capsulorhexis there are nearly no mechanical forces, making the procedure very gentle and the surgery much safer.” (Figure 11-14)

References

• Z.Z. Nagy et al., J. Refract. Surg. 2011;27:564–569.

• K. Kranitz et al., J. Refract. Surg. 2011;27:558–563.

• I. Conrad-Hengerer et al., J. Refract. Surg. 2012;28:879–883.

• N.J. Friedman et al., J. Cataract Refract. Surg. 2011;37:1189–1198.

• R.G. Abell et al., Ophthalmology. 2013;120:942–948.

• D.S. Grewal and S. Basti. J. Cataract Refract. Surg. 2014;40:521–530.

• J.L. Alió et al., J. Refract. Surg. 2013;29:590–595.

• L. Mastropasqua et al., J. Refract. Surg. 2014;30:27–33.

• B. Pajic et al., Clin Ophthalmol. 2014;8:2485–2489.

• J.H. Talamo et al., J Cataract Refract. Surg. 2013;39:501–510.

• I. Conrad-Hengerer et al., J Cataract Refract. Surg. 2012;38:1888–1894.

• T.V. Roberts et al., Ophthalmology. 2013;120:227–233.

Dr Bojan Pajic, MD, PhD, FEBO

E:  bojan.pajic@orasis.ch

Dr Pajic is the Medical Director at the Swiss Eye Research Foundation - Eye Clinic ORASIS, Reinach AG, Switzerland.

Other affiliations: University of Novi Sad, Faculty of Sciences, Departments of Physics, Serbia; Medical Faculty, Military Medical Acedemy, University of defans Belgrade, Serbia and the Division of Ophthalmology, Department of Clinical Neurosciences, Geneva University Hospitals, Switzerland.

The author declares no conflicts of interest relating to the content of this article.