Ophthalmic viscosurgical devices (OVDs) are considered an essential tool in anterior segment surgery and particularly in cataract surgery. These substances with their varying molecular weights and viscosities are applied to maintain the anterior chamber stability and protect the corneal endothelium during capsulorhexis, phacoemulsification, and lens implantation.1 Potential damage to the endothelium can be caused by turbulences, thermal injury, ultrasound energy, and mechanically by instruments or lens material.2–5
Similar to most medical devices, OVDs have advantages and some disadvantages. At the end of surgery, the complete removal of these either cohesive or dispersive substances can be manual demanding and residual OVDs might cause an increase in intraocular pressure. OVD-induced intraocular pressure increases often require antiglaucomatous therapy and it has not been unusual that new OVDs were recommended based on their ability to raise the intraocular pressure only modestly.6,7
The advent of femtosecond lasers has changed cataract surgery profoundly.8 A precise and reliable capsulotomy can be performed without destabilizing opening of the eye and a full fragmentation of the lens can reduce the amount of ultrasound energy down to zero.9–12 New injectors offer the possibility to insert intraocular lenses (IOLs) one-handed without the use of OVD. On the basis of these changes, we describe a new technique to perform cataract surgery with a femtosecond laser (Catalys Precision Laser System; OptiMedica, Sunnyvale, CA) without the use of OVDs.
This prospective case series clinical trial received approval of the local ethics committee and all tenets of the Declaration of Helsinki were observed. All patients enrolled in this study had a visually significant cataract and volunteered for the trial after giving an informed consent. The exclusion criteria were patients with advanced or mature cataracts (grade 5 or higher, LOCS III), angle-closure or uncontrolled glaucoma, active inflammation in the eye, a history of corneal surgery, opacities or corneal disease, central corneal thickness less than 500 mm or greater than 600 mm, active iris neovascularization, presence of intraocular silicone oil, ocular or systemic steroid use within 3 months before the preoperative visit, participation in another drug or device clinical trial concluding within 30 days of the preoperative visit, unsuitable for local anesthesia, poorly dilating pupils (pupil size < 6.0 mm), known zonular weakness, age younger than 22 years, known or suspected allergy to drugs required for the protocol, and pregnancy or nursing.
The laser system was installed permanently in the operating area and the entire surgery was conducted under sterile conditions on the same bed. All surgeries, including laser and manual treatment, were performed by one experienced surgeon (HBD). A video of the laser and manual treatments is available in the online version of this article.
Preoperative pupil dilation was performed using topical 0.5% tropicamide eye drops (Mydriaticum; Stulln Pharma, Stulln, Germany) and 5.0% phenylephrine eye drops (Neo-Synephrine; Ursapharm, Saarbrücken, Germany) instilled three times within 1 hour prior to surgery. After local anesthesia, the patient was positioned on the laser bed. The suction ring of the liquid optics interface was placed on the eye and filled with balanced salt solution (BSS; Alcon Laboratories, Fort Worth, TX). Surplus balanced salt solution flowed out through open channels of the liquid optics interface. The patient was swiveled under the laser and a second vacuum was used to connect the suction ring to the immersion lens. The integrated three-dimensional spectral-domain optical coherence tomography visualized the anterior segment of the eye and the software automatically created a treatment plan based on preset templates. Treatment and safety zones were confirmed in an axial and sagittal view. A 5-mm capsulotomy (4 μJ energy, 600-μm incision depth) was created, followed by full fragmentation of the lens (quadrants, grid spacing 300 μm). After vacuum release, the patient was rotated back under the surgical microscope.
Two 1.2-mm clear corneal side incisions were created manually at the 3- and 9-o’clock positions with a paracentesis knife. A 2.75-mm clear corneal incision was made on the steep corneal axis. The dimple down technique was used to confirm the free floating capsulotomy and a gentle hydrodissection was performed if necessary. After lens mobilization, the softened nucleus was aspirated using the Stellaris phacoemulsification device (Thin tip; inner diameter 0.67 mm, outer diameter 0.9 mm; Bausch & Lomb, Rochester, NY) without ultrasound energy (effective phaco-time). Residual cortex was removed bimanually using irrigation/aspiration. The anterior chamber was stabilized using the irrigation handpiece. The preloaded IOL (CT Asphina 409 MP; Carl Zeiss Meditec, Jena Germany) was injected one-handed (Bluemix 180; Carl Zeiss Meditec). Finally, the corneal incisions were hydrated for watertight wound closure if necessary.
Twenty-three cases of OVD-free femtosecond laser-assisted cataract surgery were successfully performed. No intraoperative complications were observed. The study group consisted of 9 men and 14 women with a mean age of 72 ± 7 years (range: 50 to 85 years). Thirteen right eyes and 10 left eyes were treated. The cataract grading of the nucleus (LOCS III) was 3.35 ± 0.49 (range: 3 to 4). In no case ultrasound energy was used (mean effective phaco-time: 0.00 ± 0.00 seconds). The intraocular pressure before surgery was 15.9 ± 4.2 mm Hg (range: 7 to 23 mm Hg), 12.8 ± 4.3 mm Hg (range: 6 to 20 mm Hg) 3 days after surgery, and 12.0 ± 2.3 mm Hg (range: 8 to 15 mm Hg) 1 week after surgery (Figure 1). Within the 1-week follow-up, no significant postoperative pressure increases were observed. The preoperative and postoperative corrected distance visual acuity is shown in Figure 2. Corrected distance visual acuity (logMAR) was 0.32 ± 0.15 (range: 0.5 to 0.1) preoperatively and 0.15 ± 0.13 (range: 0.3 to −0.1) 3 days after surgery. Mean corrected distance visual acuity increased to 0.13 ± 0.13 (range: 0.3 to −0.1) 1 week after surgery. All patients achieved a significant increase in corrected distance visual acuity after surgery.
Intraocular pressure before and 3 and 7 days after femtosecond laser-assisted cataract surgery without ophthalmic viscosurgical devices.
Corrected distance visual acuity before and 3 and 7 days after femtosecond laser-assisted cataract surgery without ophthalmic viscosurgical devices.
Figure 3 demonstrates the changes in corneal thickness. Corneal thickness was 558 ± 33 μm (range: 502 to 621 μm) preoperatively and 598 ± 43 μm (range: 523 to 666 μm) 3 days after surgery. Mean central corneal thickness was 588 ± 40 μm (range: 503 to 647 μm) 1 week after surgery. The total surgery time for laser and lens surgery together was 370 ± 63 seconds (range: 271 to 497 seconds) (Figure 4). Total balanced salt solution fluid after calibration of the phacoemulsification device was 97 ± 20 mL (range: 50 to 130 mL). No patient demonstrated a decrease in visual acuity 1 month after surgery, during the preoperative visit for the second eye.
Corneal thickness before and 3 and 7 days after femtosecond laser-assisted cataract surgery without ophthalmic viscosurgical devices.
Total surgery time, including laser and manual treatment.
OVDs are traditionally an indispensable part of cataract surgery. They protect the endothelium and stabilize the anterior chamber during capsulorrhexis and phacoemulsification of the lens.1 The introduction of femtosecond lasers is changing these operating steps and may allow the demonstrated omission of OVDs. No complications occurred during the procedure in this prospective case series trial. The required fluid and the total surgery time were comparable to that of standard cataract surgery. No pressure increases greater than 20 mm Hg and no excessive swelling of the cornea were observed. All patients demonstrated a significant increase in visual acuity within the 1-month follow-up.
The laser is able to cut a precise capsulotomy without opening the eye.9 Consequently no OVD injection for stabilization of the anterior chamber for the capsulorrhexis is necessary. The free floating capsulotomy disk can be aspirated under irrigation. Furthermore, a full fragmentation of the cataractous lens was performed. In combination with the described phacoemulsification device, no ultrasound energy was necessary for lens aspiration.10–12 However, ultrasound energy and shearing forces were identified to be the main cause of endothelial cell damage.3,4 In our trial, the amount of fluid that went into the eye was comparable to that of standard cataract surgery.
The elimination of OVDs during lens aspiration seems to be reasonable after femtosecond laser pretreatment. Without OVD in the anterior chamber, the corneal endothelium might be exposed to fluids or lenticular particles causing cell stress. Traditionally, the IOL is implanted after homogeneous filling of the capsular bag with OVDs. New generations of one-handed injectors establish comfortable IOL injection under simultaneous irrigation (Figure 5). However, a certain level of surgical skill is necessary to implant the IOL directly into the capsular bag without OVDs in the anterior chamber. If the IOL is not directly placed in the capsular bag and unfolds uncontrolled inside the anterior chamber, direct contact of the IOL with intraocular tissue may be a drawback of this technique. Within the follow-up of this trial, the corneal swelling—as a vicarious endothelial cell damage marker—and the reached corrected distance visual acuity were comparable to the published data after uneventful cataract surgery.13
Anterior chamber stabilization with irrigation handpiece for one-handed intraocular lens injection.
The use of a femtosecond laser-assisted capsulotomy followed by prefragmentation of the lens seems to allow experienced surgeons the complete elimination of OVDs without disadvantages.14 Furthermore, remnants of OVDs have been identified by ultrasound biomicroscopy as the cause of intraocular pressure increases and pupillary block glaucoma.15 Without the need for OVD removal, the entire procedure will be less time-consuming and compensate the additional laser treatment time. Additionally, the manual demanding OVD removal behind the IOL is not required.
OVD-free femtosecond laser cataract surgery has the potential to achieve comparable or even better clinical results achieved with standard cataract surgery using OVDs and ultrasound phacoemulsification. Prospective randomized intraindividual comparative clinical studies with a longer follow-up and endothelial cell evaluations are mandatory to prove these early clinical findings.
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- Kassar BS, Varnell ED. Effect of PMMA and silicone lens materials on normal rabbit corneal endothelium: an in vitro study. Journal American Intra-Ocular Implant Society. 1980;6:344–346.
- Glasser DB, Matsuda M, Ellis JG, Edelhauser HF. Effects of intraocular irrigating solutions on the corneal endothelium after in vivo anterior chamber irrigation. Am J Ophthalmol. 1985;99:321–328.
- Frohn A, Dick HB, Fritzen CP, Breitenbach M, Thiel HJ. Ultrasonic transmission in viscoelastic substances. J Cataract Refract Surg. 2000;26:282–286. doi:10.1016/S0886-3350(99)00361-2 [CrossRef]
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