In 2018, almost a decade after the first femtosecond laser for cataract surgery became commercially available, laser cataract surgery (LCS) continues to have a limited role in clinical practice. Although they may be in the minority, surgeons who have adopted the technique and become expert LCS users firmly believe that the laser adds value now and holds great promise for the future.
During the 36th Congress of the ESCRS in a meeting led by Julian D. Stevens, MD, Moorfields Eye Hospital, London, an international panel of LCS expert users shared their experiences with the aims of learning from each other and identifying directions for new research.
The consensus of the group was that, even for routine cases, there is a role for using the femtosecond laser because it makes cataract surgery more straightforward, more reproducible, and safer. In addition, because laser pre-treatment shortens the non-laser portion of the procedure, LCS reduces surgery-related ergonomic stress that can shorten a cataract surgeon’s career.
The experts’ discussion particularly highlighted the benefit of using the femtosecond laser for treating preexisting astigmatism, which has relevance in a large percentage of routine cases, and brought to the forefront its role in complex situations, including eyes with a dense black or intumescent cataract. Looking ahead, the participants agreed that with the expected evolution towards capsulotomy-fixated implants, access to LCS will have an unequivocal advantage for enabling delivery of optimal refractive and functional outcomes.
Intrastromal astigmatic keratotomy
Compared with manual penetrating astigmatic keratotomy (AK), femtosecond laser-assisted AK (FS-AK) has advantages for providing better rotational/angular alignment, better patient comfort, and reduced risk of infection. Data presented during the expert users’ meeting provided evidence that FS-AK is more effective than the manual approach and its result is more stable.
Professor David O’Brart, MD, St Thomas’ Hospital, London, presented findings from analyses of outcomes in groups of patients who underwent FS-AK or manual limbal relaxing incisions (LRIs) in the context of a randomised controlled trial comparing LCS and conventional surgery [J Cataract Refract Surg. 2018;44:955-963]. The analyses included eyes with no visually significant comorbidities that were treated for >1 D of corneal astigmatism with a plano refractive target.
At 1 month after surgery, postoperative cylinder was ≤0.50 D in 18 (42%) of 43 eyes in the FS-AK group and in only 8 (20%) of 41 eyes in the LRI group. Professor O’Brart reported that there were statistically significant differences favoring FS-AK in analyses of difference vector and correction index.
Dr Thomas Laube, MD, private practice, DÃ¼sseldorf, Germany, presented results from a retrospective study demonstrating the efficacy and stability of FS-AK for reducing corneal and refractive astigmatism [Open Journal of Ophthalmology. 2017;7:262-272]. The study included 42 eyes with 0.5 D to 1.5 D of regular corneal astigmatism and total corneal irregular astigmatism <0.300 Î¼m. The AKs were 8.0 mm diameter paired symmetrical arcs centred according to the scanned capsule and created at a depth between 20% and 80% of corneal pachymetry. Reference marks were placed on the conjunctiva using a sterile disposable ink pen (Devon utility marker, Covidien) that is visible on the Catalys OCT image. Maximum arc length in Dr Laube’s series was 65°. Dr Stevens noted, however, that arc lengths of 90° have been safely used for FS-AK.
“With the intrastromal cuts, there are anterior and posterior belts of intact tissue, and the corneas are relatively stiff in cataract patients who tend to be older,” he explained.
Dr Laube analysed astigmatic change using the Alpins vector method and found manifest cylinder was reduced significantly from 0.94 ± 0.62 D preoperatively to 0.64 ±0.45 D at 1 month after surgery (P=0.03). Continued follow-up showed no significant change after 12 months (P=0.90) at which time manifest cylinder was ≤0.5 D in 60% of eyes compared with just 38.1% preoperatively.
“The majority of patients were happy that they no longer needed glasses for distance vision,” Dr Laube said.
Dr Stevens noted that with LRIs, the astigmatic effect can continue to regress for up to 10 years. In contrast, he has collected data showing that the effect of FS-AK achieves stability early on and remains unchanged for at least 5 years.
Providing some tips for performing FS-AK, Dr Stevens noted that gas generated by the treatment is needed to break corneal fibers and separate the arc walls.
Therefore, it is important to use sufficient power, especially in younger patients.
Dr Stevens also said that there is an increased risk for pupil constriction when performing FS-AK because the laser treatment is commonly placed over the iris. To mitigate this effect, he pretreats the eyes with ketorolac drops and schedules the cases to minimise the delay between the laser and OR portions of the procedure.
Making complex cases more routine
Dr Frank Goes Jr, MD, private practice, Antwerp, Belgium, presented his experience using the Catalys Precision Laser System (Johnson & Johnson Vision) to perform “ultrafast” capsulotomy in an eye with an intumescent cataract.
“I have no doubt it was a good idea to use the laser when operating on an intumescent lens,” said Dr Goes.
He explained that, during manual capsulorhexis or standard laser capsulotomy, release of intralenticular pressure in an eye with an intumescent cataract creates a risk for radial tearing of the anterior capsule. Dr Goes adjusted the settings for performing the capsulotomy to shorten his capsulotomy time to just 0.3 seconds (Table 1). Importantly, the increase in speed did not compromise quality, he said.
Using trypan blue in the OR to aid visualisation, Dr Goes saw that the capsule disk was not free-floating, but it was free of tags, and he removed it successfully without any radial tearing.
The meeting participants agreed that more evidence is needed to support use of the modified settings as a standard for laser capsulotomy in eyes with an intumescent cataract. Dr Stevens noted that because a significant number of such cases present to Moorfields, he might have the opportunity to amass a series for a prospective study.
It was also noted that a double capsulotomy technique, involving an initial “mini” opening and a second larger capsulotomy, has been described as an alternative for safe capsulotomy in eyes with an intumescent cataract [J Refract Surg. 2014;30(11):742-745]. In this method, the first capsulotomy allows for release of intralenticular pressure. After fluid lens material is removed from the anterior chamber, the eye is redocked for the second capsulotomy.
Dr Stevens observed that the need for redocking adds time to the procedure and increases the risk for subconjunctival hemorrhage. Because of those issues, he called for manufacturers to modify their systems and eliminate the need for redocking after operators remove their foot from the pedal.
Dr Goes’s case also prompted a discussion about reducing capsulotomy time in routine cases in order to minimise the potential for eye movement that would affect the accuracy of laser pulse placement. Dr Stevens suggested that because the lasers work well “out of the box” with the use of the manufacturer-recommended settings, surgeons are reluctant to experiment with modifications because they are worried about higher rates of incomplete capsulotomy.
Jose Luis RodrÃguez-Prats, MD, Clinica Visahermosa, Oftalvist, Alicante, Spain, also presented a case in which use of the laser for capsulotomy proved beneficial. The case involved an eye with anterior lenticonus associated with Alport syndrome.
“Performing anterior continuous curvilinear capsulorhexis in these eyes is difficult due to the structurally abnormal anterior capsule,” he explained.
The patient described by Dr RodrÃguez-Prats underwent bilateral FLACS with the Catalys laser using the device’s software calipers to manually delineate the anterior capsulotomy. Multifocal toric IOLs were implanted with the aid of intraoperative aberrometry for power selection.
Preoperative UCVA was 0.8 OU in moderate photopic conditions; subjective refraction was -5.25 -7.25 x 180 OD and -6.75 -8.50 x 165 OD. Postoperatively, the patient achieved distance UCVA of 0.9 OU. BCVA was 1.0 OU, and his refraction was plano -0.50 x 5 OD and +0.50 -1.0 x 170 OS. At 45 days after surgery, both IOLs remained well centred.
Dense black cataract
Javier Mendicute, MD, Donostia University Hospital and Innova Begitek Ophthalmology Clinics, Donostia-San SebastiÃ¡n, Spain, reviewed the benefits of LCS when operating on very dense (black) cataracts (VIDEO). In his opinion, the possibility of using the laser in black cataracts depends on the imaging system’s ability to identify anatomic structures in the situation where there is poor media transparency as well as the accuracy and penetration ability of the laser.
The type of OCT, its working wavelength, and the speed of image capture determine the quality of the image obtained through opaque media and the possibility of identifying the posterior capsule when there is limited lens transparency. Dr Mendicute stated that he thinks swept source OCT is the best option for posterior capsule identification because it has faster acquisition time and deeper penetration than Scheimpflug technology or time domain or spectral domain OCT. He noted, however, that he has had the opportunity to use all femtosecond platforms in the market and that all of the equipment available today allows the automatic identification of anatomical references.
“Because of the imaging technology that allows identification of the posterior capsule and their precision, femtosecond lasers can be used to safely treat the lens close to the posterior capsule,” Dr Mendicute said.
The best fragmentation pattern to achieve the minimum use of energy and maximum efficiency when treating a dense black cataract is debatable. Dr Mendicute said that a grid pattern can require a lot of energy and result in a lot of bubble generation. His approach uses a pattern that he named “Microcrater, Divide & Conquer” in recognition of Dr Howard Gimbel. Using the femtosecond laser, he creates a 2-mm central disc and three radial cuts.
“After phacoemulsification of the central disc, there is a point of support to split the lens into six fragments that are easily removable,” Dr Mendicute said.
Bernardo Mutani, MD, Torino, Italy, presented his experience with LCS using the Catalys laser in an eye with a foldable posterior chamber phakic IOL (Visian ICL, Staar Surgical) (VIDEO). Because the imaging system did not recognise the anterior surface of the cataract, Dr Mutani said he needed to manually customise the anterior capsule to fit on the anterior surface of the lens. Thereafter, he was able to use his routine laser settings to successfully complete both the capsulotomy, which was centred on the pupil, and lens fragmentation.
Dr Mutani noted that trapping of cavitation bubbles in the space between the phakic IOL and the anterior lens capsule, which could impair laser energy delivery for the fragmentation step, was not a problem in this case that involved a cortical cataract.
“It is our experience that less gas is generated when treating a cortical cataract compared with a nuclear cataract,” Dr Mutani said.
In the discussion following Dr Mutani’s presentation, concern was also raised that in eyes with a phakic IOL, the laser’s imaging system may give erroneous readings of the capsule surfaces. Dr Stevens noted that due to these challenges, he chooses to do standard cataract surgery in eyes with a phakic IOL.
Dr Mutani also shared a video involving a case of IOL exchange in which he used the femtosecond laser to cut the in situ IOL (VIDEO). Dr Mutani noted that manually customising the surfaces to include the IOL into the treatment area and slightly increasing the femtosecond laser energy enabled easy cutting of the IOL.
“This technique allows less traumatic removal of the implanted IOL,” he said.
Making a difference for the future
As capsulotomy-fixated IOLs are now commercially available and showing benefit compared with capsule-fixated lenses, cataract surgeons may have a new reason to incorporate LCS into their practice.
“I think the development of capsulotomy-fixated IOLs will provide a strong argument for adopting the femtosecond laser because for the first time, the type of implant a patient receives will be determined by whether or not a surgeon has the laser for making the capsulotomy,” Dr Stevens said.
Reviewing his experience with the currently available capsulotomy-fixated Femtis IOL (Oculentis), Dr Stevens reported that it has demonstrated “exceptional” visual stability in a series of nine eyes he has followed since 2013.
“Capsulotomy fixation prevents tilt or lateral displacement of the lens. Therefore, it is an ideal platform for a toric IOL, but for all lenses, capsulotomy fixation makes biometry much more predictable and can lead to better outcomes,” Dr Stevens said.
Although other technologies are now available for automated capsulotomy creation, Dr Stevens said that the femtosecond laser has an advantage for delivering more accurate centration. Looking farther into the future, Dr Stevens said that lens technology offering predictable and stable centration opens the door to more sophisticated designs, such as lenses with more customised spherical aberration correction or that can accept an add-on lens.
“I believe patients would find it very appealing to be able to choose a lens that would give them the opportunity to take advantage of any upgrade that becomes available in the future,” Dr Stevens said.
DR FRANK GOES JR., MD
DR THOMAS LAUBE, MD
Dr Laube receives speakers’ fees from Johnson & Johnson GmbH.
DR JAVIER MENDICUTE, MD
Dr Mendicute is a consultant to and receives research grants and support from Alcon, Johnson & Johnson Vision, and Carl Zeiss Meditec, and he is a member of the speakers bureau for Alcon and Bausch + Lomb.
DR BERNARDO MUTANI, MD
PROF. DAVID O’BRART, MD
Professor O’Brart has been a consultant to and received a non-commercial research grant from Alcon.
DR JOSE LUIS RODRÃGUEZ-PRATS, MD
DR JULIAN STEVENS, MD
Drs Goes, Mutani, RodrÃguez-Prats and Stevens have no relevant financial interests to disclose.
The meeting of expert users was organised by targomed GmbH and supported by an educational grant from Johnson & Johnson Vision.