Femtosecond Lasers in Cataract Surgery: What You Need To Know

Femtosecond lasers use ultrashort pulses (10-15s) of near infra-red light to disrupt tissue with micron precision.² The surgical effect is produced by scanning thousands of pulses to produce a continuous incision or tissue separation. Guided by OCT imaging, a surgeon uses the laser to plan and automate the capsulorhexis (anterior capsulotomy), the corneal incisions and to divide the ens nucleus.¹

Four companies make a femtosecond laser with a cataract application – Alcon LenSx (Fort Worth, TX), LensAR (Winter Park, FL), Opti-medica (Santa Clara, CA) and Bausch + Lomb’s joint venture company Technolas Perfect Vision (Munich, Germany). Alcon’s LenSx Laser received the first FDA approval in 2009 and is the most progressed, with over 500 surgeons trained and over 10,000 procedures performed worldwide.³ LenSx is the only unit commercialised in Australia and Australian procedures account for 20 per cent of global.³ Two units are in Sydney, one in Melbourne and another in Hobart.

How it Works

The LenSx procedure is day surgery, under topical anaesthesia, with the laser part completed outside the operating theatre. A suction contact lens docks the eye to the laser. High-resolution video and OCT imaging help the surgeon plan the treatment. The surgeon can see the entire anterior chamber from the corneal epithelium, to beyond the posterior capsule. Before activating the laser, the surgeon checks the docking, the capsulotomy location and plans the architecture of the corneal incisions and lens fragmentation. The laser operation is less than a minute. Phacoemulsification of the nucleus and intra-ocular lens (IOL) implantation occur in theatre.

The surgeon can see the entire anterior chamber from the corneal epithelium, to beyond the posterior capsule

LenSx real-time imaging showing planned capsulotomy (pink circle), lens fragmentation (pale yellow), main cornealincision (heavy yellow) and astigmatic incisions (white). OCT images shows topographical view of lens (top right) andcross section of cornea and lens (bottom right)

Results So Far

Capsulotomy Precision and Reproducibility

Studies by Nagy show laser cut capsulotomies are more likely to have the correct diameter, shape, IOL coverage and IOL centration compared with manual techniques (100 per cent diameter accuracy +/- 0.25 mm versus 10 per cent).^4,5 Capsulotomy architecture is important in maintaining the integrity of the capsular bag for IOL implantation and also impacts the effective power of the IOL.⁶ A shift of 1mm in IOL position from an inappropriate capsulotomy can lead to a 1.25 D change in refractive error.⁷ Published clinical data is yet to confirm that using the femtosecond laser to perform cataract surgery improves the refractive outcome, but early feedback is very promising.

Dr. Paul Hughes, Senior Managing Partner, Vision Eye Institute Southline, said the predictability of the capsulotomy is one of the delights of using the femtosecond laser. “To draw a perfect exact size circle every time by hand is difficult. With the laser, I specify a 4.8mm capsulorhexis and that’s what I get. You can see the laser creating the circle perfectly.¹⁷

“Because you are not tearing the capsulorhexis manually, you are not pulling or stretching the zonules, and the effective lens position is minimally altered,” he said.¹⁷

Associate Professor Grant Snibson, Eye Surgery Associates Melbourne, believes incremental improvements in visual outcomes are likely. “Australian cataract surgery results are very good, but if you see the precision of the corneal incisions and the perfect centration and roundness of the capsulotomy, all without opening the eye or inserting an instrument – it strikes you as a very elegant and efficient procedure. It would be hard to say that there would be no visual benefit flowing from this precision. Certainly, our impression is that unaided vision is more likely to be 6/6 postoperatively, with negligible residual refractive error.”¹⁷

A small case series⁸ presented at the 2011 European Society of Cataract and Refractive Surgery meeting showed, at 1-month, 83 per cent of patients were within 0.25 D of the target refraction compared with 64 per cent with traditional surgery. Fifty-eight per cent of laser patients were 6/6 uncorrected, compared with 27 per cent with traditional surgery.

Dr. Paul McCartney from Hobart Eye Surgeons said the study is small but important because it confirms
clinically what we expected from the developmental studies.

“We are effectively bringing cataract surgery further into the realm of refractive surgery. It will add safety, but the key is accuracy and predictability. You can use the laser with any style of implant, but even a standard lens has sophisticated aspherics and filters, and we want to utilise the lens to its best ability.”¹⁷

Reduced Phacoemulsification Time

An underestimated benefit is the efficiency the laser brings to the cataract procedure. As the laser pre-softens or divides the cataract, less phacoemulsification is needed during surgery.⁵ Associate Professor Snibson is using 40-50 per cent less phaco energy, with less fluid going through the eye, and he says this should translate to fewer complications, particularly in patients with corneal disease.

Associate Professor Geoffrey Painter, from Gordon Eye Surgery, says the eyes are quieter. “We have been trying to reduce phacoemulsification energy since its introduction in the early nineties – trying to make the procedure gentler, with less trauma to the cornea. With the laser, you see the results the next morning. The eye physically looks better. The cornea is clearer, with less visible damage and less anterior chamber activity.”¹⁷ An early study has shown a low endothelial cell loss.⁹

He also thinks the laser reduces the risk of complications such as posterior capsule tear, which is the major cause of complication in manual surgery.¹⁰ “After the laser assisted lens fragmentation, the nuclear pieces are equal sized and phacoemulsification is more straight forward. You are working in the iris plane, not deep in the capsular bag, and because you are not as close to the posterior capsule, I believe it leads to a safer procedure.”¹⁷

Better Wound Architecture
Cadaver eye studies have shown the femtosecond laser can produce more intricate and more repeatable incisions than with manual surgery.¹¹

Associate Professor Painter says the laser allows you to create a reproducible multiplanar wound that is difficult to construct by hand. “We believe it produces a more robust, more watertight wound and that’s what we’re seeing. It should resist deformation, such as if the patient rubs their eye, theoretically reducing the potential for infection.”¹⁷

Three plane incisions are known to be more resistant to wound leakage.¹²

Precisely controlled incisions may also improve refractive outcomes as the IOL calculation relies on, among other parameters, an estimate of the induced astigmatism. “With manual surgery we calculate the surgically induced astigmatism and then strive to do a perfect wound every time to produce exactly that same amount of induced astigmatism, to minimise the standard deviation of the wound creation. The laser produces the same wound every time, so there is no standard deviation. We know what we’ll get before we start,” said Dr. Hughes.¹⁷

Which Patients?

Surgeons are using the laser on a high percentage of patients and especially with premium IOLs.¹³

Dr. Hughes says, “Premium lens patients want premium outcomes. We are now able to correct astigmatism intraocularly, plus the laser gives you the precision to locate the lens properly, again improving outcomes.”¹⁷

Torics account for 18.5 per cent of implants used in Australia.¹⁴

Associate Professor Painter uses the laser for all grades of cataracts, but thinks another major benefit is for the complicated cases – pseudoexfoliation, shallow chambers, high hypermetropes and endothelial compromise, like Fuch’s dystrophy.

Limitations

As with any new technology there is a learning curve as the surgeon learns how to dock the eye and interpret the imaging.¹⁵ An incomplete capsulorhexis is possible and is completed with a larger diameter treatment or torn manually.¹⁶ Surgeons have also learned to release the cavitation bubbles from behind the nucleus to avoid posterior capsule rupture.¹⁵ Patients tolerate the suction well, which is only a third of that used in LASIK, but it can cause the cosmetic concern of subconjunctival haemorrhage.¹⁶ There have been no reports of adverse events related to intraocular pressure rise.

The pupil dilation, by drops alone, needs to be beyond the intended capsulotomy size (5.5 mm). Filtering blebs, pterygium, corneal scarring may interfere with suction or visualisation of the anterior chamber. Patients need to be compliant (lie motionless and look at the fixation light) as they are conscious during the procedure.

There is an extra AUD$800 – $1,000 cost per eye, which at this time, is not covered by Medicare or insurance.¹⁷ As with premium IOLs, many patients will pay, whether motivated by potential vision, safety or simply because ‘a laser in the eye sounds much better than a needle’. If the technology proves to reduce complications, this also helps offset the extra cost.

Patient Education

New technology always interests patients and they will want to know if the laser cataract procedure suits them. Patients perceive the benefits very easily. They know a computer-controlled laser is more accurate than surgery by hand.

Ray Fortescue, EyeQ Optometrists, Ramsgate, has referred patients for laser cataract surgery and says in many cases the initial counselling comes from the optometrist. “I am already talking to cataract patients about different technologies to reduce their dependence on glasses and femtosecond laser will become part of that conversation. I think being familiar with the technology is essential for proper patient education.”¹⁷

“Manual surgery is very good, but I am seeing very neat incisions and I think there is the potential for reduced complications. The idea of the laser gives the patient a sense of comfort and if it’s the best for them, they want it.”¹⁷

The Future

Femtosecond lasers are getting considerable attention at conferences and are likely to change the way cataract surgery is done. Although we need more data to compare long-term visual outcomes, complication and infection rates, the early experience is promising. Access is improving with over 50 surgeons in Australian using the LenSx Laser, making it more available and more likely to be used. If you are interested to see a case live, most surgeons will accommodate your request. Once you are in surgery, seeing the surgeon’s approach to the workflow, seeing the incisions and the results, you’ll be in a better position to guide your patients about their surgical choices.

Jenny Saunders is an optometrist and medical writer who consults for the ophthalmic and medical device industries.

References:

1. Sutton G, Hodge C. Accuracy and precision of LASIK flap thickness using the IntraLase femtosecond laser in 1000 consecutive cases. J Refract Surg 2008 Oct;24(8):802-6.

2. Juhasz T, Loesel FH, Kurtz RM, Horvath C, Bille JF, Mourou G. Corneal refractive surgery with femtosecond lasers. IEEE Journal of Selected Topics in Quantum Electronics 1999;5:902-910.

3. Data on File, Alcon Laboratories, Australia.

4. Nagy Z, Takacs A, Filkorn T, Sarayba M. Initial clinical evaluation of an intraocular femtosecond laser in cataract surgery. J Refract Surg 2009;25:1053-1060.

5. Nagy ZZ, Kranitz K, Takacs AI, Mihaltz K, Kovacs I, Knorz MC. Comparison of intraocular lens decentration parameters after femtosecond and manual capsulotomies. J Refract Surg. 2011;27:1–6.

6. Cekic O, Batman C. The relationship between capsulorhexis size and anterior depth relation. Ophthalmic Surg Lasers 1999;30(3):185-90. Erratum in: Ophthalmic Surg Lasers. 1999;30(9):714.

7. Norrby S. Sources of error in intraocular lens power calculations. J Cataract Refract Surg 2008;34(3):368-76.

8. Cionni R. ESCRS 2011 abstract cited in http://eyeworld.org/article.php?sid=6124.

9. Packer, M. AAO 2011 abstract cited in www.aao.org/newsroom/release/20111023a.cfm?RenderForPrint=1& retrieved 15/4/2012.

10. Dooley IJ, O’Brien PD. Subjective difficulty of each stage of phacoemulsification cataract surgery performed by basic surgical trainees. J Cataract Refract Surg 2006;32:604–8.

11. Ernest PH, Kiessling LA, Lavery KT. Relative strength of cataract incisions in cadaver eyes. J Cataract Refract Surg. 1991;17(Suppl):668–71.

12. Masket S, Sarayba M, Ignacio T, Fram N. Femtosecond laser-assisted cataract incisions: Architectural stability and reproducibility. J Cataract Refract Surg 2010;36:1048–9.

13. Slade SG, Culbertson WW, Krueger RR. Femtosecond lasers for refractive cataract surgery. Cataract & Surgery Today. 2010; 9 (8): 67-73.

14. Data on File, Alcon Laboratories, Australia, 2012.

15. Bali SJ, Hodge C, Lawless M, Roberts TV, Sutton G. Early experience with the femtosecond laser for cataract surgery. Ophthalmol 2012 Feb 21. [Epub ahead of print]

16. LENSX® LASER SYSTEM OPERATOR’S MANUAL,
80-0001 Rev. D

17. Personal communication with ophthalmologists interviewed for this article.