Within 12 months of its introduction to Australia, the femtosecond laser has proved to be a safe and effective alternative to manual phacoemulsification.1,2 But is the technology limited only to the ‘straightforward’ cases?
The introduction of any new technology is exciting, but brings with it challenges and potential hazards. After a year of use in this country, the rapidly accumulating evidence is showing that the femtosecond laser is as safe and efficient as standard cataract surgery. It can perform a more predictable capsulotomy, uses less phaco energy and results in a better effective lens position with less lens tilt and less decentration.3
But what about the more challenging cases? Can the femtosecond laser be used on dense cataracts, white cataracts, patients with pseudoexfoliation, Fuchs’ Dystrophy, patients requiring concomitant retinal surgery and patients with previous corneal transplant surgery? Are we able to achieve the same improved surgical parameters or is the technology limited only to standard cataract cases? I will address each of these clinical scenarios separately.
Advanced Cataracts
I have successfully used the femtosecond laser on dense cataracts (grade IV). There was some initial concern that the technology would be limited to cataracts of grade III or less but this is not the case. The nuclear fragmentation is consistent and the ‘crack’ when using a four quadrant, central circle technique allows for reproducible removal of the cataract with less phacoemulsifcation energy. This presumably is better for the health of the endothelium. One precaution with these advance cataracts is that any intralenticular gas produced by the laser will be more significant and may need to be released before hydrodissection is performed.
The precision of femtosecond laser pulses reduces collateral tissue damage and provides consistent cuts to the desired location every time
I have also used the femtosecond on ‘white’ cataracts. These are not commonly encountered in Australia but pose challenges, especially with regards the capsulotomy. The laser will not penetrate deeply into the visually opaque lens and is therefore only useful for the capsulotomy. Figure 1 represents the first white cataract in the world that underwent laser cataract surgery. I performed this operation last year and, as can be seen in Figure 2, the result was excellent and the IOL well positioned with a symmetrical capsulotomy.
Fuchs’ Dystrophy
Fuchs’ Dystrophy is often associated with early cataract development and poses unique surgical challenges in patients with cataract. All cataract surgery is associated with some loss of endothelium cells. In Fuchs’ Dystrophy in which the endothelial cell count is already low, a straightforward perfectly performed cataract operation can still lead to corneal failure. Logically any reduction in nuclear manipulation and less phaco energy will be better for the cornea. With the femtsosecond technique both of these criteria are met. It may be that laser cataract surgery is the preferred technique for patients with Fuchs’ Dystrophy. At the point of writing this article, however, there is no evidence-based medicine to support this hypothesis.
I have performed laser cataract surgery on a number of patients with Fuchs’ Dystrophy successfully and have even used the femtosecond laser in combined cataract and endothelial transplant procedures.
Pseudoexfoliation
Pseudoexfoliation (PXF) is a common condition that is associated with increased risk in cataract surgery. There is an increased chance of zonular dehiscence and vitreous loss because the zonules are less stable and of corneal decompensation because PXF also affects the endothelium. I have used the femtosecond to treat patients with PXF and cataract without any problems. Again, there are a number of putative advantages when using this technique in patients with PXF. Firstly, less manipulation of the lens is required thus reducing stress on the weak zonules. Secondly, less phaco energy is needed placing less demand on the corneal endothelium. Thirdly, it is possible to remove the nuclear fragments without much if any nuclear rotation if need be.
One caveat is that the laser needs a pupil dilatation of 4.8mm and in some cases of PXF this is not possible to achieve.
Previous Weakening Corneal Surgery
Laser cataract surgery requires a ‘docking’ with a patient interface and a subsequent rise in intraocular pressure. Initially there was some concern that in patients with ‘weak’ corneas – such as those with previous radial keratotomy (RK) or previous penetrating keratoplasty (PKP) – there may be a risk with the raised pressure or indeed that the altered corneal structure might impact negatively on the laser itself (Figure 3). I have performed a number of cases with both previous PKP and RK and the laser works just as well as in virgin eyes. In RK patients, I do not perform the wound creation with the laser to avoid any intersection with the RK cuts. This could potentially lead to a non-watertight wound.
Laser Cataract Surgery with Vitrectomy
We have recently published a short series in which we have shown that the use of combining laser cataract surgery with vitrectomy can offer several benefits over manual surgery. The precision, centration and predictability of the capsulorhexis has consistently allowed for a circular overlap of the IOL optic. This is vital as the risk of prolapse in phacovitrectomy patients is increased when the IOL is not covered completely by the capsular bag. By further reducing the phacoemulsification power throughout the procedure the risk of corneal oedema is reduced. Oedema may obstruct the visualisation of the posterior segment making peeling the membranes more challenging.
Conclusion
The femtosecond laser can certainly be used is these more challenging cataract scenarios but it may also offer some specific advantages due to less phaco energy requirements, a more precise capsulotomy and the need for less nuclear manipulation.
Professor Gerard Sutton MBBS (UNSW) MD (AUCK) FRANZCO is the Sydney Medical School Foundation Chair of Cornea and Refractive Surgery at the University of Sydney.
He has introduced many new surgical techniques to Australia, and was the first surgeon in Australia to perform LASIK using the IntraLase femtosecond laser and the first to perform a corneal transplantation using femtosecond laser.
Catalys LaserProfessor Brendan Vote |
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In April this year, the Launceston Eye Institute acquired the first Catalys Precision Laser System – produced by the Californian-based OptiMedica – in the southern hemisphere. To date, more than 230 cases of pretreatment with the femtosecond laser have been performed. In order to look at the benefits over conventional cataract surgery, we compared our first 200 femtosecond plus phacoemulsification cases with 200 standard phacoemulsification cases performed over the same time period. TechnologyThe two-part liquid optic fits snugly around the limbus with its 13.5 mm diameter suction flange. Unlike solid docking systems, prior experience with docking using the liquid optics was not essential due to the Goldmann contact lens-style design. The liquid optics docking also resulted in minimal IOP rise. Our research showed IOP increased a mean of 11 mmHg after vacuum and 18.5 mmHg overall from baseline after the femtosecond laser treatment, returning rapidly to normal within minutes. This is important in our older cataract patients with significant comorbidities like glaucoma, in order to decrease the risk of complications. The technology is remarkably intuitive and one of the most impressive aspect that we have noticed is the intelligent force vector sensors in the horizontal and vertical planes to monitor patient’s eye movements. This also allows the surgeon to verbally correct the patient if their fixation is wandering or if their breathing is too heavy. As a safety mechanism, the laser will stop if the patient moves beyond certain limits. The OCT scan maps out anterior segment surfaces as well as iris, anterior and posterior capsule safety zones. Once the surgeon has accepted the treatment plan, a foot pedal is used to deliver the laser to the anterior segment and real-time video on the screen allows the surgeon to monitor tissue effects. The treatment overlay also appears on the screen in order to ensure the laser is proceeding correctly. Surgeons at the Launceston Eye Institute have found that the use of Catalys laser has minimal impact on patient flow, with patients normally spending less than six to seven minutes from start to finish in the laser room. AdvantagesOne of the most obvious advantages of femtosecond lasers for cataract surgery is the reduction in phacoemulsification time. After comparing our first 200 cases of femtosecond laser-assisted cases against 200 cases of conventional phacoemulsification, we have noted a 70 per cent reduction in effective phacoemulsification time. This is likely to particularly benefit patients with premorbid endothelial compromise such as guttata and Fuchs’ Dystrophy. The precision of femtosecond laser pulses reduces collateral tissue damage and provides consistent cuts to the desired location every time. Because of the precision, we were not surprised that 100 per cent of cases had a complete capsulotomy. A precise, perfectly circular capsulotomy may also improve refractive outcomes through a more consistent effective lens position (ELP), particularly with the increasing use of toric and premium IOLs. The most vital step in the learning curve is not the Catalys femtosecond laser, which is very intuitive, but rather adjusting your operating technique in theatre. Already we have found when comparing effective phacoemulsification times (EPT) between groups, there were 26 cases (13 per cent) that had zero EPT in the femtosecond group. A significant number also had minimal EPT with 21 percent less than 0.5 seconds and over 50 per cent less than four seconds compared with only one (0.5 per cent) in the conventional group. We predict that with future advances both to the laser technology and our surgical equipment and techniques, these percentages of zero phaco energy will be further improved. Associate Professor Brendan Vote is a Vitreoretinal and Cataract Specialist based at the Launceston Eye Institute in Tasmania. Dr. Robin Abell is a research fellow at the Tasmanian Eye Institute, a registered research and education charity improving ophthalmic health for Tasmanians.
A patient’s eye after treatment by the author, Assoc. Prof. Vote, with the Catalys Femtosecond Laser. |
References
1 Bali S, Hodge C, Roberts T, Lawless M, Sutton G.
‘Early Experience with the Femtosecond Laser Cataract Surgery’ Ophthalmology 119;891–899.2012
2. Sutton G, Bali S, Hodge C. ‘Laser Cataract Surgery; Clinical Outcomes’ Curr Opin in Ophthal. In press.
3. J Refract Surg. 2012 Apr; 28(4):259–63. Intraocular lens tilt and decentration measured by Scheimpflug
camera following manual or femtosecond laser-created continuous circular capsulotomy. Kránitz K, Miháltz K, Sándor GL, Takacs A, Knorz MC, Nagy ZZ.
4. Bali S, Hodge C, Chen C. Sutton ‘Femtosecond Laser Cataract Surgery in phacovitectomy’ Graefe’s Arch Clin Exp Ophth. In press 2012.
