Cataract capable femtosecond laser technology promises consistently excellent refractive results with minimal complications, but surgeons who pursue this option are being urged to conduct appropriately designed clinical trials, to determine the true advantages of this exciting technology.
In 2006, the first femtosecond LASIK procedure in Australia was performed by Professor Gerard Sutton at Vision Eye Institute in Chatswood. The introduction of the femtosecond had an immediate impact on the safety and success of the LASIK procedure.1 The advent of femtosecond laser use in cataract surgery may well have a similar impact on the surgical landscape. In this article we will discuss the current state of technology and the potential benefits both to the patient and the surgeon.
The femtosecond laser is able to replace manual surgery in three of the five main components of cataract surgery; the initial corneal incisions, creation of the capsulorrhexis and lens fragmentation. This should allow the surgeon greater control and reduce both the intraoperative surgical time and manipulation, which has the potential to improve both safety and predictability.
There are currently three separate companies attempting to bring femtosecond lasers to the cataract marketplace. The difference in approach by these companies primarily lies in the imaging of the anterior chamber and cataract. OptiMedica (Santa Clara, CA, USA) uses customised spectral-domain OCT imaging to view the anterior chamber. Once detected, laser algorithms process the images to assist the laser process. LensAR (Winter Park, FL, USA) uses scheimpflug imaging to determine the placement of the laser pulses. LenSx (Aliso Viejo, CA, USA) is assisted by pre surgical and real-time OCT images to place the treatment pattern. Both the LensAR and LenSx companies have achieved US Food and Drug Administration (FDA) clearance for capsulotomies. LenSx remains the furthest advanced in terms of bringing a robust, reproducible unit to the market.
The ability of the femtosecond laser to make precise, reproducible corneal incisions could increase the surgeon’s ability to remain astigmatically neutral
The initial procedure is similar to the Femtosecond LASIK procedure. The patient is placed under the laser. A suction ring is then placed onto the patient’s eye. This is to maintain the position and allow the ablation pattern to be manipulated. Once complete the laser begins. The laser time is approximately 35 seconds although this will depend on the case. Following the ablation the suction ring is removed and the patient can be taken into the surgical theatre. The remainder of the procedure will continue as per routine cataract surgery, albeit with the majority of the work now complete.
Although cataract outcomes have significantly increased over the past decade the unaided visual outcomes remain well short of refractive laser results. There are potential improvements to be made in both predictability and safety.
A number of variables contribute to residual refractive error following surgery. The initial corneal incisions can induce astigmatic and other high order aberration changes. The ability of the femtosecond laser to make precise, reproducible corneal incisions could increase the surgeon’s ability to remain astigmatically neutral. Furthermore, surgeons will be able to treat pre-existing astigmatism at the time of surgery through laser assisted arcuate incisions, although this is less relevant with the newer generation of toric IOLs proving to be very effective in reducing post cataract astigmatism.
Estimation of the final lens position remains the primary source of error in cataract outcomes.2,3. This makes sense, as the IOL prediction formulas are dependent on preoperative values. The contribution of the capsulorrhexis is integral in determining the placement of the IOL to achieving consistent postoperative results. Cekiç et al confirmed that the size of the capsulotomy determines the depth of the anterior chamber and therefore the final resting position of the lens.4 Published reports of the LenSx femtosecond laser indicate that 100 per cent of capsulotomies lie within 0.25mm of the intended size and position. This compares to just 10 per cent of openings created by manual manipulation.5 This is a remarkable achievement that will serve to revolutionise outcomes.
Slade6 recently suggested that cataract surgery involves up to 10 times more complications compared to laser surgery. Although these estimates highlight the worst-case scenarios, it does illustrate that safety in cataract surgery can still be improved. The use of Femtosecond laser to create the capsulorrhexis and then fragment the natural lens will allow the surgeon to minimise both the manipulation and energy required during the procedure. In the same presentation, Slade reports a 43 per cent and 51 per cent reduction in the average phacoemulsfication power and time respectively.
The goal of every surgeon is to produce consistently excellent refractive outcomes with minimal side effects or complications. Evidence so far suggests that femtosecond lasers may well help achieve these aims. The real question is whether any improvements will be clinically significant or worth the added expense to both surgeon and patient. Only properly designed prospective control studies will be able to answer this question.
There will be a number of cataract capable femtosecond lasers in Australia in this calendar year. We would strongly advocate that those Australian surgeons who pursue this technology conduct appropriately designed clinical trials so that an evidence-based assessment can be made on the true advantages of what is an exciting technology.
Chris Hodge is Director of Research, Vision Eye Institute and Professor Gerard Sutton is the inaugural Sydney Medical School Foundation Professor of Corneal and Refractive Surgery at Sydney University.