High-tech eye tech

Howard Larkin

Posted: Saturday, May 1, 2021

It is often said that technology innovation drives cataract surgery progress, and to a large extent this is true. But of the multitude of technological innovations over the past quarter century, which are most significant?
For Rudy MMA Nuijts MD, PhD, the answer is simple: the ones that have the most favourable effects on patients. And by that definition the most significant change was already well under way when he trained in the late 1980s – the transition from extracapsular cataract extraction to phacoemulsification.
“You didn’t have the sutures so there was an immediate beneficial effect in terms of the speed of restoration of visual acuity because of the smaller incision. Crucial to the adoption of new technology is, what does it do for the patient? If the patient experience is not dramatically changed, adoption will be very difficult,” said Prof Nuijts, of Maastricht University Medical Centre, The Netherlands.
Prof Nuijts offered laser-assisted cataract surgery and trifocal lenses as two examples of technologies that have not caught on as well. For routine cases, laser-assisted surgery has not been shown to improve outcomes over manual phaco, while issues such as haloes and glare continue to hold back multifocal diffractive lenses. “In my experience, patients are often willing to trade off a little less spectacle independence for less visual side-effects and greater predictability.”
Applying the same standard to technologies on the horizon, Prof Nuijts sees eliminating antibiotic and anti-inflammatory eye drops after surgery through the use of intracameral and periocular injections, and drug-infused IOLs as one of most likely to improve patient experience. The effect of subconjunctival injection of anti-inflammatory drugs is the subject of the ongoing EPICAT study sponsored by ESCRS. In addition to improving outcomes and relieving patient burden, dropless cataract surgery would reduce the expense of home care for the 9% or so of patients who require it. At €70 per day, its cost can exceed the total professional fee for surgery, he pointed out.
Prof Nuijts sees same-day bilateral cataract surgery as another change that will greatly enhance patient experience and reduce the time and cost of follow-up. Already nearly half of his procedures are bilateral, up from next to nothing two years ago. “It’s word of mouth; ‘can you do both eyes for me?’ Patients actively ask for it.”
Similarly, accelerated by COVID-19, phone and video technology have cut in person follow-up visits from four to one. Development of artificial intelligence routines may make remote follow-up even more efficient. These procedural changes will also reduce the environmental impact of cataract surgery, he added.
That said, cataract surgery has improved significantly in terms of visual outcomes, complications and ease of the procedure thanks to many incremental technical improvements. For example, as recently as 2006, the UK National Health Service benchmark for post-cataract surgery refractive outcomes in normal eyes was 55% within 0.5D of target and 85% within 1.0D. A recent study involving 10 centres in The Netherlands reached 80% within 0.5D using the Barrett Universal II intraocular lens (IOL) power formula, Prof Nuijts said. “That is 10% higher than before.” With such accuracy cataract surgery has truly become a refractive procedure.
These recent advances are due in part to improvements in optical biometry and the inclusion of factors such as posterior corneal power in IOL formulae, said Boris Malyugin MD, PhD, of the S. Fyodorov Eye Microsurgery Federal State Institution in Moscow, Russia. Incorporating artificial intelligence into formulae is further increasing their accuracy and may be particularly useful for post-refractive surgery and extremely long or short axial lengths.
Dr Malyugin sees integration of imaging technology into surgical microscopes as a significant step forward for the future, particularly for handling complex cases. For example, OCT imaging has revealed that much of the anterior chamber flattening in eyes with mature cataracts and loose zonules comes from irrigation fluid accumulating behind the posterior capsule due to rupture of the anterior hyaloid, pushing the capsule forward. Understanding this complication, which was previously unknown, helps avoid and manage it.
Improved tomographers and a better understanding of astigmatism have also improved IOL power prediction, said Soosan Jacob MS, FRCS, DNB, of Dr Agarwal’s Refractive and Cornea Foundation and Dr Agarwal’s Group of Eye Hospitals, Chennai, TN, India. She sees even better prediction of IOL power and preoperative assessment of visual needs using technologies such as SimVis (2Eyesvision) as ways to customise and improve visual outcomes.
Improvements in surgical technique, particularly reducing incision size, have also contributed to better outcomes, Dr Malyugin said. “At around 2.0mm, slightly less or slightly more, it looks like we have reached the sweet spot and do not need to decrease it further. These incisions are truly astigmatically neutral and reduce surgical trauma significantly.”
Improvements in phaco machines also helped, Dr Malyugin said. The introduction of alternatives to longitudinal ultrasound vibration, such as Ozil (Alcon) torsional and Ellips (Johnson & Johnson) elliptical vibration, improved the effectiveness and reduced ultrasound energy required for dissolving cataracts. Smaller needles and stiffer tubing allowed higher vacuum with stable fluid flow, while advanced sensors interrupted suction instantaneously. This not only enhances chamber stability, reducing the risk of corneal endothelial cell and iris damage, it can help reduce cystoid macular oedema and posterior vitreous detachment, he added.
For David F. Chang MD, access to affordable cataract surgery in the developing world is perhaps the most significant unmet eye care need. According to the World Health Organization, an estimated 94 million people worldwide have moderate or severe vision impairment or blindness due to unaddressed cataract, with prevalence four times higher in low-and middle-income regions than in high-income areas.
But advanced surgical technology is not the solution, said Dr Chang, a clinical professor at the University of California San Francisco, USA, and co-chair of the ASCRS Foundation. Certain surgical technologies are not practical in many low-resource countries for reasons ranging from cost to the reliability of electrical power and equipment maintenance.
The increasing backlog of global cataract blindness is due in large part to the lack of enough skilled surgeons who can execute more sustainable and cost-effective procedures such as manual small-incision cataract surgery (MSICS).
Enlisting visiting ophthalmologists to operate or teach in low- to middle-income countries is neither a sufficient nor scalable approach, Dr Chang added. Instead, the focus should be on developing and improving local ophthalmology training programs.
“This is potentially where new technology can really help – by enabling and supporting remote learning and virtual consultation,” said Dr Chang.
Applications such as Zoom can already allow experienced surgeons to virtually teach, mentor and provide clinical consultation to ophthalmologists and trainees anywhere in the world in real time, even as they perform surgery.
“Having the high-speed networking infrastructure to deliver these services is essential and new technology that can harness remote volunteers to help train and provide virtual consultation can accelerate the improvement of eye care in resource limited settings,” he noted.
According to Dr Chang, a leading example is Orbis’ Cybersight, which offers free online training courses and live webinars in all of the major sub-specialty areas in ophthalmology. The Cybersight platform is already virtually linking ophthalmologists in lower resource settings with volunteer consultants who can provide clinical answers and support within hours.
Cybersight’s networking technology allows a surgeon in the US to remotely monitor the live surgical microscope view of someone operating in Africa. Or they could remotely supervise a trainee using a networked surgical microscope in a wet lab.
Telemedicine holds the promise that ophthalmologists anywhere in the world could access AI-driven interpretation of uploaded fundus images.
“In addition, we’ve learned during COVID that virtual meetings, such as the ESCRS Congress, can be attended by international ophthalmologist that would not otherwise be able to travel for meetings,” Dr Chang said.
Finally, Orbis is working on an affordable surgical simulator for MSICS. Simulators are an effective and proven training adjunct, but the technology remains too expensive for most global settings. The Orbis project seeks to utilise existing gaming technology to develop surgical simulation systems that are portable, more affordable, and truly scalable, Dr Chang noted. Both he and the ASCRS Foundation have contributed support to this project.
Whatever the future holds the focus must continue to be on addressing patient needs, Dr Nuijts said. Doing so will require research into exactly what those needs are. For example, will it make sense to continue to push visual outcomes within 0.5D of target beyond the 80-85% achievable today? “I have not seen any study that addresses that.” In a world of limited resources, better defining the goals will be increasingly important to guide further progress.