NEW IOL DESIGNS

IOL designs are continuing to improve with exciting developments in improving accommodation but there is still no ‘perfect’ lens available to surgeons, Rajesh Aggarwal MD, FRCOphth told the joint Irish and UKISCRS refractive surgery meeting. Dr Aggarwal, consultant ophthalmic surgeon, Southend University Hospital, UK discussed the latest developments in the IOL market. “Ideally as we all know the ideal lens is the crystalline lens of a 21-year-old. At present we have nothing that can come anywhere near it.†However, he acknowledged there is a lot of innovation going on in IOL designs. The crystalline lens is now much better understood, as are the theories of accommodation, which Dr Aggarwal said is helping with new designs. Surgical techniques are also continuing to improve. “In future for example with femtolaser, things are going to get even more predictable and that’s allowing for new development and better IOL designs.†The four key issues new IOLs are trying to address are astigmatism, presbyopia, capsular bag transparency and higher order aberrations Dr Aggarwal said if there is rotational instability of the IOL, then a surgeon can almost forget trying to correct astigmatism with IOLs. Thankfully the newer toric IOLs are very stable and do not show the rotation that the previous IOLs used to, he noted. To tackle astigmatism Dr Aggarwal said most would agree that it is possible to reduce surgically induced astigmatism by keeping the incision below 2.0mm for implantable IOLs. Another interesting development is the attempt to manipulate higher order aberrations to actually mimic accommodation he said. Presbyopia is one of the biggest drivers of IOL design improvement, and the current premium multifocal IOLs give very good near and distance vision, but poor intermediate vision, he reported. This is now being addressed by trifocal IOLs. There are also issues with dysphotopsia, especially night vision, and reduced contrast sensitivity. The accommodative IOLs do not have issues with dysphotopsia at night or contrast, but near vision and the accommodative range is poor, according to Dr Aggarwal.

Multifocals

Dr Aggarwal said that the four most commonly used multifocal IOLs all have particular positive attributes, but indicated a preference overall for the MPlus (Topcon) lens, partly due to its better night vision results. “The other intriguing advance has been the tri-focal lens. When first this was mentioned to me I thought here we go, we are going to get more problems and I was a bit reluctant… but to my surprise it (Fine Vision Trifocal IOL) has become my standard of multifocal lens now.†He said this lens gives very good distance, reading and intermediate vision. Summarising, Dr Aggarwal said the newer multifocal IOLs have a better range of focus, reduced light loss, better contrast sensitivity profile, reduced dysphotopsia and better patient acceptance “But they are still not perfect and they never will be perfect in my opinion because you are introducing abnormalities by having more than one focus within that lens, so I think the way forward has to be accommodative lenses – if we can get them to accommodate.â€

Accommodative lenses

There remains a question as to whether the current accommodative lenses are truly accommodative or if it is pseudo accommodation, Dr Aggarwal remarked, saying that in his opinion single accommodative lenses do not accommodate well. He said dual optic accommodative IOLs give good results but have issues with delivering emmetropia. Research has shown that high accommodative amplitudes can be achieved by lens curvature changes and experiments with new lenses using that approach are yielding good results. He also briefly discussed LiquiLens and Fluid Vision lens, which he said show some progress, while he expressed excitement at the development of light adjustable lenses and the SmartIOL. Concluding, Dr Aggarwal said patient needs are key to choosing the right lens but the newer lenses coming on stream will mean more flexibility, and better results and choice.