What is the Light Adjustable Lens for cataract treatment? What is the purpose of the lens? What lens type does it belong to? Does it accommodate like a natural lens? What level of freedom off glasses may it provide?
The purpose.
The LAL is designed to solve the problem of residual refraction after cataract or RLE surgery. The problem the LAL targets is that any IOL must be specifically calculated to fit the optical system of the given eye. At the beginning of the IOL era, we had limited abilities to calculate IOLs properly. Thus, many patients, after cataract surgery, were forced to use glasses to get good visual acuity.
Nowadays, we have a lot of tools to calculate IOL precisely - newer diagnostic tools, newer formulas to calculate, including an AI-powered, and of course, the experience of every surgeon. However, in some cases precise calculation is challenging, like for post-refractive surgery patients and high hyperopia patients, sometimes extremely long eyes. It means, that some patients after the IOL implantation will end up with a refraction like -1 or +1 which will result in not optimal far visual acuity without use of glasses.
And the LAL is designed to be adjusted after the surgery. So, surgeon makes rough calculation, implants the lens and then, after measuring of the actual refraction the lens is adjusted to the proper power. All done.
What type of lens does it belong to?
By design and definition - it is a simple monofocal lens, in other words it is the 1st type of IOL in my recent review of the lenses in terms of vision range.
It is not EDOF, it is not multifocal or accommodative - it is simply monofocal lens, which might be toric. That’s all. So, it does not provide an extended range of vision without glasses by design.
And what is the reason for the perception that LAL does provide spectacle independence and it is a game-changer, ideal lens, and so on? There are 3 main reasons for that perception - the mono vision and certain level of focus depth achievable to a certain extent, which is not exclusive to LAL.
The mono vision approach is popular in the US to offer patient spectacles freedom as an alternative to presbyopia-correcting lenses. In Europe it is less popular, but used as well. Mono vision is an eye surgery where one eye is targeted to be well tuned for far vision, and another eye is targeted to deliver better bear vision, whilst the far vision will be decreased. This approach works well; however, it has some drawbacks like potential loss of stereopsis (depth perception), visual discomfort, and different visual experiences in the left/right eye. Some patients do not like that, and LAL gives an ability to try it after the surgery. It is possible to try before surgery with contact lenses, but only if the patient can wear contact lenses and does not have a mature cataract.
And what surgeons saying - this feature really reduces the so called «chair time» when they have to discuss with the patient pros and cons of mono vision. Do it, try and decide. Exactly as company says on their web site - test drive your vision. And it is definitely not possible with other IOLs. So in theory - less talks needed to explain - easier to show. And here is something important to keep in ming - a range of vision without use of glasses.
A range of vision.
The LAL is a monofocal lens, thus it can not give you multifocal or being more correct in modern terminology extended range or full range of vision experience in every eye. And that is something I want you to understand - it is monofocal lens, no more.
And as any monofocal lens, in case of certain corneal aberration profile, due to corneal aberration it might provide extended depth of focus experience to some patients.
Also, as described in some publications, there is a way to use certain spherical aberration induction with that lens to extend its focus to certain level. But again - far away from presbyopia correcting lenses.
And, according to the basic optical principles, focus elongation will lead to contrast decrease.
So, there is no miracle.
It is a monofocal lens, which may theoretically give a bit better than standard monofocal depth of focus, but not as wide as presbyopia correcting lens type, and I am not sure that similar to enhanced monofocals in terms of predictable and stable results with high amount of patients. Maybe the company will be able to deliver EDOF option later on, but now it is not the case.
If you have a complicated cornea, you are post refractive patient, you are aiming to get the highest possible visual outcomes for far vision and do not care about intermediate and neat vision without glasses - it is a perfect lens for you. In all other cases, the lens selection is relatively wide, and you may discuss with your surgeon further options to get the optimal visual results for your particular visual needs. My web site IOL-adviser.com may help you to narrow the IOL selection to have more focused discussion with your doctor.
I wish you a great visual outcomes!
More details in my resent YouTube video
Oleksii Sologub
MSc, LLB, SE MBA