February 01, 2021
2 min read
February 01, 2021
2 min read
Click here to read the Cover Story, “Corneal and lens-based refractive surgery advancements optimize vision.”
There has been quite an evolution of IOLs since their inception. In the era of refractive cataract surgery, there is an increasing demand for a full range of vision without visual aids including glasses or contact lenses.
The treatment of presbyopia with increased range of vision is clearly sought after by many patients undergoing cataract surgery. When it is discovered, a truly accommodating IOL will be a game changer. However, it is difficult to say with confidence when that might be. There are many barriers to developing this type of implant that could provide the true accommodation the natural crystalline lens provides early in life.
A patient’s natural crystalline lens is a complex three-dimensional structure. When we remove a cataract, we are traditionally putting in an artificial lens that cannot change shape, like the natural lens does. Finding a way for an artificial lens to work in concert with the ciliary body and intraocular mechanisms after removal of the natural crystalline lens is a challenging pursuit. This challenge coincides with my personal experience with available accommodating IOLs, which would often be disappointing over time often due to fibrosis of the lens capsule, rendering patients still significantly dependent on spectacles.
I am skeptical to think that a truly accommodating IOL is possible in the next 5 years. With the evolution of lens technology and innovation, it will happen.
Certain parts of the human body are obviously challenging to invent or develop if removed for many reasons. The human crystalline lens is no exception. I do think the evolution of the multifocal lenses and other implants on the pending horizon of FDA approval in the next few years will give us more options that give patients more range. We have made much progress since the advent of IOLs, but still with innovation and technology, we have a ways to go.
Kathryn M. Hatch, MD, is an OSN Technology Board Member.
A truly accommodating IOL that provides at least 3 D of actual accommodation is certainly possible but extremely difficult to achieve clinically.
There are currently no phase 3 domestic trials and extremely limited human trials offshore. It will be at least 5 years before any such IOL is available in the U.S.
The main problem is harnessing the force available from the ciliary body. In the cataract age group, the muscle is still functioning at good levels, but the force is transmitted though the zonules and the crystalline lens capsule, which is elastic when the lens is intact as a result of the lens epithelium and lens fibers. The main components of the capsule are type IV collagen and sulfated glycosaminoglycans. When a capsulorrhexis is performed, the surgeon can feel and see the rubbery-like elastic property of the capsule. Unfortunately, when the cortex is removed, the elastic properties of the capsule disappear and become rigid, like aluminum foil. It cannot be stretched and only tears when a shear force is exerted. Surgeons who have removed or tried to rotate an IOL are familiar with the change in the capsule’s elasticity after cataract surgery. As a result, trying to use the capsule to utilize the ciliary body forces have been disappointing at best.
Harnessing the electrical signal from the ciliary body is also possible, but this is much more complex than using the mechanical force and requires an electrical interface, which is only theoretical currently. An electrical IOL that can change power has all of the components available but will still require a great deal of experimental design and is only on the drawing board at present.
Accommodating IOLs will happen, but it will be more than 5 years.
Jack T. Holladay, MD, MSEE, FACS, is OSN Optics Section Editor.