Hi, I'm a second-year med student and just came home from an ophthalmology (related to the eyes) seminar. In this seminar, we discussed cataracts and the ophthalmologist holding the seminar said how cool it would be if someone invented self-accommodating lens implants and I thought, come on, how hard can it be. Ok, I'll better explain:The problem
Statistically, every person who lives to be more than 80 years old has already or will develop a cataract. This is a condition where the lens of the eye clouds over leading to vision impairment and eventual vision loss and since it's also associated with diabetes and high blood pressure it's likely going to be more common in the future.
There is a very good operation for this where the lens is taken out and replaced with a synthetic lens made of acrylic glass. It's a standard outpatient procedure in most cases. However, this acrylic lens is not flexible like the original human lens. This means that patients will have to wear glasses with multifocal or progressive lenses for the rest of their lives. And there are a lot of young patients, cataract is one of the most common conditions in pre-term babies.
The problem of making a self-accommodating lens is how the accommodation - that is focusing light from sources at different distances onto the retina - works in the human eye. The organic lens is elastic. In its relaxed state it is round, so the focus is on something close. The capsule of the lens is attached to the zonular fibers which are in turn attached to the ciliary muscle, which is a muscle ring. When this muscle contracts, the ring gets smaller and the zonular fibers relax, so the elastic lens also relaxes and the focus is on something closer to the eye. When the muscle relaxes, the ring is wider and the zonular fibers are tightened, stretching the lens into a flatter shape that focuses light from something farther away. When the lens is taken out this lens capsule and the zonular fibers and the muscle are actually left in to act as a frame for the artificial lens, but the lens is not actually attached in any way. And that's where I see the potential solution, a self-accommodating lens would need to have these properties:
- transparency (of course)
- sufficient density, so it will actually break and focus light
- somehow attached to the zonular fibers and/or ciliary muscles
- biocompatibility, so it will be accepted by the body (and at the same time sufficiently lightweight and somehow applicable)
My personal problem is that I have neither the time nor resources to research this now and am also lacking the detailed knowledge of ophthalmology and physics necessary to do this, but why should I wait until I'm actually in research (which will take another five or six years) to get thinking about it. Then again thinking about it effectively keeps me from studying the things that will be asked in my next exams. That's why I'm putting it out hereIdea one - fill up the capsule
The lens capsule is left standing anyway, but there is a hole made in the front to take out the old lens. Since the capsule is already attached to the zonular fibers, it would be cool if we could seal that hole in the front (for example by a thin acrylic sheath) and fill it up with a sufficiently dense gel.
The problem with this would be creating a sufficiently tight seal, and also the application, Also I don't know if the capsule in itself is elastic enough to keep this kind of shape. Idea two - the water ball
Okay, so all these ideas revolve around the idea of a gel-filled room (not water, because it's not dense enough). So maybe we could make a more ball-like structure filled with the above mentioned sufficiently dense gel. Of course, how round or flat this structure would be, to begin with, would also define how it would break light, but that's details to be worked out. Now if we would cut out part of the back of the lens capsule, too, we could anchor this ball inside that ring and it would be stretched when the lens capsule is stretched and relax when the capsule is relaxed.
This would also need some sort of attachment to the lens capsule, although it wouldn't necessarily have to be watertight. Alternatively, maybe there could be some kind of clasp mechanism that attaches it directly to the zonula fibers. But I think the main problem would be the material of the bag so it would be both elastic enough and also flatten in the right way.Idea three - the full prosthesis
Basically the same idea as idea two, only this time we remove the lens capsule and the zonula fibers and it might be a flat lens compressed into a ball-like shape rather than the other way around. The idea is to take a ring of elastic material and attached to the ciliary muscle. This would have rods leading to a second ring that would hold the artificial lens. Now when the ciliary muscle is contracted the rods would push on the lens that would be pressed into the more ball-like shape and focus the light differently.
The material would again be the main problem. Also, these ideas have become progressively more complicated.
Now I don't expect anything to come of this. These are just basic ideas and I'm lacking the knowledge of materials, physics, and physiology to say if any of this is even realistic. But if any of you pick up on one of these ideas and it somehow leads to something, even if that might be something entirely different, that's enough for me to write it down here. And at least for now I have it out of my head and can focus on abdominal anatomy again.
My first (and in some places still active) screen name was Ellena.
This became Ellster.
Elster is the German word for magpie.
Therefore I am sometimes called Mag Pie. Although my name is not Mag. But I do like pie.