Today, a post of a certain author appeared on slashdot, which, after implantation of an artificial lens, began to see in the ultraviolet range, more precisely about 365 nm - this is at an average upper limit for an average person of 400 nm. I was interested in this topic, and I decided to find out what was going on there, and whether the ghost of Chris Carter
So, a little excursion into ophthalmosurgery. During the Second World War, a certain English ophthalmologist, who operated on pilots shot down in aerial combat, found out that the plexiglass of the aircraft lantern that fell into the eye was not rejected by tissues. Moreover, it traumaticly changes the shape of the cornea - and since it is responsible for ~ 70% of refraction in the eyeball (the rest falls on the lens), changing its shape leads to significant changes in the refraction of the eye. Naturally, the idea immediately came to treat myopia by reducing the optical power of the cornea by cutting it and reducing the curvature. By today's standards, it resembles craniotomy of a skull with a stone knife (and without accurate measurements and calculations on accuracy it is about the same) - but it was better than nothing.
Then they guessed that if plexiglass is not torn away, then it can be put there intentionally ... after having turned it into a lens shape. What for? Because by the age of 45-50, the natural crystalline lens a) becomes rigid and loses the possibility of accommodation (which makes it impossible to refocus vision), and b) becomes cloudy for some time later, as a result of which the vision slowly drops to almost zero. So, it can be replaced.
At first, instead of the natural lens, hard lenses were put, which, quite naturally, caused a lot of unpleasant sensations, damaged internal tissues, and so on. Now, in general terms, the procedure is as follows. I will use English terminology in transliteration.
1. The patient lies under a microscope. The eyelids are fixed in the open position, anesthesia is placed in the optic nerve.
2. On the side of the eye, approximately on the border of the iris, a small incision is made using an ultra-sharp scalpel, about 2 mm in length.
3. The lens is located inside the capsular bag. The tool through which this bag is incised penetrates the eye through this incision.
4. The phacoemulsifier probe penetrates the inside of the bag through these two incisions. This device a) ultrasound crushes the hardened natural crystalline lens, and b) simultaneously sucks the crushed pieces. It is important not to tear the capsular bag - it is fraught with a lot of problems and complications, and not to touch the iris. Its consistency is reminiscent of a blotter, and its damage leads to vision problems - for example, the patient may begin to see halos around point light sources.
5. After phacoemulsification, a viscoelastic gel is pumped through a microsyringe into the capsular bag - so that this bag is not deflated, because the lens is no longer there.
6. Fanfare and drums - we implant a lens. The lens itself is made from materials like silicone, and it can be folded. That is why a cut of just 2mm is enough, although the lens is noticeably larger. It is delivered in a cartridge that is inserted into a syringe, which is gently inserted through the incision into the eye, then into the capsular bag, and is simply squeezed there. There she turns around and takes on her original appearance, in which the surgeon helps her. In half a minute she is ready.
7. If the lens is aspherical, then it can also help with astigmatism. In this case, it must be tightened to the desired angle. Subsequently, the eye tissue will grow together through certain protrusions on the outer, optically non-functional part of the lens, and fix it from turning. There are often cases where the lens is still rotated uncontrollably - this is corrected by re-operation.
8. The eye is moistened, closed with a bandage. The incision will heal itself. The patient goes home.
Such an operation can cost from 3 to 20 thousand dollars, depending on various reasons. The recovery period before removing the dressing takes a day or two. Yes, it is sometimes hard to believe, but in our practice there were cases when 70-year-old grandmothers received vision in 80% the day after the operation ... I never saw it myself, but as they say, people start crying with happiness.
And now on the topic. Why did that patient start seeing UV? Because the lens usually absorbs UV rays, preventing them from reaching the retina. Old lenses were made of materials that often quietly let in UV, and patients began to see in the UV range. But it did not last long, because the retina is damaged by ultraviolet. Therefore, in the new lenses there are additives that filter out UV rays. The Crystalens lens was installed to that patient, which apparently contains fewer such additives (or does not contain them at all), hence we have the result. The chief somehow operated on one patient, for whom for different reasons one lens was shown on one eye and the other on the other, and the UV absorption coefficient was different. The patient was then quite surprised that with one eye he could see UV and others could not. It did not bother him, and everyone was very pleased.
PS The material was written after consulting with my chief, an ophthalmic surgeon with more than 10 years of experience. If there are errors in the text - I fully accept all responsibility for the curve translation, and I ask you to point out these.
PPS What do I do, being a programmer, to write such texts? Good question. Our company advises others on the calculation of the correct lenses for each particular eye ... and I am engaged in the implementation of the calculated software. Incredibly interesting topic, and very rewarding, especially when they write to us about grandmothers and grandfathers who received eagle vision.
Health to you, take care of your eyes :)