Phakic Intraocular Lens
Phakic Intraocular lenses or PIOLs are a type of lens that will be surgically attached to your eye in order to correct myopia or nearsightedness. The word phakic is from an ancient word that states that means that nothing on the natural lens of the eye will be touched. These lenses tend to get the most attention because the can only be inserted whenever the natural lens is removed during cataract surgery, and that is when it will be called pseudophakic.
The intraocular focal points will be shown for those who happen to have high refractive errors after they have thought about the options with laser surgery like Lasik or PRK are not approved to have the surgery. These types of IOLs are supposed to he able to handle elevated levels of nearsightedness that go from -5 to -20 D, and that means that will need to be enough tissue as well as density within the anterior chamber of the eye that is at least 3mm.
There are only 3 main styles of these IOLs that are found on the market right now and they are the iris fixated lens, implantable collamer lenses, and the angle supported lenses.
However, Lasik will only handle nearsightedness that have a range between -14 and -12 D and the higher that the correction needs to be, then the cornea will be flatter and thinner after the surgery. In order to have any type of laser eye surgery, a person will have to have a certain amount of the stromal bed left which is at a range of at least 250 micrometers, but 300 micrometers are preferred. Anything beyond those limits will have an increase risk of developing bulging of the cornea, which is also called corneal ectasia. This is caused because of a thin stromal bed which will cause your vision quality to be poor. Because of risks of large aberrations, research has shown that there is now a common form that will reduce the higher levels of PRK and Lasik to -10 to -8 Diopters. The PIOLs are much safer than having excimer laser surgery for those who have high levels of myopia.
These lenses are best for those haven’t had a level of error for a term of 6 months, or who are over the age of 21. Any eye disorders like uveitis, will stop a person from receiving this type of eye surgery. However, these are being researched for use in those who have hyperopia, but there is not a lot of enthusiasm for use of them because the anterior chamber will be thinner than those who have myopia.
Theses PIOLs have a large advantage for being able to treat a wider range of hyperopic and myopic refraction errors that are able to effectively as well as safely treated unlike normal laser surgery for the cornea. There are skills that are needed to insert these lenses, even with a few exceptions, are going to be close to those that are used in average cataract surgeries. The type of equipment that is used will be much cheaper than using an excimer laser and it is also seen to be cheaper than what is used in cataract surgery. Additionally, they are removable, which means that in theory, if you wanted to have the lenses removed, you could have that done and your vision would be reversible. However, any type of damage that is done to the eye by the lens would not be reversible and it would be considered permanent. Whenever this is compared to an exchange of refraction lenses, these are able to preserve the natural vision and will actually end up providing a low risk of there being any type of post-operative detachment of the retina. This is due to the preservation of the crystalline lens and this means that there is very little vitreous destabilization.
The depth of the anterior chamber, which is the how far it is between the cornea and crystalline lenses and this includes the thickness of the cornea will be needed before the surgery can ever happen and it can be measured using an ultrasound. There are different IOLs, such as iris fixated one which is implanted onto the iris, which means that there is an advantage of there only being one size of the lens which is around 8.5 mm. The sulcus supported ones will have to be placed on the ciliary sulcus and these could all vary in size based on the person. So, the ACD will have the measurements done using caliper or it will need to be measured using imaging equipment like high frequency ultrasound or Orbscan. The Orbscan and caliper will be able to provide a measurement of external diameters from white to white within the eye, which is able to provide an approximate estimate on the diameter of the anterior chamber however using OCT and UBM are going to be the best way to get an adequate measurement on the white to white diameter and these should be used whenever it is available.
There are different surgical techniques that may be used such as the Verisyse or Artisan lens which will be implanted while under pharmacological miosis. Once the right incision is done, the lens will then be picked up using curved forceps and then inserted into the eye. Once the lens is in the anterior chamber and while the lens is still be held firmly, the nasal iris and temporal tissue will then be enclavated using a special type of needle. The whole surgery is done with an iridectomy and then the incision will then be sutured. ICL is also done under a pharmacological mydriasis and the lens is implanted in retropupillay position which is located between the crystalline lens and the iris of the eye, using forceps. Both of your eyes can be done on the same day. Once the surgery has been completed, steroid antibiotic eye drops will then be prescribed, and they will need to be used for at least 4 weeks after the surgery is done. Then there will be regular follow-ups.