More about Phakic IOL lens implants



This is a recent development most likely inspired by the success in lens replacement for people with cataracts. Doctors use the Greek name for lens, “Phakos,” to describe the procedure. Phakic IOLs are clear implantable lenses that are surgically placed either between the cornea and the iris (the coloured portion of your eye) or just behind the iris without removing your natural lens. Essentially, it is a contact lens you wear inside your eye rather than on your eye

Phakic lenses enable light to focus properly on the retina for clearer vision without corrective glasses or contact lenses. These lenses avoid the problems of contact lenses and Lasik surgery. However, as there are always complications involved with any surgery, Phakic lens implants are associated with their own side effects. Also, it is important to remember that lens implants do not actually deal with your myopia. Like glasses and contact lenses, they only correct your vision.

The in-office procedure takes about 15 mins and costs approximately US $4,000 per eye. It may take about a month before everything settles and you can expect 20/40 vision or better, allowing you to drive legally without glasses. Although you may have great distance vision, you may need glasses for reading, so doctors recommend that you get mono vision, where one eye is fitted with a lens that enables you to read and the other lens enables you to see in the distance. Mono vision, of course, means that your 3D vision is gone. Furthermore, people should not expect their accommodative abilities to be restored to perfect or even near perfect function. Though vision is significantly improved, the degree of improvement will not be the same for all, and some will still need glasses after the surgery.

The clinical trial for the Verisyse phakic IOL noted that 92 percent of Verisyse patients achieved 20/40 or better visual acuity without the use of corrective lenses. Still, about 60% of the patients had less than 20/20 vision.

The FDA has approved two phakic IOLs that are currently available in the United States. Your eye surgeon will recommend the most appropriate implantable lens for you. The Visian ICL (Implantable Collamer Lens) marketed by Staar Surgical is a posterior chamber phakic IOL, meaning that it is positioned behind the iris and in front of your natural lens. It received FDA approval in 2005 for correcting nearsightedness ranging from -3.00 to -20.00 diopters. 

They are notorious for their negative impact on the corneal endothelial lining, which is vital for maintaining a healthy clear cornea. Because the Visian ICL is placed behind the iris, it is undetectable to the naked eye and can only be seen through a microscope. The Visian ICL is made of a soft, biocompatible collagen copolymer. Due to its flexibility, the lens is able to be folded during the implant procedure, allowing for a much smaller surgical incision (about 4 mm).
The Verisyse (Abbott Medical Optics) is an anterior chamber phakic IOL, meaning that it is positioned in front of the iris. In 2004, the Verisyse phakic IOL received FDA approval for correcting moderate to severe nearsightedness within a range of -5.00 to -20.00 diopters. These lenses have special vaulting so as to not be in contact with the normal lens. The main complications with this type of lens are its tendency to cause cataracts and/or pigment dispersion. 
The Ve r i s y s e lens is made of medical grade plastic, (polymethylmethacrylate, or PMMA) and is rigid in form, thus requiring a larger 6 mm incision in order to implant the lens. In Europe, it is approved and marketed under the trade name Artisan. Because the lens is implanted over your iris, you may see the lens if you look closely in the mirror. Neither of the two FDA-approved lenses treats astigmatism, an eye problem that often accompanies nearsightedness.

Are you a candidate for Phakic lens implants?

  • Not all patients are candidates for phakic intraocular lens implants, just like not all patients are candidates for LASIK. You are probably NOT a good candidate for phakic lenses if: You are less than 21 or are more than 40 years old. There are no phakic lenses approved by the FDA for persons under the age of 21. You are not a risk taker. Certain complications are unavoidable in a percentage of patients, and there are no long-term data available for phakic lenses. You required a change in your contact lens or glasses prescription in the last 6 to 12 months in order to obtain the best possible vision for you. This is called refractive instability. People who are in their early 20s or younger, whose hormones are fluctuating due to disease such as diabetes, who are pregnant or breastfeeding, or who are taking medications that may cause fluctuations in vision are more likely to have refractive instability and should discuss the possible additional risks with their doctor.
  • You may jeopardise your career. Some jobs prohibit certain refractive procedures. Be sure to check with your employer/professional society/ military service before undergoing any procedure. Cost is an issue. Will the price of phakic IOLs — from prescreening to ongoing regular checkups — be covered by your insurance? You have a disease or are on medications that may affect wound healing. Certain conditions, such as autoimmune diseases (e.g. lupus, rheumatoid arthritis), immunodeficiency states (e.g. HIV) and diabetes, and some medications (e.g. retinoic acid and steroids) may prevent proper healing after intraocular surgery. You have a low endothelial cell count or abnormal endothelial cells. If the cells that pump the fluid out of your cornea, the endothelial cells, are low in number relative to your age, or if your endothelial cells are abnormal, you have a higher risk of developing a cloudy cornea and may require a corneal transplant. You actively participate in sports with a high risk of eye trauma. Your eye may be more susceptible to damage should you receive a blow to the face or eye, such as a blow to the head during boxing or hit in the eye by a ball during baseball. Your eye may be more susceptible to rupture or retinal detachment, and the phakic lens may dislocate.
  • You only have one eye with potentially good vision. If you only have one eye with good vision with glasses or contact lenses due to disease, irreparable damage, or amblyopia (eye with poor vision since childhood that cannot be corrected with glasses or contact lenses), you and your doctor should consider the risk of possible damage and/or loss of vision to your better eye as a result phakic lens implantation. You have large pupils. If your pupil dilates in low lighting conditions to a size that is larger than the size of the lens, you have a higher risk of experiencing visual disturbances after surgery that may affect your ability to function comfortably or normally under such conditions (e.g. while driving at night).
  • You have a shallow anterior chamber. If the space between the cornea and the iris, the anterior chamber, is narrow, you have a higher risk of developing complications, such as greater endothelial cell loss, due to implantation of the phakic lens. You have an abnormal iris. If your pupil is irregularly shaped, you have a higher risk of developing visual disturbances.
  • You have had uveitis. If you have had inflammation in your eye, you may have a recurrence or worsening of your disease and/or may develop additional complications, such as glaucoma, as a result of surgery. You have had problems with the posterior part of your eye. If you have had any problems in the back part of your eye or are at risk for such problems, for example, proliferative diabetic retinopathy (growth of abnormal vessels in the back of the eye due to diabetes) or retinal detachment, you may not be a good candidate for phakic lens implantation.
  • The phakic lens may not allow your eye doctor to get a clear view of the back part of your eye, preventing or delaying detection of a new or worsening problem, and/or the phakic lens may prevent or make treatment of a problem in the back of your eye more difficult. The safety and effectiveness of phakic lenses have NOT been studied in patients with certain conditions. If any of the following apply to you, make sure you discuss them with your doctor:
  • You have glaucoma (damage to the nerve of the eye resulting in loss of peripheral and then central vision due to too high pressure inside the eye), ocular hypertension (high eye pressure), or glaucoma suspect (some indications, but not clear, that you have glaucoma). You may have a higher risk of developing or worsening your glaucoma as a result of phakic lens implantation.
  • You have pseudoexfoliation syndrome (abnormal deposits of material in the eye visible on the structures in the front part of the eye, such as on the front of the natural lens and the back of the cornea). This syndrome is associated with glaucoma and weakness of the structures holding the natural lens in place (the zonules). You may have a higher risk of surgic complications and/or complications after surgery if you have this syndrome. 
    You have had an eye injury or previous eye surgery.
  • Your need for visual correction is outside the range for which the phakic lens has been approved. Ask your eye doctor if the phakic lens that he or she recommends for you has been approved to treat your refractive error and/or check FDA approval.


The FDA provides the following comment: U.S. Food and Drug Administration Protecting and Promoting Your Health

What are the risks?


Implanting a phakic lens involves a surgical procedure. As with any other medical procedure, there are risks involved. That's why it is important for you to understand the limitations and risks of phakic intraocular lens implant surgery.

Before undergoing surgery for implantation of a phakic intraocular lens, you should carefully weigh the risks and benefits and try to avoid being influenced by other people encouraging you to do it.
You may lose vision. Some people lose vision as a result of phakic lens implant surgery that cannot be corrected with glasses, contact lenses, or another surgery. The amount of vision loss may be severe.

You may develop debilitating visual symptoms. Some people develop glare, halos, double vision, and/or decreased vision in situations of low level lighting that can cause difficulty with performing tasks, such as driving, particularly at night or under foggy conditions.

You may need additional eye surgery to have the lens repositioned, removed, or replaced if the lens does not stay in the right place, is not the right size, and/or causes debilitating visual symptoms. These surgeries may be necessary for your safety or to improve your visual function. If the lens power is not right, then a phakic lens exchange may be needed. Every additional surgical procedure has its own risks. Doctors are usually very reluctant to remove lens implants due to the exceedingly difficult procedure.

You may be undertreated or overtreated. Many treated people do not achieve 20/20 vision after surgery. The power of the implanted phakic lens may be too strong or too weak. This also means that you may need a second surgery to replace the lens with another if the power of the originally implanted lens was too far from what you needed. This is because of the difficulties with determining exactly what power lens you need. This means that you will probably still need glasses or contact lenses to perform at least some tasks. For example, you may need glasses for reading, even if you did not need them before surgery.

You may develop increased intraocular pressure. You may experience increased
pressure inside the eye after surgery, which may require surgery or medication to control. You may need long-term treatment with glaucoma< medications. If the pressure is too high for too long, you may lose vision.

Your cornea may become cloudy. The endothelial cells of your cornea are a thin layer of cells responsible for pumping fluid out of the cornea to keep it clear. If the endothelial cells become too few in number, the endothelial cell pump will fail and the cornea will become cloudy, resulting in loss of vision. You start with a certain number of cells at birth, and this number continuously decreases as you age since these cells are not replenished. Normally, you die from old age before the number of endothelial cells becomes so low that your cornea becomes cloudy.

Some lens designs have shown that their implantation causes endothelial
cells to be lost at a faster rate than normal. If the number of endothelial
cells drops too low and your cornea becomes cloudy, you will lose vision
and you may require a corneal transplant in order to see more clearly.
You may develop a cataract or clouding of the natural lens. The amount of time for a cataract to develop can vary greatly. If your cataract develops and progresses enough to significantly decrease your vision, you may require cataract surgery in which your doctor will have to remove both your natural and your phakic lenses. The lens implant greatly complicates this otherwise simple procedure.

You may develop a retinal detachment. The retina is the tissue that lines the inside of the back of your eyeball. It contains the light-sensing cells that collect and send images to your brain, much like the film in a camera. The risk of the retina becoming detached from the back of your eye increases after intraocular surgery. It is not known at this time by how much your risk of retinal detachment will increase as a result of phakic intraocular lens implantation surgery. In any case, the risk of retina detachment is significantly higher for individuals with high degree of myopia, which are the candidates for Phakic lens implants.
You may experience infection, bleeding, or severe inflammation (pain, redness, and decreased vision). These are rare complications that can sometimes lead to permanent loss of vision or loss of the eye.

Long-term data are not available. Phakic lenses are a new technology and have only recently been approved by the FDA. Therefore, there may be other risks to having phakic lenses implanted that we don't yet know about.

Source:

http://www.fda.gov/medicaldevices/productsandmedicalprocedures/implantsandprosthetics/phakicintraocularlenses/ucm059239.htm!

Leo Angart

www.vision-training.com

Comments

Popular posts from this blog

Meet Your Eye Musckes

More about the Bates Method

More about fluorescent lights