Intraocular lenses

Short description of different lenses.

• PRL™ 
  A flexible posterior chamber phakic refractive lens. The IOL is designed to float on an aqueous layer above the natural lens and to self-center behind the iris. CE Mark approved. FDA Phase III Clinical Trials are ongoing in the U.S.
• Vivarte™ 
  A foldable, angle-supported phakic refractive lens, the Vivarte IOL is designed to provide optimum safety as a result of its design and material. The three points of the lens are designed to increase the stability of the lens. CE Mark approved; European launch planned for 2002. FDA Phase II Clinical Trials are ongoing in the U.S.
• Artisan Phakic Intraocular Lenses (PIOLs)
  The lenses are manufactured from Perspex CQ-UV, polymethylmethacrylate (PMMA) and are available in negative and positive powers. The procedure is done under local or, if your prefer, general anaesthesia. The small plastic lens is inserted like a letter in a envelop via a slit like wound of 5-6 mm on the top of the cornea. After fixation of the lens the wound is closed. The whole procedure takes about 20 minutes. Vision is usually stabile and good after about three days. The main risks (glaucoma, and corneal dystrophy) are very remote. Everything is done to prevent this form happening.

Some of the many aspects:

• Long clinical history; First Phakic IOLšs were implanted during the 1980šs. There was already extensive experience with intra-ocular lenses in cataract surgery since the 50šs.
• Reversibility of fixation; One of the main advantages of these lenses is the option of reversibility. They can be explanted or repositioned when necessary. Once fixated, the lens will not decenter.
• High predictability; 70% of patients obtain a refractive result within 1 D of the predicted power. This is considering the fact that very high myopia and hypermetropia are included a very good result. The special Astigmatic Artisan lens allows for precise correction of astigmatism.
• Relatively safe
• Safe distance from crystalline lens; No lens related capsular pacificationšs
• Pupil Dilation not inhibited. Fixation arms attached to immobile iris.
• No obvious effect of the inner-layer of the cornea

Advantages:

• In general good vision returns after one day to 2 weeks.
• If necessary, the lenses can be removed. This, however, is not something to be considered easily. Every time the eye is opened up for whatever reason, you run the risk of infection. Removing an intra ocular lens is only done with strong positive indications .
• Astigmatism can be reduced by a tiny incision.

Disadvantages:

• The eye is opened with a tiny incision varying between 1,5mm-6mm. This increases the chance of infection. In general., the modern eye drops available today are sufficient in preventing infection.
• The incision and especially a larger incision that needs stitching can cause astigmatism.
• The contact between the artificial lens and one's own lens can cause a cataract. This can make cataract surgery unavoidable. This isn't a big problem; just a nuisance. During the surgery the intra ocular lens is removed, as well as the cataract, and then replaced by a new adjusted intra ocular lens. However at a young age one loses the accommodation. This is necessary for reading distance. This can be very irritating at a young age since some form of additional correction will be required for reading. The front eye chamber lenses cause cataract a loss let frequently than others.
• All lenses increase the chance of eye pressure. This usually because apparent within hours. One will experience a headache, nausea and vomiting. By puncturing two tiny holes before or during the implantation in the iris the chance of eye pressure forming will be eliminated.
• By closing off small veins in the iris (through glaucoma or direct touch) the possible scar formation on the iris may lead to a change of shape.
• The optical zone of the lens in relation to the lens' size can lead to problems with night vision.