PRELEX (Presbyopic Lens Exchange) is the name now given to the surgical procedure to replace the natural lens of your eye, when it is no longer focusing correctly for near targets, with a multi-focal or pseudo-accommodative intra-ocular lens implant (IOL).
Whilst the application of the technology is new, the surgical techniques employed have been proven successful over many years of use. That’s because the procedure itself is similar to that used to treat cataract patients. The most significant difference between a cataract patient and a PRELEX patient is the clarity of the lens prior to surgery.
The Procedure
The operation is similar to that performed on cataract patients. On the day of surgery you will be given eye drops to dilate the pupil. The area around your eye will be washed and cleansed. The operation usually lasts about 20 minutes and is essentially painless as it is generally performed under a local or topical anaesthetic. Intravenous conscious sedation can be used to help anxious patients relax during, and forget about afterwards, the procedure.
The technology used during the surgery is a machine called a phacoemulsifier (phaco). The surgeon makes a micro-incision, approx. 2.85mm, on the side of the cornea and inserts a tiny probe into the eye. This ‘phaco’ probe emits ultrasound waves that break up the lens and the same probe removes the lens material by suction. Once removed, the original lens is replaced by the advanced lens implant (IOL) which is folded and inserted through the tiny incision. This IOL then unfolds once in place in the eye. There are often no stitches, you can return home to relax the same day and look forward to a rapid and pain-free recovery.
If you have astigmatism your surgeon may correct it with specifically placed miniature incisions around the edge of the cornea.
Many patients remark on the early improvement in their vision. The level and quality of unaided vision at this early stage, in this eye, can help the surgeon confirm what power lens implant to use in the second eye. Patients can often return to work and other usual activities within a few days but will return to hospital to have the second eye done within a couple of weeks. The true benefit of PRELEX is not evident until both eyes have been done and the brain has had time to adjust to its new visual system.
Mr Ikram is amongst a small and progressive group of international ophthalmologists to offer PRELEX. Their patients are now able to have clear vision and to reduce or eliminate their need for glasses. They will also never need treatment for cataracts.
Your Questions Answered
How long will the surgery take?
The operation itself will take about 20 minutes, however you will need to allow for about 3 hours in total, so that your eye can be prepared before the surgery and you have a chance to relax for a short while afterwards. You will need someone to collect you or we can arrange transport for you.
What happens after the operation?
After the operation you will rest for a while and have refreshments. You will be given a dressing pack to swab the eye clean the following day, and some antibiotic and anti-inflammatory eye drops to apply at home after the surgery, for 2-4 weeks.
Can I have both eyes done at once?
You will need to have each done separately, although they can both generally be done within about 2-6 weeks of each other.
What is special about the Lens technology in PRELEX?
Traditionally replacement lens implants were all fixed-focus which usually gave clear distance vision but required the use of reading glasses. New advances in lens technology means that specialized lenses can give:
- Multi-focal vision providing patients with clear vision up close and far away and reasonably good vision at intermediate distances.
- Pseudo-accommodation. Accommodative lenses mimic the eye’s natural lens by changing shape and position within the eye. These lenses generally give very good distance and intermediate vision, whilst also allowing quite good reading vision.
Mr Ikram will discuss the most appropriate lens for you, your eyes and your lifestyle. The objective will be to reduce, or if possible eliminate, your need for bifocals or reading glasses.
How safe is the procedure?
PRELEX uses new advanced technology in the form of the multi-focal lens or pseudo-accommodative lens, combined with a well proven surgical procedure. Every year in the UK alone around a quarter of million people undergo cataract surgery, in which the lens is replaced with a lens implant using the same surgical techniques required for PRELEX. The procedure is safe in the hands of a surgeon who is highly skilled and trained in both the procedure itself and the new technology.
As with all surgery there are risks, even though cataract surgery is now considered one of the quickest and safest surgical interventions available. PRELEX is the same surgical procedure but in a non-cataract patient. Although the vast majority of patients achieve excellent results without complications, it should not be forgotten that PRELEX is a surgical procedure and, as with all forms of eye surgery, PRELEX has risks and whilst we make every effort to minimize them, they cannot be totally eliminated. You can discuss these risks further with your surgeon, but in the end, only you can determine if the benefits of having PRELEX are worth it for you. As an elective procedure, there always exists the alternative of wearing reading glasses, bifocals or contact lenses.
What are some of the common or more serious risks of PRELEX?
Although the vast majority of patients achieve excellent results without complications, it should not be forgotten that PRELEX is a surgical procedure. As with all forms of eye surgery, PRELEX has risks and whilst we make every effort to minimize them they cannot be totally eliminated.
- Retinal Detachment – occurs when the retina detaches from its normal position and can result in severe loss of vision if surgical correction is not successful. The approximate risk of a retinal detachment in the general population is 0.01 % per year. Someone who is hyperopic has a smaller risk than this, whereas a myopic patient has a slightly higher risk than this.
- Infection - every time there is an incision made in an eye for any reason it is possible to get an infection inside the eye which has the potential to cause severe visual loss. This problem is extremely rare and our rate of endophthalmitis is less than 0.03%. After the PRELEX operation, to help protect against infection eye-drops are prescribed which must be used as directed.
- Bleeding – there is a small risk of a serious peri-operative bleed either in the orbit, or within the eye
- Macular Oedema – is an accumulation of fluid at the central retina which can cause temporary or permanent reduction in vision after surgery. The postoperative eye-drops also help to reduce this risk.
- Floaters – are often noticeable immediately after surgery but usually become less noticeable with time.
- Posterior Capsule Opacification (PCO) – is thickening of the residual lens membrane which supports the lens implant. Approximately 25% of patients will, at some stage, notice a reduction in their vision due to PCO.. This incidence increases for patients having the pseudo-accommodative lens implant. It may occur months or even years after surgery and is easily and quickly dealt with by outpatient laser treatment.
- Other possible complications include tearing of the lens capsule (<1%) which could mean that it is more difficult to implant an intraocular lens. There are other extremely rare complications which your surgeon will discuss with you prior to surgery.
- Glare/Haloes/Dazzle – especially with some types of multifocal lenses, which may cause these symptoms, especially in dim-lighting conditions such as night-time driving, in about 20% of individuals.
Am I a candidate for PRELEX?
There are many factors that contribute to the 'ideal' PRELEX candidate. Your particular circumstances, lifestyle, glasses prescription and pupil size can all affect the possible outcome. All these factors are best discussed with the Consultant Surgeon. It is also essential to have realistic aims/expectations for your vision following even uneventful surgery. Having a multi-focal IOL or accommodating lens is the same as having a new visual system fitted. It will take some time for your brain to adjust and adapt to the new images it is seeing.
How long does PRELEX last?
The lens implants we use are left in place for life. A cataract cannot grow after PRELEX, but some patients develop thickening of the residual lens tissue left in place to support the lens. Should this occur it is easily dealt with by an outpatient laser procedure known as a YAG laser capsulotomy.
How do I select a surgeon for my PRELEX?
Experienced consultant ophthalmic surgeons will have performed thousands of cataract procedures and so are highly skilled in the removal of the natural lens using the latest micro-incision phacoemulsification technology.
They have been using foldable IOLs and multi-focal lenses for many years. When using a multi-focal or accommodative lens, particularly in the PRELEX patient, accurate biometry is absolutely crucial to select the right power for your eyes and your consultant surgeon will be particularly careful about this aspect of the planning.
The consultant you choose should use the latest technology to measure all aspects of the eye enabling them to achieve the best visual outcome, thereby eliminating or reducing your dependence on glasses.