Refractive lens exchange/Clear lens extraction

Refractive lens exchange, like implantable contact lenses are capable of treating very high degrees of hypermetropia and myopia and are often considered when your prescription falls beyond the range of either Lasik or Lasek. If your prescription is higher than -10.00 (short sighted) or +5.00 (long sighted) then refractive lens exchange may be suggested to you by your surgeon.

Unlike implantable contact lenses, refractive lens exchange is generally considered for people over the age of 45 who already have problems with their near vision. Such people will be most likely wearing varifocals, bifocals, separate distance and reading glasses or be wearing multifocal contact lenses.

About Refractive lens exchange:

Put simply, the refractive lens exchange procedure involves removing your eyes natural lens and replacing it with an artificial lens (lens implant) whose power is calculated to eliminate the prescription in your glasses or contact lenses, hence resulting in your vision improving. Your natural lens in your eye sits inside a lens capsule (like a bag) and when it is removed this capsule is left intact. The new artificial lens is then placed back into this capsule in the exact same position as your natural lens was located.

Who is Refractive Lens exchange/Clear lens extraction suitable for:

Refractive lens exchange is generally recommended for those aged 45 years and over and this is because such people will have already started to develop presbyopia. Presbyopia describes the natural ageing process of the lens in your eye, which results in reduced ability to focus things close to you e.g. reading. Consequently, when the natural lens in your eye is removed during refractive lens exchange, so you will no longer have the ability to focus things close to you. If you already need spectacles for near vision as a result of your age, then this is much less likely to have an impact on you.

Refractive lens exchange can be carried out on people below the age of 45, but it is important to understand that your near vision following surgery is likely to be worse than it was before. This may mean that you need to put reading spectacles on for near tasks after refractive lens exchange. However, this may be a small price to pay for those with very high prescriptions if it means they no longer have to wear their incredibly thick glasses for walking around in! Over the past few years however, refractive lens exchange has advanced considerably, meaning that not only your distance vision but also your near vision can sometimes be treated. The ways in which refractive lens exchange can treat both distance and near vision is as follows:

How Refractive Lens exchange can treat both distance and near vision:

• Monovision: Monovision refers to refractive lens exchange whereby one of your eyes (dominant eye) is corrected for distance vision and the other eye (non dominant eye) is corrected for near vision. This means that one of the new artificial lenses (lens implant) that is placed in your eye focuses for distance vision and the other focuses for near vision.

• Accommodating lens: During standard clear lens extraction the natural lens in your eye will be replaced with a single vision distance lens to eliminate your prescription. If this is done to both eyes, the aim is to leave you with perfect distance vision, with reading glasses used as required for close visual tasks. If an accommodating lenses (e.g. tetra flex) is used instead, then you should still retain some near vision. The lens implant is placed in the lens capsule where your natural lens was removed from and it works in tandem with the existing muscles in your eyes. As the focussing muscles in your eye contract to look at something up close so the accommodating lens moves forward (as it would with your natural lens) which results in clear near vision. The lens moves backwards and forwards as you change from distance to near vision and vice versa. It is important to realise that refractive lens exchange using an accommodating lens will not result in perfect near vision but may well be fine for reading for short periods of time and for tasks such as checking your phone, reading a menu etc. Prolonged reading and especially when the print is small will most likely still require reading spectacles.

• Multifocal refractive lens exchange: This is an alternative to an accommodating lens and is similar in design to a multifocal contact lens or varifocal in that there are different power zones on the lens for different visual requirements. E.g. there are zones on the lens for distance, intermediate and near vision. Such a lens relies on your brain to select the appropriate zone for a particular distance and therefore it is important that people considering such a lens have had a successful trial of multifocal contact lenses. Generally speaking multifocal refractive lens exchange results in better near vision than the accommodating lenses but distance vision is often not as good. In addition to this, multifocal lenses are generally associated with more visual aberrations such as glare and haloes. It is because of this, that surgeons often combine a multifocal lens (non dominant eye) with an accommodating lens (dominant eye) to get the best out of both lenses.

Final Points on Refractive lens exchange:

As surgeons become increasingly confident with refractive lens exchange and the lenses available become more and more sophisticated so they try new ways of combining lenses. Some surgeons are starting to combine different types of multifocal contact lenses so as to get the best overall results. For example one multifocal lens may have a bias towards distance vision and the other towards near vision and so combining them may produce an optimal visual performance. Exactly which refractive lens exchange combination is best for you should be left to the expertise of the surgeon. Your surgeon will weigh up your prescription, lifestyle and visual requirements and come up with the best solution for you.

As yet refractive lens exchange is still considered a little bit of a compromise as you are unlikely to get perfect distance, intermediate and near vision. However if you go into the surgery with realistic expectations and your surgeon has fully explained everything to you, then it is likely to be a life changing surgery.

If there is still anything you are uncertain of why not ask a question in our laser eye surgery forum.