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Experience Canterbury Eye Specialists Conductive Keratoplasty (CK) is an exciting new procedure designed to treat farsightedness and presbyopia without using 

a laser.
Our highly skilled professionals

 
Here is some information you need
to know about intraocular lenses


The human lens

The human eye has a natural lens to focus light. When the lens becomes cloudy this is called a cataract. To clear your vision, the cloudy lens is removed and replaced with an artificial lens - an intraocular lens (IOL) or implant.

Removal of the natural lens in your eye may also be appropriate to correct long or short sightedness (refractive lens removal) even if a cataract is not present.

In both cases, to avoid the need for thick glasses after surgery, it is necessary to replace your natural lens with an artificial “intraocular lens” or implant.

How do we work out the power of the lens?

As all eyes are different, we need to work out the power of the lens for each of your eyes. We need to take several measurements including keratometry, a measurement of the curvature of your cornea (the clear window at the front of your eye which also acts as a lens) and the distance between the front of your eye and the retina, called the axial length. These measurements are taken with highly sophisticated equipment and in most cases, are very accurate.

The information obtained from these measurements is fed into computer calculations, which predict the power of the lens most likely to achieve focused vision. 

How accurate are these predictions?

In most cases, the predictions are accurate but occasionally, an individual’s eye may not fit the normal pattern, and an unexpected result may follow.  It is therefore not possible to guarantee that the lens we implant in your eye will give perfect focused vision without the need for a spectacle correction, even though this is usually the case. An unexpected result is most common in patients who are either very long-sighted or very short-sighted or who have had laser vision correction in the past.

Do these lenses change focus at different distances?

No - the lens we place in your eye has a fixed focal distance. In other words, unless you have a multifocal lens implant or you have astigmatism (see below), the lens will provide a clear focused image at only one distance.

If we select the lens for distance vision, then intermediate and near vision will be out of focus. 

If we select a lens for intermediate vision (which would be useful say for computer work, mobile phones and menus), distance vision will be compromised and near vision such as reading fine print will also be difficult.

 

So will I need glasses or not?

The best quality of vision is achieved if both eyes are focused for distance and glasses are used for intermediate and near.  Quality of vision refers to the type of vision you would require to get to the lowest line of the vision chart in low light situations, and which you may require for certain activities or occupations eg a jet fighter pilot or a jeweller. 

However, for many people this clarity of vision is not required for day-to-day activities and patients who are willing to tolerate a degree of compromise, can usually achieve good functional vision without glasses.  This means they are likely to be able to perform most daytime activities (such as driving, playing sport, using a computer or mobile phone) most of the time without glasses, but glasses might be required for fine print or driving at night.

I really want to be free of glasses. How do we achieve this?

You can achieve good functional vision, and have a good chance of spectacle independence for most activities most of the time, with either monovision or multifocal lens implants.

Monovision means having one eye focused for distance and the other eye focused for intermediate or near. It sounds strange but most patients tolerate this extremely well. Many people who do not have cataracts but have difficulty reading, use contact lenses for monovision and we can do the same with an intraocular lens. If you do not have significant cataract, it may be possible for your optometrist to perform a simulation to determine whether or not monovision after cataract surgery would suit you. 

Multifocal lens implants use a completely different principle, with two or more distances in focus. Your brain will concentrate on the in-focus clear object of interest.  With multifocal lenses, there is a higher chance of being completely spectacle independent but most patients will be aware of halos around images particularly at night for some time after surgery.

I have astigmatism - will this mean I still need glasses?

Astigmatism is when the curvature of your cornea is not spherical - the cornea is shaped more like a dessert spoon than a soup spoon and light is not focused uniformly. 

There are now special implants which can reduce or eliminate astigmatism and thereby reduce your dependence on glasse and these can be used to create monovision as described above or they are also now available as multifocal implants.

Finally,…..
All of these issues require careful consideration and discussion with your optometrist and me.  For us to have the greatest chance of meeting your expectations, we need to be aware of your visual requirements and you need to be aware of the advantages and disadvantages and limitations of the various combinations of intraocular lenses available and suitable for you.

 
         
Conductive Keratoplasty Surgery - A new and exciting procedure Canterbury Eye Specialists

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