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Cataract Surgery and Refractive Lens Exchange (RLE)

What's the difference?

Cataract surgery and refractive lens exchange (RLE) are two of the most commonly performed procedures by Mr Turnbull.

Whereas cataract surgery and RLE are the same in terms of the actual surgery, the reasons for having surgery, the preoperative evaluation and the objectives are quite different.


With cataract surgery, the aim is to remove your natural lens that has become cloudy or opaque, and replace this with an artificial lens to improve the clarity of vision. Cataract surgery is available on the NHS, although most hospitals set criteria that must be met before cataract surgery will be provided. While we aim to select an appropriate artificial lens based on the measurements of your eye, the aim is not to reduce your dependence on glasses. Many people having cataract surgery will still require glasses afterwards to achieve the best level of vision. Reading glasses will also be required unless a monovision strategy is chosen, or multifocal lenses are implanted (see Refractive Cataract Surgery below).

What is a cataract? Find out more here.


The aim of refractive lens exchange (RLE) is to reduce spectacle dependence by replacing your clear, natural lens with an artificial lens that is designed to reduce your spectacle prescription, correct astigmatism and / or provide an extended range of focus by treating presbyopia. By definition, RLE can only be performed when no cataract is present, and having RLE also means that you will not develop cataracts in the future. Whereas with cataracts, the only option for improving vision is cataract surgery, if you do not yet have cataracts then there may be options other than RLE that are better suited to your needs. Read more about treatment options for short and long-sightedness, astigmatism and presbyopia.


Refractive cataract surgery is a combination of the two: cataract surgery as above, but with a particular emphasis on reducing spectacle dependence postoperatively by addressing astigmatism and the need for reading glasses (presbyopia). This is achieved either via monovision or multifocal lens implants. As with RLE, additional measurements and more complex calculations are performed to identify the artificial lens that will be best suited to the precise shape of your eye, and offer you an enhanced level of spectacle freedom after surgery. Generally, refractive cataract surgery is not available on the NHS, although toric lenses may be funded occasionally and some surgeons including myself offer monovision in selected cases who are deemed to be good candidates for this approach.

What are the risks?

The vast majority of patients have no problems during or after cataract or lens replacement surgery and are delighted with the outcome. However, the surgery involves operating inside the eye, a small and delicate structure, and therefore there are some risks you must be aware of.

The risk of a serious, sight-threatening complication that could cause complete loss of vision is often quoted as 1 in 1,000 

In the very rare cases that this happens, the cause is usually an infection inside the eye or severe bleeding.

There is a 1 in 100 risk of less serious but still problematic issues arising that may require further surgery, further treatment, or cause a delayed or incomplete visual recovery 

This includes conditions such as persistent inflammation or raised pressure in the eye, swelling of the retina or cornea, retinal detachment, instability of the lens inside the eye, or exacerbation of pre-existing eye conditions.

There is a 1 in 14,000 risk of a highly unusual condition called sympathetic ophthalmia

This is where surgery on one eye causes an inflammatory problem in the other eye, with the potential for loss of vision. This is particularly relevant if one of your eyes is much stronger than the other, and you are having surgery on your weaker eye. 

Posterior capsule opacification (PCO) is a common occurrence after cataract surgery and RLE, whereby the natural capsule supporting your artificial lens becomes cloudy. This can be treated with a simple outpatient procedure called a YAG laser capsulotomy.

Residual refractive error

The measurements and calculations employed in modern lens surgery are very accurate, and this is a topic I lecture on regularly. However, even with the best technology and methods, there is still a 1 in 10 chance that the precise refractive target is not achieved. Residual refractive error can be managed with an updated prescription for glasses or contact lenses, but some patients may wish to pursue further surgery to enhance their vision - for example with laser vision correction or an adjustment to the lens inside the eye.


There can be no guarantee that you will be 100% free from glasses after any kind of refractive surgery

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