Cataract Surgery and Refractive Lens Exchange 

Definitions, Risks and Artificial Lens Options

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.

What is a cataract? Find out more here.


The aim of 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 presbyopia. 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.

Risks of lens / cataract surgery

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 usually 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, which 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. 

The measurements, calculations and formulae that are employed in modern lens surgery are highly accurate. 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.


Artificial Lens Options

This section provides a broad overview of the different artificial lenses available for implantation during cataract and lens replacement surgery at South Coast Vision.


IMPORTANT: Neither Andrew Turnbull nor South Coast Vision have any financial interest in any products mentioned. Choice of lens is based purely on scientific evidence and careful tracking of outcomes, with no financial or commercial inducement of any type.

Monofocal non-toric lenses

This is the type of lens used in standard cataract surgery, including on the NHS.

J&J ZCB00 IOL.png

The specific model of monofocal non-toric lens that I use most frequently is the TECNIS PCB00, manufactured by Johnson & Johnson Vision. This lens is specially engineered to provide excellent optical clarity, long-term stability inside the eye and very few adverse visual side effects. 

Read more about the TECNIS PCB00 lens here.

I have implanted over a thousand TECNIS lenses since 2011 and am very satisfied with its safety and visual outcomes. The fundamental TECNIS model is the basis of several other newer, more specialised lenses that I use in RLE and refractive cataract surgery (see below).

The drawbacks of monofocal non-toric lenses are that they cannot correct astigmatism and they only offer a single point of focus (with the usual target being distance). Monofocal non-toric lenses can be used to achieve increased spectacle freedom via monovision, whereby one eye is targeted for long distance and the other for intermediate to near vision.

Monofocal toric lenses

Toric lenses have two meridians of focus at 90 degrees to each other, allowing them to compensate for regular astigmatism (rugby-ball shaped eye). They require accurate measurements of the eye before surgery, sophisticated calculations and careful marking and positioning to achieve the best results.

The specific model of monofocal toric lens that I use most frequently is the TECNIS Toric 1-Piece Aspheric IOL (ZCT). This has all the benefits of the monofocal non-toric TECNIS PCB00, but with the additional advantage of reducing astigmatism.

Astigmatism correction is highly complex, and occasionally re-rotation of the toric lens is required. The aim is to minimise astigmatism as far as possible, but it is rare (and unnecessary) to eliminate it completely.

Reducing astigmatism with toric lenses is one of my key interests. Read more here.

Multifocal (toric and non-toric) lenses

Multifocal lenses are designed to provide two or three different points of focus. Bifocal lenses were the first multifocal lens option available, providing distance and near vision. More recently, trifocal lenses have become available to provide:

  • distance vision (driving; most sports; watching television)

  • near vision (reading a book; using a smartphone)

  • intermediate vision (desktop computer; car dashboard)

The specific type of multifocal lens I use most frequently is the TECNIS Synergy trifocal lens, manufactured by J&J Vision. This lens is available in both a toric and non-toric version, meaning it can also correct astigmatism when necessary. As with all lenses in the TECNIS family, it has an excellent track record of safety and outcomes. Unlike many multifocal lenses, the TECNIS Synergy is made of hydrophobic acrylic plastic - the same as all TECNIS lenses. A major advantage of this material is that it is highly unlikely to opacify, a problem that can afflict hydrophilic acrylic lenses.

The TECNIS Synergy trifocal lens provides an excellent level of spectacle freedom, with over 9 in 10 people finding they can abandon glasses altogether. But as with all strategies for spectacle freedom, there is a compromise. The drawback with all multifocal lenses is that patients will be aware of some degree of halos and glare around lights, due to the concentric ring design of the lenses. This phenomenon is most noticeable for the first few days to weeks. It then gradually reduces, but will always be present to some extent, particularly at night. The vast majority of patients find they learn to ignore this and simply enjoy the benefits that multifocality brings. However, a small proportion of patients (less than 1 in 100) find the halos and / or glare difficult to tolerate and may choose to have the lenses removed.

Extended depth of focus ["EDOF"] (toric and non-toric)

Extended depth of focus lenses aim to offer a good level of spectacle freedom, with fewer visual side effects (halos and glare) compared with multifocal lenses. Rather than splitting the vision into two or three separate focal points, EDOF lenses stretch the focal point to provide a greater, continuous range of focus. They tend to provide excellent distance (driving / TV) and intermediate (computer / dashboard / smartphone) vision, but low powered reading glasses may still be needed for small print or in dimly lit environments (for example, reading a menu in a restaurant). 


They are an excellent option for people who desire spectacle freedom for most activities but are happy to wear reading glasses occasionally. Night-time visual disturbances still occur, but tend to be fewer and milder compared with multifocals.

The specific EDOF lens I use most frequently is the TECNIS Symfony lens, manufactured by J&J Vision. This is available in both non-toric and toric models, meaning that it can also be used to correct astigmatism when necessary.

Other lenses

A wide variety of excellent artificial lenses are available. I primarily use the TECNIS family of lenses from J&J Vision as they are supported by good scientific evidence and I have been satisfied with their performance to date. Nonetheless, I am continually evaluating new technology and will offer new options once I am convinced that they offer genuine advantages.


Other lenses I use on an occasional basis (usually for more abnormal or complex eyes) include the Zeiss Asphina, Rayner T-Flex and Rayner Sulcoflex.

I do however have access to all lenses that are CE approved and on the market for use in Europe, so if you are interested in a particular lens, please let me know and we can work together to establish whether it would be the right choice for you.

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© South Coast Vision Ltd. 2020