What is a cataract?


This is an image of a cataract – this causes blurred vision
particularly in the distance and when driving at night.

A cataract is a misting or opacity of the lens of the eye. It prevents light entering the eye properly, causing a loss of focus, glare and dim vision. Cataracts are caused mainly by the body’s ageing process, by injury, diabetes or some drugs.

How can a cataract be treated?

The treatment for a cataract is to have an operation. A small pen-like probe is used to break up the old lens and to remove soft lens tissue. A new clear lens is then inserted into the pocket left by the old lens. This new lens cannot be felt and remains in the eye for a lifetime.

What lenses are available?

There are several different types of lenses; some can give good distance vision, others can treat astigmatism and still others give near and distance vision. Pre-operative measurements and personal visual needs can be assessed to find the right lens for each individual.

Cataract Surgery


Removal of a lens with a phaco probe.


Insertion of a new lens into the eye


At the end of the operation the lens is centred and
antibiotics is injected into the eye to prevent infection.

What about the anaesthetic?

Cataract surgery is now routinely done under topical anaesthetic (drops). A patient is awake, with the eye and the eyelids numbed, with a drop. Some people may feel a pressure sensation in the eye and a slight sting as anaesthetic is used in the eye.

What are the benefits?

Around 99% of my patients have a significant improvement in vision following cataract surgery. This helps with driving, reading, working, hobbies, safety and self-confidence. However, sometimes other eye conditions mean that the results are not be as good as this. Often there is no need for distance glasses following surgery.

What are the risks?

As with all surgery, cataract surgery carries risks. The most severe risk is of infection following the surgery. This occurs in about 1 in 1000 cases and can lead to a drop in vision permanently. If an infection develops, the eye becomes blurred, painful, and bloodshot. This usually occurs within 4 days of surgery. It must be treated as an emergency and the patient needs antibiotics to avoid blindness.

In about 1 in 100 operations, the capsule of the lens may be broken leading to an increased risk of retinal detachment. This can be sorted out with another operation.

Other complications include a rise in eye pressure, corneal or retinal swelling.

The lens capsule can cloud, causing a misting of the vision. Laser treatment is used to restore vision, done as an outpatient procedure. However there is a permanent reduction of vision in about 1% of cases

How quickly does my vision recover after cataract surgery?

In general the eye is blurred for 24-48 hours following surgery and then improves gradually over 2 weeks. One may find sunlight uncomfortable, but wearing dark glasses can help.

Multifocal lenses in cataract surgery

Multifocal intraocular lenses, know as ‘multifocals’ are transforming patients’ vision following cataract surgery. Multifocals allow people to see near objects as well as distance objects without glasses. The following paragraphs explain how the eye focuses light on the retina and how multifocals could work for you.

How does the eye make a focused image?

The cornea and lens focus light onto the retina (the light sensitive part of the eye). The retina contains light sensitive cells (photoreceptors) which convert the light to electrical impulses that travel to the brain. Key to this process is the formation of a focused image on the retina. A normal eye is called emmatropic, and forms clearly focused images from  parallel light (distance objects)  onto the retina.

What about near objects?

Near objects create light which is diverging (rather than parallel light). The normal eye has to bend the light through a larger angle to focus light on the retina. In people under 45 years-old the normal lens changes shape slightly to refocus light from near objects. This is called accommodation. Over time the lens becomes stiff and accommodation reduces. It becomes difficult to see near objects without reading glasses. This is know as presbyopia and typically happens for those over 45 years.

What is Short-sightedness?

Short-sightedness (myopia) occurs when the eye is longer than normal. This means that light is focused before it reaches the retina.  The light cannot be focused on the retina without glasses or contact lenses. During lens replacement surgery we can replace the lens in the eye enabling light to be focused on the retina.

However light from objects near the eye can be focused on the retina without accommodation, short-sighted people take their glasses off to see small near objects.

What is long-sightedness?

Long-sighted eyes are too short to naturally focus the light on the retina. However until the age of 45-years the eye can adjust the lens (accommodate) and bring distance objects into focus. The focusing of near objects requires effort, and may cause headaches when reading / studying.

What is astigmatism?

Astigmatism is a common condition of the eye – it occurs typically when the cornea is curved more in one direction than another. This means that light is focused as a line and not as a single spot. The image becomes distorted and blurred.

What are the symptoms of refractive error ?

The main symptom is blurred vision for distant objects, near objects, or both. Headaches  and eye strain can also occur due to squinting and forcing the eye to focus. The ocular surface can become irritated and sore.

What is a cataract?

Cataract is thickening or clouding of the lens. This is caused by a natural ageing process. Some conditions such as diabetes can age the lens prematurely as can previous eye surgery or inflammation. Occasionally drugs such as steroids can also be cause cataract formation.

What are the symptoms of a cataract ?

Cataract can cause a blurring or dimming in vision they can also change the power of the eye and requirement for glasses (myopic shift). Glare at night or in bright sunlight can also cause problems and some patients also note a loss of colour vision and drop in sensitivity of vision at night.

Does the cataract need to be ripe?

In previous generations cataracts required to be ripe, as equipment and techniques have improved we can operate on cataracts when the patient wants.

Are there risks to cataract surgery?

All surgery carries some risk. Cataract surgery can be complicated by rupture of the posterior capsule and vitreous loss (<1%), infection (<1:1000), retinal detachment (1:1,000), and haemorrhage (1:1,000). Sometimes a refractive error may occur, particularly in very long or very short sighted eyes (2:100), but a lens exchange is a relatively simple operation and often gives good results. Retinal swelling (1:100) and iris inflammation (2:100) can occur, but can be treated with eye drops. Many of these complications delay recovery, but are treatable particularly if they are reported to the ophthalmologists in a timely manner.

How can cataract surgery improve my refraction?

Cataract surgery removes the old lens and replaces it with a new lens, tailored specifically for your eye. Before cataract surgery the curvature of the corneal and the length of the eye are measured and a replacement lens calculated from the results.

Your surgeon will discuss your visual requirements and match them to the refraction of your eye. They will discuss whether you require presbyopia correction and assess the degree of astigmatism.

Will I need laser surgery after my cataract operation?

The new intraocular lenses can correct most optical problems however in some particularly complex refractions a post operative corneal laser (LASIK) treatment may also be required for the best possible optical outcomes. Sometimes the scar tissue can grow behind the lens and become cloudy, this is easily treated with a YAG laser at the Spire hospital.

What other information is there?

There are many different types of lens available and each has slightly different properties. Choosing the right lens for your eye will take time and discussion with your ophthalmologist. To help you choose we have put together an information sheet about the three of the most successful lenses, the Zeiss Trifocal lens, the Oculolentis Comfort, and the Symphony lens by Abbott Medical. We hope that this will be of use to you as you make the important decision about which lens you choose for your cataract surgery.


The TECNIS Symfony Lens is an excellent lens for those wanting near and distance vision without the need for glasses. The Symfony lens does this by having small ridges on the lens which separate some of the light into an elongated focus area. This helps the vision by reducing the need for reading glasses.



The Symfony lens is particularly useful for patients who drive. In simulated driving tests the great vision this lens improves safety of the driver by giving a 13.5m identification advantage or 0.5 second reaction time speed. Enough to bring a car safely to a halt.


Zeiss Trifocal Lens – AT LISA tri 839MP

Zeiss have a great reputation for lens manufacture in glasses, cameras and microscopes. They have used their expertise to produce is innovative intraocular lens. The 939MP gives excellent near and distance vision but also allows for intermediate (computer) vision. 

Ziess Lens Vision Data

The Zeiss Tri-Focal lens AT LISA tri 839MP works by having a series of lenses etched the surface of the lens. These focus the light at different parts of the eye generating a defocus curve for the light and giving people to see distance and near vision.


Patients are generally satisfied or very satisfied with the visual results for this lens

Research shows that this lens gives stable visual results over a one year period. Usually if the refraction is stable for one year it will continue to be stable long term.

This lens comes with Toric (astigmatic correction). So patients with low level astigmatism can also enjoy the power of this multifocal lens post surgery.


Oculentis comfort M-Plus

The Oculentis comfort lens comes from a well recognised family of lenses that are widely used throughout the UK. The Comfort lens (also known as the MF-15 lens), has a distance lens and an intermediate lens similar to wearing a +1.5 reading glasses (not full correction for near). Better intermediate vision and some near vision can be gained with a M-Plus MF-20 lens (similar to wearing a +2.0 reading glass) and full near vision can be gained with an M-Plus MF-30 lens (similar to wearing +3.00 reading glasses). 

Oculentis MF lens

This family of lenses uses two refractive elements within the lens to give near and distance vision. The near lens sometimes develops glare and haloes under bright objects.


Oculolentis MF lens

The Comfort lens is very well tolerated with little glare. With the higher power lenses MF-20 and MF-30 glare increases and there are some reports of glare and intolerance. However they are often used in combination with the MF-15 lens to successfully give distance and near vision.

High Patient Satisfaction

In a representative survey, by 92% of 192 surveyed patients, who were treated with a LENTIS Comfort IOL confirmed that they would opt for this lens again at any time due to the good visual results.

The MF range is available with Toric corrections (anti-astigmatism). These lenses are made to the exact patient specification and therefore can give exceptional vision to patients.


Which lens is right for me?

Lens choice is key for excellent vision depends on the individual needs. It is about lifestyle choices, balance with the optics of the eye. Each of the above lenses gives the patient slightly different post operative vision with slightly different potential downsides.

With some lenses there is an slight increase in glare – in bright sunlight or when driving. With others the eye can be confused with the different focal points and neuro-adaption is required to get the best out of a lens.

Due to subtle differences in corneal curvature pre surgery some patients are able to read very well even with the Symphony and Comfort lens. Some patients have strongly dominant vision in one eye, typically we use this eye for distance vision and the non-dominant eye we use for near vision.

A combination of lenses is often the most successful and preoperative assessment and discussion with your ophthalmologist is vital in ensuring the optimum result.  When tailored to your refraction and requirements the post operative visual results can be stunning and literally life changing.