What is a Cataract?
A cataract is a clouding of the natural focusing lens in your eye. It is usually a part of the normal ageing process and most people over the age of 70 have some signs of lens change. However it can occur at any age from birth onwards. The passage of light through a cataract is impaired so the retina receives blurred and distorted images and can only pass these signals to the brain. Other symptoms include excessive dazzle from car headlights or bright sunshine and the need to change glasses frequently due to changes in prescription. If cataracts progress to an advanced stage, they can impair vision completely. The decision as to whether or not to have cataract surgery depends on how much your daily life is affected, not on the maturity of the cataract. Fortunately, almost all cataracts can be successfully removed and vision restored through modern microsurgery techniques.
Cataract Microsurgery
Modern cataract surgery is carried out through a very small incision. Mr Packard introduced microincisional cataract surgery to the UK in 2001. Incisions are now about 2.2 mm. These small incisions seal themselves immediately after surgery and heal over the following few weeks. No stitches are used, and normal daily activities can be resumed very soon after surgery. These very small incisions are less likely to change the shape of the cornea. This reduces the chance of inducing astigmatism which can occur from larger incisions.
After the incision has been made a circular opening is made in the elastic bag around the lens called the capsule. Then a special hollow curved tube surrounded by a thin plastic sleeve called the phacoemulsification tip is inserted through this opening to remove the cataractous lens. Phacoemulsification uses vibrations at ultrasonic frequencies of 32000 vibrations per second to break the cataract into tiny pieces which are then sucked out of the eye through the centre of the hollow tip. This technology is currently the most effective method for removing cataracts.
Once the cataract has been removed, a lens implant is placed in the lens capsule to replace the original lens.
Lens implants are very small (6 mm optical zone and 12.5mm overall in size), made of biocompatible plastics and are designed to fit permanently within the lens capsule. They will thus not be rejected by the eye. You will have been measured prior to your surgery to determine the lens power required for your eyes. This may mean that lens implants not only improve the vision but may give greater freedom from glasses than enjoyed before the development of cataracts.
Recent advances in lens technology now allow for the shape of the intraocular lens to be adjusted to the profile of the cornea. This should improve both contrast sensitivity and visual acuity post-operatively. Special lenses also allow correction of astigmatism and multifocal lenses give the possibility of good reading and distance vision without the aid of spectacles post-operatively .
Step 1. A clear corneal incision is made with the Packard designed Windsor knife.
Step 2. The cataract is removed using vibrations at ultrasonic frequencies delivered via a thin phacoemulsification tip designed by Richard Packard.
Step 3. A replacement intraocular lens is inserted through a microincision and then unfolded in the eye.
Step 4. Following completion of surgery the new lens can be seen sitting just behind the iris and in the capsule. No stitches are required to close the wounds.
Anaesthesia for Cataract Surgery
Cataract surgery is normally a painless experience and the vast majority of operations are now done as a day case procedure. Your surgery is most likely to be done with topical anaesthesia although very occasionally other forms are used.
Topical anaesthesia is very popular with many people because no injections are required. Instead, topical anaesthesia simply uses a gel or drop which numbs the eye. You may be aware of touch around the eye and fluid dropped on it during the operation but there is no pain. Although of course, general anaesthesia is still available for patients who prefer to be completely asleep. The surgery generally takes about 15 minutes and even if general anaesthesia is used there is no need for an overnight stay. Local anaesthesia however avoids the risk of post-operative drowsiness, which can occur from a general anaesthetic.
What will happen during your cataract surgery?
Many patients worry that they will see what is happening during the operation. Most patients notice, in the eye being operated on, a bright light and vague shapes but you cannot see the actual instruments. The other eye is covered by a drape. You will be asked to stare at the light as much as possible during the surgery. Although it is preferable for you to lie fairly still you can adjust your position or even cough or sneeze, provided some warning is given. In order to assist in keeping your head from inadvertent movement, the operation bed has a groove which will hold your head in place.
A clear shield is placed over the eye and patients usually normally notice improved vision by the next day when the effects of the operation have worn off.
Risks and Benefits
In recent years there have been enormous advances in cataract surgery that make the operation safer and improve the visual outcome. However, you should be aware that there is a small risk of complications, either during or after the operation.
Complications are usually treatable, possibly requiring further surgery. In very rare cases serious problems such as infection or retinal detachment occur which may result in visual loss.
Overall benefits of cataract surgery include:
Greater Freedom From Corrective Lenses – Because lens implants are selected to compensate for pre-existing focusing problems, most people find that their vision improves considerably after surgery. Ideally, people are able to see clearly without glasses after surgery, although glasses may be necessary for some activities such as reading or driving. Even people who still need to use glasses can usually use thinner lenses than they relied upon in the past.
Toric Lenses (Removal of Astigmatism) – Newly developed Toric lenses allow the power of the lens to be different at different orientations within the eye. This allows correction of abnormal corneal curvature, known as astigmatism, and increases independence from spectacles post-operatively without the need for additional incisions on the cornea.
Multifocal Lenses – no reading glasses: These lenses now offers the possibility of clear focus for distance, intermediate and near vision without the use of glasses following cataract surgery in selected cases. Most people are delighted with this option but it will not produce perfect vision as in a 20 year old with normal vision. All lenses for correction of both far and near vision combined are a compromise. Mr Packard and members of staff will be happy to this discuss with you in more detail.
Toric-Multifocal Lenses – these lenses correct astigmatism and can provide good distance, intermediate and near vision after surgery. These lenses have now removed the need for additional incisions on the cornea for those patients who wish to have a multifocal lens inserted and are a great step forward.