Understanding Cataracts
A cataract is a clouding of the natural lens inside your eye. The lens normally helps focus light clearly so you can see sharp images.
When it becomes cloudy, vision becomes blurred or misty, colours may fade, and bright lights can cause glare or haloes. Cataracts usually develop with age and can affect one or both eyes.
Treatment for Cataracts
The only effective treatment for cataracts is surgery. Cataract surgery is a safe and common procedure, but successful in the vast majority of cases. During the operation, the cloudy lens is gently removed and replaced with a clear artificial lens called an intraocular lens (IOL). This will restore the clarity of vision and reduce the dependence on glasses after surgery. However, the level of spectacle independence after surgery depends on the type of intraocular lens used.
The operation is usually performed under local anaesthetic (eye drops or a small injection around the eye) and takes about 15 to 30 minutes per eye.
You will normally be fully awake during the procedure, but the eye will be completely numb so you should not feel pain. In some cases-such as if you are particularly anxious or if your surgeon feels it would make you more comfortable-a mild or “light” sedation may be offered to help you relax.
Types of Intraocular Lenses
Different intraocular lens can be implanted during cataract surgery:
Monofocal intraocular lens: able to provide clear vision at one distance (usually far), in which case reading or computer glasses are still required.
Multifocal intraocular lens: these are designed to give good vision for distance, intermediate (computer), and near (reading) activities, reducing the dependence for glasses; see the section “What are the possible benefits of taking part?” and “What are the possible risks of taking part?” for additional details.
In this study, we are looking to compare the visual performance of two modern multifocal intraocular lens. Both holds European Conformity mark (CE marked) and they are commercially available in UK. These indicate that they meet European Union and UK safety, health, and environmental protection requirements.
Correction of Astigmatism during cataract surgery
If you have astigmatism (a difference in the curvature of the cornea between the 2 principal meridians), this can blur vision at all distances. During cataract surgery, astigmatism can be corrected with:
1. Corneal incisions – tiny, precise extra-cuts made in the cornea to reduce astigmatism.
OR
2. Toric intraocular lenses (T-IOLs) –lenses designed to correct astigmatism.
Corneal incisions and T-IOLs implantation are safe and common procedures. In this study, smaller degrees of astigmatism will be addressed by corneal incisions whilst higher degrees by T-IOLs. There is a limit to how much astigmatism can be corrected, and if you have astigmatism on the cornea greater than 2.50 dioptres, you may not be eligible for this study. If a T-IOL is to be used to correct astigmatism, approximately 1 in 100 eyes will require a second minor operation to reposition the lens to obtain the best visual result, if possible
It is important you understand that not everyone will be completely free from glasses, even when multifocal intraocular lenses are used. Usually, a small prescription may be needed after surgery to achieve the best possible vision. This should be something you are comfortable with before deciding to take part in the study..
Multifocal lenses can provide great independence from glasses but are known to cause visual side effects such as halos, starburst, or glare (dysphotopsia). These symptoms are more noticeable at night, in artificial light, and when driving. Therefore, these lens implants are not ideal for people who drive a lot at night (e.g., taxi drivers).
Likewise, dysphotopsias will be more bothersome in patient that have a perfectionist like personality trait, as they tend to focus more on imperfections.
Outside of the study and in the private sector, there are multifocal lenses that can cause less dysphotopsia-like symptoms. However, these lenses usually do not address the full range of vision. These implants are not part of this study, nor available on the NHS. The only standard option available on the NHS outside this research is monofocal or fixed focus lenses.
Multifocal intraocular lens in bilateral cataract surgery is the G-PERFECT study. The study is sponsored by Moorfields Eye Hospital NHS Foundation Trust and funded by Alcon Eye Care UK Limited.
