What is a cataract?
The best way to understand a cataract is to have brief understanding of the structure of the eye. The diagram shows the structure of the eye. The front of the eye is covered by clear structures i.e. the cornea and the crystalline lens, which together bring the image to a sharp focus on the retina, which lines the inside of the back of the eye.
The best way is to think of the eye is as a cinema, where the cornea and the lens are the projectors and the flat retina on which the image is focused is the cinema screen.
Whilst the cornea has a fixed curvature and shape, the lens is able to change its shape to bring objects of different distances to a sharp focus on the retina.
A cataract is a condition when the lens of the eye loses its clarity thus either prohibiting light from passing through or misdirecting light rays thereby interfering with the projection of a bright and sharp image on the retina.
What is the treatment for cataracts?
The only definitive treatment for cataract is exchanging the lens of the eye with an artificial lens implant. This is what is referred to as cataract surgery or extraction. Occasionally when symptoms are very mild you may find that spectacles may temporarily resolve the symptoms.
Do I need to have cataract surgery, if I have cataract?
No. The final visual outcome is not dependent on the time of intervention. The most important factor determining the need for surgery is whether or not you are troubled by your visual symptoms. If you are satisfied with your level of vision, then you do not need to have cataract surgery, just because you have a cataract and you can defer the option of surgery.
There are however exceptions where cataract surgery would be recommended even though you may not wish to have surgery or not troubled by your vision. These are:
a) If your vision does not meet the legal minimum requirements for driving and you wish to continue to drive.
b) If the cataract prohibits adequate view to enable monitoring or treating the back of the eye (retina), for example in diabetic patients who can develop changes in the back of the eye (diabetic retinopathy).
Cataract surgery
Cataract surgery involves removal of the crystalline lens (cataract) and replacing it with a clear artificial lens implant.
It is normally carried out under a local anaesthetic as a daycase procedure with the patient being awake during the surgery.
After the pupil is dilated and the eye is anaesthetised, a small (2-3 mm) self-sealing incision (opening) is made on the periphery of the cornea (limbus). The thin capsular bag enclosing the lens is opened and the lens material removed. An artificial lens implant is implanted into the empty capsular bag. Normally there is no need to use stitches. The artificial lens can stay in place indefinitely.
What is the risk of cataract surgery?
Whilst cataract surgery has a very high success and satisfaction rate, like any procedure it carries risks. The most serious risks generally relate to complications occurring during (intra-operative) or after (post-operative) complications, which may result in less than desirable visual outcomes and on rare occasions loss or deterioration of vision.
Whilst it is imperative that you are aware of these risks and take them in to consideration as part of making an informed decision, it is important to highlight that the overall risks of cataract surgery are low. Please also see next section.
Will I still need to wear glasses after cataract surgery?
The most common indication for cataract surgery remains, the inability to achieve satisfactory vision even with updated spectacle prescription. Cataract surgery however provides a unique opportunity to try and influence your prescription (refractive outcome). Prior to surgery the surgeon measures the lens implant power required to achieve the desirable target, which is agreed with the patient.
Traditionally the objective is to achieve a visual outcome, which renders the individual independent of glasses for distance, but dependent of glasses for near (reading). This is however a personal matter, which you can discuss with your surgeon. More recently implants (multifocal, accommodative) have been introduced which can offer the benefit of both distance and near vision, although not all candidates may be suitable for these implants.
It is important to realise that despite all the calculations and efforts there are a proportion of patients who may not achieve the predicted refractive outcome and may still need to wear spectacles i.e. refractive surprise.
