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Cataract
What is a cataract?
Inside the eye, behind the coloured part (the iris) and the black hole in the centre (the pupil) is your natural lens. A cataract is clouding (opacity) of the natural lens. In a normal eye, the lens is clear and helps focus light rays on to the back of the eye (the retina). The retina sends messages to the brain which allows you to see. When a cataract develops the lens becomes cloudy. This prevents light rays from passing through causing blurry vision.
What are the symptoms?
Cataracts usually form slowly over many years with the most notable symptom being blurry vision. To begin with your glasses may be adjusted to minimise the blur, but eventually the blurring will not be correctable by glasses. In some people vision can deteriorate quickly. Other symptoms of cataract include increased sensitivity to glare, difficulty with night-time driving, double vision or multiple images in one eye, and difficulty reading fine print, especially in low light. The symptoms of cataract worsen as the cataract progresses. Cataracts do not spread from one eye to the other, however it can develop in both eyes.
Types of cataract
There are several different types of cataracts. Most cataracts are age-related, but others may be present at birth (congenital), medication-induced or may develop following and eye injury. Age-related cataracts can occur at any time after the age of 40 but are generally more common in later life. Cataracts develop as part of the normal aging process causing the lens to gradually become cloudy. Cataracts do not always cause immediate visual symptoms with many people only becoming aware of their cataract following a trip to the optometrist. As the cataract develops over time your vision will start to become blurry. In most cases, eyes with a cataract look normal, but may have a white or cloudy appearance if the cataract is advanced.
Treating cataract
In most cases cataract is harmless and may be left in the eye until it becomes bothersome. When the cataract progresses to the point that it is interfering with your daily activities then cataract surgery is required. Surgery is currently the only treatment option for cataract. There is no known method of preventing cataract.
Do I need any special tests before the operation?
Yes. Special tests are required to determine the strength of the new lens required for implantation into your eye. These tests are undertaken prior to the operation day. If you have previously undergone corrective laser surgery, it is important that you tell the ophthalmologist and technician during your assessment.
What does cataract surgery involve?
Cataract surgery involves removing your natural lens and replacing
it with a customised, artificial lens implant known as an intraocular lens. Your eye surgeon will carry out your operation. Cataract surgery is a day procedure. The surgeon will make a small cut in your eye through which the natural lens will be removed and the new lens inserted. The wound is very small and most patients do not require stitches, although very fine stitches are sometimes necessary. Normally you will be lightly sedated for your operation. You will not feel any pain and usually won’t remember the procedure. Your ophthalmologist and anaesthetist will determine the safest anaesthetic option for you.
After your operation
Recovery time following cataract surgery is usually about one week but may be longer for some. Following surgery, you will be required to use eye drops for several weeks. The drops are used to reduce the risk of infection and reduce inflammation and irritation. A little swelling and redness after surgery is normal. After your operation you will be provided with instructions to follow and a follow-up appointment date.
Intraocular lenses (IOLs)
There are several different types of IOLs available which will achieve different visual outcomes. There are benefits and drawbacks to each type of IOL and these should be discussed with your surgeon. Your choice of IOL will depend on your visual preferences, lifestyle and the shape of your eye.
All IOLs are associated with glare and halos to varying degrees. This is most problematic for night-time driving. Often this will become less noticeable over time as your brain adapts. Keep in mind that despite a thorough investigation of your eye using sophisticated measuring equipment, it is likely that you will still require near, far or both distance spectacle correction following your surgery.
Types of IOLs
Monofocal
This lens type focuses light to a single point on the retina. Light cannot be focused from near and far objects simultaneously with a monofocal lens. This means that a monofocal lens will correct your vision at one distance only, that is either near or far. Most people choosing this lens type will opt to have good distance vision allowing them to perform activities such as driving and playing golf. In this instance you will need glasses after your surgery for near tasks such as reading and sewing.
With this lens type you may choose to have monovision. This is when the dominant eye is “set” for seeing far objects clearly while the other eye is made slightly shortsighted to enable you to see near objects clearly. However, monovision can be confusing to the brain and may reduce your depth perception (‘3D vision’). Monovision is not suitable for all people and you should discuss this with your ophthalmologist. Of all the IOL types, monofocal IOLs are generally the least problematic for glare and halos.
Multifocal
Multifocal IOLs offer greater spectacle independence than monofocal lenses as they can focus light at multiple points on the retina. This means that you may be able to see clearly at near, intermediate and far distances. However, because the lens is comprised of distinct optical zones people with multifocal lenses can only focus at one distance at a time. There is also a greater incidence of halos and glare as well as reduced contrast sensitivity with this lens type. This may be quite bothersome for some patients and is an important consideration when choosing your IOL. If you frequently drive at night a multifocal lens may not be the lens of choice for you.
Extended Depth of Focus
Extended depth of focus (EDOF) IOLs are designed to create a single elongated focal point to enhance your range of vision. The special design of EDOF IOLs means that halos and glare are less of a problem with these lenses compared to multifocal IOLs. EDOF IOLs are most effective at far and intermediate distances with most people requiring some near vision correction after surgery.
Toric
Toric IOLs are used to correct astigmatism. Astigmatism is a physiological condition in which the front surface of the eye (the cornea) is irregularly shaped. In individuals with corneal astigmatism, their cornea is more football-shaped rather than being round. This means that light entering the eye cannot be focussed to a single point on the retina. If you have astigmatism your vision will usually be blurry without correction. The amount of blur depends on the degree of the asymmetry of your cornea. Toric IOLs are designed to ‘balance out’ the asymmetry of your cornea, allowing you to see clearly without glasses at far distances following cataract surgery. The aim of using toric IOLs is to achieve a post-operative refraction of within +1.00D of distance emmetropia, that is an eye that is ‘perfectly’ focussed. Toric IOLs are available in monofocal, multifocal and EDOF.
