Cataract is the clouding of the natural lens of the eye which results in unclear vision.
The most common cause is that as you get older, the lenses of your eyes gradually become less transparent, which is a natural consequence of ageing. The first symptoms of cataracts are vision problems at dusk, such as blur, haze and glare, and the need for more light to read. If left untreated, cataracts become increasingly cloudy and dense, which can ultimately reduce vision to a point where a person becomes blind. Fortunately, cataract surgery enables people to regain their vision. Thereby, the cloudy lens is replaced with a new artificial intraocular lens (IOL). Modern cataract surgery and advanced, premium IOLs can correct for many other vision disorders like long or short-sightedness and astigmatism, so in many cases patients have the option to become far less reliant on wearing spectacles after the surgery.
As cataracts are not exactly a disease, but rather part of the normal ageing of the body, it is very common amongst the population above the age of 50. 1 in 5 people aged between 65 and 74 have cataracts, and above this age, the proportion rises to 1 in 2.
The word “cataract” comes from the Greek for “waterfall”, καταρράκτης, as rapidly flowing water in waterfalls appears to be white, just like advanced cataracts appear in the eye.
Ageing is responsible for around 90% of cases of cataract but there are several other risk factors that can cause cataract or contribute to its formation. These include:
Very occasionally, children are born with cataracts, often to mothers who are infected with measles or rubella during pregnancy.
As the lens ages with the years, just like the rest of the body, almost every person will eventually get cataract. However, there are a number of steps you can take to slow the development of cataracts. These mainly include avoiding the risk factors:
The first stages of cataract formation are often not noticeable. However, vision slowly gets worse, and images start to become blurry. People usually first notice this at dusk, as glare, halos and blurring are most noticeable. People often describe their vision as looking through fog, and people tend to report needing more light in order to read.
As your cataract continues to develop, your contrast sensitivity starts to get worse, making it harder to read texts, that are not pitch black on white. If the cataract is advanced enough, it can eventually be seen through the pupil of the eye, as a grey, cloudy substance. At this point, a person is close to blindness.
The clouding of the lens itself cannot be reversed. However, it is very well possible to remove the cloudy lens and replace it with an artificial intraocular lens (IOL). This is a very quick surgery, which immediately eliminates the symptoms you have due to the cataract. Nowadays, there are many different types of intraocular lenses, and choosing the right one for you is crucial. If a cataract has been diagnosed we carefully evaluate the right time for the procedure, as well as the right IOL and type of surgery. Many measurements of your eye are made in order to calculate the “refractive power” that your eye needs.
Please remember, that the cataract might not be the only factor in the eye that reduces the visual acuity. The surgery might therefore provide a person with a better vision, but still not with 100% visual acuity.
Cataract is diagnosed and graded by an eyecare professional. It is also evaluated, how much the visual acuity decreases in the presence of glare. If it is medically necessary to do the surgery (e.g. in very advanced cases, if the cataract poses a risk to the eye), the doctor will recommend it. If it is medically not necessary yet, the choice on when to do the surgery is mainly based on how much a patient is restricted and disturbed by the decreased vision.
Cataract surgery is a day surgery and usually takes about 20 minutes per eye. The operation is performed under local anesthesia with light sedation and assisted ventilation under the supervision of an anesthesiologist. General anesthesia is necessary only in exceptional cases.
The natural, cloudy lens of the eye sits in a capsular bag. Under the microscope, this capsule must be opened so that the lens can be broken into smaller pieces and removed. In order to reach the lens with the instruments, three small incisions are made at the edge of the cornea. The artificial clear lens (intraocular lens, IOL), which will take over the function of the normal human lens, is then also inserted through these.
There are two main ways of performing cataract surgery: manually, and with a femtosecond laser.
In manual surgery, the incisions in the cornea to introduce surgical instruments and the new lens, are performed manually by the surgeon. Then the surgeon uses an instrument to tear an approximate 8-mm-diameter circular hole in the capsular bag that contains the lens; this process is called capsulorhexis. The surgeon then liquifies and breaks down the lens with ultrasound energy in a process called phacoemulsification, and removes the lens fragments through suction. The new lens is placed into the bag through the circular hole, and the optical part of the lens is positioned so it fits in the middle of the hole.
Femtosecond laser surgery involves the use of a laser to make all of the incisions with micrometer precision, as well as making a perfectly circular opening in the capsular bag to place the lens inside. Furthermore, the laser pre-cuts the cloudy lens, so that less ultrasound-energy is required to break down the lens. Ultrasound energy can damage cells at the base of the cornea, so it’s important to keep the amount of energy delivered into the eye to liquify the lens as low as possible.
The precision of the laser ensures that the lens fits as perfectly as possible in the hole, and some premium lenses require an extremely precise fit. Having the laser perform this step is also a safer method of making this opening, essentially reducing the possibility of something going wrong, like the formation of a radial tear which compromises the formation of a required circular hole.
Monofocal lenses are an excellent option and give you a good vision at one distance, if your eyes are otherwise healthy. The distance, where the clear image is, can be chosen and usually lies in the far distance. Spectacles / reading glasses will be necessary for you to see at other (closer) distances.
Multifocal lenses involve splitting the light that comes into the eye into two or more sharp images, e.g. near and far, or near, intermediate distance, and far. Your brain then chooses the image you want to see in focus. The trade-off is that incoming light is split between the images, and this reduces your contrast sensitivity (although it will be better than before surgery).
Extended depth-of-focus (EDOF) IOLs use specialized optics to spread the sharp image focus along a greater range of distances. Again, this can come with the drawback of reduced contrast sensitivity, and depending on the design of the lens, glares and halo.
Toric lenses are designed to also correct for any astigmatism in your eye. These exist in monofocal, multifocal and EDOF forms.