A cataract is the clouding of the originally clear lens of the eye. The lens sits behind the pupil and ensures a clearly focused image. If the lens becomes cloudy, the amount of light entering the eye is reduced. This clouding of the lens is generally a process of natural ageing.
The Greek word cataract means waterfall: in earlier times, it was thought that the whitish-grey colour of the pupil was a congealed fluid.
The most frequent cause (over 90%) of cataracts is simply age-related (cataracta senilis), which occurs without any particular cause.
This disease usually occurs from the age of 60 and progresses with age. The deterioration of vision usually occurs only at a later stage. Further causes can include eye injuries, effects of radiation, medications (e.g. cortisone), chronic eye inflammations or systemic diseases (e.g. diabetes). A very rare cause is a congenital cataract, resulting for example from a pre-natal infection.
The initial symptom is usually a grey veil, which impairs the contrast vision. Patients frequently complain of deteriorating vision (blurred or distorted vision), sensitivity to glare, double vision or altered perception. The first sign is an increased sensitivity to light. The sense of vision at dawn or dusk is usually better than in broad daylight, since strong light is “scattered” by the clouded lens, resulting in glare. This is frequently compounded by short-sightedness. This means that elderly people suffering from presbyopia can sometimes suddenly read again without the need for glasses.
Over the course of time, the veil becomes increasingly thicker, to the extent that the eye can distinguish nothing more than light and dark.
The location and the severity of the clouding are not the same with every patient. If the clouding is not in the centre of the lens, patients themselves may not even notice anything. The impairment frequently takes place very late.
An operation is the only possible way to remove cataracts. The clouded lens is removed, and replaced by an artificial, intra-ocular lens. Cataracts are the most common eye disease which is treated by operation. The cataract operation is one of the most frequent operations carried out in medicine in general (with around 500,000 cataract operations per year in Germany alone). The cataract operation is usually carried out under local anaesthetic (by means of drop or gel application). The operation often takes less than 30 minutes and is a painless routine procedure with a very low complication rate or stress to the patient. The success rate is over 95%.
The operation begins with the usually local anaesthetic. This is carried out either by means of a drop anaesthetic or injection of an anaesthetic near the eye, making the eyeball and the surrounding area insensitive and pain-free. The cataract operation is a microsurgical procedure, and is carried out under an operation microscope.
The cornea is first opened up with an incision of about 2 to 6 mm (making subsequent suturing unnecessary). The core of the lens is then generally removed by phacoemulsification, i.e. the clouded lens is destroyed by ultrasound and removed by suction. An intra-ocular lens is then inserted into the capsular bag (sheath of the lens) in place of the removed lens. The refractive power of the intra-ocular lens is carefully calculated before the operation, so that the patient has better close-range or long-range vision after the operation. After the operation, patients usually regain their full vision. The cataract operation results in no complications in over 95% of cases.
Intraocular lenses (artificial lenses) are made of a type of plastic. The optics (optically effective part) have a diameter of about 6 mm.
At the edge are the haptics (elastic tabs), which ensure the optimum seating of the artificial lens in the capsular bag.
Various different basic materials are used for the manufacture of intraocular lenses. There are also different types of intraocular lenses, which can either be implanted complete (e.g. PMMA IOLs) or folded (acrylic IOLs).
Today, almost all patients suffering from cataracts can be provided with an intraocular lens, and tolerate them very well. Only in extremely rare cases can the intra-ocular lens not be tolerated or causes complications.
An operation should be performed when the loss of vision is so severe that it hinders the carrying out of everyday work. It is not correct that the cataract must be “ripe”. You must decide whether you can still cope with everyday life (work, driving a vehicle, taking medications, shopping, etc.) without difficulties. After a thorough examination, your ophthalmologist will decide together with you when is the right time for an operation. The overall outcome of the operation also depends on whether the cataracts are accompanied by other eye diseases or other illnesses which might influence the overall successful outcome.
Admission to hospital is today not usually necessary. Most operations are now carried out on an out-patient basis. Whether you might need to be admitted to hospital depends amongst other things on other factors, such as internal diseases or your social circumstances. Your ophthalmologist will arrange the corresponding procedure together with your general practitioner.
First, your general health condition should be established by your general practitioner, so that special supervision during the operation can be prescribed if necessary. Your ophthalmologist will then examine your eyes thoroughly and measure the refractive power (biometry) required for your artificial lens.
The operated eye will be covered at the end of the operation by a salve bandage. Attend the follow-up examinations and use the prescribed eye medications as instructed.
Do not drive a vehicle until an eye test has been carried out, and your ophthalmologist has given you his approval.