What Causes Cataract
Cataract is an opacity in the crystalline lens in the eye. The lens resides behind the pupil, the dark part through which the light enters the eye. It focuses the light, although it does so more effectively when we are young as it can change in focus. It is a remarkable piece of biologic engineering. Most tissue is opaque but the lens manages to stay clear for a great number of years by virtue of a high level of organisation in its structure. Any loss of that organisation, either with cross-linking of proteins, or water seeping into the lens, or disorganisation of cells, produces opacity in the lens, which we call a cataract.
In many ways, the question should be not ‘what causes cataract’ but ‘why does the lens remain clear for as long as it does?’
Cataracts are related to family history, they are also related to injury, to inflammation in the eye, to illness in the rest of the body, particularly diabetes, and medication use such as steroid, but mostly they are due to having birthdays, and it is probably that most of us will get one.
Types of Cataract
Although cataract is inevitable, some forms of cataract really do not bother the eye and person too much. Cataracts come in different types, although the exact type does not alter the way we deal with them.
Cataracts are an opacity in the lens in the eye that can exist more in the surface, called cortical cataract, or more in the centre, called a nuclear cataract.
In truth most cataracts are an amalgam of different types. Rarer types of cataract include posterior subcapsular cataracts, anterior subcapsular cataracts, posterior polar cataracts, embryotic cataracts, Christmas tree cataracts, and the rare Morganian cataracts, when they become very advanced.
Cataract surgery is a remarkably evolved form of surgery. It started many hundreds of years ago as a very imprecise and damaging process, intended basically to dislodge the lens. Later iterations involved the wholesale removal of the lens, leaving the sufferer with very thick glasses. After about 1980 the use of the intraocular lens to replace the cataract became commonplace and the use of very thick glasses post-cataract became a rarity. In the early 1990s small incision cataract surgery developed and has been evolving ever since. Small incision cataract surgery involves no sutures and the use of a foldable lens, which sits in the space where the original cataract was. It is not sewn in or stitched or glued in, and it is gradually “shrink-wrapped” by the capsule of the original cataract such as the lens becomes very stable and does not require replacement.
In recent times there has been a new laser developed for doing part of a cataract operation. This is often called Femto II or laser assisted cataract surgery. Although it is a very elegant procedure, there is no data currently to suggest that it offers any benefit to patients. All the studies so far fail to prove non-inferiority; in other words, at this stage it is not possible to prove that it is better than the current highly evolved cataract surgery, in fact it is not possible to prove that it is not inferior.
Although very impressed with the technology, Melbourne Eye Specialists does not perform Femto II laser for our cataract patients as at the present time its cost and complication profile prohibits it from something that we would want done on ourselves or we would offer to our nearest and dearest.
Intraocular lenses have evolved significantly over the years. Current intraocular lenses are foldable devices, which have a high level of both stability and refractive capacity. They come in a great range of sizes and powers, and now include the capacity to reverse even high levels of astigmatism.
Some intraocular lenses have two areas of focus in them. Although on the face of this, this sounds like a good idea, there are some down sides to this process and these lenses still occupy less than 1% of the market for intraocular lenses. The main reason is that the process of creating two places of focus reduces the contrast in both of them and produces some difficulties, particularly at night.
It is reasonable to assume as we age that the value of these lenses will reduce for the patient and that some of the problems associated will increase.
Melbourne Eye Specialists does offer these lenses, but the choice of them will be made in consultation with the treating ophthalmologist.
Cataract Surgery in Glaucoma
Glaucoma and cataract run hand in hand. Cataracts can cause, or certainly worsen, glaucoma, and the removal of the cataract can make glaucoma substantially better. Cataract surgery when performed before glaucoma surgery can often be quite effective at lowering intraocular pressure, although not always, but when performed after cataract surgery can often raise the pressure. The timing of cataract surgery in glaucoma is a significant one, and any decisions around intervention for cataract will need to be considered in the context of glaucoma.
These decisions will be made in consultation with your treating ophthalmologist.
Cataract with trauma
Cataract commonly occurs in the context of penetrating or blunt trauma to the eye. It may occur quite quickly or may develop over time, but the main concern is that the cataract surgery at this stage is more difficult technically and involves a high level of complication. In addition it may not be possible to place an intraocular lens in the same place or support it in the way that it normally is, and certain steps need to be taken to reduce the risk associated with this.
The management of trauma is particular interest of A/Pr Michael Coote and the management of cataract in trauma, including the use of specially made anti-glare lens (Morcher lenses) is a particular interest.
High Risk Cataract Surgery
Most of the risks associated with cataract surgery fall well below 5% and mostly well below 1% for people undertaking cataract surgery, who are otherwise reasonably well, with eyes that do not have significant other pathology, and in the hands of experienced surgeons.
There are, however, eyes that have much higher levels of risk associated with other disease in the eye, including glaucoma and trauma and uveitis, and these eyes need particular care in managing them as they have a much higher risk profile than standard.
High risk cataract surgery is a particular interest of A/Pr Michael Coote, who has managed a very significant number of these over 20 years with good result.
Laser for post Cataract
Intraocular lenses are implanted within the shell of the original cataract. This shell is called the capsule and the capsule is living tissue, which over time may become thicker and less transparent. Adding layers of cells to this produces an opacification in the posterior capsule, which we laser away in the office.
This is sometimes called the ‘after cataract’, but it is a common problem, occurring in somewhere between 10-25% of patients who undertake cataract surgery. It can be anywhere from three months to five years, but we recently lasered a capsule whose cataract operation was 25 years ago.
Laser capsulotomy is a simple, safe procedure, which is done on site, is painless, and is never needed to be done again.
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