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The crystalline lens

Just through the pupil (i.e. the black hole) and behind the iris (i.e. the coloured part of the eye), there is a lens situated inside the eye. This is formally referred to as the crystalline lens and is partly responsible for focusing rays of light entering the eye on to the retina (i.e. the light-sensitive layer at the back of the eye). Its shape can also be altered in order to help us both focus on objects at different distances and change our focus between objects at different distances in a process referred to as accommodation. It is therefore an important part of the eye.

What is a cataract?

The crystalline lens is normally transparent but over time it is not uncommon for this to change. It tends to yellow in colour and become hazy in its appearance and this may then lead to the formation of a cataract.

The term ‘cataract’ is derived from the Latin ‘cataracta’ or ‘waterfall’ and is essentially used to describe an opacity of the crystalline lens. Once a cataract develops and then continues to progress, the crystalline lens becomes more opaque. This generally happens very slowly over a period of years but as it does progress it begins to affect the way that rays of light pass through the crystalline lens and can then also start to impact on vision. A useful way of appreciating this is to imagine the difference between looking out of your kitchen window and then looking out of your bathroom window.

There are many different types of cataract and sometimes a person may have more than one type of cataract affecting one and/or both of their eyes at the same time. It may also be that that person has more signs of cataract in one eye than the other or that they have signs of cataract in one and/or both eyes but are not necessarily experiencing the associated symptoms. It is therefore a considerably variable condition and really does depend on the person in question.

However, the key point is that a cataract does not have to be permanent and if/when it reaches that point when it is deemed ready then there is a surgical procedure that can be carried out to remove it.

Are cataracts a common occurrence?

Cataracts are extremely common and in a way are inevitable in all of us at some point during our lifetime. They are the most common cause of visual impairment worldwide and in the UK the majority of people over the age of 65 years will have some degree of cataract present in one and/or both of their eyes. However, everyone’s eyes are unique and so the time and rate of development and/or progression of the cataract(s) will always vary from one person to the next. The diagnosis of cataract also depends on the practitioner checking your eyes as what may be deemed a cataract to one practitioner may not be seen in the same way to another.

What causes a cataract?

The most common type of cataract that is seen in clinical practice is referred to as age-related cataract and so it stands to reason that age is the most common risk factor. However, no one really understands what it is about age that causes a cataract to develop and/or progress. It has been suggested that it is due to proteins within the crystalline lens naturally breaking down over time and aggregating to form the said opacity.

Although we generally associate cataract as being something that happens later on in life, the truth is a cataract can occur at any age and unfortunately it is also possible to either be born with a cataract (i.e. congenital cataract) or to develop a cataract during childhood (i.e. developmental/infantile/juvenile cataract).

Other risk factors that have been associated with the development and/or progression of cataract include:

  • Diabetes
  • Family history of cataract
  • Previous surgery to the eye(s)
  • Previous injury to the eye(s)
  • Previous inflammation of the eye(s)
  • Medications (e.g. corticosteroids)
  • Smoking
  • Lifelong exposure to ultraviolet (UV) radiation (i.e. the Sun)


What are the symptoms associated with cataract?

Because cataracts normally develop very slowly over a period of years, most people do not notice the effects of them until they either start to interfere in their day-to-day lives or indeed it is pointed out to them by the practitioner.

Symptoms will vary between individuals, even depending on the extent of the cataract, but could include any and/or all of the following:

  • Blurred/Misty/Cloudy vision
  • Issue with glare from bright lights (e.g. vehicle headlights)
  • Desaturation of colours
  • Yellow/Brown tinge to vision
  • Ghosting/Shadowing of objects
  • Haloes around bright lights (e.g. vehicle headlights)
  • Ineffectiveness of spectacles and/or contact lenses (due to the changing prescription)


Obviously as the cataract progresses, these symptoms would become progressively worse over time.

How are cataracts treated?

As mentioned previously, cataracts do not have to be permanent and if/when they reach that point when they are deemed ready then something can be done about them. Currently, the only way to remove a cataract is by means of a surgical procedure called phacoemulsification. This is a straightforward operation and there can be many indications for having it done. For example, it could be that no further improvement in vision can be obtained by means of spectacles and/or contact lenses. Alternatively, the cataract could be affecting the person’s ability to drive, live independently and/or provide care to others. However, generally the operation is always carried out with a view to improving the person’s vision and quality of life.

What does the operation entail?

The operation to remove a cataract is one of the most common surgical procedures being carried out today. It is also one of the quickest surgical procedures being performed, usually taking up to 20 – 30 minutes to complete. This generally makes it a day case and so the person in question will usually be able to go home on the same day.

The operation itself is typically done under local anaesthetic (i.e. the person is awake throughout). With the eyelids held open and the pupil dilated, a self-healing incision is made at the edge of the cornea (i.e. the transparent front surface or ‘window’ of the eye). A probe is then inserted into the eye through this opening in order to manipulate the crystalline lens.

The crystalline lens itself is contained by an outer lens capsule. This essentially makes it like a bag, with the cataract and the rest of the lens contents being inside that bag. The aforementioned probe breaks into the bag and using ultrasound continues to break up the cataract and lens contents inside. This is then all cleared away and a different probe used to insert an artificial lens implant that folds out and replaces the lens contents inside the bag. The result is to make the person’s vision much clearer and brighter and within a few days of having the operation most people can notice a vast improvement. The person is always given a course of drops in order to reduce any post-operative inflammation and they will be seen again for a follow-up appointment about 4 – 6 weeks later in order to review their eyes and their prescription (as the artificial lens implant will have caused the prescription in the operated eye to change). A decision will then be made about the status of the second or non-operated eye if necessary.

The main purpose of this operation is to provide visual improvement. However, a person’s eyes and visual needs are unique to them and so prior to the operation several measurements will be taken in relation to the operative eye in order to establish what will be the best power of artificial lens implant for that person. This is with a view to providing the best visual outcome possible and the hope is to try and limit the person’s need for a refractive correction (i.e. spectacles and/or contact lenses) after the operation. However, sometimes this is not always possible but at least the person’s vision will be clearer and brighter than before.

There are two main categories of artificial lens implant. These are:

  • Monofocal lens implants

This is the most common type of lens implant to be used and is the only type of lens implant available if the operation is being carried out through the NHS. This type of lens implant will generally only correct the person’s vision for a set distance, the usual scenario being to correct their distance vision as best as possible so that hopefully they only require a refractive correction for their near vision.

  • Multifocal lens implants

With these lens implants, there is a high probability of enabling the person to see at all distances without the need for a refractive correction. However, they may still experience a reduction in their contrast sensitivity (especially in poor light conditions) as well as issues with glare and haloes around bright lights. Generally though, most people who opt for this type of lens implant are prepared to accept these drawbacks if it will reduce their need or reliance on a refractive correction. The pre-operative preparation and post-operative management required for this type of lens implant tends to be more in-depth, which is why this type of lens implant is only available privately and not on the NHS.

What are the risks?

As with any surgical procedure, there are risks associated with cataract surgery. However, it should be said that cataract surgery is a highly successful surgical procedure and the chance of any severe complications occurring is small.

The most common complication of uncomplicated cataract surgery tends to occur about 2 years after having had the operation (although sometimes it can occur earlier). This is referred to as Posterior Capsular Opacification (PCO) and is essentially when a layer of cells develops on the back surface of the outer lens capsule (i.e. the bag). This can then start to cause the same issues that a cataract would but the key point here is that it is not a cataract. If the person is symptomatic then this PCO can be treated by means of a simple outpatient procedure. This involves the use of a laser to clear those cells away and return vision to normal again.

Other complications can occur with respect to the operation itself and sometimes the process can cause changes to the vitreous (i.e. the gel that fills the main cavity of the eye) and/or the retina (i.e. the light-sensitive layer at the back of the eye). It has also been reported that approximately 1 in 1000 people can develop an infection that leads to permanent vision loss directly after the operation. However, the risk here is obviously very small.

If you have any queries or concerns regarding anything relating to cataracts then please do not hesitate to contact us.

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