What are cataracts? Types, Causes, Symptoms, Treatments

The human lens consists of layers of protein that are laid down over time and continue to grow throughout life and at all decades from 10 to 70 years; the male lens is heavier than its female counterpart.  

A cataract is a dirty lens inside the eye, and this lens serves an important role. When you are young, the lens is clear and flexible and allows your eye to focus at near, but as you get older, the lens becomes cloudy. Once your vision from the cloudy lens impacts your quality of life, the treatment is cataract surgery.  

The layered structure of the lens is much like an onion or tree trunk, albeit clear before loss of clarity and cataract occurs. The cataract causes blurred vision, loss of contrast and can make everyday tasks such as driving difficult. This can occur at any age but is more common in people over 60 years old. 

Cataract surgery removes the cloudy lens protein and replaces this with a lens implant that can correct your glasses prescription for distance and near vision. 

The different layers of the lens give rise to different types of cataract as follows: 

Cortical cataract:  A cortical cataract begins as whitish, wedge-shaped opacities or streaks on the outer edge of the lens cortex. As it slowly progresses, the streaks extend to the centre and interferes with light passing through the centre of the lens. 

Nuclear cataract: A nuclear cataract may at first cause more near-sightedness or even a temporary improvement in your reading vision. But with time, the lens gradually turns more densely yellow and further clouds your vision. As the cataract slowly progresses, the lens may even turn brown. Advanced yellowing or browning of the lens can lead to difficulty distinguishing between shades of colour. 

Posterior sub-capsular cataract: A posterior subcapsular cataract starts as a small, opaque area that usually forms near the back of the lens, right in the path of light. A posterior subcapsular cataract often interferes with your reading vision, reduces your vision in bright light, and causes glare or halos around lights at night. These types of cataracts tend to progress faster than other types do and is more common in diabetic patients. Taking steroids can cause this type of cataract. It causes a small, cloudy area to form underneath the eye’s lens. While cataracts are a known side effect for some people when taking steroids, they’re highly treatable. 

Other less common types of cataract include: 

• Blue dot or cerulean cataract: These types of cataract appear as discrete blue dots within the lens and are usually seen from a young age and don’t affect vision. 
• Christmas tree cataract: Branching patterns of scintillating, crystal-like colour can be seen within these lenses. These changes are typically age-related. 
• Bear skin cataracts: These can occur in patients who have severe eye allergies and after some cases of trauma. 
• Black cataracts: These are rock-like types of  cataracts seen in advanced cases where the lens has solidified 
• Morgagnian cataracts: A rare form of a cataract where the cortex liquefies and the nucleus sinks to the bottom of the lens. The lens can shrink and collapse.  
• Traumatic cataracts: Serious eye injuries can damage your lens and cause a cataract. The cataract could form soon after the injury — or it could form many years later. 
• Radiation cataracts: Some types of radiation can cause cataracts. This includes ultraviolet (UV) rays from the sun and radiation treatment for cancer. 

Risk factors 

Factors that increase your risk of cataracts include: 

• Increasing age  
• Diabetes 
• Excessive exposure to sunlight 
• Smoking 
• Obesity 
• High blood pressure 
• Previous eye injury or inflammation 
• Previous eye surgery 
• Prolonged use of steroid medications 
• Drinking excessive amounts of alcohol 

Symptoms 

Signs and symptoms of cataracts include: 

• Clouded, blurred or dim vision 
• Increasing difficulty with vision at night 
• Sensitivity to light and glare 
• Need for brighter light for reading and other activities 
• Seeing “halos” around lights 
• Frequent changes in eyeglass or contact lens prescription 
• Fading or yellowing of colours 
• Double vision in a single eye 

At first, the cloudiness in your vision caused by a cataract may affect only a small part of the eye’s lens and you may be unaware of any vision loss. As the cataract grows larger, it clouds more of your lens and distorts the light passing through the lens. This may lead to more-noticeable symptoms. 

Diagnosis 

To determine whether you have a cataract, your consultant will review your medical history and symptoms, and perform an eye examination. Your consultant may conduct several tests, including: 

• Visual acuity test. A visual acuity test uses an eye chart to measure how well you can read a series of letters. Your eyes are tested one at a time, while the other eye is covered. Using a chart or a viewing device with progressively smaller letters, your eye doctor determines if you have 20/20 vision or if your vision shows signs of impairment. 
• Slit-lamp examination. A slit lamp allows your eye doctor to see the structures at the front of your eye under magnification. The microscope is called a slit lamp because it uses an intense line of light, a slit, to illuminate your cornea, iris, lens, and the space between your iris and cornea. The slit allows your doctor to view these structures in small sections, which makes it easier to detect any tiny abnormalities. 
• Retinal exam. To prepare for a retinal exam, your eye doctor puts drops in your eyes to open your pupils wide (dilate). This makes it easier to examine the back of your eyes (retina).  
• Applanation tonometry. This test measures fluid pressure in your eye. There are multiple different devices available to do this. 

Treatment

When your prescription glasses can’t clear your vision, the only effective treatment for cataracts is surgery. 

Delaying the procedure generally won’t affect how well your vision recovers if you later decide to have cataract surgery. Take time to consider the benefits and risks of cataract surgery with your consultant. 

What happens during cataract surgery 

Cataract surgery 

Cataract surgery involves removing the clouded lens and replacing it with a clear artificial lens. The artificial lens, called an intraocular lens, is positioned in the same place as your natural lens. It remains a permanent part of your eye. 

For some people, other eye problems prohibit the use of an artificial lens. In these situations, once the cataract is removed, vision may be corrected with eyeglasses or contact lenses. 

Cataract surgery is generally done on an outpatient basis, which means you won’t need to stay in a hospital after the surgery. During cataract surgery, your eye doctor uses a local anaesthetic to numb the area around your eye, but you usually stay awake during the procedure. 

Cataract surgery is generally safe however, it does increase the risk of retinal detachment. 

After the procedure, you’ll have some discomfort for a few days. Healing generally occurs within a few weeks. 

If you need cataract surgery in both eyes, your doctor will schedule surgery to remove the cataract in the second eye after you’ve healed from the first surgery. 

Interesting facts about Cataracts

Cataracts are the most common cause of blindness in the world today: According to the World Health Organisation, 51% of worldwide blindness is caused by cataracts – a figure that equates to around 20 million people. When broadened out to include all cases causing “moderate to severe disability”, the number of people estimated to be affected rises to 53.8 million.

References to cataracts and the treatment of them date back around 2000 years: The earliest known references to the condition come from the 29 AD De Medicinae, written by the Roman encyclopaedist Aulus Cornelius Celsus. There is also archaeological evidence that points to eye surgery being performed in Roman times.

The earliest written record of cataract surgery dates from around the 3rd or 4th Century AD, though that’s only the age of the surviving copy. The text itself is attributed to an Indian physician called Sushruta…who is believed to have lived as long ago as the 6th Century BC!

Diabetes can increase the risk of cataracts: People with diabetes are more likely to develop cataracts and also to develop them at a younger age, particularly Cortical cataracts.

The only treatment for cataracts is surgery: The only treatment that will target the cataract itself is surgery. Options such as stronger glasses or using a reading light may bring symptomatic improvement in the early stages of a cataract but this improvement is unlikely to last.

A local anaesthetic is usually all you need: Operations can be carried out on a day-patient basis, with only a local anaesthetic required.

Most people over 65 in the UK have some cataract development: Cataracts tend to be age-related and, according to the NHS, over half of British over-65s have some stage of cataract development in one or both eyes.

The potential of artificial lenses as a cataract treatment was discovered during World War II: Sir Harold Ridley was an ophthalmologist who treated RAF patients with eye injuries during the war. He noticed that when acrylic splinters from shattered cockpit canopies became lodged in the eyes of wounded pilots, the eye didn’t reject them in the way that it would reject glass. This observation led him to propose the use of artificial lenses as a corrective measure in cases of cataracts.

Cataracts can’t ‘grow back’: Cataracts can’t ‘grow back’ after surgery. The lens is the part of the eye that is affected by the cataract and it is removed and replaced with a plastic one, on which cataracts can’t develop. It is possible for some clouding of the membrane holding the new lens to occur, but were that to happen it can be cleared up with laser treatment and no further need for surgery.

If you are facing symptoms of cataracts, book an appointment with one of our eye specialists and make sure you have healthy eyes throughout your whole life!