The lens is a transparent structure that lets light into the eye. Cataracts are cloudy areas that form in the lens. Cataracts are the leading cause of vision loss in people over the age of 40, but cataract surgery is a routine operation nowadays and the most common kind of eye surgery.
The number of cataracts is increasing with the aging population. In the United States in 2010, there were 20.48 million cases, rising to 24.41 million in 2015. By 2050, nearly 50 million Americans are expected to have cataracts.
A cataract causes a part of the lens to becomes opaque, or cloudy. Light does not pass through easily, and vision becomes blurry, like looking through a fogged-up window. The cloudier the lens, the worse the vision will be.
Congenital cataracts may be present at birth or appear shortly after, or at some time during infancy or childhood.
Age-related cataracts appear later in life and are the most common type. This article will focus on age-related cataracts.
Contents of this article:
How do cataracts affect vision
Cataracts cause the lens to become cloudy.
Cataracts can make it hard to read or drive a car, especially during the night. Seeing people's facial expressions can become difficult.
They develop slowly, so most people do not know they have them at first, but as the clouding progresses, the vision gradually gets worse. Long-distance vision is more severely affected at the beginning.
Stronger lighting and glasses can help improve vision, but eventually it becomes harder to carry out everyday tasks, and the individual will need surgery. This is usually a safe and effective procedure.
Cataracts cause more vision problems globally than any other eye condition or disease.
Cataracts normally take years to develop, and they tend to appear in older age. The lens gradually becomes cloudy.
Cataracts often affect both eyes, but rarely equally.
People with cataracts may have the following symptoms:
- Blurry, cloudy, or misty vision
- Vision may be affected by small spots or dots
- The patient sees small patches that blur parts of the field of vision
- Vision worsens when lights are dim
- Vision is sometimes worse when there is very bright light, or glare
- Some people with cataracts also comment that colors appear less clear and faded
- Reading becomes difficult and eventually impossible
- Glasses need to be changed more frequently
- Eventually wearing glasses becomes less effective
- Rarely, the person may see a halo around bright objects, such as car headlights or street lights, or have double vision in one eye
As vision deteriorates, and the glare of oncoming headlights and street lights gets worse, driving becomes dangerous. Drivers with cataracts start to experience eyestrain and find themselves blinking more frequently as they try to clear their vision.
Cataracts do not usually change the appearance of the eye. Any discomfort such as irritation, aching, itching or redness is more likely caused by another eye disorder.
Cataracts are not hazardous to the health of the person or the eye. If the cataract becomes hypermature, or completely white, there may be inflammation, headache, and some pain. A hypermature cataract that causes pain or inflammation needs to be removed.
Who is at risk?
Anyone can develop a cataract, because the greatest risk factor is age.
In the U.S., over 40 percent of people aged 75 years or above have some degree of lens clouding. Over half of all Americans aged 80 or greater have their vision significantly impaired by cataracts.
Factors that may increase the chance of developing cataracts include:
- Family history
- Long-term exposure to bright sunlight
- Previous eye inflammation
- Previous eye injury
Airline pilots are more likely to develop nuclear cataracts, because of exposure to ionizing radiation.
Anybody who experiences vision problems should see a doctor, who then may refer them to an ophthalmologist or optometrist.
An eye examination and some tests can reveal a cataract.
An ophthalmologist specializes in the medical and surgical care of the eye, while an optometrist provides eye care, but not surgery.
The eye specialist will carry out tests.
These may include:
- A visual acuity test, to find out how clearly the person can see an object. It involves reading a list of letters from across a room.
- A slit-lamp examination uses a microscope to inspect the cornea, the iris, the lens, and the space between the iris and the cornea.
- Tonometry measures the pressure inside the eye.
- A retinal examination is carried out after using eye drops to dilate the pupils.
In a retinal examination, dilating the pupils provides a larger window to the back of the eyes. The specialist examines the lens for signs of a cataract, and to see how dense any clouding is.
Treatment and prevention
If the impact is mild, surgical treatment may not be needed. During the early stages, stronger glasses and brighter lights may help improve vision.
The following tips may help people who are not ready yet to have surgery:
- Make sure any glasses have the most accurate prescription possible
- Use a magnifying glass for reading
- Get brighter lamps for the house, such as halogen lamps
- Wear sunglasses to reduce glare on sunny days
- Avoid driving at night
For severe cataracts, the only effective treatment is surgery.
The specialist will recommend surgery if the patient:
- Is having trouble looking after themselves or someone else
- Cannot drive or finds driving difficult
- Has problems leaving the house
- Finds it hard to see or recognize people's faces
- Has problems doing their job
- Cannot read or watch television properly
Patients who take alpha-blockers or are considering taking alpha-blockers should be aware that these drugs may increase the difficulty of cataract surgery.
The surgical process: What to expect
Pre-operative assessment: Before surgery, the specialist will assess the patient's eyes and general health. The eye will be measured so that the replacement artificial lens can be prepared.
Routine eye surgery can correct a cataract.
Before the operation: Eye drops will be given just before the procedure, to dilate, or widen, the pupils. Sometimes the eye drops will contain an anesthetic, or the doctor may inject local anesthesia into the tissue around the eye.
As the anesthetic starts working, the area will become numb, and the patient will feel nothing. During the operation they will be aware of a bright light, but they will not be able to see what is happening. Cataract surgery is normally keyhole, or minimally invasive, surgery, and the patient will return home on the same day.
Various types of replacement lens may be used:
- A monofocal lens is a fixed-strength lens that is set for one level of vision, usually distance
- A multifocal lens may have two or more different strengths, providing for near and distance vision
- An accommodating lens is most similar to the natural human lens. It allows the eye to focus on near and distant objects
The operation involves removing the cloudy lens from the eye and putting an artificial, clear, plastic one in its place. This is an intraocular implant, or an intraocular lens.
This is known as phacoemulsification or phaco-extracapsular extraction.
The eye surgeon makes a tiny cut in the cornea at the front and inserts a minute probe through the cut. The probe uses ultrasound and breaks up the cloudy lens into very small pieces. These are sucked out.
The artificial lens is then inserted through the cut. The lens capsule acts as a pocket, to hold the lens in place. When it is first inserted the lens is folded, but it unfolds when in position.
The whole procedure takes around 30 minutes. Most patients will wear an eye pad for protection for a short while.
In manual extracapsular extraction, the lens is removed in one piece, and no ultrasound is used to break it up. The surgeon will make a slightly larger cut in the eye.
In intracapsular extraction, both the lens capsule and the lens are removed. The artificial lens is sewn into the eye. This type of procedure is much less common.
If both eyes need operating, this will usually be done 4 weeks apart.
Cataract surgery surgery may be done using traditional tools, or it may be laser-assisted.
Laser may later be used to solve a complication known as after-cataract surgery that may occur months or years later.
After the operation
For most patients, vision improves almost immediately. It may take a while for the eye to settle down completely. Sometimes, the cut in the eye needs a stitch, but this is normally small enough to heal by itself.
Patients should avoid vigorous activities for a while, but most people find they can go about their daily activities as soon as they get home.
The patient will need a vision test, because they will probably need different glasses after their operation. The new glasses can only be determined after their vision has settled down, but this can take several weeks.
To minimize the complications of cataracts, people should have regular eye exams, especially as they get older.
The following tips can reduce the risk of developing cataracts. Some have been proven to work, while others are not confirmed.
Giving up smoking
Smoking raises the risk of a number of eye conditions, and studies have linked it to a 3-fold increase in cataracts. There are also indications that smokers may experience cataract symptoms earlier.
Healthy food reduces the risk of disease, including eye problems. A healthy diet has plenty of fruits, vegetables, whole grains, unrefined carbohydrates, good quality fats, such as avocado, olive oil, and omega oils, and either plant-sourced proteins or lean, animal-sourced proteins.
Lutein and zeaxanthin have been described as "promising" in preventing cataracts.
Obesity and diabetes
Obesity significantly raises the risk of developing type 2 diabetes, a cataract risk factor. Maintaining a healthy weight and keeping diabetes under control will help reduce the risk.
The following can help to protect against cataracts:
Research has suggested that pycnogenol, a pine bark extract, may help reduce the risk of cataracts.