Cataract

Jai Ganesh · Yesterday 16:29:12

Cataract

Gist

A cataract is the gradual clouding of the eye's natural lens, usually caused by aging, which results in hazy vision, light sensitivity, and faded colors. Primarily affecting adults over 60, risks include smoking, diabetes, and UV exposure. Treatment requires a safe, 15-30 minute outpatient surgery to replace the cloudy lens with an artificial one, typically allowing quick recovery.

The main cause of cataracts is aging, as proteins in the eye's lens break down and clump together, causing clouding, but other major factors include long-term UV light exposure, smoking, diabetes, eye injuries, and steroid medication use. These risk factors accelerate the natural aging process, leading to vision becoming hazy or cloudy over time.

Summary

A cataract is a clouding of the lens of the eye, which is typically clear. For people who have cataracts, seeing through cloudy lenses is like looking through a frosty or fogged-up window. Clouded vision caused by cataracts can make it more difficult to read, drive a car at night or see the expression on a friend's face.

Most cataracts develop slowly and don't disturb eyesight early on. But with time, cataracts will eventually affect vision.

At first, stronger lighting and eyeglasses can help deal with cataracts. But if impaired vision affects usual activities, cataract surgery might be needed. Fortunately, cataract surgery is generally a safe, effective procedure.

Symptoms

Symptoms of cataracts include:

* Clouded, blurred or dim vision.
* Trouble seeing 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 colors.
* Double vision in one eye.

At first, the cloudiness in your vision caused by a cataract may affect only a small part of the eye's lens. You may not notice any vision loss. As the cataract grows larger, it clouds more of your lens. More clouding changes the light passing through the lens. This may lead to symptoms you notice more.

When to see a doctor

Make an appointment for an eye exam if you notice any changes in your vision. If you develop sudden vision changes, such as double vision or flashes of light, sudden eye pain, or a sudden headache, see a member of your health care team right away.

Details

A cataract is a cloudy area in the lens of the eye that impairs vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colours, blurry or double vision, halos around light, trouble with bright lights, and difficulty seeing at night. This may result in difficulty driving, reading and recognizing faces. Poor vision caused by cataracts may also result in an increased risk of falling and depression. In 2020 Cataracts caused 39.6% of all cases of blindness and 28.3% of visual impairment worldwide. Cataracts remain the single most common cause of global blindness.

Cataracts are most commonly due to aging but may also be due to trauma or radiation exposure, be present from birth or occur following eye surgery for other problems. Risk factors include diabetes, longstanding use of corticosteroid medication, smoking tobacco, prolonged exposure to sunlight and alcohol. In addition, poor nutrition, obesity, chronic kidney disease and autoimmune diseases have been recognized in various studies as contributing to the development of cataracts. Cataract formation is primarily driven by oxidative stress, which damages lens proteins, leading to their aggregation and the accumulation of clumps of protein or yellow-brown pigment in the lens. This reduces the transmission of light to the retina at the back of the eye, impairing vision. Additionally, alterations in the lens's metabolic processes, including imbalances in calcium and other ions, contribute to cataract development. Diagnosis is typically through an eye examination, with ophthalmoscopy and slit-lamp examination being the most effective methods. During ophthalmoscopy the pupil is dilated and the red reflex is examined for any opacities in the lens. Slit-lamp examination provides further details on the characteristics, location and extent of the cataract.

Wearing sunglasses with UV protection and a wide brimmed hat, eating leafy vegetables and fruits and avoiding smoking may reduce the risk of developing cataracts or slow the process. Early on, the symptoms may be improved with glasses. If this does not help, surgery to remove the cloudy lens and replace it with an artificial lens is the only effective treatment. Cataract surgery is not readily available in many countries, and surgery is needed only if the cataracts are causing problems and generally results in an improved quality of life.

About 20 million people worldwide are blind owing to cataracts. They are the cause of approximately 5% of blindness in the United States and nearly 60% of blindness in parts of Africa and South America. Blindness from cataracts occurs in 10 to 40 per 100,000 children in the developing world and 1 to 4 per 100,000 children in the developed world. Cataracts become more common with age. In the United States, cataracts occur in 68% of those over the age of 80 years. They are more common in women and less common in Hispanic and Black people.

Additional Information

A cataract is a cloudy or opaque area in the normally clear lens of the eye. Depending upon its size and location, it can interfere with normal vision.

Most cataracts develop in people over age 55, but they occasionally occur in infants and young children or as a result of trauma or medications. Usually, cataracts develop in both eyes, but one may be worse than the other.

The lens is located inside the eye behind the iris, the colored part of the eye. Normally, the lens focuses light on the retina, which sends the image through the optic nerve to the brain. However, if the lens is clouded by a cataract, light is scattered so the lens can no longer focus it properly, causing vision problems. The lens is made of mostly proteins and water. The clouding of the lens occurs due to changes in the proteins and lens fibers.

Types of cataracts

The lens is composed of layers, like an onion. The outermost is the capsule. The layer inside the capsule is the cortex, and the innermost layer is the nucleus. A cataract may develop in any of these areas. Cataracts are named for their location in the lens:

* A nuclear cataract is located in the center of the lens. The nucleus tends to darken with age, changing from clear to yellow and sometimes brown.
* A cortical cataract affects the layer of the lens surrounding the nucleus. The cataract looks like a wedge or a spoke.
* A posterior capsular cataract is found in the back outer layer of the lens. This type often develops more rapidly.

Causes & risk factors

Most cataracts are due to age-related changes in the lens of the eye that cause it to become cloudy or opaque. However, other factors can contribute to cataract development, including:

* Diabetes mellitus. People with diabetes are at higher risk for cataracts.
* Drugs. Certain medications are associated with cataract development. These include:
** Corticosteroids.
** Chlorpromazine and other phenothiazine related medications.
* Ultraviolet radiation. Studies show an increased chance of cataract formation with unprotected exposure to ultraviolet (UV) radiation.
* Smoking. There is possibly an association between smoking and increased lens cloudiness.
* Alcohol. Several studies show increased cataract formation in patients with higher alcohol consumption compared with people who have lower or no alcohol consumption.
* Nutritional deficiency. Although the results are inconclusive, studies suggest an association between cataract formation and low levels of antioxidants (for example, vitamin C, vitamin E, and carotenoids). Further studies may show that antioxidants can help decrease cataract development.
* Family History. If a close relative has had cataracts, there is a higher chance of developing a cataract.

Rarely, cataracts are present at birth or develop shortly after. They may be inherited or develop due to an infection (such as rubella) in the mother during pregnancy. A cataract may also develop following an eye injury or surgery for another eye problem, such as glaucoma.

Symptoms

Cataracts generally form very slowly. Signs and symptoms of a cataract may include:

* Blurred or hazy vision.
* Reduced-intensity of colors.
* Increased sensitivity to glare from lights, particularly when driving at night.
* Increased difficulty seeing at night.
* Change in the eye's refractive error, or eyeglass prescription.

Diagnosis

Cataracts are diagnosed through a comprehensive eye examination. This examination may include:

* Patient history to determine if vision difficulties are limiting daily activities and other general health concerns affecting vision.
* Visual acuity measurement to determine to what extent a cataract may be limiting clear distance and near vision.
* Refraction to determine the need for changes in an eyeglass or contact lens prescription.
* Evaluation of the lens under high magnification and illumination to determine the extent and location of any cataracts.
* Evaluation of the retina of the eye through a dilated pupil.
* Measurement of pressure within the eye.
* Supplemental testing for color vision and glare sensitivity.

Further testing may be needed to determine how much the cataract is affecting vision and to evaluate whether other eye diseases may limit vision following cataract surgery.

Using the information from these tests, your doctor of optometry can determine if you have cataracts and advise you on your treatment options.

Treatment

Cataract treatment is based on the level of visual impairment they cause. If a cataract minimally affects vision, or not at all, no treatment may be needed. Patients may be advised to monitor for increased visual symptoms and follow a regular check-up schedule.

In some cases, changing the eyeglass prescription may provide temporary vision improvement. In addition, anti-glare coatings on eyeglass lenses can help reduce glare for night driving. Increasing the amount of light used when reading may be beneficial.

When a cataract progresses to the point that it affects a person's ability to do normal everyday tasks, surgery may be needed. Cataract surgery involves removing the lens of the eye and replacing it with an artificial lens. The artificial lens requires no care and can significantly improve vision. Some artificial lenses have the natural focusing ability of a young healthy lens. Once a cataract is removed, it cannot grow back.

Two approaches to cataract surgery are generally used:

* Small-incision cataract surgery involves making an incision in the side of the cornea (the clear outer covering of the eye) and inserting a tiny probe into the eye. The probe emits ultrasound waves that soften and break up the lens so it can be suctioned out. This process is called phacoemulsification.
* Extracapsular surgery requires a somewhat larger incision in the cornea so that the lens core can be removed in one piece. The natural lens is replaced by a clear plastic lens called an intraocular lens (IOL). When implanting an IOL is not possible because of other eye problems, contact lenses and, in some cases, eyeglasses may be an option for vision correction.

As with any surgery, cataract surgery has risks from infection and bleeding. Cataract surgery also slightly increases the risk of retinal detachment. It is important to discuss the benefits and risks of cataract surgery with your eye care providers. Other eye conditions may increase the need for cataract surgery or prevent a person from being a cataract surgery candidate.

Cataract surgery is one of the safest and most effective types of surgery performed in the United States today. Approximately 90% of cataract surgery patients report better vision following the surgery.

Prevention

There is no treatment to prevent or slow cataract progression. In age-related cataracts, changes in vision can be very gradual. Some people may not initially recognize the visual changes. However, as cataracts worsen, vision symptoms increase.

While there are no clinically proven approaches to preventing cataracts, simple preventive strategies include:

* Reducing exposure to sunlight through UV-blocking lenses.
* Decreasing or stopping smoking.
* Increasing antioxidant vitamin consumption by eating more leafy green vegetables and taking nutritional supplements.

Researchers have linked eye-friendly nutrients such as lutein and zeaxanthin, vitamin C, vitamin E and zinc to reducing the risk of certain eye diseases, including cataracts. For more information on the importance of good nutrition and eye health, please see the diet and nutrition section.

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Cataract

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