Cataract: Understand the Causes & What to Expect with Surgery
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A cataract is a clouding of the lens of the eye. Symptoms include blurry vision, difficulty seeing at night, glare, difficulty discerning colors, and increased nearsightedness. The only treatment option is the surgical replacement of the old lens with a synthetic lens.
What is a cataract?
A cataract is when the lens, a crystalline structure in the eye that normally allows light into the eye, becomes cloudy. Symptoms of a cataract include blurry vision, difficulty seeing at night, glare, difficulty discerning colors, and increased nearsightedness.
The diagnosis is made by examination by an ophthalmologist (eye doctor) using a slit lamp. The only way to treat cataracts is surgery to remove the cloudy lens and replace it with a clear, synthetic lens.
You should go see your primary care doctor, who can do an exam and refer you to an ophthalmologist, if necessary.
There are three main types of cataracts: nuclear cataracts, cortical cataracts, and posterior subcapsular cataracts. These types of cataracts differ based on the location of the opacification within the lens and may have slightly different symptoms. Symptoms that can be seen in all types of cataracts include:
- Blurry vision: Most people with cataracts will experience blurry vision in one or both eyes. The blurry vision usually develops gradually over months or years and may be worse in one eye compared to the other. The blurry vision may be worse at distance or at near, depending on the type of cataract. For example, blurry vision tends to be worse at a distance in nuclear cataracts, and worse when near with posterior subcapsular cataracts.
- Difficulty seeing at night: This is because cataracts decrease the amount of light that enters the eye, and their effects are exacerbated in low-light conditions.
- Glare: Some people with cataracts may develop glare, or seeing halos or streaking around lights. This can be especially prominent with posterior subcapsular cataracts.
- Difficulty discerning colors: Colors may appear duller to an eye with a cataract compared to an eye without a cataract.
- Increased nearsightedness ("myopic shift"): This is when it is harder to see objects far away than up close. This can occur because changes in the shape and density of the lens may alter how much it bends the light entering the eye.
- Sudden eye pain or redness: Cataracts by themselves do not cause eye pain or redness. However, uncommonly a cataract can cause the development of glaucoma, a condition in which the pressure in the eye rises rapidly. This will cause the eye to become red and painful.
Causes of cataracts include aging, pediatric cataracts, trauma or injury to the eye, certain eye diseases, diabetes or other medical conditions, smoking, increased exposure to ultraviolet B radiation, certain medications, and genetic factors.
The most common cause of cataracts is aging. An age-related cataract usually develops between 45 and 50 years of age. Over time, the proteins in the lens change in structure and become less transparent. In addition, the center of the lens tends to stiffen and become compacted. Finally, the color of the proteins in the lens change to a yellow or brown color.
Pediatric cataracts include cataracts that present at birth (congenital cataracts) or during the first year of life (infantile cataracts). The causes of these cataracts generally differ from the causes of age-related cataracts. Approximately one-third of pediatric cataracts are inherited; approximately one-third are associated with certain ocular or system syndromes such as Down syndrome, and approximately one-third are due to undetermined causes.
Trauma or other injuries to the eye
Cataracts can occur after either blunt or penetrating trauma to the eye. They can also occur if the eye is injured by a chemical burn, electricity, or radiation.
Having certain eye diseases
One common example is uveitis, which is an inflammation of a part of the eye. Other examples include glaucoma (a disease of the optic nerve usually associated with increased pressure in the eye) and certain diseases of the retina (the "film" in the back of the eye that senses light).
Having diabetes or other medical conditions
The following conditions increase the risk of developing cataracts.
- Diabetes: This is a condition causing abnormally high levels of sugar in the blood. Overall, individuals with diabetes develop cataracts approximately 20 years earlier than individuals without diabetes. The risk is higher if the diabetes is poorly controlled. This is because, in poorly controlled diabetes, sugar levels increase in the eye, and enzymes in the lens can convert the sugar into a substance that makes the lens less transparent, leading to the development of a cataract.
- Other conditions: These include myotonic dystrophy (a genetic disorder affecting muscles) and Wilson disease (a disorder involving the abnormal buildup of copper in the body).
Environmental factors can be related to certain exposures or lifestyle habits.
- Smoking: The reason for this is unclear, but may be due to the effect of toxins on the lens.
- Increased exposure to sunlight and ultraviolet B (UVB) radiation
Using certain medications
Using certain medications can increase the risk of developing cataracts.
- Steroids: Using steroids in any form, including in eye drops, inhaled, as pills, or intravenously for a long time can lead to the development of cataracts.
- Other medications: These include certain miotics (eye drops used to constrict the pupil), phenothiazines (a class medications used to treat psychiatric disorders and nausea), and busulfan (a chemotherapy drug).
Approximately 50 percent of congenital cataracts have a genetic cause, with more than 50 associated genes identified. Genetics are also thought to play an important role in the development of age-related cataracts, but less is known about the specific genes that cause age-related cataracts.
Treatment options and prevention for cataract
The only way to treat a cataract is by undergoing a surgery to remove the cataract and replace it with a clear, synthetic lens. However, surgery may or may not be recommended based on the type of cataract or other factors below. Cataract surgery is actually an elective procedure that you can choose to undergo if you feel the cataract is causing enough symptoms to interfere with your quality of life.
- Age-related: In most cases of age-related cataracts, there is no medical reason that you need to have cataract surgery.
- Medical reasons: In some cases, your doctor may recommend you undergo cataract surgery for medical reasons, such as if the cataract is causing glaucoma, or if removing the cataract would make it easier to monitor another eye disease in the back of the eye.
- Pediatric: Most cases of pediatric cataracts require removal at an early age, usually between 6-10 weeks of life. This is to prevent the development of visual problems such as amblyopia, which is decreased vision that results from decreased visual input to the brain during the critical period of vision development.
The following describes cataract surgery protocol and outcomes.
- Before the procedure: Prior to the surgery, the surgeon will conduct a comprehensive eye exam and testing, including measuring visual acuity, examining the back of the eye, and calculating the required refractive power of the implanted lens (biometry).
- Duration: This surgery generally takes less than half an hour and is done as an outpatient procedure at a hospital or surgery center. The surgery is usually done with topical or local anesthesia and monitored sedation.
- Procedure details: The surgeon will make a small incision in the eye and remove the cataract, either in a single piece or by breaking it up with a device that utilizes ultrasound energy. Once the cataract is removed, the surgeon will insert a clear synthetic lens. In most cases, the incision will seal without needing sutures.
- Recovery: You will likely go home with a number of eye drops to decrease inflammation and prevent infection.
- Prognosis: Overall, cataract surgery is safe and effective, with 84 to 94 percent of eyes achieving a best-corrected visual acuity of 20/30 (two lines above perfect vision on the vision chart) or better at six months after surgery.
There are currently no validated ways to prevent the development of cataracts since the primary cause is changes associated with aging. Some observational studies have suggested that taking a multivitamin supplement may be moderately protective against developing cataracts.
When to seek further consultation for cataract
If you develop symptoms of cataracts such as blurry vision, poor night vision, or glare, you should go see your eye doctor. Your eye doctor can examine your eyes to see if your symptoms are due to a cataract, and then discuss treatment options.
If you develop decreased vision or eye pain after cataract surgery
You should go see your eye doctor right away. These symptoms may be due to a complication of the cataract surgery, and your doctor can examine your eyes and offer the appropriate treatment.
Questions your doctor may ask to determine cataract
- Have you been feeling more tired than usual, lethargic or fatigued despite sleeping a normal amount?
- Have you ever been diagnosed with diabetes?
- Any fever today or during the last week?
- Do you currently smoke?
- Have you experienced any nausea?
Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.
Dr. Liu received his medical degree from the University of Pennsylvania Perelman School of Medicine and is pursuing a career in ophthalmology. He graduated Phi Beta Kappa from Swarthmore College with a BA in biology. He has published research in multiple ophthalmology and healthcare journals and has received awards from Research to Prevent Blindness. In his free time, he enjoys running, biking, and spending time with his friends and family.
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- Lam D, Rao SK, Ratra V, et al. Cataract. Nat Rev Dis Primers. 2015;1:15014. PubMed Link
- Wilson ME. Pediatric cataracts: Overview. Knights Templar Eye Foundation. Published November 11, 2015. AAO Link
- Milton RC, Sperduto RD, Clemons TE, Ferris FL. Centrum use and progression of age-related cataract in the Age-Related Eye Disease Study: A propensity score approach. AREDS Report No. 21. Ophthalmology. 2006;113(8):1264-1270. PubMed Link