<Things you should know> Correct knowledge about cataracts: Causes, symptoms, and treatments for cataracts
Cataracts are a relatively common eye disease for people over 50.
Cataracts develop with age, and it is said that almost everyone over 80 experiences some symptoms. If you've recently noticed symptoms such as blurred vision, increased sensitivity to light, or double or triple vision, you should get checked out.
This article, supervised by an ophthalmologist, provides a detailed explanation of cataracts, including their causes, symptoms, surgery, and treatment options.
![What is a cataract?]()
What is a cataract?
Cataracts are a disease in which the lens of the eye, which acts as the eye's lens, becomes cloudy, making it difficult to see. They are very common in the elderly, and the number of people who develop them increases with age.
A study found that 37-54% of people in their 50s, 66-83% in their 60s, 84-97% in their 70s, and nearly 100% of those 80 and older showed some degree of cataract symptoms ("Research on the Development of Evidence-Based Cataract Treatment Guidelines").
Based on calculations using the Ministry of Health, Labour and Welfare's "2nd NDB Open Data," it is estimated that approximately 1 million people undergo surgery annually to treat cataracts.
Thanks to advances in surgical treatment in Japan, the number of people who go blind due to cataracts has become very small.
However, in developing countries, many people still go blind due to cataracts because of poverty, a shortage of doctors, and insufficient medical facilities, making cataracts the leading cause of blindness worldwide.
Structure of the eye
The clouding that occurs in cataracts is in a tissue called the "lens" inside the eyeball.
The lens is colorless and transparent, and its function is to refract light that enters through the cornea and focus it on the retina.
The macula is the center of the retina, and when the macula functions normally, we can see fine details clearly.
![Main symptoms of cataracts]()
Main symptoms of cataracts
Cataracts occur when the lens of the eye becomes cloudy, blocking incoming light or preventing it from traveling in a straight line. This can lead to difficulty focusing, blurred vision, and other symptoms.
Besides those, there are actually a variety of other symptoms, such as blurred vision in bright places, sensitivity to light, seeing small objects double or triple with one eye, and difficulty seeing in dark places.
Differences in symptoms depending on the degree of turbidity
The lens has a structure in which a somewhat hard part called the nucleus is surrounded by a cortex, and the whole thing is enclosed by a thin membrane called a capsule (anterior capsule and posterior capsule).
The way symptoms manifest varies from person to person, depending on which part of the lens is cloudy.
In the case of the nucleus, it becomes cloudy and hardened, making it difficult for light to enter, resulting in symptoms such as difficulty seeing in dim light. Myopia may also progress rapidly in a short period of time.
When the cortex becomes cloudy, symptoms are often not noticeable at first, but as the cloudiness spreads to the center, you may experience glare or blurred vision.
If the posterior capsule becomes cloudy, symptoms such as difficulty seeing both near and far, even in bright light, will be observed early on.
![Main causes of cataracts]()
Main causes of cataracts
The following are considered to be the main causes of cataracts:
![cause]()
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Aging
It is said to be the leading cause of clouding of the lens.
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diabetes
Obesity itself is considered a risk factor for cataracts. Furthermore, people with diabetes are said to be about five times more likely to develop cataracts than healthy individuals.
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infrared
Cataracts are common among people whose occupations involve prolonged exposure to strong infrared radiation, such as glassblowers. This condition is sometimes called "glassblower cataracts."
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UV rays
It has been found that the prevalence of cataracts is high in regions near the equator where the amount of ultraviolet radiation is high.
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Steroid drugs
It has been shown that using large amounts of oral or inhaled steroids increases the risk of developing cataracts. Long-term use of eye drops is also said to increase the risk of developing cataracts.
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radiation
The lens of the eye is susceptible to radiation, and it has been reported that healthcare workers who perform radiation-related tasks have a higher risk of developing cataracts than those who do not.
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Genetics
It's not yet well understood whether it's hereditary. However, there's a possibility that a predisposition to developing cataracts is inherited.
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smoking
It is said that people who smoke 20 or more cigarettes a day are 2 to 3 times more likely to develop cataracts than non-smokers.
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others
It can also be caused by trauma, eye diseases other than cataracts such as uveitis, or atopic dermatitis.
![Types of Cataracts]()
Types of Cataracts
Cataracts can be classified into the following types based on their cause:
![cause]()
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Age-related cataracts
This is the most common type of cataract. It is thought to be caused by the denaturation of proteins in the lens due to aging.
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congenital cataract
This is a type of cataract where the lens of the eye is cloudy from birth. It is thought to be caused by genetics or infection with the rubella virus during fetal development.
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Major cataracts associated with systemic diseases
- ■ Diabetic cataract
This type of cataract develops as a complication of diabetes. Opacification of the cortex and posterior capsule is frequently observed.
- ■ Atopic cataracts
This is a type of cataract that occurs in conjunction with atopic dermatitis. It is thought that rubbing the eyes due to itchiness may be a contributing factor. The characteristic symptom is clouding around the anterior and posterior capsules, and the entire lens may become cloudy relatively quickly.
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traumatic cataract
Cataracts develop when the lens of the eye is damaged after an injury or other trauma. They can also occur due to strong impacts, such as being hit in the eye by a ball or being slapped in the eye.
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Other types of cataracts
Cataracts can occur in conjunction with other eye diseases, such as uveitis. Additionally, cataracts can be caused by medications.
![Cataract examination and treatment]()
Cataract examination and treatment
Main testing methods
In ophthalmology, the following tests are performed to diagnose cataracts.
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Vision test
This test checks for vision loss due to cataracts. We measure your vision both with and without corrective lenses (glasses or contact lenses). If your vision does not improve even with corrective lenses, you may have cataracts.
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Refractometer
This device measures the refraction of light entering the eye. If the lens is cloudy, an abnormality in refraction will be observed.
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Slit-lamp microscopy
By shining a narrow beam of light into the eye, the inside of the eyeball is examined in detail under a microscope. This allows us to determine where and to what extent there is clouding.
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Intraocular pressure test
This test measures the internal pressure of the eyeball. It checks for other co-existing conditions such as glaucoma.
Main treatments
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Use eye drops
Even if an examination reveals cataracts, if there are no significant problems in daily life, the patient may be monitored while using eye drops. The purpose of the eye drops is to slow the progression of the disease.
As cataracts progress, glaucoma may also develop, so it's a good idea to have regular eye examinations at an ophthalmologist.
Currently, there are two types of eye drops approved in Japan.
- ■ Pirenoxine eye drops (Trade names: Karyuni, Catalin K)
The goal is to prevent the denaturation of proteins that cause clouding of the lens, thereby suppressing the progression of cataracts.
*There are reports that it has shown a slowing effect on progression in early-stage cortical cataracts in people under 60 years of age.
- ■ Glutathione eye drops (brand name: Tathione)
It has antioxidant properties and inhibits oxidation.
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surgery
Cataract surgery has advanced significantly and is now much safer.
Surgery not only makes your vision brighter and clearer, but by inserting an intraocular lens during the procedure, it can also improve nearsightedness, astigmatism, and farsightedness.
In cases of cataracts occurring in conjunction with other illnesses, treatment of the underlying condition may be prioritized.
The surgical procedure will proceed as follows:
Once surgery is decided upon, pre-operative tests are performed to select the type of intraocular lens to be implanted.
On the day of the surgery, the area around the eye and the surface of the eye will be disinfected, and eye drops will be used to dilate the pupil.
The surgery will be performed under local anesthesia. After removing the cloudiness from the lens, the selected intraocular lens will be inserted. Because local anesthesia is used, you will not feel any pain and you will be able to talk to the doctor. The surgery will be completed in 20 to 30 minutes.
After surgery, if it was an outpatient procedure, you will rest at the hospital for a while before going home. If you were hospitalized, you will rest in your hospital room.
Before and after surgery, sterilizing eye drops will be prescribed to prevent bacteria from multiplying in the eye.
- ■ Cataract surgery methods
Cataract surgery involves removing the cloudy lens, leaving the capsule intact, and replacing it with an intraocular lens. Currently, the most common surgical method is "phacoemulsification," which involves making a small incision of a few millimeters and using ultrasound to break up and aspirate the contents of the lens.
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![Cataract surgery method (phacoemulsification)]()
What is an intraocular lens?
Intraocular lenses (IOLs) play the role of focusing the eye, replacing the removed natural lens. There are two main types: monofocal and multifocal. Currently, lenses made of soft acrylic material are the most common.
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Monofocal intraocular lens
This is a typical intraocular lens that focuses on a single point. You can choose where to focus based on your lifestyle. The key is to choose an intraocular lens that won't drastically change your current lifestyle. For example, if you often wear glasses and do close-up work, an intraocular lens that focuses about 30 cm from your eye would be convenient. In modern life, a lens that focuses at a distance where you can operate a smartphone without glasses might be more suitable. However, if you have an intraocular lens that focuses on near vision, you will need glasses for nearsightedness when looking at distant objects. If you want to see distant objects, you can choose an intraocular lens that focuses on a distant point. In that case, you will need reading glasses when looking at close objects.
Surgery to implant a monofocal intraocular lens is covered by health insurance.
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Multifocal intraocular lenses
These intraocular lenses, like bifocal glasses, focus on two distances: far and near. Lenses that focus at three distances and those with extended depth of focus (EDOF) are also available. However, currently, surgery for these lenses is generally not covered by health insurance. (Some lenses are covered by insurance.)
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Astigmatism-correcting intraocular lenses (toric intraocular lenses)
These lenses correct astigmatism. Both monofocal toric intraocular lenses and multifocal toric intraocular lenses are available. The surgery is covered by health insurance.
Post-operative precautions and things to understand
- After surgery, continue to follow your doctor's instructions regarding follow-up appointments and administration of eye drops.
- You may experience symptoms such as a foreign body sensation or redness in the eye. These usually subside over time.
- For the first week after surgery, refrain from washing your face and hair, and only wipe them with a towel. You can wash your face and hair once you are given permission, but be careful not to rub your eyes or get shampoo or other products in your eyes.
- Please avoid drinking alcohol and smoking for one week after surgery.
- Desk work, housework, and light walks are possible from the day after surgery, but you should avoid strenuous exercise and anything that puts pressure on your eyes, such as carrying heavy objects, for one month.
- Post-operative vision varies from person to person; some people see clearly immediately, while others experience a gradual improvement. Some may experience symptoms such as a bluish tint to their vision (cyanopsia), increased sensitivity to light at night (glare), or halos around lights, but these usually subside over time.
- Seeing black spots floating in your field of vision (floaters) is often due to aging, but it could also be a sign of another illness, so it's best to get checked out just in case.
- Some time after surgery, blurred vision or difficulty seeing may reappear. This is called "posterior capsule opacification," and it occurs when the remaining capsule becomes cloudy. It can be removed in an outpatient setting using a laser.
![Cataract prevention methods]()
Cataract prevention methods
Since aging is the leading cause of cataracts, it is impossible to completely prevent them. However, it is possible to slow their progression by avoiding factors that increase the risk of developing them.
It's important to continuously monitor your symptoms, as cataracts can progress and potentially lead to other conditions like glaucoma. Regular eye examinations are recommended.
- no smoking
- People with diabetes need to keep their blood sugar levels low.
- To combat reactive oxygen species that damage cells, ensure you get plenty of antioxidant vitamins from vegetables and fruits. Alternatively, take vitamin supplements or lutein.
- Use sunglasses with UV-blocking lenses outdoors to protect yourself from ultraviolet rays.
- Be careful of eye injuries.
Cataract self-check
It's also helpful to check occasionally to see if you've developed cataracts without realizing it.
If you answered yes to two or three or more of the following questions, you may have cataracts.
- I have difficulty seeing and feel inconvenienced.
- When looking with one eye at a time, there is a significant difference in how the left and right eyes see.
- Being in a bright place or in strong sunlight can feel very dazzling.
- My vision is blurry and easily fatigued (it looks like it's foggy).
- My vision feels dim.
- When looking with one eye, objects appear doubled or tripled.
- I can see things up close more easily (I no longer need reading glasses).
- Even after changing my glasses, I still couldn't see well (I couldn't get new glasses made).
- Unable to renew driver's license (for license holders only)
- There are some abnormalities in my vision, but I don't have any eye pain or redness.
- You are 50 years of age or older.
(Quoted from the Japanese Society of Cataract Research website: Cataract self-diagnosis test)
![Common concerns regarding cataract surgery (Q&A)]()
Cataract surgery
Frequently Asked Questions (Q&A)
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When is the best time to have cataract surgery?
If you experience inconveniences such as decreased vision interfering with housework or work, difficulty going outdoors due to glare, double or triple vision making driving impossible, or inability to renew your driver's license, you should consider surgery.
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Is cataract surgery a painful procedure?
Since local anesthesia is used, there is almost no pain. You can see the light during the surgery, but you cannot see the movement of the instruments.
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Why shouldn't cataracts be left untreated?
As vision gradually worsens, work, household chores, and driving become difficult, leading to a decline in quality of life (QOL). Furthermore, there is a risk of complications and injuries due to impaired vision. Ignoring this condition is not advisable.
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Is hospitalization required for the surgery?
If you are physically fit, can easily commute to the hospital, and have no other illnesses, hospitalization is usually unnecessary. However, if you are elderly, have other illnesses, are worried about post-operative care, or have difficulty commuting to the hospital, hospitalization is recommended for peace of mind.
Supervised by: Dr. Masayoshi Kajita, Director of Kajita Eye Clinic
After graduating from Fukushima Medical University in 1983, he worked as a researcher at the University of California, Berkeley, before opening Kajita Ophthalmology Clinic in 2003. From 2018 to 2021, he served as a Clinical Professor at Tokyo Medical and Dental University School of Medicine. In 2022, he was awarded Honorary Membership by the Japan Contact Lens Society, and in 2023, Honorary Membership by the Japanese Society of Ophthalmic Optics. He currently serves as a councilor of the Japan Ophthalmological Society and a member of the drafting committee for the Japanese Medical Optics JIS standards.