Blurred vision: Symptoms, causes, treatment, when to seek medical attention

 Key takeaways

• Blurred vision is an eye defect where the patient can't see things clearly. It is a medical condition on its own and also a symptom of other eye conditions. 
• Blurred vision can happen to people of all ages. Pay attention to your children when they act strangely or complain about their eyes. 
• An eye doctor (an ophthalmologist) is the best person to talk to when you notice a change in your vision. They'll diagnose, test, treat, and help manage your condition.

According to a World Health Organization report in 2019, at least 2.2 billion people have a vision impairment or blindness, of whom at least 1 billion have a vision impairment that could have been prevented or has yet to be addressed.

Blurred vision occurs when your vision changes, and you can no longer see things clearly—images are neither crisp nor sharp.

Blurred vision can happen to one eye only or both eyes. It can also affect a part of the eye, or the whole eye(s). If left untreated, your vision can worsen, leading to more complex eye defects.

Blurred vision is different from cloudy vision. Images appear out-of-focus in the former, while there is a film or cloudy layer in front of the eyes in the latter. An easy way to differentiate the two is that blurry vision becomes clear when you squint. Squinting doesn’t affect cloudy vision.

 Symptoms of blurred vision

Symptoms of blurred vision include:

• Headache
• Tunnel vision
• Loss of vision
• Light sensitivity

Blurred vision can also be a symptom of other conditions like 

• Migraine 
• Stroke 
• Diabetes 
• Low blood sugar 
• Brain tumor, and 
• Pre-eclampsia

 Causes of blurred vision

Blurred vision has many causes. They are categorized into two, namely:

1. Refractive errors
2. Non-refractive errors

 Refractive errors

Refractive errors are the most common type of vision problem. These errors depend on the eye's refractive system, which involves the ability of the lens and cornea to focus images on the retina.

Refractive errors happen when images do not form correctly on the retina, a light-sensitive thin layer of tissue at the back of the eye. The retina receives light/images from the lens and converts them into neural signals. It then sends them to the brain for interpretation.

Refractive errors include: 

• Myopia (shortsightedness): Myopia occurs when the eyes can only see things close to them. Distant images look blurred and unclear. Myopia happens when images form in front of the retina instead of on the retina. Light/images do not reach the retina for proper conversion and interpretation. Contact lenses can correct myopia.
• Hyperopia (long-sightedness): Hyperopia is the opposite of myopia. It occurs when the eyes can only see objects far away from them. Close images, like the texts of a novel, appear blurred. This happens when images form behind the retina instead of on the retina. A contact lens also corrects this condition.
• Presbyopia: Presbyopia happens with age. As you get older, the eye muscle fibers become weak due to prolonged use. Using a reading glass corrects and manages the condition.
• Astigmatism: Astigmatism occurs when the cornea or lens changes in shape. The change in shape bends the light rays so that the images do not form on the retina. The cause is unknown. But some people are born with astigmatism. Others develop it during childhood or young adulthood. Contact lenses also correct this error.
• Other refractive errors include anisometropia, aphakia, and high-order aberrations.

 Non-refractive errors

These errors are independent of the eye’s refractive system. They are not directly linked to the image-forming ability of the lens and cornea on the retina. Defects in other parts of the eye, failing health, or the presence of external bodies are among the causes. The external bodies could be microorganisms and allergens. 

They include:

• Uveitis (Inflammation of the uvea - the middle tissue of the eye) 
• Cataract (formation of a cloudy area in front of the lens) 
• Dry eyes (your eyes do not produce enough tears for lubrication) 
• Amblyopia (decrease in vision, usually in one eye, from early childhood) 
• Strabismus (both eyes do not look at the same place at the same time) 
• Optic neuritis (Inflammation of the optic nerves) 
• Conjunctivitis (Inflammation of the conjunctiva - the transparent membrane of the eyelid and eyeball) 
• Color blindness (inability to differentiate colors) 
• Retinoblastoma (cancer of the retina)
• Diabetic retinopathy (High sugar level causes damage to the blood vessels of the retina) 
• Age-related Macular Degeneration (with age, the retina weakens, which affects central vision) 
• Eye infections (Presence of bacteria in the eye)
• Glaucoma (Increase in the intraocular pressure of the eye fluid)

 Can blurred vision occur in children?

At birth, the human eye is not fully developed. It is about 70% the length/size of a grown adult eye. However, it undergoes massive growth and development within the first two years of life.

Blurred vision occurs in children. But because most kids do not express themselves properly, they experience unclear visions without anyone knowing. Parents who are not watchful may miss out on tiny details that could indicate their child has blurred vision. These details could help to prevent the problem from the outset. 

Refractive and non-refractive errors also cause blurred vision in kids. Refractive errors are present in almost 20% of children. 

Parents should look out for some signs and behaviors in their kids. This can help them detect when their child has blurred vision.

The signs include:

• Constant rolling of the eyeballs (problem with eye muscle control)
• Tears always coming out of the eyes (a sign of blocked tear ducts) 
• Extreme sensitivity to light (increased pressure in the eye)
• The appearance of a white pupil (eye cancer)
• Red eyelids (a sign of infection)

Some of the behaviors that may indicate blurred vision in your child include:

• Squinting
• Tilting the head
• Sitting too close to the TV
• Constantly rubbing the eyes
• Eye pain or severe headache
• Difficulty concentrating on schoolwork
• Writing or reading books too close to the eyes

 Diagnosis

First, the doctor will ask you questions to better understand your condition, such as questions about when you first noticed the blurred vision, and what makes it better or worse. 

For further diagnosis, the ophthalmologist runs some tests depending on your answers. 

These tests are classified into eye tests or blood tests

The eye tests include:

• Ophthalmoscopy
• Refraction test
• Slit lamp Examination
• Tonometry

 Ophthalmoscopy (also called funduscopy)

It’s an examination of organs at the back part of the eye, including the retina, choroid, blood vessels, and optic disc.

Ophthalmoscopy is 90% to 95% accurate. It can detect the early stages and effects of many serious diseases.

 Refractive test

This test checks for refractive errors. It's the most common type of eye test.

The patient sits in a chair with a device called a refractor attached to it. The refractor contains different contact lenses. The patient looks through the refractor to focus on an eye chart 20 feet away. The doctor tests each eye separately. 

Reading out the writings on the chart tells the doctor whether you have any refractive error. 

 Tonometry

This is a measure of the eye’s intraocular pressure using a tonometer. Intraocular pressure is the measurement of the fluid pressure in the eye. The fluid preserves vision and prevents eye conditions like glaucoma and ocular hypertension. 

According to a 2022 study, the normal intraocular pressure range is 10–21 millimeters of mercury.

 Slit lamp examination

It involves using a microscope and a bright light called a slit lamp to check for abnormalities at the back of the eye. It is similar to and could be a type of ophthalmoscopy.

 Blood tests

Blood tests check for the presence of microorganisms (bacteria) in the blood vessels of the eye. If present, these bacteria can cause infections.

The eye doctor also uses a blood test to obtain your white blood cell count. This also checks for infections in the eyes. 

 Treatment of blurred vision

Treatments for blurred vision vary depending on the cause. The treatment options can be grouped into:

• Use of eyeglasses or contact lenses
• Use of medications
• Use of eye drops
• Surgery

Eyeglasses or contact lenses are efficient at managing refractive errors. They correct eye defects by ensuring the images form correctly on the retina.

The use of eye drops and medications is effective for eye infections, conjunctivitis, and uveitis. 

In extreme cases, the doctor performs (laser) surgery on the problematic eye, or both eyes. These include cases of glaucoma, cataracts, and diabetic retinopathy. 

Surgery is usually the last line of treatment for blurred vision.

 Tips for preventing blurred vision

There are natural ways to prevent blurred vision. They include precautions to help the eye remain in optimal health. Some of them are:

• Give your eyes a rest at intervals. Use the 20-20-20 rule if you stare at the computer or phone screen all day. The rule suggests taking a 20-second break and looking at an object 20 feet away after staring at a  screen for 20 minutes. Although there’s no concrete evidence to support this, you may feel relief when you practice it.
• Avoid foods that contain refined sugar. Sugar causes diabetes, which can lead to diabetic retinopathy. 
• Take foods that promote eye functions: fruits and vegetables. Carrots, spinach, broccoli, omega-3 fatty acids, and yeast are good examples. 
• Manage your weight to avoid obesity. Obesity can also cause diabetic retinopathy. 
• Use protective sunglasses
• Improve the quality of the air you're exposed to. 
• Wash your hands before rubbing them in your eyes
• Drink enough water to stay hydrated. Dehydration isn't good for the fluid pressure in the eye. 
• Avoid substances you are allergic to, like dust, that can cause conjunctivitis.
• Go for regular eye check-ups. Once a year or once every 2 years is the recommended frequency.
• See a doctor once you notice any changes in your vision

 When to seek medical attention

Blurred vision can develop suddenly or over time and may be caused by a chronic medical condition. Hence, it is important to take precautions to prevent it from getting worse.

If the blurred vision happens suddenly, seek urgent medical attention. It may come with all or any of these symptoms

• Dizziness
• Headache
• Loss of vision
• Pain in the eyes, and
• Numbness on one side of the body

Also, seek medical attention if you experience any of these: 

• Stroke 
• Head injury, and 
• Carbon monoxide poisoning

 Wrap up

Blurred vision is one of today's leading eye problems. It is a problem on its own or a sign of a much bigger problem. 

Most of its causes, like the distortion of the cornea, are beyond your control. The most you can do is look out for the symptoms and avoid any form of injury to the eye. 

Kids are not left out; blurred vision affects them too. Treatment options cut across all age brackets. The faster you visit your eye doctor, the better your chances of avoiding blindness.