Having a clear, sharp vision is important to help us see a clear view of the world. From watching near and far objects to making sure we don't miss a step and fall, our eyes are constantly moving to give the brain new information about our surroundings. But, when your vision becomes poor and blurry and you can't see objects clearly, you may be having blurred vision. In this article, we will discuss the causes, symptoms, diagnosis and treatment of blurred vision.
What Is Blurred Vision?
Blurred vision refers to a decrease in the sharpness of vision, which makes it difficult to see fine details. A problem in any part of the eye, such as the cornea, retina or optic nerve, can lead to blurred vision. Blurred vision can also occur due to certain eye diseases or it can be a symptom of numerous medical conditions such as diabetes or stroke ,. Medications such as chloroquine, a drug which is used for the treatment of malaria has side effects such as temporary blurring of vision .
Depending on the cause, blurred vision can occur in one eye or both the eyes.
What Causes Blurred Vision?
There can be many causes for blurred vision, these include the following:
• Astigmatism - According to the American Optometric Association, astigmatism is a common eye condition that causes blurred vision. It occurs due to the irregularly curve shaped cornea or lens inside the eye, which prevents light from focusing properly on the retina (the light-sensitive surface at the back of the eye), resulting in blurry or distorted vision .
Astigmatism frequently occurs with other eye conditions such as myopia (nearsightedness) and hyperopia (farsightedness). And a combination of these eye conditions is called refractive errors because they affect how the eyes bend or refract light.
• Myopia (near-sightedness) - It is a common eye condition in which you can see close objects clearly, but far away objects look blurry. People with myopia have difficulty in seeing things clearly while watching television or driving often causing blurred vision .
• Presbyopia - It is an age-related vision disability that makes it difficult to focus on near objects, causing blurry vision.
• Hyperopia (farsightedness) - It is another common eye condition, in which you can see distant objects clearly, but close objects look blurry.
• Cataract - It is a cloudy area that covers the clear lens of the eye. Normally, the lens (located behind the iris) focuses light on the retina, which transports the image through the optic nerve to the brain. But, if the lens is clouded by a cataract, it interferes with the light reaching the retina at the back of the eye, resulting in blurred or hazy vision .
• Age-related macular degeneration - This disorder affects the macula, which is located near the centre of the retina responsible for sharp central vision. When age-related macular degeneration becomes advanced, the central vision deteriorates causing blurriness and vision loss . Dry age-related macular degeneration is when the vision loss progresses slowly and the wet age-related macular degeneration is the rapid and severe form of vision loss.
• Glaucoma - It is a group of eye conditions that damage the optic nerve. A study was conducted in 99 patients diagnosed with various types and stages of glaucoma. They filled out a questionnaire which showed that all the patients, including patients with early or moderate glaucoma experienced needing more light and blurry vision, which was reported as the most common symptoms .
• Iritis -Iritis, also known as acute anterior uveitis, is the inflammation of the iris (coloured part of the eye) and it also affects the front part of the eye between the cornea and the iris (anterior chamber). Chronic and posterior uveitis causes symptoms like blurred vision .
• Retinal detachment -It occurs when your retina tears away from the back of your eye and there is a reduction in the blood supply. According to a study published in the Community Eye Health Journal, the common symptoms of retinal detachment are blurred vision or sudden, painless loss of vision in the affected eye. Some patients with partial retinal detachment will experience field loss (vision loss in one part of the visual field) .
• Retinal vein occlusion - It is the second most common retinal vascular disease that causes vision loss in older patients. There are two types of retinal vein occlusion: branch retinal vein occlusion (BRVO) and central retinal vein occlusion (CRVO). Patients with central retinal vein occlusion often experience blurry vision in one eye that happens suddenly, which will be painless .
• Hyphema - It is characterised by the accumulation of a large pool of blood in the anterior chamber that occurs after sustaining trauma to the eye. Patients experience a sudden decrease or loss of vision. Vision loss depends on the level of hyphema; microhyphema patients may have normal vision or blurred vision (the blood pooling can prevent the light from reaching the retina which causes blurred vision at times) and patients with full hyphema may almost have complete vision loss .
• Diabetes mellitus - People with diabetes mellitus can experience changes in their vision. Studies have shown that diabetes mellitus patients often have symptoms of blurred vision during hyperglycemia (high blood sugar levels), which could be a result of transient refractive alterations due to changes in the lens or retina .
• Stroke - After a stroke, central vision problems are common and the symptoms include blurred vision among others. A study was conducted among 915 patients aged 69 years. Out of them 479 patients had visual field loss, 51 patients experienced no visual symptoms, half of the symptomatic patients had only visual field loss and other half experienced blurred vision, difficulty in reading, diplopia, and perceptual difficulties .
• Brain tumour - It is the growth of abnormal cells in the brain. Blurred vision is a common symptom of brain tumour.
• Multiple sclerosis - It is a disease that attacks the central nervous system affecting the optic nerves, brain and spinal cord. About one quarter of patients with multiple sclerosis diagnosed with unilateral or bilateral INO (an eye movement disorder) tend to have blurred vision and other symptoms .
• Myasthenia gravis - It is a chronic neuromuscular disease that causes muscle weakness in the face and eyes. Ocular myasthenia gravis affects the eye muscles and eyelids, causing common symptoms like blurred vision and drooping of the eyelids.
• Diabetic retinopathy - It is a complication of diabetes that affects the eyes. Diabetic retinopathy occurs when there is a damage of the blood vessels in the retina. The symptoms are blurred vision, poor night vision and impairment of colour vision among others.
• Migraine - Migraine is a common headache disorder that causes severe headaches that may come first or accompany by different visual symptoms. Vision problems caused by migraine could range from blurry or foggy vision, vision loss in one or both eyes and persistence of images .
• Corneal abrasion - Corneal abrasion occurs when small objects enter your eye and may cause damage on the surface of the cornea. The cornea has numerous nerve fibres, which are sensitive to touch and injury, so when a foreign object like a grain of sand or a small insect gets in your eye, it starts watering and hurts. As a result, you will start experiencing blurry vision and sensitivity to light .
• Allergic conjunctivitis - Allergic conjunctivitis is of three types: acute, seasonal and perennial. Acute - infections or GPC (giant papillary conjunctivitis), seasonal - hay fever conjunctivitis or vernal form and perennial- atopic forms. The symptoms of seasonal conjunctivitis are usually blurred vision, pain, etc.; for perennial conjunctivitis the symptoms include blurry vision, pain and photophobia and patients with giant papillary conjunctivitis report symptoms like worsening pain and blurred vision .
• Digital eye strain (computer vision syndrome) - According to the American Optometric Association, digital eye strain causes many eye and vision-related problems and its most commonly seen in people who use cell phone, computer and tablet for a prolonged period of time. One of the most common symptoms of digital eye strain is blurred vision.
• Bacterial keratitis -It is an infection of the cornea caused by bacteria like S. aureus, coagulase-negative staphylococci, S. pneumoniae and pseudomonas aeruginosa. Pseudomonas aeruginosa is the most common type of bacteria that affects contact lens wearers. Patients with bacterial keratitis often have symptoms like blurred vision, photophobia and pain .
• Medications - Certain medications can have adverse effects on the eye and cause blurry vision. Erectile dysfunction drugs have been shown to cause blurry vision and increased light sensitivity . Non-steroidal anti-inflammatory drugs like indomethacin when used long-term can cause blurred vision . And chloroquine, an antimalarial drug can cause blurry vision as well.
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Symptoms Of Blurred Vision
Depending on the cause, blurred vision may or may not accompany other symptoms, these include:
• Light sensitivity
• Eye pain
• Floaters or spots in front of your eyes
• Eye strain and fatigue
• Double vision
• Dryness and soreness of the eyes
• Eye discharge
• Signs of trauma to the eye
• Headache and nausea
• White pupil
When To See A Doctor
You should immediately seek medical attention if you have sudden blurry vision and you have any of these symptoms following blurred vision, such as severe headache, difficulty in speaking, trouble in seeing, facial drooping, lack of coordination and weakness in the face, leg or arms muscles.
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Diagnosis Of Blurred Vision
The doctor will diagnose the cause of your blurred vision by asking questions such as 'When did you first start experiencing blurred vision?', 'What are the other symptoms you have with blurred vision?' and other such questions such as asking about your medical history and family history of eye conditions. This will help the doctor to understand what exactly the patient is feeling because most patients may describe blurred vision as missing a step or inability to see clearly or read a book.
The doctor may further perform a visual acuity test, a physical eye examination that checks how well you can see the details of a letter or symbol from a specific distance. Ideally, visual acuity test is done either by using a standard printed Snellen eye chart with the patient standing 20 feet (six metres) away or using an eye chart held about 14 inches (35 cm) away. Each eye is tested while the other eye is covered with a solid object. If a patient wears distance spectacles they should be worn during testing. For patients aged above 40 years who is wearing bifocal spectacles, the eye chart should be used at 14 inches.
Then, the patient is asked to read small and large letters in the eye chart. If the patient can't read all the letters even at the closest distance, the examiner then asks the patient to do finger counting to see whether the patient can count them accurately. If finger counting isn't possible, the examiner tests whether the patient can see hand motions. If this doesn't work out, a light is shined into the eye to see whether the patient can see the light.
If the patient doesn't have their glasses, a pinhole is held close to the eye, which is an efficient way to diagnose refractive errors.
For young, challenged or illiterate patients, the Snellen chart is used with pictures or other symbols on it .
Other eye tests such as slit lamp examination and ophthalmoscopy are done.
A slit lamp examination is done by using a microscope which has a bright light. The ophthalmologist will first dilate your pupilswith dilating drops. And then the doctor will take a closer look at the different structures in the front and inside of your eye. It will help in determining the exact cause of blurred vision.
Ophthalmoscopy is another eye test that is done by using an ophthalmoscope to look into the back of your eyes. With it the doctor checks the retina, the optic nerve and blood vessels. This eye test helps the doctor check for diseases and other eye problems.
Treatment Of Blurred Vision
Depending on the cause of blurred vision, the treatment is done. We've listed down a few:
• Astigmatism - A comprehensive eye exam can help diagnose astigmatism and it can be treated with the help of eye glasses, contact lenses, orthokeratology and laser surgery.
• Age-related macular degeneration - A complete eye examination and other diagnostic tests will help in the diagnosis of age-related macular degeneration. The treatment for dry age-related macular degeneration includes nutrition therapy and supplements and for wet age-related macular degeneration includes anti-VEGF (vascular endothelial growth factor) therapy.
• Glaucoma - A thorough eye exam is done to diagnose glaucoma. Eye drops and laser surgery are used for the treatment of glaucoma.
• Stroke - Depending on the type of stroke, the treatment is done.
• Migraine - Medications and certain home remedies can bring relief from migraine headache.
• Cataract - A complete eye examination is done to diagnose cataract. And cataracts can be removed with the help of cataract surgery.
• Diabetes - Depending on the type of diabetes the treatment is done and this includes a healthy diet, blood sugar monitoring, physical activity, insulin and oral medications.
• Corneal abrasion - Eye drops or ointment can help treat corneal abrasion.
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Prevention Of Blurred Vision
• Go for regular eye checkups
• Wear sunglasses to protect your eyes from the UV rays.
• Eat foods rich in vitamin C, vitamin E, beta-carotene, zinc, lutein, zeaxanthin and omega 3 fatty acids as these nutrients reduce the risk of age-related eye diseases .
• Use safety eyewear if you are doing hazardous work.
• Avoid spending long hours on your computer, tablets or cell phones.
• Stop smoking 
• Control your blood sugar levels.
Q. What can cause sudden blurred vision?
A. Retinal detachment, stroke, macular degeneration and eye injury are the top serious causes of sudden blurred vision.
Q. Is sudden blurred vision an emergency?
A. Seek medical care immediately, if you experience a sudden loss of sharp vision.
Q. Can blurry vision go away?
A. Temporary blurry vision can go away with the help of eyeglasses, however, if it's a symptom of an underlying condition consult your doctor.
Q. Is blurry vision a symptom of dehydration?
A. Dehydration causes eye strain which can lead to symptoms like blurry vision.
Q. Can lack of sleep cause blurred vision?
A. Lack of sleep can cause dry eyes and this can cause light sensitivity, pain or even blurry vision.
Q. Can phones cause blurry vision?
A. Yes, phones and other electronic devices can cause blurry vision.
Q. Why is my vision suddenly cloudy in one eye?
A. Cloudy vision is usually a symptom of cataract, an eye condition that causes a cloudy area in the eye lens.
Q. Can too much screen time make eyes blurry?
A. Yes, too much screen time can make your eyes blurry.
Q. How can I stop my eyes from being blurry?
A. Ensure that you don't strain your eyes too much, get plenty of sleep, drink plenty of water and eat foods that will help keep your eyesight healthy.