Blurred Vision; Causes, Symptoms, Diagnosis, Treatment

Blurred vision means, lack of sharpness of vision with, as a result, the inability to see fine detail. Blurred vision can occur when a person who wears corrective lens is without them. Blurred vision can also be an important clue to eye disease . It  may result from abnormalities such as nearsightedness, farsightedness, presbyopia, or astigmatism that can be improved with corrective lenses (eyeglasses) or it may signal the presence of eye disease.

Types of Blurred Vision

• General blurred vision – inability to see an image clearly – it’s important to establish whether the blurring occurs more at close distance, or when objects are further away.
• Decreased peripheral vision – blurring may occur around the sides of a vision, leading patients to bump into items or have trouble parking.
• Alteration of an image – sometimes blurring can cause images to appear smaller or larger, or even distorted.
• Diplopia – this is when blurred vision causes double vision, when the eye is unable to focus on an item or image.
• Dry eye blurring – this occurs when a dry eye is unable to focus on an item, leading to blurring and discomfort that can be temporarily reduced by blinking.

Causes of Blurred Vision

There are many causes of blurred vision:

• Use of atropine or other anticholinergics
• Presbyopia – Difficulty focusing on objects that are close. Common in the elderly. (Accommodation tends to decrease with age.)
• Cataracts – Cloudiness over the eye’s lens, causing poor night-time vision, halos around lights, and sensitivity to glare. Daytime vision is eventually affected. Common in the elderly.
• Glaucoma – Increased pressure in the eye, causing poor night vision, blind spots, and loss of vision to either side. A major cause of blindness. Glaucoma can happen gradually or suddenly if sudden, it is a medical emergency.
• Diabetes – Poorly controlled blood sugar can lead to temporary swelling of the lens of the eye, resulting in blurred vision. While it resolves if blood sugar control is reestablished, it is believed repeated occurrences promote the formation of cataracts (which are not temporary).
• Diabetic retinopathy – This complication of diabetes can lead to bleeding into the retina. Another common cause of blindness.
• Hypervitaminosis A – Excess consumption of vitamin A can cause blurred vision.
• Macular degeneration – of central vision, blurred vision (especially while reading), distorted vision (like seeing wavy lines), and colors appearing faded. The most common cause of blindness in people over age 60.
• Eye infection, inflammation, or injury.
• Sjögren’s syndrome, a chronic autoimmune inflammatory disease that destroys moisture producing glands, including lacrimal (tear)
• Floaters – Tiny particles drifting across the eye. Although often brief and harmless, they may be a sign of retinal detachment.
• Retinal detachment – Symptoms include floaters, flashes of light across your visual field, or a sensation of a shade or curtain hanging on one side of your visual field.
• Optic neuritis – Inflammation of the optic nerve from infection or multiple sclerosis. You may have pain when you move your eye or touch it through the eyelid.
• Stroke or transient ischemic attack
• Brain tumor
• Toxocara – A parasitic roundworm that can cause blurred vision
• Bleeding into the eye
• Temporal arteritis – Inflammation of an artery in the brain that supplies blood to the optic nerve.
• Macular degeneration and macular holes – The macula is the central part of the retina at the back of your eye. It allows you to see detail, colour, and things directly in front of you. Macular degeneration and macular holes damage the macula, causing central vision to become blurred.
• Retinal detachment – A detached retina is a serious medical emergency that can cause sudden blurred vision. It may also cause a number of other symptoms, such as flashes and floaters, and sudden blindness.
• Retinal vein occlusion – If the blood vessels that feed the retina (the focusing surface at the back of the eye) become blocked, it is known as a retinal vein occlusion. This can cause sudden blurred vision, and also sudden blindness.
• Pterygium – A pterygium is a benign growth that occurs on the surface of the eye. Sometimes, a pterygium can grow onto the cornea. If this occurs, it can alter the shape of the cornea, causing blurred vision.
• Vitreous haemorrhage – If blood leaks into the vitreous ‘gel’ that fills your eye, it can block the light that enters your eye, causing blurred vision. Vitreous haemorrhage can be caused by trauma or injury, or it may be a result of an eye condition, such as diabetic retinopathy.
• Migraine headaches—Spots of light, halos, or zigzag patterns are common symptoms prior to the start of the headache. A retinal migraine is when you have only visual symptoms without a headache.
• Myopia – Blurred vision may be a systemic sign of local anaesthetic toxicity
• Reduced blinking – Lid closure that occurs too infrequently often leads to irregularities of the tear film due to prolonged evaporation, thus resulting in disruptions in visual perception.
• Carbon monoxide poisoning – Reduced oxygen delivery can effect many areas of the body including vision. Other symptoms caused by CO include vertigo, hallucination and sensitivity to light.
• Sometimes medications cause blurry vision. There are many prescribed drugs, over-the-counter drugs, and supplements that can cause this problem, including:
  • Certain anticholinergics
  • Some antihypertensives
  • Some asychotropic drugs
  • Oral contraceptivesheart
  • Cortisone
  • Some antidepressants
  • Some medications

Symptoms of Blurred Vision

In some cases blurred vision may be accompanied by additional symptoms in one or both eyes. There is usually some other underlying cause. Symptoms can include:

• Photophobia (sensitivity to light)
• Floaters or spots
• Eye pain
• Discharge from eye
• Loss of peripheral vision
• Loss of central vision
• Dry eyes
• Itchy eyes
• Increased tear production
• Poor night vision
• Red bloodshot eyes
• Bleeding from eye
• Poor near vision

Diagnosis of Blurred Vision

• Diabetes – Fingerstick or random glucose measurement

• Poorly controlled hypertension and acute hypertensive retinopathy (hemorrhages, exudates, or papilledema) – Urinalysis, renal function testing, BP monitoring, and ECG

• HIV/AIDS and retinal abnormalities – HIV serology and CD4+ count

• SLE and retinal abnormality: Antinuclear antibodies, ESR, and CBC

• Waldenström macroglobulinemia, multiple myeloma, or sickle cell anemia – CBC with differential count and other testing (eg, serum protein electrophoresis) as clinically indicated

A refraction test – this test is designed to measure the prescription you could need for contact lenses or eyeglasses. A device known as a refractor or phoroptor will be used, and by looking through the device, you will be asked to focus on a Snellen eye chart. As your doctor asks for you to read the chart, they will also put lenses of different strengths in and out of your view to determine whether you are in need of a prescription.

Slit-lamp examination – Your eye doctor will have you place your chin on a resting pad at first. Then he or she will use a machine to focus on different structures in the front and back of the eye. This helps them see if the eye is functioning properly or not. When necessary, the doctor may adjust the light and the level of magnification in order to see better.

Tonometry – Using the glowing eye drops mentioned above, your eye doctor will measure your eye pressure. This is done with a device called a tonometer, which is attached to the slit-lamp. You will be asked to keep your eyes wide open and to breathe normally.