Several distinct patterns of visual disturbance fall into the general category of blurred vision. Sometimes everything a person sees seems fuzzy, as if petroleum jelly has been smeared over the eyes or glasses. Sometimes just the edges of objects within the field of vision seem blurred. In other cases, objects are clear but flashing lights or floating spots obscure them.
The most common causes of blurred vision are near- or farsightedness, which can be corrected with glasses or contact lenses. This kind of blurring develops slowly, over a period of months or years. Near- and farsighteness are benign conditions that an eye doctor can easily remedy.
In most other cases, blurred vision indicates the presence of an eye disorder that can be treated but requires prompt medical attention. Some conditions that cause blurred vision are true medical emergencies that could result in blindness without immediate treatment.
Some systemic conditions also cause blurred vision. In these illnesses, visual distortion derives from diseases centered elsewhere in the body, such as in the central nervous system.
Causes of blurred vision
If blurred vision occurs without pain but in conjunction with bulging eyes, it may be a symptom of exophthalmos, an inflammation of tissue behind the eye. This condition may arise independently or in conjunction with hyperthyroidism, tumors of the eyeball, or an eye socket infection known as orbital cellulitis.
In someone over 50 whose vision has slowly become blurry over a period of weeks or months, the cause is probably a cataract — an opacity developing in the lens of the eye. Cataracts are quite common and easily treated with surgery.
Far- or nearsightedness
Nearsightedness (myopia) is a chronic condition people are born with. The condition is usually identified early in life and corrected with glasses. Farsightedness that begins early in life is called hyperopia; glasses also correct the condition. Farsightedness that develops gradually in midlife is called presbyopia. In order to retain the ability to read printed material, people with presbyopia need progressively stronger glasses or contact lenses throughout their later years.
Acute glaucoma results from a sudden buildup of fluid pressure in the eyeball and can cause permanent blindness if not treated immediately. Symptoms of glaucoma include blurred vision in one eye, apparent halos around lights, and eye pain.
If blurred vision, red eyes, and eye discomfort develop over the course of a few days, the problem may be iritis — an inflammation of the iris, which is the colored part of the eye. Iritis is a fairly rare disorder, but it merits prompt medical attention.
Blurred central rather than peripheral vision in those who are over 50 may indicate the development of a chronic condition known as macular degeneration.
Flashing lights or wavy spots and blurred vision that occurs immediately before a severe headache, which may also be accompanied by nausea and vomiting, suggest a type of vascular headache known as a migraine.
Blurred vision in one eye, a headache, dizziness, and sensory disturbances such as numbness or tingling in one part of the body, may signify a transient ischemic attack, a small stroke that often precedes a larger one.
Flashing lights or floating spots in one eye's field of vision are symptomatic of retinal detachment. Immediate medical treatment is needed.
In poorly controlled diabetes, high blood sugar can damage blood vessels in the retina, a condition called diabetic retinopathy. Sometimes this complication is the first sign of Type II or adult-onset diabetes.
Advice about blurred vision
- If a person wears corrective lenses — or is over age 40 — and gradually develops blurred vision with no other symptoms, a stronger prescription may be all that is needed.
- If blurred vision is a prelude to a migraine, take preventive measures. Often a cup of coffee or other source of caffeine taken with aspirin, followed by resting in a quiet, darkened room at the first sign of symptoms, may ward off or ease a migraine headache.