The seven most common causes of red eyes

Courtesy of Geoffrey Fairchild on Flickr

Courtesy of Geoffrey Fairchild on Flickr

Almost everyone has experienced symptoms of irritated, red, and bloodshot appearing eyes at some point in their lives. There are several different underlying conditions that can cause the blood vessels that are visible on the white part of the eye to become swollen or dilated, which makes the eye appear more red than usual. In addition to redness, some people may also experience accompanying symptoms of itching, watering, swollen eyelids, discharge, pain, and changes in vision, while other people may experience no further irritation at all. The redness can affect either one or both of the eyes and can appear suddenly, or in some cases it can develop and progress over a longer period of time.

The following seven conditions are the most common causes of a red, bloodshot-appearing eye:

  1. Dry eyes:  Dry eye syndrome occurs when there are insufficient tears to properly lubricate and nourish the front surface of the eyes. This can be a consequence of either inadequate production of tears by the glands around the eyes, or as a result of poor quality of the tears that are produced. Chronic dry eyes can cause the surface of the eye to become inflamed over time, making your eyes appear red. Additionally, people may also feel as though their eyes are sandy and gritty, and in some cases vision can also be affected. Although there is no single and direct cure for dry eye syndrome, most of the symptoms can be managed by lubricating eye drops and prescription medications. Your eye doctor will be able to determine which type of dry eye you have in order to recommend the most appropriate treatment plan for your specific needs.
  2. Allergies: People with allergies affecting the eyes commonly have watering, itchiness, and swelling of the eyelids in addition to the ocular redness. Redness resulting from ocular allergies can be caused by a reaction to irritants such as pollen, pet dander, dust, contact lens solutions, and even chemicals in cosmetic products. When your immune system reacts to one of these substances, your body will release histamine, which causes the blood vessels on the white part of the eyes to dilate, making the eyes appear bloodshot. If your redness is due to an allergy, your eye doctor will be able to recommend and prescribe you anti-histamine eye drops in order to help your symptoms.
  3. Contact lenses: Improper contact lens hygiene is a very common cause of ocular redness. Overwearing contact lenses attributes to a number of ocular symptoms that subsequently lead to red eyes. Redness in these cases can be due to dryness of the contact lenses, poor fitting of the contacts, build-up of irritating deposits and protein on the contact lenses, lack of oxygen to the front surface of the eyes, infection, or a corneal ulceration. Contact lens-related red eyes can be a sign of a very serious and potentially sight-threatening condition; therefore, if you notice redness and you wear contacts, remove your contact lenses immediately and contact your eye doctor. You can minimize your risk of contact lens related problems by not sleeping in your contacts, keeping them clean and disinfected with solution (never use water with your contacts), regularly replacing your contact lens case, and discarding your contacts according to your doctor’s recommended schedule.
  4. Conjunctivitis: Conjunctivitis is a bacterial or viral infection of the normally transparent membrane that covers the white part of the eye. When this area is infected, the blood vessels within it become dilated and swollen, which gives the eyes a reddish or pinkish color- thus the reason it is also called “pink eye.” Conjunctivitis is most commonly found in school-aged children and it is contagious. Along with redness of the eyes, people also tend to experience watery or mucous discharge, as well as some swelling of the eyelids. Because there is not only one single underlying cause of conjunctivitis, it is important to see your eye doctor immediately so that you may be properly diagnosed and treated with the appropriate medications.
  5. Broken blood vessel: Sometimes a tiny blood vessel will break in the area between the white part of the eye and the clear membrane that covers it, leaking blood into that space. Often times people don’t realize that a blood vessel has broken until they see the redness of the eye as they look in the mirror because it does not usually cause any pain or irritation. Most of the time it is difficult to pinpoint what caused the blood vessel to leak, but in some cases it can be attributed to straining, a strong sneeze or cough, hard rubbing of the eyes, or as a result of certain medications. Less frequently, this condition can be associated with certain systemic diseases. Because of the number of possible causes, you should alert your eye doctor any time these occur so that further testing could be performed if needed.
  6. Blepharitis: Blepharitis is a term used for inflammation of the eyelids that can lead to redness, irritation, itching, and crusting of the eyelashes and skin around the eyes. It is a very common disorder that can be caused by bacteria, allergies, skin disorders, an infestation of the eyelashes, or clogging of the glands around the eyes. If left untreated, blepharitis can lead to dryness and redness of the eyes, and bumps or styes along the eyelids. Common forms of treatment for blepharitis include warm compresses and cleansing of the eyelid margins, along with lubricating drops or ointments. In some cases, your eye doctor will prescribe other medications to help manage your symptoms.
  7. Pinguecula and pterygium: A pinguecula is a slightly raised, usually yellowish thickening of the tissue that covers the white part of the eye. If this growth starts to move onto the cornea (clear part of the eye), it is called a pterygium. Pinguecula and pterygium are more commonly found in people who spend a considerable amount of time in the sun. Occasionally, a pinguecula or pterygium can become inflamed and swollen, causing the eye appear red. This usually occurs as a result of exposure to wind, dust, or very dry environmental conditions. Artificial tears and lubricants can often help alleviate these symptoms, but in some cases, your eye doctor can prescribe other anti-inflammatory eye drops to help manage the redness and irritation.

These conditions listed above are only a few of the most common causes of red eyes. Other eye condition that can cause ocular redness include herpes infections, use of whitening eye drops, smoking, environmental factors, swimming, lack of sleep, and so much more. It is important to know that redness of the eyes can sometimes signal a very serious eye condition or disease which could potentially cause long-lasting effects on vision, such as glaucoma or uveitis. Therefore, if your eyes develop redness that persists or worsens, is associated with pain or decrease in vision, or you are a contact lens wearer, you should contact your eye doctor immediately so that the underlying cause can be accurately determined and you can be properly treated.

~ Amanda K. Dexter, O.D.
California Optometric Association

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