Blindness and low vision can occur as a result of a number of different diseases, conditions or accidents. Some eye diseases are present at birth, others are caused by a disease or infection and others can be brought on by accidents or through exposure to ultraviolet (UV) light or chemicals. Many of the most common eye conditions, such as cataracts and glaucoma, are primarily age-related and have no known cause.
This section provides information about 4 of the most common eye disorders that can cause either blindness or low vision: refractive errors, age-related macular degeneration, cataract and glaucoma. You can learn more about each specific disease, how to recognise the symptoms, and what steps you can take to treat them before your vision deteriorates further.
Refractive errors occur when the shape of the eye prevents light from focusing directly on the retina. Refractive errors can be caused by the length of the eyeball (longer or shorter), changes in the shape of the cornea, or aging of the lens. The most common types of refractive errors are near-sightedness (myopia), far-sightedness (hyperopia), astigmatism and presbyopia.
Blurred vision is the most common symptom of refractive errors. Other symptoms may include double vision, haziness or a glare around bright lights. Squinting, headaches and eye strain can also indicate refractive errors.
An eye care professional can diagnose refractive errors during a comprehensive dilated eye examination.
Refractive errors can be corrected with eyeglasses, contact lenses, or in some cases surgery. Eyeglasses are the simplest and safest way to fix refractive errors. Your eye care professional can prescribe appropriate lenses to correct your refractive error and give you optimal vision. Contact lenses work by becoming the first refractive surface for light rays entering the eye, causing a more precise refraction or focus. They are also a safe and effective option if fitted and used properly. However, if you have certain eye conditions you may not be able to wear contact lenses.
Surgery for refractive errors aims to change the shape of the cornea permanently. This change in eye shape improves vision by allowing the light rays to focus precisely on the retina. There are various types of refractive surgeries. Your eye care professional can help you decide if surgery is an option for you.
Age-related macular degeneration (AMD) is a common eye condition among people as they age. In fact, Vision Australia ranks AMD the leading cause of severe vision impairment in people aged over 40 years in Australia.
This condition gradually destroys the macula, the part of the eye that provides sharp, central vision needed for seeing objects clearly. The vision loss makes it difficult to recognise faces, and to do daily tasks such as reading and driving.
There are two types of AMD, described as either dry or wet. The following is a brief description of each:
Dry AMD has few symptoms in the early stages. One of the most common early signs of dry AMD is drusen, tiny yellow or white deposits under the retina. In the later stages, blurred vision and a gradual decline in the ability to see objects clearly can occur. Objects also may not appear to be as bright as they used to be. An early symptom of wet AMD is that straight lines appear wavy. People with wet AMD may also develop dark or empty spaces blocking the central field of vision.
The early and intermediate stages of AMD usually start without symptoms. Only a comprehensive dilated eye exam can detect AMD.
There is currently no treatment for dry AMD but treatments are available for wet AMD that are aimed at maintaining the vision for as long as possible. The main treatment for wet AMD is Lucentis injections. The injections aim to reduce the progression of the disease and further loss of vision by preventing the growth of new abnormal blood vessels in the retina. Photodynamic therapy and laser surgery may also be used to treat AMD, however these treatment are less common.
A cataract is a clouding of the eye's natural lens. While cataracts most commonly occur in those who are older, they can be present at birth and develop at any age due to a variety of causes. Types of cataracts include:
A cataract starts out small and at first has little effect on your vision. You may notice that your vision is blurred a little, like looking through a cloudy piece of glass. Other common symptons include weaker vision at night and colours appearing faded or yellowed. A cataract may cause light from the sun or automobile headlights to feel blinding or uncomfortable glary. When a nuclear cataract first develops, it can bring about a temporary improvement in your near vision, called ‘second sight’. Unfortunately, the improved vision is short-lived and will disappear as the cataract worsens.
An eye care professional can diagnose cataracts during a comprehensive dilated eye examination.
When symptoms begin to appear, vision may be corrected with a change in prescription eyeglasses, bifocals or contact lenses. If your vision loss cannot be corrected with new glasses and cataracts interfere with your daily life, you may be a candidate for cataract surgery, which involves removing the clouded lens and replacing it with a clear, artificial one. Cataract surgery is often very successful in restoring vision.
Glaucoma refers to a group of eye diseases that can damage the optic nerve, which carries information from the eye to the brain. In most cases, glaucoma is associated with higher-than-normal pressure inside the eye. If untreated or uncontrolled, glaucoma first causes peripheral vision loss and eventually can lead to blindness.
There are two major categories of glaucoma, ‘open angle’ and ‘closed angle’. Open angle, is a chronic condition that progresses slowly over a long period of time without the person noticing vision loss until the disease is very advanced and has caused significant damage. Angle closure can appear suddenly and is accompanied by severe pain. While visual loss can progress quickly with angle closure glaucoma, the pain and discomfort usually leads patients to seek medical attention before permanent damage occurs.
Glaucoma is often called the "silent thief of sight", because most types typically produce no symptoms until noticeable vision loss occurs. For this reason, glaucoma often progresses undetected until the optic nerve has already been irreversibly damaged, with varying degrees of permanent vision loss.
However, with angle-closure type of glaucoma, symptoms include the sudden onset of severe throbbing eye pain, headaches, blurred vision, rainbow halos around lights, redness in the eye, nausea and vomiting. If you have these symptoms, make sure you see an eye care practitioner or visit the emergency room immediately so steps can be taken to prevent permanent vision loss.
Glaucoma is detected through a comprehensive dilated eye exam conducted by an eye care specialist.
Depending on the severity, glaucoma can be treated with medication, laser treatment or surgery. Eye drops with medication aimed at lowering eye pressure usually are tried first to control glaucoma. Early detection and treatment of this condition can prevent or delay vision loss.