Blindness in North America is not properly defined, at least not among the vast majority of people NOT suffering from it. Blindness, contrary to what many people may think, is defined so as to include persons with some sight. To be considered legally blind a person must come within 20 feet of an object in order to be able to see it – a sighted individual can see the same object from 200 feet away. People who suffer from this disability preferred to be called “visually impaired”.
The two major causes of blindness, glaucoma and macular degeneration, share some characteristics, one of which is that early diagnosis is helpful for treatment and prognosis. An eye examination once every two years is recommended for those over forty. Symptoms, risk factors, and treatment of the two conditions vary as follows:
Macular degeneration is a disease that destroys central vision, which is necessary for driving, reading, close work, and even recognizing faces. The cause of macular degeneration was not clear until recently, but research now points to a thinning of the macular pigment as the probable source of the disease. There are two versions of the disease: ‘wet’ and ‘dry.’ All patients start with the dry form, but it may develop at any time into the wet version. The wet version involves the formation of abnormal blood vessels that leak fluid into the eye; this version can cause damage quickly. The advanced stage of the dry version also causes serious vision loss.
Symptoms include problems reading or doing close work, dimming of colours, blind spots. Sometimes straight lines appear wavy. Risk factors include: age, eye colour, family history, smoking, gender, obesity, high cholesterol, and blood pressure.
Treatment for wet macular degeneration has varied, with some doctors advocating the use of laser surgery. Until recently, there was no available treatment for dry macular degeneration, but in 2006 a large decade-long study was completed, and researchers recommended that patients in the intermediate stage of the disease take a specific formulation of antioxidant vitamins, betacarotene and zinc. Even more encouraging, new studies point to a nutritional supplement containing lutein, zeaxanthin, and meso-zeaxanthin as a means to restoring the macular pigment. This approach has even shown some reversal of symptoms.
Glaucoma is a term that encompasses a number of conditions that cause pressure inside the eyeball to increase. In a normal eye, a liquid called the aqueous humor is continually drained and replenished. With glaucoma, fluid builds up and this causes increased pressure. This pressure often damages the optic nerve directly, or cuts off blood supply to the optic nerve. Glaucoma can cause blind spots in the visual field, and if untreated, can lead to severe vision loss.
Symptoms of glaucoma include blurred vision, loss of peripheral vision, sensitivity to light and glare, and poor night vision. Risk factors for developing the condition include: age, race, family history, eye injury, diabetes, and steroid usage.
There is no cure for glaucoma, and if the optic nerve is damaged, it cannot be repaired. However, with early diagnosis, the progression of the disease can be slowed. Available treatments include:
Drugs such as beta blockers to slow production of aqueous humor
Drugs such as prostaglandins to increase outflow of aqueous humor
Surgery to drain the eye and improve the outflow of aqueous humor or to implant a drainage shunt