Types of Eye Problems
Major causes of low vision and blindness in the United States include macular degeneration, cataracts, glaucoma, and diabetic neuropathy. Serious vision loss can also be caused by inherited eye diseases, traumatic eye injuries, stroke, blockage of eye blood vessels, infection, and retinal detachment. Many people are affected by more than one cause of vision loss (NEI 2014; Congdon 2004; MedlinePlus 2014; Yanoff 2011; AOA 2014b).
Macular degeneration involves loss of nerve function in the central portion of the retina or macula (AMDF 2014). People with macular degeneration experience a gradual loss of vision - especially in the central visual field. About 1.75 million people in the United States have macular degeneration - most of them over 50 years old with a peak incidence from age 75 to 80 (Eichenbaum 2012; Yorston 2006; Chiang 2013). Macular degeneration is the most common cause of blindness among adults of European descent (Coleman 2008). Macular degeneration involves a number of harmful (pathological) processes including: 1) formation of yellow deposits in the retina called drusen, 2) areas of retinal cell death or atrophy, and 3) leakage of blood or other fluids from fragile and newly formed blood vessels within the eye. About 80% of people with macular degeneration have the “dry” type in which cell death or atrophy is the predominant factor. “Wet” macular degeneration occurs when there is extensive leakage of blood or fluids from newly formed blood vessels in the eyes. While wet macular degeneration accounts for 20% of the total cases of macular degeneration, it accounts for 90% of the severe cases of macular degeneration (when vision is reduced to less than 20/200) (Eichenbaum 2012). More information and treatment strategies are outlined in the Macular Degeneration protocol.
Cataracts are caused when protein fibers in the lens undergo harmful changes that cause them to become cloudy and impair vision. Diabetics are more likely to experience cataracts since high blood sugar levels promote binding of sugars (glycation) to proteins in the eye lens (Stevens 1995; Gul 2009). This glycation causes the lens to become cloudy and blurs vision. About 20.5 million US adults have cataracts (Eichenbaum 2012). Factors that significantly increase risk for cataract development include diabetes; smoking; regular alcohol consumption; family history of cataracts; excess exposure to sunlight; certain occupational exposures like welding, glassblowing, and radiation; eye cancers; and trauma to the eye (Megbele 2012; Shah 1945; West 1995; Finzi 2005; Muhit 2004; Kase 2008; Graham 2012). More information and treatment strategies are outlined in the Cataracts protocol.
Glaucoma typically involves a gradual increase in eye pressure, which causes damage to the optic nerve (Chiang 2013). People with glaucoma experience reduced vision, especially in the outer (peripheral) field of view. About 2.2 million US adults have glaucoma (Eichenbaum 2012).
About 90% of glaucoma cases are called open angle glaucoma and usually occur slowly and gradually. About 10% of glaucoma cases are closed angle glaucoma, which can cause rapid vision loss. Both open and closed angle glaucoma involve blockage of fluid flow out of the eye (Eichenbaum 2012). More information and treatment strategies are outlined in the Glaucoma protocol.
Diabetic retinopathy damages vision in persons with long-term type 1 or type 2 diabetes. About 2.5% of all US adults and 28.5% of diabetic adults have diabetic retinopathy (Zhang 2010).
Diabetic retinopathy involves damage to tiny blood vessels (capillaries), formation of advanced glycation end products (AGEs), oxidative damage to cells, and inflammation. Low oxygen levels (ischemia) can develop in the retina, leading to increases in inflammatory chemicals (such as vascular endothelial growth factor [VEGF], cytokines, and angiotensin II) and increases in blood pressure. The resultant damage to eye blood vessels can cause further ischemia and promote growth of new eye blood vessels (neovascularization) which can reduce vision (Bandello 2013). More information and treatment strategies are outlined in the Retinopathy protocol.
Inherited Diseases and Genetics
Although genetic factors can affect the incidence of many types of eye problems, people with certain genetic conditions are likely to experience moderate-to-severe vision loss sometime in their life. Inherited (genetic) eye conditions include retinitis pigmentosa, Leber’s hereditary optic neuropathy, and others. Worldwide prevalence of retinitis pigmentosa is about 1 in 4000 (Hamel 2006; Hartong 2006). Retinitis pigmentosa first causes night blindness, then progressive loss of the peripheral (outer) field of view during daytime, and may lead eventually to total blindness (Hamel 2006). Leber’s hereditary optic neuropathy is a rare condition caused by harmful mitochondrial DNA mutations. Leber’s hereditary optic neuropathy first causes central vision loss which can progress to blindness by early or middle adulthood (Puomila 2007).
Other Common Eye and Vision Concerns
Double vision. Double vision or diplopia is the perception of a single object as two duplicate objects. Diplopia can be caused by many problems including lens cataracts, corneal infections or scars, hormone problems (eg, Grave’s disease), diabetes, autoimmune diseases (eg, multiple sclerosis), stroke, brain tumors, brain trauma, and migraine headaches (Kim 2013; Krol 2014; Ponto 2013; van Dijk 2013; Subei 2012; Rathore 2002; Kaiser 1999; Galli 2012; MNT 2009; Myers 1951; Tachibana 2013; Bothun 2009; Fujikado 2006; Melen 1978; Hsieh 1989).
Night blindness. Night blindness involves a greatly impaired visual ability in low-light conditions. Night blindness has many causes including cataracts, use of certain drugs, vitamin A deficiency, and genetic problems (eg, retinitis pigmentosa) (Loeffler 2013).
Eye floaters. Eye floaters are small spots that appear in the field of vision. Floaters are relatively common and the majority are caused by age-related changes to the vitreous humor. However, floaters require immediate medical attention if there is sudden onset of new floaters. Immediate medical attention is especially important if they are accompanied by flashes of light or losses of peripheral vision, as these conditions may be due to retinal detachment. Most cases of floaters do not require treatment. In rare, severe cases that significantly impact vision, surgery that removes and replaces the vitreous may be considered (Mayo Clinic 2012).
Dry eyes. Tear production often declines with age (Furukawa 1978). Eyes can also often become dry in windy or arid conditions. Dry eyes can lead to itching and blurred vision. Artificial tears can often provide short-term relief for dry eyes (Yanoff 2011).
Eye fatigue. Eye fatigue commonly occurs after spending long hours looking at small objects; straining to see in dim light; or when driving or using a computer screen for long periods. Eye fatigue can be minimized by placing computer screens at the proper location (about 20-26 inches away from and just below eyes) and taking breaks from long-term computer screen viewing (AAO 2011; Agarwal 2013).
Infection. A number of bacteria, fungi, and viruses can infect the eye or related structures like the eyelid. Prompt medical attention with antibiotics and sometimes surgery are often required to successfully treat eye infections (Yanoff 2011).
Refractive errors are common and are due to problems in the structure and function of the cornea, lens, and shape of the eye. The 3 main types of refractive errors include (Resnikoff 2008; Merck 2013; NEI 2010):
- Myopia (near-sightedness): difficulty seeing objects far away. In 2010, about 34.1 million US adults over age 40 had myopia (NEI 2014).
- Hyperopia (far-sightedness): difficulty seeing objects close-up. In 2010, about 14.2 million US adults over age 40 had hyperopia (NEI 2014).
- Astigmatism (blurry outer [peripheral] vision): Astigmatism is usually caused by an irregularly-shaped lens or cornea. In 2008 a study of 12 010 US adults reported that 36.2% of all adults over age 20 years have significant astigmatism in one or both eyes (Vitale 2008).
Most common refractive eye problems can be corrected by the use of eyeglasses or contact lenses.