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1Vision loss is widespreadBackground/causes of vision impairmentNormal vision means attaining 20/20 on a routine eye exam ie, one can read 3/8-inch letters at 20 feet. Readers who explore this presentation will gain an understanding of the epidemiology of vision impairment world, the worldwide distribution of the most common causes and the cost of treating conditions that affect at least 285 million people worldwide. Learners will also develop a better understanding of risk factors and management strategies for common eye diseases.Who is affected?Causes
Worldwide distribution of vision impairmentCost
Vision loss is widespreadWho is affected?
~285 million people worldwidecannot pass a routine eye examSight problems range from normal to moderate or severe visual impairment. Thirty-nine million people are blind and ~90% of visually impaired people live in low-income settings. Nearly two-thirds of visually impaired (65%) and 82% of blind people are over the age of 50, although this group comprises only 20% of the worlds population. Moreover, the preventable causes of the global visual impairment burden are as high as 80%.
Vision loss is widespread19902010 data*
Cataracts, uncorrected refractive errors,and macular degeneration widespreadIn 2010, higher proportions of blindness or moderate and severe vision impairments (MSVI) were caused by cataracts and macular degeneration in women than men. Uncorrected refractive errorscaused a larger proportion of MSVI in South Asia than other regions (65.4% vs. 43,2% 48.1%). However, macular degeneration in South Asia was low, compared to regions with older populations (2.6% compared with >15% of blindness attributed to macular degeneration in Central and Eastern Europe). Lowest and highest glaucoma rates were seen in east sub-Saharan Africa and tropical Latin America, respectively (4.0% vs. 15.5%).
*lack of epidemiological data in countries with trachoma may affect data.
CausesUncorrected refractive errors, cataracts, age-related macular degeneration, diabetic retinopathy, and eye cancer
Major causes of vision problems range from treatable to lethal diseasesUncorrected refractive errors, cataracts, and glaucoma are the major causes of visual impairments. ii.Cataracts, glaucoma and age-related macular degeneration are the major causes of blindness. Diabetic retinopathy (DR), a key microvascular complication of diabetes mellitus, is also a major cause of visual impairment in 20- to 74-year-old adults. Eye cancer, whether occurring as primary tumors in the immune-privileged eye, or as secondary diseases that started somewhere else and spread to the eye, is an umbrella term for a group of rare diseases that can also cause vision impairment.
CostThe high costs of low or no vision worldwide
At $139 billion in 2013, vision impairments are costly to the USADirect costs equal $66.8 billion ie, medical costs for diagnosingeye disorders/low vision, medical vision aids, vision assistive devices and adaptations, and direct services including special education and assistance programs. Indirect costs of $72.2 billioncapture the burden of consequences of low vision, including productivity losses, long-term care, informal care, and the costs of transfer and entitlement programs.
Overview of vision impairments
image placeholderimage placeholderRefractive errorsCataractsGlaucomaAge-relatedmaculardegenerationDiabeticRetinopathyEye cancers
3Age-related eye diseasesBackground/causes of vision impairmentVision changes are a normal part of the aging process. The National Eye Institute recommends a dilated eye exam for anyone at or over the age of 50. In addition to low vision and dry eyes, older adults may be affected by two forms of age-related macular degeneration (AMD), suffer clouding of lenses known as cataracts, or may be affected by a secondary complication of diabetes mellitus known as diabetic eye diseases. Diabetic retinopathy is the most common diabetic eye disease and the leading cause of vision impairment and blindness among working-age adults in the USA.
3Dry AMDBackground/causes of vision impairmentDry AMD (also called non-neovascular or non-exudative AMD) is characterized by progressive thinning and loss of function of layers of the macula (including the photoreceptors and the retinal pigment epithelium) . The color of the macular changes and tiny piles of cellular debris called drusen appears on the retina.Description
AMD is more common among whites and is the leading cause of permanent vision loss in the elderly. Dry or atrophic AMD lowers the central vision and can affect the preception of color. Although not as severe as the wet form of the disease, dry AMD can lead to profound vision loss over time. More information can be found at amd.orgMerck Professional Manual: Funduscopic changes in dry AMD include drusen, areas of chorioretinal atrophy, and changes to the retinal pigment epithelium
3Wet AMDBackground/causes of vision impairmentWet AMD (also called neovascular AMD or exudative AMD) is characterized by choroidal neovascularization. Fluid, lipids, and blood from the new, weaker vessels may leak into the retina (including layers of the macula)- resulting retinal scarring and reduced function Description
While most people have the dry version of the disease, up to 90% of severe vision loss is due to the wet type.
Merck Professional Manual: Funduscopic changes in wet AMD include retinal edema and localized elevation, detachment of the retinal pigment epithelium, a gray-green discoloration under the macula, and exudates in and around the macula.
3CataractsBackground/causes of vision impairmentBlindness around the world is predominantly caused by cataracts. Most cataracts form as part of the aging process and reflect clouding of the lenses in eyes. The lens which is mostly made up of lens and water becomes cloudy with clumps of protein which reduce the sharpness of images reaching the retina. Over time, a barely noticeable cataract may change the lens to a yellowish/brownish color, adding a brownish tint to vision.ManagementOther symptomsClouded, blurred or dim visionIncreasing difficulty with vision at nightSensitivity to light and glareNeed for brighter light for reading and other activitiesSeeing "halos" around lightsFrequent changes in eyeglass or contact lens prescriptionFading or yellowing of colorsDouble vision in a single eyeCataracts can be diagnosed by visual acuity, slit lamp or retinal examinations. Cataract surgery a routine procedure in which the cloudy lens is replaced by an artificial lens is typically used as treatment. Continuing vision problems may be corrected with glasses or contact lenses.
3Diabetic Retinopathy (DR)Background/causes of vision impairmentDR can cause cause blood vessels in the retina to leak fluid or hemorrhage (bleed), distorting vision. In its most advanced stage, new abnormal blood vessels proliferate (increase in number) on the surface of the retina, which can lead to scarring and cell loss in the retina. Asymptomatic patients may experience vision fluctuations related to blood glucose levels or as a symptom of cataracts, while symptomatic patients may have gradual or acute vision loss, depending on the nature of the underlying changes eg, macular edema/vitreous hemorrhageDiagnosisSymptomsMild or moderate nonproliferaive DR (NPDR) symptoms may include microaneurysms, intraretinal hemorrhage, cotton wool spots and lipid exudatesSymptoms may be more severe in severe NDPRNPDR may progress to proliferative DR (PDR)Strong risk factors include young-onset diabetes, longer duration of diabetes, poor glycemic control, hypertension, renal diseaseChange from the first photograph of the fundus; Change from the first scan by optical coherence tomography scanning; Fluorescein angiography or B scan ultrasonography may also be used as tests.
3Diabetic Retinopathy (DR)Treatment ApproachHypertensive and glycemic control are key priorities in order to stem vision sight-threatening loss. Once symptoms of DR are present, ophthalmic treatment should include macular laser therapy, intravitreal therapy, pan-retinal photocoagulation, vitrectomy surgery, or combinations of these treatments.TreatmentCurrent
For non-severe NPDR, prescribed treatments may be intravitreal anti-VEGF therapy macular laser therapy; Non-high-risk NPDR or severe PDR may be treated with intravitreal anti-VEGF therapy macular laser therapy pan-retinal photocoagulation or pan-retinal photocoagulation may be considered as 1st line treatment; High risk PDR with iris neovascularization may require urgent pan-retinal photocoagulation as a single treatment or in combination with intravitreal anti-VEGF therapy and macular laser therapy; A vitrectomy may be prescribed for severe PDR.
Very common and rare vision impairmentsUncorrected refractive errors/eye cancer
Prevalence of vision problemsCollectively, uncorrected refractive errors affected an estimated 153 million people worldwide in 2013. This number does not include uncorrected presbyopia. The most common conditions are myopia, hyperopia, astigmatism, and presbyopia. At the other end of the spectrum, eye cancer comprises a group of rare primary or secondary tumors that can occur in and around the eyeball/conjunctiva/eyelid of an adult or child. Most of the new primary intraocular cancers estimated to be diagnosed in the USA in 2016 are likely to be melanomas (2,810 adults).
Uncorrected refractive errors (REs)~$268.8 billion US dollars lost per year in lost productivity (2014 estimate)