Types of Vision Loss
 

The Centers for Disease Control and Prevention (CDC) estimate that approximately 80 million Americans have a health condition that can lead to vision loss or blindness. That equates to approximately 1 in 4 individuals - more than 1.1 million people in GDABVI's Southeast Michigan service area.

There are many conditions that cause people to become blind, legally blind, or visually impaired. Vision loss is often the result of disease, age-related conditions and injury. Many of these conditions can be prevented with proper eye screening and by paying attention to factors that lead to underlying health conditions such as proper nutritional support, access to medical care, physical activity, and stress reduction.

Other health conditions, such as diabetes, hypertension, HIV and sickle cell - even being born prematurely, can also lead to specific types of retinopathies that cause visual impairment. The types of vision loss we see most often at the Agency are macular degeneration, diabetic retinopathy, glaucoma, cataracts, and retinal detachment.

PLEASE NOTE: The information on this page is not to be construed as medical advice. Please consult your eye specialist or health provider regarding your specific condition.

Cataracts


A cataract is a clouding of the lens of the eye. The lens of the eye is normally clear. It acts like the lens on a camera, focusing light as it passes to the back of the eye. Until a person is around age 45, the shape of the lens is able to change. This allows the lens to focus on an object, whether it is close or far away. As we age, proteins in the lens begin to break down and the lens becomes cloudy. What the eye sees may appear blurry. This condition is known as a cataract. In many cases, the cause of cataract is unknown.

 

Factors that may speed up cataract formation are:

  • Diabetes

  • Eye inflammation

  • Eye injury

  • Family history of cataracts

  • Long-term use of corticosteroids (taken by mouth) or certain other medications

  • Radiation exposure

  • Smoking

  • Surgery for another eye problem

  • Too much exposure to ultraviolet light (sunlight)

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Glaucoma


Glaucoma refers to a group of eye conditions that lead to damage to the optic nerve. This nerve carries visual information from the eye to the brain. In most cases, damage to the optic nerve is due to increased pressure in the eye, also known as intraocular pressure (IOP). Glaucoma is the second most common cause of blindness in the United States. There are four major types of glaucoma:

  • Open-angle (chronic) glaucoma

  • Angle-closure (acute) glaucoma

  • Congenital glaucoma

  • Secondary glaucoma

 

The front part of the eye is filled with a clear fluid called aqueous humor. This fluid is always being made behind the colored part of the eye (the iris). It leaves the eye through channels in the front of the eye in an area called the anterior chamber angle, or simply the angle. Anything that slows or blocks the flow of this fluid out of the eye will cause pressure to build up in the eye. This pressure is called intraocular pressure (IOP). In most cases of glaucoma, this pressure is high and causes damage to the optic nerve.

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Macular Degeneration

 

The retina is at the back of the eye. It changes light and images that enter the eye into nerve signals that are sent to the brain. A part of the retina called the macula makes vision sharper and more detailed. AMD is caused by damage to the blood vessels that supply the macula. This change also harms the macula.


Macular degeneration slowly destroys sharp, central vision. This makes it difficult to see fine details and read. The disease is most common in people over age 60, which is why it is often called age-related macular degeneration (ARMD, or AMD).

There are two types of Age-Related Macular Degeneration:

  • Dry AMD occurs when the blood vessels under the macula become thin and brittle. Small yellow deposits, called drusen, form. Almost all people with macular degeneration start with the dry form.

  • Wet AMD occurs in only about 10% of people with macular degeneration. New abnormal and very fragile blood vessels grow under the macula. This is called choroidal neovascularization. These vessels leak blood and fluid. This form causes most of the vision loss associated with the condition.

 

Scientists are not sure what causes AMD. The condition is rare before age 55. It is most often seen in adults 75 years or older. In addition to heredity, other risk factors are: Caucasian race, cigarette smoking, high-fat diet, female gender, obesity.

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Retinal Detachment

 

The retina is the clear tissue in the back of the eye. It helps you see the images that are focused on it by the cornea and the lens. Retinal detachment is a separation of the light-sensitive membrane in the back of the eye (the retina) from its supporting layers.

The most common type of retinal detachments are often due to a tear or hole in the retina. Eye fluids may leak through this opening. This causes the retina to separate from the underlying tissues, much like a bubble under wallpaper. This is most often caused by a condition called posterior vitreous detachment. However, it may also be caused by trauma and very bad nearsightedness. A family history of retinal detachment also increases your risk.

Another type of retinal detachment is called tractional detachment. This is seen in people who have uncontrolled diabetes, previous retinal surgery, or have chronic inflammation. When the retina becomes detached, bleeding from area blood vessels may cloud the inside of the eye, which is normally filled with vitreous fluid. Central vision becomes severely affected if the macula, the part of the retina responsible for fine vision, becomes detached.

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Retinopathies

Diabetic Retinopathy

Diabetic retinopathy is a diabetic eye disease that damages the small blood vessels in your retina, the back part of your eye. Diabetes also increases your risk of having glaucoma, cataracts, and other eye problems.

 

It is caused by damage to blood vessels of the retina. The retina is the layer of tissue at the back of the inner eye. It changes light and images that enter the eye into nerve signals that are sent to the brain. Diabetic retinopathy is the leading cause of blindness in working-age Americans. People with type 1 and type 2 diabetes are at risk for this condition.

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Hypertensive Retinopathy

When your blood pressure is too high, the retina’s blood vessel walls may thicken. This may cause your blood vessels to become narrow, which then restricts blood from reaching the retina. In some cases, the retina becomes swollen.

Over time, high blood pressure can cause damage to the retina’s blood vessels, limit the retina’s function, and put pressure on the optic nerve, causing vision problems. This condition is called hypertensive retinopathy (HR).

The following conditions put you at a higher risk for HR:

  • prolonged high blood pressure

  • heart disease

  • atherosclerosis

  • diabetes

  • smoking

  • high cholesterol

  • being overweight

  • eating an unhealthy diet that’s high in fat proteins, trans fats, sugary foods, and sodium

  • heavy alcohol consumption

(Source: Excerpts from https://www.healthline.com/health/hypertensive-retinopathy#symptoms)

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HIV Retinopathy

Most people do not experience any HIV-related problems affecting their sight. Taking HIV treatment will prevent the severe damage to the immune system that can lead to sight problems. However, about 70% of people with HIV who have very weak immune systems develop serious eye diseases. These may lead to blindness if not treated promptly.

The most common of these conditions is HIV retinopathy. This is a condition where the retina is damaged, probably because uncontrolled HIV is damaging the blood vessels in the eye. It can eventually lead to blindness, but can be treated in the early stages. Having diabetes is another risk factor for retinopathy, a condition that is more common in people living with HIV, especially as they age. (Excerpts from:  https://www.aidsmap.com/about-hiv/sight-problems)

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Retinopathy of Prematurity

Retinopathy of prematurity (ROP) is a potentially blinding eye disorder that primarily affects premature infants weighing about 2¾ pounds (1250 grams) or less that are born before 31 weeks of gestation (a full-term pregnancy has a gestation of 38–42 weeks). The smaller a baby is at birth, the more likely that baby is to develop ROP. This disorder — which usually develops in both eyes — is one of the most common causes of visual loss in childhood and can lead to lifelong vision impairment and blindness. ROP was first diagnosed in 1942.

 

ROP occurs when abnormal blood vessels grow and spread throughout the retina, the tissue that lines the back of the eye. These abnormal blood vessels are fragile and can leak, scarring the retina and pulling it out of position. This causes a retinal detachment. Retinal detachment is the main cause of visual impairment and blindness in ROP.

About 1,100–1,500 infants annually develop ROP that is severe enough to require medical treatment. About 400–600 infants each year in the US become legally blind from ROP.

(Excerpts from: https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/retinopathy-prematurity)

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Sickle Cell Retinopathy

In sickle cell retinopathy, blockage of blood vessels in the retina and choroid (pronounced CORE-oid) results in abnormal blood vessel growth and thinning of the retina. These physical changes and their consequences can impair vision. (Excerpts from: https://www.asrs.org/patients/retinal-diseases/41/sickle-cell-retinopathy)

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