Types, Causes, and Characteristics of Vision Impairment
Your eyes are highly developed sensory organs. In fact, more of the brain is dedicated to sight and vision compared to smell, touch, taste, and hearing combined. Most people usually take their vision for granted, yet when they develop complications with their eyesight, they are willing to do almost anything to get things back to normal.
At least 2 billion people worldwide have distance or near vision impairment, and in almost half of these cases, vision impairment has not been addressed yet or could have been prevented. Most people with blindness and vision impairment are over 50 years old, but that does not mean they cannot affect anyone.
This article will highlight some common types of vision impairments and what causes them.
Types of Vision Impairments
Myopia, or nearsightedness, results from images being concentrated in front of your retina instead of on it, leading to the blurring of distant objects. Nearsighted people who have not corrected their eyesight will need to sit close to the screen in the cinemas or close to the white/blackboard in class to see clearly and hold books closer when reading.
This is a condition that affects both women and men and often runs in families, typically appearing in childhood or adolescence. The prevalence of nearsightedness is rising, and people often blame the increased use of computers and handheld devices.
The opposite of myopia is hyperopia or farsightedness. The farsighted eye concentrates images and pictures slightly behind your retina, blurring nearby objects. Kids can sometimes outgrow hyperopia as they age, and their eyeballs reach adult sizes.
Yes, the eyes grow during childhood– the eye’s length elongates almost by 1/3 between birth and the age of five. It is also common among family members.
Visible light rays form the images that reach your brain, and for this to happen, your retina needs to be able to turn those light signals into nerve impulses. Retinas are like silky wallpapers that line the insides of eyeballs. However, unlike wallpaper, there is no glue.
Tiny holes can develop where your retina is damaged or exceptionally thin. If this occurs, the vitreous (eye fluid) that fills your eyes can leak behind the retina, causing the so-called ‘wallpaper’ to slide off. This is what is known as a detached retina or retinal detachment.
Light rays that enter your eyes first cross their clear cornea. Surprisingly, almost two-thirds of your eyes’ concentration power happens along the cornea or tear film (the eye’s front surface). A normal cornea has a semi-spherical contour that looks a lot like a baseball.
This allows your eye to create single-focused images. If you do not have a uniform or symmetrical cornea, we say it is ‘astigmatic.’ Usually developing with symptoms of farsightedness or nearsightedness, astigmatism develops when your clear cornea lacks a non-round curvature.
Near vision needs accommodation or focusing. The level of near-focusing power reduces throughout your lifespan. This eye condition results in blurred vision at normal reading distances in people with normal distance vision (whether they have glasses or not).
Presbyopia happens when your eyes develop insufficient amounts of focusing power for reading. This vision impairment usually starts at around age 40 and above and is a huge reason why many older people need glasses to read.
Causes of Vision Impairments
Several different things can lead to impaired vision, and some of them include;
The human eye’s lens focuses light rays so that the eye can see images and objects clearly at different distances. It contributes almost 1/3 of your eye’s focusing power and needs to remain transparent if you want clear vision.
The clouding of eye lenses is known as cataracts. As you grow older, cataracts distort or block light rays from entering your eyes, resulting in a painless, persistent, gradual blurring of vision as if you are looking through a cloud or haze.
Cataract vision can sometimes get worse when the surrounding light is dim. This condition is one of the leading causes of blindness, accounting for over 20 million cases globally.
Over two million people in the U.S suffer from glaucoma, which is a leading cause of irreversible vision impairment. The common types of glaucoma include chronic open-angle glaucoma (which often appears in middle age), closed-angle glaucoma (which can either be acute or chronic), and secondary glaucoma (which is associated with trauma to the eye).
Doctors refer to COAG (chronic open-angle glaucoma) as the ‘silent thief of sight.’ Why? Because it slowly and gradually steals the patient’s vision. Glaucoma is when high eye pressure damages the retina’s delicate nerve layers. Most patients do not have any symptoms and can even lose sight if it is not identified in time.
Another leading cause of vision impairment is macular degeneration, which affects many older people. Because symptoms do not show in adults under 55 years, the condition is usually referred to as AMD (age-related macular degeneration).
AMD affects your central vision because the macula is the retina’s central part. This is the detailed vision required for reading, driving, and close tasks like writing, sewing, etc.
When you develop this condition, you will not be able to see the middle parts of a photo, for instance, but you can still see its edges. This disorder comes in dry and wet forms, and the wet (less common) needs immediate medical attention.
Many things can cause visual impairments; the ones in this article are just a few of them, and so are the different types.
Most vision impairment disorders will decrease your ability to see in one way or another and will cause issues that cannot be fixed by usual means, like medication and glasses.
However, not all of them necessarily result in the complete loss of sight. Hopefully, you now understand more about the different kinds of vision impairments and what causes them. If you think you have any of the impairments above, consult with our experts for an accurate diagnosis.