Uncorrected refractive error is the most common cause of vision impairment, and the second leading cause of blindness in the world. Uncorrected refractive error needs to be diagnosed by an eye care professional, after a dilated eye examination. Read on to learn more.
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Click on the link to jump to sections that you're most interested in! WHAT IS UNCORRECTED REFRACTIVE ERROR? WHEN DOES REFRACTIVE ERROR HAPPEN? WHAT ARE THE MAIN TYPES OF REFRACTIVE ERROR?
SYMPTOMS OF UNCORRECTED REFRACTIVE ERROR Myopia in China
Refractive error happens when an eye is misshapen, preventing successful refraction. Uncorrected refractive error is when we don't do anything about it. Refraction is when the eye bends light so that it can pass through the sections of your eye; the cornea, the lens, and eventually the retina. The retina is the thin, light-sensitive tissue at the back of the eye.
Image credit: National Keratoconus Foundation
In order to process what we see every day, the brain needs to receive messages from the retina, sent through the optic nerve. If your retina doesn't receive light-rays correctly, it won't be able to pass messages to the optic nerve and then to the brain for interpretation. If this happens, images can appear blurred or unclear, resulting in vision loss.
Refractive errors can happen when the eyeball grows or reduces in length, when the cornea changes shape, or simply with age. Overuse of the eye does not cause refractive error. Rather, if refractive error runs in your family, you may have more chance of developing a condition. People of all ages are affected by refractive errors, but some conditions are more common in certain populations. For example, presbyopia is present in most adults over 35-45, while myopia is more common among Asian people! We often use glasses to correct long or short sightedness caused by refractive error, as well as the inability to change focus properly.
Usually an inherited eye condition, myopia causes far away images to be seen blurred, while images are clear up close. This happens because the distance between the cornea and the retina is too long. So, instead of the light focusing on the retina, it focuses in front of the retina. Myopia is usually identified during childhood and exacerbated during puberty, when the body goes through a lot of change.
Hyperopia - sometimes called hypermetropia - occurs when the distance between the cornea and the retina is too short. This causes the light rays to focus behind the retina, rather than on it. We experience hyperopia on a scale; mild levels make images appear blurred close up, and clear when they're far away. For individuals with high levels of hyperopia, images can be blurry at all distances. In childhood, hyperopia can be difficult as children may not always notice their vision problems until they are older.
Presbyopia is one of life’s inevitable burdens brought on by the ageing process. As we age, our lenses become rigid, allowing less close-range focusing flexibility. Signs of presbyopia start to emerge from around 35-45 years of age. Presbyopia is a normal result of the ageing process, unfortunately, but can be corrected by using reading glasses.
When the cornea has asymmetric stigmatism (uneven curvature), we call that astigmatism. Rather than the equal curves of a sphere, the front surface of the eye ends up more like a football. This causes the light coming through the cornea to focus unequally on the retina, resulting in a distorted or ‘stretched out’ image. In most cases, a person with astigmatism will have blurred vision both near and far.
Some of the symptoms of uncorrected refractive error are:
Uncorrected refractive error needs to be diagnosed by an eye care professional, after a dilated eye examination.
China has the highest rate of myopia among children and adolescents. In April 2019, China’s National Health Commission surveyed more than one million young children and students in China. The survey revealed that more than half of the children were suffering from myopia, increasing to 81% by the time they reached high school. Wearing glasses is the easiest way to correct refractive error. However in remote villages in China, there are still many misconceptions about wearing them. Nurse Jie-qin Wang from Yunnan recalls that when she was in her early secondary school years, short-sightedness made her unable to see the blackboard clearly. She wanted to have a pair of glasses, but her parents said no. “They thought once I started wearing glasses, I would have to wear them for the rest of my life,” Jie-qin said. “When I wore the glasses to visit my grandmother in a very old village, people looked at me as if I was a monster and gossiped about my glasses.” Jie-qin believes that changing how people think will also save their sight. Besides traditional beliefs, there are a range of issues that contribute to the incidence of refractive error in China and throughout the world, including:
The Fred Hollows Foundation works to correct refractive error in more than 25 countries. By improving eye care services in remote areas, training eye care professionals and school teachers, organizing screening services at school and setting up follow-up systems, we are determined to promote eye health and ensure young people reach their potential.
*Disclaimer - The content on this page is not intended to be medical advice. For medical advice, please contact your local health professional. All statistics quoted use the most recent information available, to the best of our knowledge.
Imagine not being able to access the basic eye care needed to lead your life. There are millions of people throughout the world who live like this. Vision impairment and blindness can affect every aspect of one's life; school, work, relationships, and basic human rights. The Fred Hollows Foundation is an ally to these people. We provide basic eye care services, ensuring that hundreds of thousands of people have their lives transformed every single year. Please, consider being a part of this life-changing humanitarian movement, and donate today.