Refractive Errors: Types, Causes, Symptoms, Diagnosis, and Treatments

Refractive errors are a type of vision issue that causes blurry vision due to the shape of the eye keeping light from focusing correctly on the retina. Refraction is the bending of light rays as they pass from one object to another and eye refraction occurs when the cornea and lens bend light to focus on the retina. The types of refractive errors are astigmatism, presbyopia, hyperopia and myopia. The main symptom of a refractive error is blurry vision but other symptoms include eye strain, seeing a halo or glare near bright lights and squinting. Refractive errors may be treated using prescription glasses, contact lenses and eye surgery. Keep reading to learn more about the types, causes, symptoms, diagnosis and treatments for refractive errors.

What are Refractive Errors?

Refractive errors are a type of vision issue that causes blurry vision and other visual problems. Refraction is a term that describes the bending of light rays as they pass from one object to another, according to the National Eye Institute. Regarding the eye, refraction occurs when the cornea and lens bend light to focus on the retina. A refractive error occurs when the shape of the eye stops light from focusing correctly on the retina. This could mean that light entering the eye hits before or behind the retina. In summary, the answer to, what is refraction of the eye, is the way light enters the eye and is bent by the lens and cornea so it focuses on the retina. Therefore, if there is a refractive error, there is a problem with light focusing in the eye.

How Common are Refractive Errors?

Refractive errors are the most common type of eye problem in Australia according to the Centre for Eye Research Australia. According to the Australian Institute of Health and Welfare, over an approximately ten-year period from 2007 to 2017, there was an increase in the prevalence of myopia (22% to 25%) and hyperopia ( 25% to 28%). Presbyopia is an age-related refractive error that is common in people over 40 as the lens of the eye becomes harder and less flexible due to the natural ageing process.

What is the Other Term for Refractive Errors?

Another term for a refractive error is ametropia. The term refractive error is more commonly used than ametropia however they can be used interchangeably. Both terms are the scientific names for this eye condition.

What are the Different Types of Refractive Errors?

There are four main types of refractive errors which are presbyopia, nearsightedness (myopia), farsightedness (hyperopia) and astigmatism. A refractive error is a vision issue that occurs when the shape of the eye stops light from focusing correctly on the retina. These refractive errors and their definitions are listed below.

Presbyopia: Presbyopia is an age-related refractive error that causes near vision to be blurry due to the hardening of a person’s lens. It is common in those over 40 because of the natural ageing process.
Nearsightedness (myopia): Nearsightedness, scientifically known as myopia, is a refractive error that causes a person’s distance vision to be blurry due to a misshapen eye that disrupts the eye’s ability to receive and bend light.
Farsightedness (hyperopia): Farsightedness, scientifically known as hyperopia, is a refractive error that causes a person’s near vision to be blurry due to light that enters the eye focusing behind the retina.
Astigmatism: Astigmatism is a refractive error that causes blurry vision due to either the cornea or the lens being deformed or misshapen which disrupts the eye’s ability to focus light onto the retina.

Four eyeballs representing a person with astigmatism, presbyopia, myopia and hyperopia.

1. Presbyopia

Presbyopia is an age-related refractive error that causes near vision to be blurry due to the hardening of a person’s lens. It is common in those over 40 because of the natural ageing process which disrupts the lens. Symptoms of Presbyopia include headaches, blurred vision close-up, requiring a great focus distance when reading and eye strain. Presbyopia can be treated with prescription glasses such as reading glasses or multifocals and is diagnosed through an eye test performed by an optometrist. Myopia vs. hyperopia vs. presbyopia: These three refractive errors are similar in certain ways and different in others. Myopia causes distance vision to be blurry, hyperopia causes near vision to be blurry and presbyopia also causes near vision to be blurry but it is due to age.

2. Nearsightedness (Myopia)

Nearsightedness, scientifically known as myopia, is a refractive error that causes a person’s distance vision to be blurry due to a misshapen eye that disrupts the eye’s ability to receive and bend light. Symptoms of nearsightedness (myopia) include frequent squinting to see clearly, eye strain, objects in the distance appearing blurry or fuzzy and headaches. There are certain groups that are more at risk for developing myopia which are those that have a family history of myopia, those with diabetes and people who spend less time outside. Nearsightedness can be treated with prescription glasses such as distance glasses or multifocals. Nearsightedness can be diagnosed through an eye test performed by an optometrist.

3. Farsightedness (Hyperopia)

Farsightedness, scientifically known as hyperopia, is a refractive error that causes a person’s near vision to be blurry due to light that enters the eye focusing behind the retina instead of on the retina as normal. The symptoms of farsightedness include trouble with close-up vision, eye strain, squinting and headaches. Farsightedness (hyperopia) can be treated with prescription glasses such as reading glasses or multifocals. While farsightedness and presbyopia have similar symptoms, they are different in how they affect vision, the eye shape that causes the condition and how light focuses on the eye. Farsightedness can be diagnosed through an eye test performed by an optometrist.

4. Astigmatism

Astigmatism is a refractive error that causes blurry vision due to either the cornea or the lens being deformed or misshapen which disrupts the eye’s ability to focus light onto the retina. According to the National Eye Institute, astigmatism can cause nearby and distant objects to appear blurry or distorted. Astigmatism may be caused by keratoconus, an eye injury, age, eye surgery and a family history of astigmatism. Symptoms of astigmatism include squinting, seeing glares or halos around lights at night, headaches and eye strain. Astigmatism can be treated with prescription glasses such as single vision glasses or multifocals. Astigmatism can be diagnosed through an eye test performed by an optometrist.

What Causes Refractive Errors?

There are four types of refractive errors, each with similar but different causes. According to Johns Hopkins Medicine, a refractive error can occur due to one or more of the following causes which include the eye being too short or long, a change in the eyeball’s shape, a flatter or steeper surface of the eye and a thinner or thicker lens than normal. Each refractive error disrupts a person’s clear vision which is caused by the shape of the eye keeping light from focusing correctly on the retina. The retina is a light-sensitive layer of tissue located at the back of the eye according to the National Eye Institute. Therefore, what causes refractive errors is the shape of the eye.

What are the Risk Factors of Refractive Errors?

The risk factors of refractive errors refers to certain people who are more prone to developing astigmatism, presbyopia, hyperopia and myopia. According to an article published in the International Journal of Community Medicine and Public Health, the risk factors associated with refractive errors are spending hours at a time reading, watching television, mobile phone use, family history of a refractive error and inadequate lighting. This article also found that refractive errors were more present in women than men.

What are the Symptoms of Refractive Errors?

The symptoms of refractive errors are mainly the same across presbyopia, astigmatism, hyperopia and myopia. The symptoms of refractive errors include blurred vision, trouble seeing up close, seeing a halo or glare near bright lights, eye strain, double vision, squinting and headaches. These symptoms of refractive errors and their definitions are listed below.

Blurred vision: Blurred vision is a common symptom of many vision issues and is defined by the eyes being unable to focus properly which results in hazy and unclear vision.
Trouble seeing up close: People who have trouble seeing up close may have the refractive error presbyopia or hyperopia which causes their near vision to be blurry.
Seeing a halo or glare near bright lights: Seeing halos or glare near bright lights is a symptom of refractive errors due to the misshapen eyeball which disrupts the eye’s ability to perceive light.
Eye strain: People with uncorrected refractive errors may experience eye strain, also known as eye fatigue, as the eyes are working overtime to bring objects into focus and make them clearer.
Double vision: The refractive error astigmatism may cause monocular double vision, which occurs even when one eye is shut.
Squinting: Squinting is common in people who have refractive errors but do not have devices such as glasses or contacts to correct them.
Headaches: Headaches may be a symptom of refractive errors if they are not corrected due to eye strain and squinting. A headache is a feeling of pain and throbbing concentrated in the head area.

$A list of symptoms of refractive errors accompanied by a woman expressing these symptoms.$

1. Blurred Vision

Blurred vision is a common symptom of many vision issues and is defined by the eyes being unable to focus properly which results in unclear vision. Presbyopia and hyperopia (farsightedness) cause blurry vision when looking at close-up objects, myopia (nearsightedness) causes blurry vision when looking at far away objects and astigmatism causes blurry and distorted vision both close-up and far away. Blurred vision can be treated with corrective devices if this vision symptom is caused by refractive errors.

2. Trouble Seeing Up Close

People who have trouble seeing up close may have the refractive error presbyopia or hyperopia which causes their near vision to be blurry. Presbyopia causes blurry close-up vision due to age-related changes in the lens which causes the eye to lose its ability to change shape to allow for a greater level of focus. Hyperopia, also known as farsightedness, leads to blurry near vision as the light entering the eye is incorrectly refracted, landing behind the retina instead of on it. Presbyopia and hyperopia can be treated with corrective devices such as glasses and contact lenses.

3. Seeing a Halo or Glare Near Bright Lights

Seeing halos or glare near bright lights is a symptom of refractive errors due to the misshapen eyeball which disrupts the eye’s ability to perceive light. According to Very Well Health, seeing halos and glares around lights is known as diffraction and is caused by light bending while entering the eye. Halos and glare near bright lights are caused by refraction errors as the disruption to vision caused by these vision issues also affects the eye’s ability to perceive light and glare, creating a distortion.

4. Eye Strain

People with uncorrected refractive errors may experience eye strain, also known as eye fatigue, as the eyes are working overtime to bring objects into focus and make them clearer. Refractive errors such as presbyopia and farsightedness may be underlying causes of eye strain as they can cause a person’s near vision to be blurry, resulting in the eyes working extra hard to see clearly. Eye strain can cause the eyes to become more exhausted and strained, causing an uncomfortable feeling in the eyes and possibly headaches. Eye strain may be treated with prescription glasses if it is caused by an uncorrected refractive error.

5. Double Vision

The refractive error astigmatism may cause monocular double vision which occurs even when one eye is shut. Double vision is a common symptom of astigmatism as problems with the cornea distort the eye’s surface, affecting how light is received which can cause double vision. Double vision caused by astigmatism may be corrected using prescription glasses as they can counteract the curvature of the eye and correct the passage of incoming light, according to Medical News Today.

6. Squinting

Squinting is common in people who have refractive errors but do not have devices such as glasses or contacts to correct them. Squinting is defined as partly closing the eyes to improve vision as this allows less light into the eyes and makes the lens change shape in order to focus more clearly. People may squint to focus on objects in the distance or close-up. Frequent squinting can also lead to eye strain and headaches as the eyes are overcompensating for diminished vision. Wearing prescription glasses or contacts can help relieve squinting by correcting the vision issue whether that is presbyopia, astigmatism, hyperopia or myopia.

7. Headaches

Headaches may be a symptom of refractive errors if they are not corrected due to eye strain and squinting. A headache is a feeling of pain and throbbing concentrated in the head area such as the eyes and frontal lobe. Refractive errors such as presbyopia, astigmatism and farsightedness can cause the eyes to strain in order to see objects up close. This can lead to a headache, especially if this occurs for extended periods of time. To prevent headaches caused by refractive errors, corrective devices are prescribed to magnify near objects, stopping the eyes from straining and focusing too hard.

How are Refractive Errors Diagnosed?

Refractive errors are diagnosed through an eye test with an optometrist. The tests performed in an eye exam that assess a person’s vision include a visual acuity test and a refractive test. There are three common tests used to assess the refraction of a person’s eyes. These three tests are retinoscopy, autorefraction and phoropter refraction. Retinoscopy uses a retinoscope which shines a light into the eye so an optometrist can determine how light reflects off the retina. An autorefraction test involves an autorefractor which is a computer-controlled machine that assesses refraction. Finally, phoropter refraction uses a phoropter which is a device composed of prisms, lenses and cylinders to determine the prescription needed to correct a refractive error.

How is the Test for Refractive Errors Done?

The tests for refractive errors are done by an optometrist. These tests include a visual acuity test and a refraction test. A visual acuity test measures the sharpness and clarity of a person’s vision using a letter chart, one eye at a time. This test involves a patient looking at a letter chart 6 metres away and reading out the letters which get progressively smaller as they go down until they are unable to identify the letters. Whatever the lowest line a person can read is expressed as a fraction and can be used to describe your visual acuity. A refractive error can also be tested using refractive tests which are retinoscopy, autorefraction and phoropter refraction.

How Serious are Refractive Errors?

Refractive errors are not typically serious, rather they are the most common type of eye condition that can be easily treated with glasses or contact lenses. According to the World Health Organisation, a refractive error can sometimes be so severe that it leads to visual impairment, which is a serious vision issue.

Are Refractive Errors a Sign of a Serious Eye Disease?

No, refractive errors are not a sign of a serious eye disease, rather they are a very common eye condition that can be treated with corrective devices such as glasses or contact lenses. If you are having issues with your vision, book an eye test with an optometrist and they can assess your vision and the health of your eyes.

What are the Treatments for Refractive Errors?

There are three main treatments for refractive errors (astigmatism, presbyopia, hyperopia and myopia). The treatments available for refractive errors include contact lenses, glasses and eye surgery. Refractive error treatments and their definitions are listed below.

Contact lenses: Contact lenses are a corrective device used to give the wearer clear and comfortable vision. Contact lenses are thin lenses that are placed directly on the eye’s surface to correct refractive errors.
Glasses: Glasses are corrective devices worn on the face that contain a prescription in the lens to correct vision issues such as refractive errors. Glasses can have different types of lenses including multifocals and bifocals.
Eye surgery: Eye surgery for a refractive error includes LASIK (Laser-Assisted In Situ Keratomileusis) and PRK (photorefractive keratectomy). Eye surgery for refractive error correction typically involves changing the shape of the cornea.

$The three main treatments for refractive errors which are glasses, contact lenses and eye surgery.$

1. Contact Lenses

Contact lenses are a corrective device used to give the wearer clear and comfortable vision. Contact lenses are thin lenses that are placed on the eye’s surface to correct refractive errors. Contacts are similar to glasses in that they are either convex or concave in design which are used to help the wearer see clearly. These corrective devices help treat refractive errors by directing the light that enters the eye to the proper place on the retina, allowing the eye to see properly. Contact lenses are convenient, offer a wide range of vision and are safe to wear when playing sports. There are multiple types of contact lenses which include soft contact lenses, hard contact lenses, extended-wear contact lenses and daily-wear contact lenses.

2. Glasses

Glasses are corrective devices worn on the face that contain a prescription in the lens to correct vision issues such as refractive errors. Glasses can have different types of lenses such as multifocals and bifocals. Glasses will contain a prescription lens to correct refractive errors. For nearsightedness, glasses with a concave lens can be used to correct the focal issues, giving the wearer clear vision. The glasses lenses that correct farsightedness are called convex lenses or plus lenses. If you think you need glasses, book an appointment with an optometrist who can assess your vision and provide you with a prescription for glasses if needed.

3. Eye Surgery

Refraction eye surgery for a refractive error includes LASIK (Laser-Assisted In Situ Keratomileusis) and PRK (photorefractive keratectomy). According to the National Eye Institute, LASIK eye surgery is performed using a laser that changes the shape of a person’s cornea and is used to correct astigmatism, farsightedness and nearsightedness. PRK is a type of eye surgery performed to treat hyperopia, myopia and astigmatism using an excimer laser which reshapes the cornea, according to the American Academy of Ophthalmology. It is common for people to use glasses or contact lenses before being recommended for eye surgery, according to the Cleveland Clinic, however, some may be an ideal candidate immediately.

Can a Refractive Error be Cured Naturally?

No, a refractive error is a visual issue that cannot be cured or fixed naturally, rather it requires treatment from an optometrist. There is a misconception that eye exercises can improve a person’s vision but this is incorrect. Treatment for a refractive error includes prescription glasses, contact lenses and eye surgery.

Can a Refractive Error be Cured Permanently?

Refractive errors are considered to be corrected or fixed, rather than cured permanently. Corrective devices such as prescription glasses and contact lenses can be used to give the wearer clear and comfortable vision, however, this does not cure the refractive error but is a temporary correction while wearing these devices. Eye surgery is different as it is used to fix the eyes permanently so a patient does not need glasses. However, this does not prevent the eyes from developing a refractive error in the future, eye surgery fixes a current vision issue.