Understanding the different types of vision

• Myopia – Distant objects appear blurry, while nearby objects remain clear.
• Hyperopia – Nearby objects may appear blurry, while distant vision is often clearer.
• Astigmatism – Irregular corneal shape causes blurred or distorted vision at all distances.
• Presbyopia – Age-related loss of near focusing ability that usually begins after age 40.
• Myopia and hyperopia cannot occur in the same eye, but can occur in different eyes (anisometropia).

Good vision depends on more than just the eye being healthy and free of disease. Clear, glasses-free vision relies on well-matched anatomy between the eye structures for precise optics.

Many tissues in the eye contribute to vision, from the transparent tissues at the front of the eye (such as the cornea and the lens), to the back of the eye, where light is converted into visual signals (such as the retina and optic nerve). Not only do these tissues need to be healthy, their shape and structure need to align correctly so that light passing through the front of the eye is focused accurately at the back of the eye. When light lands precisely on the retina, vision becomes clear and in-focus.

Focusing errors caused by mismatched optics in the eye (called refractive errors) cause blurry vision, and require corrective lenses, such as glasses or contact lenses. Refractive errors include myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia. Although refractive errors are extremely common, they are a leading cause of vision impairment and avoidable blindness worldwide.1 

Myopia is becoming increasingly common among children worldwide. A child with myopia can usually see nearby objects clearly but may struggle to see distant objects, such as the whiteboard in school, road signs, or television subtitles. It usually results from an eyeball that has grown too long, or a cornea (clear window at the front of the eye) that is too curved.

Potential signs of myopia include:

• Squinting to see distant objects
• Sitting very close to the television
• Holding books or devices close to the face
• Complaining of blurry distance vision
• Frequent headaches or eye strain

Early detection is important, because myopia often progresses as children grow. Rapid eye growth increases the focusing errors in the eye, which lead to a vision prescription that worsens over time. Longer eyes – as seen in higher degrees of myopia (i.e. -6.00 dioptres or more), have a dramatically increased risk of developing serious eye diseases later in life, including retinal detachment, glaucoma, and myopic macular degeneration.

Hyperopia, also known as farsightedness, occurs when the eye focuses light behind the retina, due to either having an eyeball that is too short, or a cornea that is too flat. Most children will have a small amount of hyperopia during early childhood, which naturally decreases by the time they reach secondary school.

Children with mild hyperopia may not notice any symptoms because their eyes can naturally compensate with focusing ability, by using eye muscles to re-focus images that appear blurred. Mild levels of hyperopia are normal and often don’t require any correction. However, higher degrees of hyperopia can cause significant issues with near vision including eye alignment and coordination.

Potential signs of hyperopia include:

• Blurred near vision
• Eye strain during reading
• Difficulty concentrating on close-up tasks
• Headaches after schoolwork

Astigmatism describes an uneven shape of the cornea (the clear front window of the eye) which causes light to be focused unevenly at the back of the eye. This leads to blurred or distorted vision at both near and far viewing distances, unlike myopia or hyperopia – where one is affected more than the other. A small amount of astigmatism is common and fairly normal, and it tends to remain stable from childhood to adolescence and adulthood.

Potential signs of astigmatism include:

• Blurred or distorted vision at all distances
• Squinting to see clearly
• Frequent headaches
• Eye strain
• Difficulty seeing fine details

Astigmatism can occur on its own or together with myopia or hyperopia, and glasses or contact lenses are used to treat blurred vision.

Presbyopia is an age-related vision condition that affects nearly all adults as they get older. It typically begins around the age of 40 and gradually worsens into the mid to late-60s.

Presbyopia occurs as a result of natural aging changes within the eye, where the crystalline lens loses its flexibility. A stiffer lens makes it more difficult for the eye muscles to apply effort in order to focus on near objects clearly, so activities such as using a smartphone, or viewing small print become more challenging. In addition, the ability to quickly adjust focus from near to far (and vice-versa) deteriorates with presbyopia.

Potential signs of presbyopia include:

• Holding reading materials farther away
• Difficulty reading small print
• Eye strain during near work
• Headaches after prolonged reading
• Needing brighter light for reading

While there is no cure to restore the eye’s natural focusing ability, there are many effective methods to correct near vision in presbyopia. Solutions can be as simple as reading glasses, progressive (multifocal) lenses, to more complex vision correction options that may be offered by an eye doctor.

Yes, it is possible for a combination of vision conditions to exist in the same eye.

Hyperopia or myopia can occur together with astigmatism and presbyopia within the same eye. However, because hyperopia and myopia are opposites (affecting near vision and far vision respectively), these are the only conditions that cannot occur simultaneously in one eye.

Anisometropia refers to instances where an individual has two eyes with a significant difference in prescription, such as myopia in one eye and hyperopia in the other (mixed anisometropia), or severe myopia in one eye and mild myopia in the other (compound anisometropia). It can even refer to cases where one eye is affected and the other has no prescription (simple anisometropia). While small differences in prescription between both eyes are common, large imbalances can potentially lead to blurred vision, double vision (diplopia), lazy eye (amblyopia), and crossed eyes (strabismus) if left untreated.

Myopia and presbyopia are two different conditions that develop at different times in life, and have different effects on vision. Myopia usually develops during childhood and causes difficulty seeing distant objects. Presbyopia is an age-related condition that develops during adulthood, affecting near vision.

A person with myopia can also develop presbyopia because it is a normal part of the aging process. People with mild to moderate myopia often find that they can read clearly by simply removing their glasses. This happens because myopia naturally assists their near vision, compensating for some of the loss of focusing ability caused by presbyopia. However, changing focus from near to far objects quickly and accurately will become noticeably harder for adults with myopia in their 40s and above.

Refractive errors are extremely common, and many people live with uncorrected or under-corrected vision without realising it. Symptoms such as blurry vision, headaches, eye strain, or difficulty seeing at certain distances are all reasons to attend a comprehensive eye examination with a qualified optometrist or eye doctor.

A comprehensive eye examination will determine whether a refractive error is present, and identify its type and severity. This allows a personalised prescription to be prescribed to restore clear, comfortable vision – whether in glasses or contact lenses. In children, early assessment is especially important, as some refractive errors, particularly myopia, have significant effects on vision and eye health later in life.