It is estimated that around 1.4 million Australians suffer from astigmatism*, a common refractive error whereby the shape of the cornea prevents light from focusing correctly on the retina, resulting in imperfect vision. Fortunately, astigmatism can be easily corrected. Abernethy Owens is home to a team of professional optometrists highly experienced in a wide range of optical services. Here we will outline the causes of astigmatism, and the ways in which it can be treated.
Understanding Astigmatism
Astigmatism essentially means that that the cornea, or the eye, is shaped more cylindrical than spherical. When the cornea is not curved equally in all directions, it affects how light rays bend and therefore, the clarity of vision. In a normal eye, the cornea and the lens help focus light rays onto the retina to allow for clear vision. However, astigmatism causes light to focus on different parts of the eye, resulting in fuzzy or blurry vision. It can also cause halos, glare, or streaking around objects.
There are two main types of astigmatism, regular or irregular, and in addition to the amount of astigmatism, there is also the axis- or the direction in which it occurs.
Regular Astigmatism
An eye with astigmatism has a steep curve and a flat curve - known as the two principal meridians.
Regular astigmatism is when the two principal meridians are 90 degrees apart, with one meridian being steeper than the other. This is the most common type of astigmatism and can be corrected by glasses, contact lenses, or laser surgery.
Irregular Astigmatism
This occurs when the two principal medians are not symmetric and is typically caused by disease, such as keratoconus, corneal degeneration, corneal scarring, or ocular surface disease. As the curvature is uneven, irregular astigmatism is more difficult to correct. Rigid gas permeable lenses are generally the best solution for correcting irregular astigmatism. Scleral lenses are larger, hard contact lenses that go onto the white part of the eye and correct this astigmatism as well.
Testing
A comprehensive eye exam is the most accurate way to test for astigmatism. An optometrist may use a number of devices to test visual acuity and the curvature of the cornea, including:
- A phoropter - an instrument with lenses and dials to test refractive errors. This helps determine which type of lens correction is required.
- An autorefractor - this device measures how well light focuses on the retina. It shines light into the eye and when the light bounces off the back it records any distortions in the return image.
- A keratometer – this measures the axis or the curvature of the cornea.
- A corneal topographer – a device which provides detail about the cornea.
Symptoms
Symptoms of astigmatism may include:
- Blurry or distorted vision
- Eyestrain
- Double vision or ‘ghosting’ around images
- Headaches
- Squinting
It is important to note that these symptoms may be related to a variety of refractive vision errors so if you experience any of these, it’s important to make an appointment for a thorough eye examination.
Treatments
There are three main ways to correct astigmatism:
- Glasses - One of the most common ways to fix regular astigmatism, glasses contain a cylindrical lens that compensates for the uneven curves in the cornea or lens.
- Contact Lenses - There are several types of lenses available to correct astigmatism:
- Soft contact lenses: Toric lenses are a specific type of soft contact lenses that are weighted to ensure they remain aligned properly. They also have varying powers in different meridians.
- Custom hard contact lenses:, Sometimes known as RGP lenses, these lenses are rigid to help maintain their shape on the eye. Fitted correctly, they can lead to sharp vision and effectively correct irregular astigmatism.
- Hybrid contact lenses: These lenses use rigid gas permeable lens material for the centre of the contact with a soft material on the outside.
- Refractive Surgery - LASIK eye surgery can treat astigmatism by reshaping the cornea. This improves how the eye focuses light rays on the retina, resulting in sharper vision.
Book an Eye Examination at Abernethy Owens Today
A comprehensive eye consultation is the best way to determine if you have astigmatism and discuss the best treatment options. Our experienced team of Optometrists are available for appointments Monday to Saturday. Book an appointment online today or give us a call.
* Australian Bureau of Statistics (ABS) 2017–18 National Health Survey (NHS).