Contact lenses for Astigmatism
Soft contact lenses were first introduced in the 1960s but many still found themselves excluded from using lenses as there were no contacts for astigmatism available.
People with astigmatism (in most cases) have an irregularly shaped cornea. This results in light focusing through the surface of the cornea to fall on two different points.
A popular analogy to explain astigmatism is to describe the cornea as being shaped more like the curve of an AFL football, which differs depending on whether you follow the curve sideways or lengthways. As opposed to a soccer ball which is the same spherical surface no matter which direction you follow.
While most cases of astigmatism arise from the cornea at the front surface of the eye, some result from the lens inside the eye, known as lenticular astigmatism
, and the amount of astigmatism will vary from person to person.
People with astigmatism often experience the following symptoms:
A starburst-type glare of lights, like oncoming car headlights at night
Headaches and eyestrain
Ghosting or shadowing of images
How do Contact Lenses for Astigmatism Work?
As medical technology has developed, so have techniques and materials used to create contact lenses. Thus, we now have contact lens options for correcting astigmatism, as well as a much wider range of other parameters, and visual acuity.
Nowadays, you have the choice of standard soft lenses, toric design lenses, RGP lenses (rigid gas permeable contact lenses), and more.
In the late 1970s contact lenses for astigmatism, also known as toric lenses, became available. Toric contacts tend to be slightly wider in diameter to other lenses, to help provide better stability.
Eye care is of course of the most important, particularly when it comes to contact lenses. It’s therefore essential that your toric contact lens fits well. If not, they can be unstable on the eye between blinks or eye movements, resulting in fluctuating vision.
Ensuring a contact lens for astigmatism remains aligned on the eye is a concept known as stabilisation, and is essential in maintaining non-fluctuating vision. Different manufacturers achieve this in different ways.
The basic principle is varying lens thickness (and weight) across different zones of the lens, taking advantage of gravity to orientate the lens in a specific way on the eye.
Eyelid anatomy and the dynamics of blinking and eye movements vary from individual to individual. One toric lens that fits well on one eye will not fit well on the next.
Some patients with astigmatism are frustrated that they cannot achieve adequate vision with contact lenses.
Intraocular Contact Lenses
Intraocular contact lenses are considered to be a safe and effective method of permanent vision correction. Also known as implantable contact lenses, are a biosynthetic collagen lens designed to be surgically inserted inside the eye. They are placed between the iris (the coloured part of the eye) and the natural lens of the eye.
A small incision is made in the cornea for the lens to be inserted. Intraocular contact lenses are considered to be a safe and effective method of permanent vision correction.
The procedure itself is quick and recovery time is short. The greatest advantage of implantable contact lenses is the vast range of prescriptions they can cover.
Options in regular contact lenses are scarce once they exceed -2.75 dioptres of astigmatism. And those few toric lenses available past this degree may have a greater likelihood of being unsuitable for an astigmatic patient.
Implantable contact lenses however can treat astigmatism of up to -4.5 dioptres, myopia of up to -18 dioptres, and hyperopia of up to +8 dioptres.
As the lens sits within the eye, it is not subject to the dynamics of eyelid movement and difficulties of stabilisation. This makes it an excellent option for vision correction. Especially in patients who are unsuccessful with toric contact lenses but wish to reduce dependency on glasses.
Intraocular contact lenses are often also a viable option for patients looking into refractive surgery but find themselves falling outside of the parameters of LASIK or PRK. Unlike these procedures, implantable contact lenses do not rely on minimum corneal thickness in order to provide prescription correction.
To find out more, book your free initial consultation with Eye Laser Specialists today, call us on 0390 700 910.