Astigmatism: A Basic Guide

Astigmatism, an often misunderstood term is more like any other refractive error problem. Yes! A simple problem in how the eye focusses light.


Before we delve deeper, it is important to get a basic idea of how an eye generates vision. Very simply, when you see an object, the light emitted from it falls on the eye. The eye then focusses this light on the retina and generates the image of what you see and even how you see it.

Understanding Astigmatism

So, then what is astigmatism? Well, when the eye is unable to focus the light on the retina and manages to do so in front of it or even behind it, the person is likely to be suffering from some degree of astigmatism. Just like nearsightedness and farsightedness, the solution for astigmatism also lies in opting for the right lens. Primarily there are three types of astigmatism.

First is myopic astigmatism where one or both principal meridians of the eye are nearsighted, basically myopic in differing degree. Second is the hyperopic astigmatism where one or both principal meridians of the eye are farsighted and the third type is mixed astigmatism where you see symptoms of both nearsightedness and farsightedness. Many lens makers specialise in offering lens for astigmatism and we will tell you more about them a little later in this article. Another off shoot of this variation is the irregular astigmatism which is often a result of some accident or injury, involving the eye.

Symptoms and detection

Those suffering from astigmatism are likely to experience blurred or distorted vision. Primarily astigmatism is of two types – regular and irregular. The regular one is more like a refractive error arising from the eye’s inability to focus light while the irregular one is more often a result of injury or damage to the eye, from an accident. Since astigmatism usually occurs early in life, a regular eye exam is the best way to detect it. Ideally, it is always advised to check if your customer has sought medical diagnosis before approaching you for an astigmatism lens.

Correcting astigmatism

Astigmatism, like nearsightedness and farsightedness, usually can be corrected with eyeglasses, contact lenses or refractive surgery. Now let’s move towards the lens correction options for those who suffer from astigmatism. Usually, a spherical lens is used to correct nearsightedness or farsightedness. For astigmatism, an additional “cylinder” lens power is added to the above options. This cylindrical lens power is used to correct the difference between the powers of the two principal meridians of the eye. The cylindrical lens power is what the optician will likely see as a cylindrical axis in the ophthalmologist’s prescription.

Option for lens wearers 

Soft toric contact lenses are also used for astigmatism correction, just that the lens prescription will include a sphere power, cylinder power and axis designation. Gas permeable contact lenses are also an option as they can optically replace the cornea as the refracting surface of the eye. However, these lenses are rigid and therefore avoided. There are cases when a cylinder power and axis may not be needed. It all depends on the type and severity of astigmatism correction required. A similar theory can be applied for the hybrid contact lenses as well. Refractive surgery such as LASIK can also be used to correct astigmatism.

What brands offer?

Now that we have taken you through the basics of astigmatism, here is a look at what leading lens brands offer for those with astigmatism.

Essilor

Their Crizal range is designed to accommodate cylindrical power as well. The lenses are durable, smudge-free and easy to clean. The Crizal range comes with various options with different coatings making them an excellent choice for customers who come in with an astigmatism prescription. The lenses have been designed to give a clearer vision experience to the wearer as well as protect the eyes from the harmful rays of light, in the long run.

Hoya

As every pixel on the lens surface has its own calculation value, each individual’s prescription can be uniquely cut into these lenses. The brand’s range of single vision lenses cover the requirements of those diagnosed with astigmatism. This range includes Hoya’s Dynamic Sync lenses which are designed to keep the eyes energised throughout the day. Wearers can enjoy comfortable vision even after long hours of work involving strain for the eyes, with smooth transition when viewing from far to near.

Another option in this category is Hoya’s Nulux lenses which offer wearers optimised visual performance and a natural image perception. The Nulux range is Hoya’s successful attempt at designing flatter lenses that are easy-to-clean, scratch-resistant and are durable as well. Wearers also have the option of choosing from Hoya’s extensive range of coatings to further improve their seeing experience through the lens.

Cooper Vision

Biofinity toric lenses by Cooper Vision are developed using Aquaform® Technology. These lenses allow plenty of oxygen to pass through to the wearer’s eyes. And their natural wettability won’t rinse off very easily allowing the wearer to enjoy excellent vision with a soft, comfortable lens that’s healthier for the eyes.

Johnson & Johnson

The Acuvue range of lens by Johnson & Johnson work well for astigmatism patients. The unique design of these lenses offer wide coverage guaranteeing clear vision. The design of the lens ensures that the eye remains moist, making these lenses a comfortable choice even when worn for extensive durations. Currently, the three options available in this category exclusively for astigmatism patients include: 1-DAY ACUVUE® MOIST, ACUVUE OASYS®  and ACUVUE OASYS® 1-Day.

HOYA

The HOYA Airy One Month (Toric) is a lens developed for astigmatic patients. The lens has been developed using silicone hydrogel material that is able to supply a sufficient amount of oxygen to the cornea without relying on moisture content. The use of Silicone Hydrogel in making the lens and the plasma coating on the surface help in maintaining the moisture level of the eye. This in turn guarantees all day long comfort for the wearer. The plasma coating also prevents the harmful UV radiation from reaching the eyes.