Toric Lenses

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Lenses are used as a corrective measure to help people see perfectly. Their vision can be affected by several factors and lead to one or more conditions. These conditions are broadly classified into myopia and hyperopia or nearsightedness and farsightedness. These conditions lead to the creation of different focal points. This makes it difficult for the light rays to fall on the retina. Using lenses of a particular power adjusts the focal lengths to make the light fall on the retina which results in an improved vision. Different types of lenses are used but concave and convex lenses are the most common ones of them. Another type of lens is the toric lens. So, what are Toric lenses? They are lenses that are used to correct the astigmatism condition. Toric lenses are two lenses that are placed perpendicular to each other. 

The reason for it to have two orientations is that one acts as a spherical lens while the other acts as a cylindrical lens. The blurred visions that are caused due to astigmatism can be corrected using these lenses. The results are more accurate if these lenses are used after undergoing an astigmatic surgery.

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When it comes to the Toric lens vs Regular lens, their functioning is quite different but their aim is the same. To understand the use of these lenses, let’s find out what astigmatism is!

What is Astigmatism?

Astigmatism is one of the conditions that occur in the cornea of a person. It is said to be a reflective error that occurs because of the irregular shape of the cornea or due to the eye lens’s curvature. What happens in this condition is that when light enters the eye, it does not get evenly focused on the retina. The uneven focus results in a blurred vision at all distances.

It is necessary to see all the things around us with clarity. The occurring blurred vision due to astigmatism can cause many health issues like:

  • Headaches

  • Eyestrain

  • Eye irritation

  • Squinting

  • Difficulty with night vision

The causes of astigmatism aren’t known but there is a high possibility that it can be caused due to genetics. A person may develop the signs of astigmatism later in his/her life when it is usually present at the time of their birth. It can also occur due to an eye injury or post eye surgery.

Usually, it happens that astigmatism occurs along with either nearsightedness or farsightedness. 

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Types of Astigmatism

There are mainly two types of astigmatism; corneal and lenticular. As the name suggests, corneal astigmatism occurs when the cornea is irregularly shaped and lenticular astigmatism occurs when the curvature of the eye lens is irregular.

Multiple focal points are created in astigmatism and the light does not entirely fall on the retina. This is the cause of blurry vision. By using lenses, these multiple focal points can be adjusted to a single focal point on the retina. This is done by using a toric lens that has two orientations of focal length and optical power.

The lens acts as a combination of both, spherical and cylindrical lenses to adjust the focal point on to the retina. They are usually used after eye surgery to ensure that there isn’t any last sign left of astigmatism.

Fun Fact

Did you know that many people in the world suffer from Astigmatism without being aware of it? Yes, that’s right. Astigmatism is one of the most commonly occurring errors of the human eye. It is a situation in which the cornea is irregularly shaped or the curvature of the lens present in the eye is not proper. 

The actual cause of astigmatism is not known but this error can be corrected by using Toric lenses of the right power. It is the choice of a person to opt for spectacles, contact lenses, or surgery to help them overcome their blurred vision.

Solved Example

1.  Calculate The Focal Length Of A Lens That Is At A Distance Of 20 Centimeters From The Object And 5 Centimeters From The Obtained Image.

Answer: The focal length of a lens can be calculated by using the formula

1/u + 1/v = 1/f

Here, the distance between the object and the lens is denoted by “u” and the distance between the obtained image and the lens is denoted by “v”. The focal length is represented by “f”. The focal length for the given lens would be:

1/20 + 1/5 = 1/20 + 4/20 = 5/20 or 1/4

The focal length of the given lens is 4 centimeters.

FAQ (Frequently Asked Questions)

1. Explain The Toric Lens vs Regular Lens.

A lens is a device that is used to correct the focal power and the refractive errors that occur in someone’s cornea. They help to correct those errors by adding or subtracting the focusing power to the eye’s cornea. Similarly, a toric lens is used as an optical device that has focusing length and optical power in two different orientations that are perpendicular to each other.

Toric lenses are used to correct the astigmatism issues that may arise in a person’s eyes. Regular lenses on the other hand are used to correct myopia and hyperopia. Different power of the lenses is used depending upon the condition of a person’s cornea.

2. What Are The Toric Lenses Used For?

Certain factors affect the focal power of a person’s cornea and cause problems in their vision. To correct a person’s vision, Toric lenses are used. They are specifically used to correct astigmatism. It is a condition that causes a person’s vision to be blurred. It is caused due to the curvature of the lens present inside the eye or due to the irregular shape of the cornea.

These lenses have two orientations of focusing length and optical power that are perpendicular to each other. A toric lens behaves like a combination of the cylindrical lens and the spherical lens. This combination helps to solve the issue of a person’s blurred vision.