What are toric contact lenses? What is meant by “toric”? Think “T” for “two”.
Toric lenses come in two different powers in order to help folks with astigmatism.
Three types of ocular problems need corrective measures taken either through the use of lens or through corrective spectacles – myopia or nearsightedness, hypermetropia or farsightedness and Astigmatism or Cylindrical vision.
Of the three defects, astigmatism is a little interesting as it is hitherto unknown to most people.
Astigmatism is an optical problem wherein vision is blurred due to the curved nature of the cornea.
Owing to the irregular shape of the cornea, a sharp focused image becomes blurred, owing to a shift in the focal point.
Astigmatism can be corrected by the use of a corrective contact lens called the toric lens.
This is different from the other types of corrective lenses; in it, the lens has a surface which is a combination of a sphere and a cylinder.
One surface is spherical and the other is slightly cylindrical.
The lens comes with two different levels of power.
A regular contact lens is either spherical or cylindrical in shape, shifting the focus of the uncorrected eye to the appropriate position, rendering a sharp image on the retina.
Toric contact lenses are specially made to correct mismatching foci, especially if the cornea is a little on the curved side.
The lens has two curvatures suited to correct eye related ailments specifically astigmatism.
Astigmatic patients usually are prescribed cylindrical lenses, but to correct additional problems such as far-sightedness which could get coupled with this defect, an additional spherical component would help rectify this problem.
Here is where this special lens comes into play.
It has got both a spherical component as well as a cylindrical component and can help aid patients who have both these disorders in their eyes.
The lens is available in all forms – soft, hard and gas permeable contacts – all flavors are available in the markets.
The lens is asymmetric meaning that the curvature is not the same all round.
This means that the lens needs to be maintained in the same position irrespective of the movement of the eye, so as to keep the focal length constant, providing the correct visual sharpness.
This requires the lens to be made with tiny striations or irregularities at the curved surfaces so as to provide the grip, keeping the contacts in the same position.
This makes the lens slightly expensive when compared to the normal spherical lenses.
Contact lenses are increasingly being preferred over spectacles due to their convenience and ease of use.
Moreover, considering their cosmetic value, they are preferred over other forms of vision correction.