How to treat Cylinder Number (Astigmatism) in Eyes
How To Treat Astigmatism or Cylinder Number in your Eyes
What is Astigmatism?
Astigmatism, is an error of refraction or focusing of light, like near sightedness and far sightedness. It is not an eye disease per se, even though it does sound scary. The front of the eye has the transparent curved surface called the cornea, which accounts for how the eye focuses light, along with the natural lens of the eye. In myopia, this curve is exaggerated, focusing light in front of the light sensitive retina, while in hypermetropia it is flattened, thereby focusing light behind the retina. Consequently, one needs to use a system of lenses, either convex or concave (plus or minus), to ensure proper focusing of light.
What Causes Astigmatism?
In astigmatism, the corneal surface is shaped like an American football or bottle gourd, with the curvature not being the same in both axes. Therefore, different rays of light entering the eye get focussed at multiple points, some in front of the retina and/ or some behind it. This results in a blurred image, which may also be distorted, to some degree for both near and distance.
The most common symptoms of astigmatism are eye strain and headaches, especially after reading or watching a movie.
Correction of astigmatism with glasses requires a special cylindrical formulation, and the glasses so made are not different to look at from that of regular glasses for near or far sightedness. As is true for the use of glasses for myopia or hypermetropia, they come with a certain set of advantages and disadvantages.
Doctors often prescribe special contact lenses for those patients who do not wish to wear glasses. Regular soft contact lenses can correct mild astigmatism, while mild to moderate astigmatism can be corrected by specialized toric soft lenses. For higher degrees of astigmatism, special Rigid Gas Permeable or RGP lenses may be required. In fact, hybrid contact lenses, with a rigid central zone and a soft peripheral frill, can also be used. These lenses are especially customised, and require the services of a contact lens expert.
Laser Vision Correction: LASIK and its variants:
It was earlier presumed that LASIK may not correct astigmatism or cylindrical error as well as it corrects the spherical error. However, long term results of clinical trials as well patient-doctor experience has proved that LASIK can correct both spherical and cylindrical error as well.
During LASIK, the cornea is reshaped on the basis of the existing corneal topography. The LASIK machine is linked with a state of the art computer and can be programmed correct each of the axes, with great precision and accuracy.
In fact, the newly available technology of Contoura Vision Topography-Guided Laser Correction maps as many as 22000 data points on the cornea, and corrects them with customization, providing the kind of visual results that were, till now, considered impossible to achieve. The first Contoura Vision Topography-Guided Laser Correction in Delhi was carried out by Dr Sanjay Choudhary in Eye 7 Hospital, New Delhi. It is also available at Dr R P Centre, AIIMS, New Delhi and at Medanta hospital, Gurugram.
SMILE or small incision lenticule extraction is only approved by the US FDA for upto 0.5 dioptres of astigmatism, so is not really a treatment option for patients with astigmatism.
LASIK is contraindicated in a disease called Keratoconus, a progressive eye disease which is often associated with astigmatism.
Toric Implantable Collamer Lenses, ICL
ICLs are very thin lenses that are placed permanently inside the eye, like the lenses used in cataract surgery, but without removing the natural lens of the eye, so that your vision can improve without the use of spectacles. In patients with very thin corneas, high refractive errors, as well as some cases of stable keratoconus, toric ICLS are the best refractive surgery available. The Toric ICL can correct upto -3 to -23 D of sphere and + 1.0 to + 6.0 D of cylinder as well. The Toric ICL is highly effective, therefore, in correcting your nearsightedness as well as your astigmatism.
Which option to choose?
As is true for any other medical condition, your treating ophthalmologist is the best person to talk to. You can discuss with him or her your visual needs, as well as apprehensions and fears. After a thorough eye examination your doctor will help you choose the best fit for your eye, and will offer you the safest and the most effective solution for your problem.
You may decide to wear glasses, or contact lenses, or look for a permanent solution. Long gone are the days when people with astigmatism were considered ineligible for refractive surgeries: there are enough options which your eye doctor can help you choose from.