Like myopia (nearsightedness) and hypermetropia (farsightedness), astigmatism is also a refractive error, meaning it is not an eye disease or health problem; it’s simply a problem with how the eye focuses light and forms image. Astigmatism is a form of error in which parallel rays of light entering the eye cannot form a point focus on retina. Astigmatism usually causes vision to be blurred or distorted to some degree at some distances.
CAUSES OF ASTIGMATISM
In Astigmatism, light do not focus on single point but on two or more points. It is due to
- irregular shape of cornea (is shaped more like an American football)
- eye injury
- changes on refractive power of cornea and lens
- decentralized Lenz
- Changes in refractive index of lens
- chronic exposure to UV rays
- shape of lens inside the eyes
- Vision is decreased because sharp image is not formed by accommodation mechanism.
- Half closure of eyelid occurs to get good vision.
- blurred vision
- scattering of light
- migraine (if not treated)
HOW IT IS DIAGNOSED?
To the observer, patient presents with blurred vision, asymmetrical shape of cornea, eye strain and scattering light perception. It is diagnosed by proper history, retinoscopy, keratometry and astigmatic fan test.it should diagnose as earlier as possible because if it is continuous to increased, effected eye will stop accommodation effort to achieve good effort and eye will be atrophied.
First Discuss with your eye doctor which procedure is best for you.in early stages, doctors prescribed the glasses or lenses but in more severe or advance stage, surgery has to be done to safe eye further.
- Photorefractive keratectomy
- Limbal relaxing incision (to decrease curvature)
- Extra suture (to increase curvature)
- Refractive surgery such as LASIK also can correct most types of astigmatism.
NON SURGICAL TREATMENT
Like astigmatism, like nearsightedness and farsightedness, usually can be corrected with eyeglasses, contact lenses.
In addition to the spherical lens power used to correct nearsightedness or farsightedness, astigmatism requires an additional “cylindrical” lens power. It used to correct the difference between the powers of the two principal meridians (surfaces) of the eye.
So an eyeglasses prescription for the correction of myopic astigmatism could look like this: -3.50+1.00x 180(as an example).
The first number (3.50) is the sphere power for the correction of myopia in the (less nearsighted) principal meridian (surface) of the eye.
The second number (-1.00) is the cylinder power for the additional myopia correction required for the more curved part of principal meridian. In this case, the total correction required for this meridian is 4.50 D (3.50 + -1.00 = 4.50 D). D stands for diopters (power)
The third number (180) is called the axis of astigmatism. Where 90 degrees designates the vertical meridian of the eye, and 180 degrees designates the horizontal meridian.
If you wear soft toric contact lenses for astigmatism, your contact lens prescription will include a sphere power, cylinder power and axis designation same as glasses
Gas permeable contact lenses are also a good option. Because these lenses are rigid. They optically replace the cornea as the refracting surface of the eye. a cylinder power and axis may or may not be needed, depending on the type, severity and cause of astigmatism correction required.by using contact lenses or by wearing cylindrical glasses, person not only prevent Astigmatism but also can stop further vision loss.
Accumulation of UV light in your eyes can also cause cataracts. Sunlight exposure is also a contributing factor to Change the refractive power of eye and surface of cornea. UV light can be responsible for ageing your eyes by creating unsightly yellowish coloration to the whites of your eyes which not only diminishes the whitening appearance of sclera but also effect the surface of cornea.
Not only do sunglasses protect your eye but also give a shiny look to eyes