Astigmatism is considered one the most misunderstand vision problem. Many people may call this condition astigmatism rather than astigmatism. Similar to nearsightedness or farsightedness, astigmatism is a work that occurs meaning it a disease or eye health problem. It’s simply an issue with how the focuses light.
In the eye with astigmatism, light does not come into single focus on the retina to produce clear vision. Instead, multiple focus points occur, either in front of the retina’ or behind it both.
Symptoms of an Astigmatism
Astigmatism usually causes vision to be distorted or blurred or distorted to some degree at all distances.
Symptoms of unfixed astigmatism are eye strain and headaches, especially after reading or other prolonged visual task.
What causes Astigmatism
An unnaturally shaped cornea causes astigmatism. With astigmatism, the cornea is shaped like an oval or football, with one meridian being significantly more curved than the meridian perpendicular to it. In a normal eye, the cornea has a symmetrically round shape (like a baseball).
A simple way to understand meridans is to think of the front of the eyes as a clock, and the line that connects the 12 and 6 are the medians, and the 3 and 9 is another one.
The steepest and flattest meridians of an eye with astigmatism are referred to as the principal meridians.
There are three types of Astigmatism
- Myopic astigmatism – This occurs when one or principal meridians of the eye are nearsighted ( if both other meridans are nearsighted, they are myopic in different degree)
- Hyperopic astigmatism. One or both principal meridians are frightened ( if both are farsighted, they are hyperopic in different degree.
- Mixed astigmatism. One principal meridian is nearsighted, and the other is farsighted.
Astigmatism also categorized by regular or irregular. With a regular astigmatism, the principal meridian is 90 degrees apart ( perpendicular to each other). In regular astigmatism, the principal meridians are not vertical. Most cases astigmatism tend to be regular corneal astigmatism, which gives the front surface the eye a football shape.
How common is Astigmatism?
Normally astigmatism often happens early in life, so it essential to schedule an eye exam for your child to avoid vision problems in school from uncorrected astigmatism.
In a recent study children age 5-17 years old, more than 18% of them had astigmatism that was 1.0 diopter(D) or higher
There are also significant differences an astigmatism prevalence based on ethnicity. Hispanic and Asian children have the highest likelihood of-of astigmatism at 36.9 and 33.6%, respectively, followed by white children 26% and African Americans 20%.
Another study on 11, 000 people who wear eye glasses, (including children and adults) 47% had astigmatism of 0.75 D or greater in at least on of their eyes. In 24.1% people astigmatism was in both eyes. There was a high prevalence of myo[oc astigmatism (31.7 %) which was double that of hyperopic astigmatism 15.7%
Astigmatism is detected during a routine eye exam, wth the same techniques and instructions used to detect nearsightedness and farsightedness.
Your eye doctor can do the retinoscopy will be able to estimate the level of astigmatism you have by shining a light into the eye while manually adding a series of lenses between the light and your eye.
Although many doctors still use retinoscopy, this is manual and new teleology and eye care practices provide supplemental and replacement for testing astigmatism and other refractive errors, automate instructions can provide faster preliminary results.
In any case, whether your doctor uses automated refraction or both, the optometrist or ophthalmologist will perform another test to refine the results of preliminary astigmatism and other refractory errors.
In a manual refracture (also a manifest refraction or subjective refraction ) your eye doctor uses instruments called phoropter in front of you eyes. The phoropter includes many lenses that can be included in front of your eyes one at a time so you can compare them.
Looking through the phoropter at an eye chart at the end of the room, you will be shown different lens and the doctor will ask you questions such as which of the two lease makes the letter and number clear” lens A or lens B: You answer to the question helps determine your eyeglass lens.
Options for Astigmatism Correction Options
Along with spherical lens, the power used to correct nearsightedness or farsightedness, treating astigmatism requires additional “cylinder ” lens power to remedy the variation between the force of the two principal meridians of the eye.
The eyeglass prescription for the correction of myopic astigmatism. An example of this could be -2.50 -1.00 X90
The first number -250 is the sphere power in diopters for the correction of myopia in the flatter less nearsighted principal meridian of the eye.
The second number -100 is the cylinder power for the additional myopia correction required for the more curved principal meridian.
The tried number (90_ is called the axis of astigmatism. This the location (in degrees ) of the latter principal meridian, on an 180-degree rotary scale where 90 degrees indicates the vertical meridian of the eye, and 180 degrees designates the horizontal meridian.
If you decide to wear soft toric contact lens for astigmatism, your contact lense prescription will also include a sphere power, cylinder power, and axis designation.
Gas a permeable contact lens are an option because these are rid and optical replace the cornea as the fraction surface of the eye a cylinder power and axis may or may not be required, depending on the type and severity of astigmatism correction required.