It has been reported that the first one to acknowledge astigmatism and to report it was Thomas Young, back in the year of 1801. Young was an English physician/physicist that discovered the principle that is now known as the ‘interference of light’ and brought to life the wave theory of light. Young was also a Egyptologist, and he used his knowledge to help in decipher the well known Rosetta Stone.
This occurs when the eye(s) has one of the many different types of refractive errors. This can cause the eye(s) a disability where the eye(s) is unable to focus when light falls upon the retina, creating a distribution of light that is uneven. This results in the eye(s) being distorted and regardless of the distance, vision may become blurry. The amount of blur that occurs depends on what the distance is. What kind the eyes have is extremely significant on the shape and/or to the lens, including the way that the eye(s)are cared for. The eye(s) will usually exhibit aberration because of the imperfections of the cornea. Where initially, there is an underlying mechanism which involves the cornea having an irregular curvature or there could be some abnormalities within lens of the eye(s). It is still unclear what causes astigmatism, however, it is thought to be linked to factors that are related genetically. It is a condition that can be diagnosed through a regular eye examination.
There is a total of three various treatments available for correcting this condition. The first option being the easiest way to go, and consists of getting fitted with prescription glasses. However, the second option would be contact lenses, and this will consist of being perfectly prescribed for contact lens instead of glasses, and on the plus side contacts offer a wider range for a persons field of vision, which are the best option for those who would rather not wear glasses. The third option is refractive surgery and this will change the shape of the eye(s) permanently.
The principle meridians are the areas of the eye(s) that are the flattest and steepest. The following are different types that fall under the category of regular astigmatism. These kinds of principle meridians are found to be perpendicular and they are the flattest and steepest meridians to have been found within the eye(s).
Different kinds fall under one of the three different categories for the type, which are: focusing on the principle meridian and the axis of the principal meridian.
- Irregular: With this type the principle meridians will not be perpendicular.
- Oblique: The steepest of all curves will be found lying between 1200 and 1500 , and also between 300 and 600.
- Against-the-rule: The steepest meridian is the horizontal, which resembles an American football (standing on one end or another) or rugby ball.
- The following is a list of different types, which fall into the category of focusing on the Principle Meridian.
- Simple myopic: The first focal line can be found to the front of the retina and the second focal line is found directly on the retina itself.
- Simple hyperopic: Both the first and the second focal lines can be found to the back side of the retina.
- Compound myopic: Both the first and the second focal lines will b located at the front of the retina.
- Compound hyperopic: Both the first and the second focal lines can be found at the back of the retina.
- Mixed astigmatism: The retina is being straddled by both the first and the second focal lines and they can be found on each side of the retina. Some signs and symptoms
When the condition is at higher degrees there may be symptoms like double vision, eye(s) strain, blurry vision, fatigue, squinting, including headaches. There have been research studies which pointed out that those who have astigmatism have shown to have a higher prevalence in migraine headaches.
How is it diagnosed?
There are several different tests that is used when having eye examinations that let the doctor determine whether or not there is a presents of astigmatism, and if so, the doctor will also quantify the axis and the amount that it has. Throughout the eye examination the doctor can find out how much one’s visual acuity has decreased with the use of Snellen charts, eye charts, the Corneal topography is used for finding the shape of the cornea, and a keratometer is used to determine the curvature for the flattest meridians and the steepest meridians located at the front of the cornea. Then there is the autorefractor (also referred to as a retinoscopy), which is used to provide an estimate that is more objective for the refractor error.
Depending on a variety of different considerations that involve the eyes health, including one’s lifestyle and the status of the refractive error as to which of the three options may work better than the others. However, it may be possible to correct the issue by prescribing contacts or eyeglasses, and now, there is also the option of refractive surgery. Another option has became available in recent years which is (LASIK and PRK) or rather, Laser eye surgery, which has proven to be beneficial in the treatment of astigmatism.
Regarding the different types of refractive errors
When refractor errors appear at a young age, there is always the possibility of resulting in amblyopia. The initial cause is still unknown; however, it is thought that it could be linked to genetic factors. What is known about it is that it consists of underlying mechanisms that have irregular curvature within the cornea and it is also a possibility that the lens of the eye(s) have abnormalities.