Astigmatism, often mispronounced as ‘stigmatism’ is a vision error which is generally not categorized as an optical health problem. In fact, scientific explanation notes that the more commonly occurring astigmatism is a refractive error caused due to uneven corneal curvature of the eye.
Types Of Astigmatism:
Although corneal astigmatism is what one refers to when the condition is talked about; there are other forms of astigmatism such as Myopic astigmatism, which is a condition when one or both the principal meridians of the eye are nearsighted. As with Hyperopic astigmatism, one or both of the principal meridians of the eye are farsighted. In Mixed astigmatism, one of the principal meridians is nearsighted while the other is far sighted.
Regular astigmatism occurs when the principal meridians of the eye are 90 degrees apart from each other or perpendicular to each other; whereas in Irregular astigmatism, the principal meridians are not perpendicular to each other.
Apart from these types of astigmatism, another condition called lenticular astigmatism occurs in individuals which is related to the irregular shape of lens in the eyes.
What Is Astigmatism?
Refractive error in corneal astigmatism occurs because the eye cannot focus evenly on the light rays that pass through it. A person suffers from astigmatism when light rays are unable to fall uniformly at a given point or if it fails to adjust or come together in a single focus on the retina of the eye.
Astigmatism is caused when rays of light passing through the eye, come at multiple focus points, sometimes in front of or behind the retina. This leads to blurring of images as focus is not steady on the surface of the retina, which is then unable to refract properly.
This effect is primarily seen when the cornea has a curvature that is shaped like an ellipse or like a football or resembles the back of a spoon.
This irregular curvature prevents light to focus evenly and gets refracted in more than one direction, enabling the eye to focus only on parts of an object rather than the whole. Person is unable to focus well on the object and sees blurred visions or wavy apparition of the same object.
As against this, a person with normal eye vision has symmetrical curvature of the cornea, more like a baseball which can then refract light evenly in one direction; hence the focus on the object is better.
Because astigmatism is caused due to uneven curvature of the cornea, this is considered as a common eye problem that can be corrected by appropriate use of eyeglasses, contact lenses or also through surgical intervention.
Causes Of Astigmatism:
Astigmatism is known to be hereditary and occurs since birth. However, the condition can also be acquired due to pressure on the eyelids which could add extra pressure on the cornea of the eye. Sometimes incorrect posture or excessive intense use of the eyes without relaxation, could also trigger astigmatism.
Symptoms Of Astigmatism?
As with other eye conditions, undetected astigmatism could be due to persistent headaches, fatigue, straining of the eye following excessive reading. Blurred vision at all distances could be a trigger to go in for an eye check up for astigmatism. One should watch out for one or all of these symptoms which might lead to astigmatism.
Diagnosis Of Astigmatism
Eye examination is the primary mode of diagnosis. Diagnosis by a qualified optometrist or ophthalmologist could pinpoint astigmatism which sometimes also occurs with other refractive errors such as myopia or nearsightedness and hyperopia or farsightedness. However, the condition is very difficult to diagnose in school going children and can remain undiagnosed for a long time until it becomes more pronounced at later stages!
Testing Astigmatism:
A routine eye examination could be the first step to detect astigmatism. This eye test is similar to that performed to investigate the occurrences of near-sightedness or far-sightedness. During the test, a light is shone on the eye while the eye physician introduces a series of lenses between the light and the eye. This is a manual test and the most basic eye check to determine existence of astigmatism. This process is known as retinoscopy.
Manual retinoscopy has now been replaced or enhanced by making use of automated instruments that provide quicker preliminary test for astigmatism and other refractive errors.
In most cases the optometrist or ophthalmologist will usually re-asses the preliminary finding with another manual refraction procedure before issuing any prescription eyeglasses.
Treating Astigmatisms
Eyeglasses or Contact Lenses: A common mode of treating moderate to higher degree of astigmatism is by wearing either prescription eyeglasses or lens. In individuals with a lower degree of astigmatism, corrective lenses might not be required at all especially if the person is not suffering from either farsightedness or near sightedness.
The commonly used prescription lens used to correct astigmatism is called toric lenses. These lenses effectively bend the light rays in one direction enabling uniform refraction of light. A qualified optometrist would generally determine the type of toric lens to be used once eye tests are examined determining the error levels.
Rigid gas permeable contact lenses are also used to correct astigmatism. The rigidity of these lenses can optically replace the cornea. The lens then acts as the refracting surface of the eye, providing a cylindrical power and axis which may or may not be needed. This again depends on the type and intensity of the astigmatism and related correction factor is brought in.
Refractive surgery: Refractive or laser eye surgery is a method to alter the shape of the cornea which can correct the non-uniform curvature on the cornea. There are different types of refractive surgeries which are tailored as per an individual’s requirement; also depends on the intensity of the astigmatism. However, refractive surgeries can be performed only on individuals whose eyes are free from other retinal problems, corneal scars or any other type of eye disease.
In recent times, refractive intervention such as LASIK method is known to correct almost all types of astigmatism.
However, a word of caution is that despite the new procedures available, it is always safe to discuss the treatment procedure with a qualified eye physician for correcting astigmatism.
Also, it becomes essential to be aware of the modalities of progressing technology in eye care treatments. Especially, with refractive surgeries, the methods vary as per the severity of the astigmatism; hence heed guidance from a qualified eye doctor on the best course of treatment!
