What is Astigmatism?
Astigmatism is a common eye condition characterized by an optical deficiency particularly blurry vision as a result of irregularity in the curvature of the cornea of the eye. It is known as a refractive error that can occur to everyone in all age levels.
The eye has to focus on a single plane in order to see clearly in which the focus in light is thrown back onto the retina. In people with astigmatism, the focus of eye towards the light is directed in two planes that make the visual blurry. Normal eye takes on a spherical shape with refraction evenly distributed which makes a clearer vision of a certain object or focus. In astigmatism however, the shape of the eye is irregular and somewhat like the shape of the football that the light is concentrated in one direction when refracted resulting to a blurry vision when visualizing at a distance.
Astigmatism can either be corneal or lenticular. Corneal astigmatism is the result of deformity in the shape of the cornea while lenticular astigmatism resulted from a deformity in the shape of the lens. Both types of astigmatism cause blurred visual in horizontal, diagonal or vertical in one direction of vision.
Test for Astigmatism
Ophthalmologist or an optometrist is the proper doctors to diagnose astigmatism and they need to do a thorough test to verify this condition of refractive error. Astigmatism is diagnosed according to the measure of light reflected and the shape or curvature of the cornea and lens of the patient. Various test for the eye can be utilized to gauge and verify suspicion of astigmatism in patient. Such tests include the following:
Corneal topography is used to accurately determine the shape of the cornea of the patient. The color coded curvatures of the cornea is mapped out to give eye doctors better understanding of the shape of the cornea. It is a non-invasive imaging technique and this diagnostic procedure is also called photokeratoscopy or videokeratography. The corneal shape is revealed through reflected pattern captured during the procedure where the patient is made to face an illuminated pattern or concentric rings.
Snellen chart is utilized in measuring the visual acuity where it reveals a decrease in the visual acuity of patient suspected of suffering from astigmatism. Patient is asked to read the chart from a standard distance with one eye while covering the other eye and vice versa.
Keratometer or ophthalmometer is used for measuring the curvature of the anterior surface including the extent of astigmatism and its axis.
Retinoscopy is applied to measure the refractive error in the eye of the patient suffering from astigmatism. The measurement is gathered through the use of a retinoscope by observing the reflex of the retina when a light is shined to the eye of the patient.
The test for astigmatism not only confirm the refractive error condition but the type of astigmatism a patient is suffering from can clearly be identified basing the principal of meridian in axis or in focus and such types are the following:
- Regular astigmatism has principal meridian in perpendicular direction
- Irregular astigmatism has principal meridian not perpendicularly directed
- Simple astigmatism
- Compound astigmatism
- Mixed astigmatism
Symptoms of Astigmatism
Astigmatism in mild form may not have any symptoms that it may go unnoticed although may tend to develop to higher degree if left untreated. Manifestations of symptoms occur to those with high degree of astigmatism and patient may experience the following symptoms:
- Blurry visual resulting from the inability of the eye to focus that leads the retina unable to produce a sharp image focused
- Fine details whether in close distance or from a distance is difficult to visualize
- Headache is common which is the result of distorted image being reflected
- Difficulty to see reflect or see images clearly can lead to eyestrain and eye fatigue.
It is necessary to have the eye checked if there is the presence of changes in visuals as not all symptoms mentioned are direct confirmation of astigmatism. The condition of this refractive error ca hinder in the daily activities and quality of life.
The etiology of astigmatism is implicated on the irregularity in shape of the cornea of the eye where the curvature in astigmatism is similar to the shape of football instead of spherical. The development of this condition can occur on one eye or even both eyes.
Hereditary factor is also considered for the etiology of astigmatism with the onset present at birth or may develop during early childhood to young adulthood although the amount of astigmatism is considerably small.
Astigmatism may also develop after an injury or surgery such as in the removal of cataracts and may also occur in association with other refractive errors such as myopia and hyperopia. Infection of the eye has also been linked to astigmatism such as the condition of keratoconus where the cornea is cone shaped and the apex of the cornea is pushed forward.
Another etiology being implicated in astigmatism is reading with poor light or watching television too close to the screen although these have no concrete evidence yet or proof that this can make this refractive condition worse.
Treatment for Astigmatism
The condition of astigmatism can be corrected while therapeutic medicine approach is applicable to uncomplicated cases or for astigmatism caused by an underlying condition that requires treatment prior to correction of vision. The aim for treating and managing is to deal with the irregularity in the curvature of the cornea which is the main cause of this refractive error. Correction of astigmatism depends on the severity and degree as measured with the utilization different test for astigmatism. Approaches for correcting astigmatism include the following:
- Eyeglasses are among the corrective lenses recommended to be worn by patient in order to address the unevenness in the curvature of cornea.
- Contact lenses come in variety and can also correct astigmatism.
- Refractive surgery has different methods in correcting astigmatism while this method is done to reshape the curvature of cornea.
- It is better to seek the advice of doctors in determining which is best for correcting astigmatism.