Astigmatism is a vision disorder when the rays that have passed through the eye’s optical system intersect in not one but two foci. This is the result of a blurry image on the retina.
Reasons
An irregular shape, position or damage to the cornea or lens causes astigmatism. In order for a person to see clear, sharp images, his cornea and lens must be of correct shape, healthy, and undamaged. With astigmatic changes, the eye refracts rays differently in the horizontal and vertical planes. For example, an image may be clearly focused on the retina in the horizontal plane, but the rays intersect in front of or behind it in the vertical plane. This means that astigmatics do not see horizontal and vertical elements equally well, so objects in the environment appear as if stretched vertically or flattened along the horizontal direction and blurred.
Astigmatism always reduces a person’s visual acuity. Accommodation and its long-term tension do not always help to see better and very often turn into spasms. Uncorrected astigmatism is very often the cause of blepharitis and blepharoconjunctivitis. Astigmatics feel eye fatigue not only after small work but also after looking into the distance for a long time (show, movie, driving a car) because they can never see clearly without wearing glasses.
Astigmatism types
There are two types of astigmatism:
- correct – when the refractive power of the eye is the highest in one plane and the lowest in the other. Such astigmatism is found most often and is hereditary and congenital. Basically, it is a congenital hereditary anomaly that changes little throughout a person’s life. Straight, regular, small (up to 0.5 D) astigmatism occurs very often. People rarely complain about it, and it is also called physiological. Acquired, regular, relatively significant astigmatism often occurs after intraocular operations (especially after cataract extraction).
- irregular – when the refractive power of the eye varies in the same plane. It is caused by corneal damage (scarring), keratoconus, etc.
Astigmatism is also divided into:
- simple – when the refraction is normal in one plane (emmetropia);
- composite – when the strength of refraction is the same in both planes;
- mixed – when farsightedness is detected in one plane and nearsightedness in the other.
Symptoms
With a slight astigmatism – up to 0.25 – there are usually no signs. However, in the case of more substantial astigmatism, the symptoms are pretty obvious:
- blurred vision
- constant desire to squint,
- asthenopia or otherwise eye fatigue,
- severe headaches.
Some studies show a link between astigmatism and migraine headaches. It has also been observed that in case of nearsightedness or farsightedness, the probability of astigmatism is higher. So, when these symptoms appear, you shouldn’t put your hand on them and put all the blame on stress or fatigue.
To have a perfect vision
Eyes, like other organs, must be taken care of. Everyone, regardless of the condition of their eyes, should see an ophthalmologist at least once a year for comprehensive vision and eye exams. Tests are especially important if you have already been diagnosed with a visual impairment – remember, if you are nearsighted or farsighted, you are also more likely to have astigmatism. It is also very important to check children’s eyesight in time. A child should visit an ophthalmologist for the first time before the age of one, then at three and six. If there are people in your family with vision problems, children’s eyes should be checked more often.
During general eye and vision tests, your doctor may already notice signs of astigmatism. In this case, special tests are performed: keratometry (refractive ability of the cornea), corneal topography, autorefractometry, retinoscopy, etc. After examining the eyes, the doctor indicates the degree and direction of astigmatism in the patient’s card (or prescription for glasses/lenses or laser eye surgery).
Astigmatism is a fairly common eye defect – even about 30% of the population has astigmatism greater than 0.5 D. Minimal astigmatism – up to 0.5 cylindrical diopters – does not significantly affect vision. However, vision is considered good if there is no more than 0.0 – ± 0.2 D deviation from the norm. However, for some people, the irregular shape, position or damage of the cornea or lens is clearly expressed, so the images they see are not only blurry but sometimes even double. This occurs with astigmatism greater than 0.5 cylindrical diopters. Some specialists recommend wearing special glasses or lenses for the correction of astigmatism already in the presence of 0.25 cylindrical diopters of astigmatism, but when the astigmatism exceeds 0.5 D, vision must be corrected with special cylindrical glasses or toric contact lenses.
However, glasses and contact lenses are only temporary help and do not eliminate vision impairment and its causes. Astigmatism can be removed with the help of surgery, and sometimes, it is the only chance to regain perfect vision. One of the most advanced methods is excimer laser corrective surgery. During it, the shape of the cornea is changed, or a special intraocular toric lens is implanted. However, the treatment method is determined by the type of astigmatism, the condition of the eye and general health.
An eye care specialist will determine which treatment method is most suitable for you. Do not forget to visit the ophthalmologist’s office once a year – this way you will avoid eye diseases and their complications.