No, the two have nothing to do with each other
Definition: Different refractive powers on different meridians of the eyeball or different parts of the same meridians prevent light from gathering at the same focus.
Astigmatism has What Symptoms and Signs
Astigmatism is a defect in the eyeball in which images from distant objects appear as a line on the retina rather than as a clear point. This is due to the cornea or lens not being round enough. Astigmatism mainly occurs in the cornea, and different parts of the cornea have different focusing abilities. The refractive power of the cornea is different on two mutually perpendicular meridians. The result is a distorted or tilted view. In other words, the light reflected by external objects entering the eye cannot form a focus on the surface of the retina, but instead forms a focal line, making it difficult to see far or near clearly. Eyes with this state are called astigmatism. Many myopia and hyperopia are accompanied by varying degrees of astigmatism. Astigmatism is not a disease, but it does often cause vision problems. In fact, 100% of people have some degree of astigmatism.
1. Astigmatism is often intertwined with myopia or hyperopia. The situation is more complicated and can usually be divided into the following categories:
(1) Irregular astigmatism: various parts of the cornea The refractive power is different, and it is very difficult to correct without rules.
(2) Regular astigmatism: The cornea has different curvatures and different refractive powers on two mutually perpendicular meridians, which is called regular astigmatism. It can be corrected.
a. Simple hyperopic astigmatism: the refractive power of the eyeball is normal on one meridian, but the other meridian perpendicular to it is hyperopic.
b. Simple myopic astigmatism: the refractive power of the eyeball is normal on one meridian, but the other meridian perpendicular to it is myopic.
c. Compound hyperopic astigmatism: The eyeballs are hyperopic on two mutually perpendicular meridians, but the degree of hyperopia is different.
d. Compound myopic astigmatism: The eyeballs are myopic on two mutually perpendicular meridians, but the degree of myopia is different.
c. Mixed astigmatism: The eyeball is on two mutually perpendicular meridians, one is farsightedness and the other is myopia.
2. Astigmatism can be divided into 4 types according to the degree of astigmatism:
Mild: less than +1.00 diopters
Moderate: +1.00 ---- +2.00 diopter
Severe: +2.00---- +3.00 diopter
Height: greater than +3.00 diopter
3. Astigmatism What are the signs and symptoms?
a. Blurred vision: Blurred vision is closely related to the degree and pattern of astigmatism. People with mild astigmatism usually have normal vision, but may experience headaches, eye strain, and blurred vision when looking at objects at certain distances. People with severe astigmatism have blurred and distorted vision.
b. Visual fatigue: The blurred image on the retina requires continuous fine adjustment, and the visual distortion occurs, so astigmatism, especially patients with hyperopic astigmatism, are prone to visual fatigue. Young people with compound hyperopic astigmatism can often make up for it with adjustment. Depending on the degree of adjustment, pseudo simple hyperopic astigmatism, pseudo simple myopic astigmatism or pseudo compound myopic astigmatism can form.
c. Abnormal head and eye positions: People with highly asymmetrical astigmatism in both eyes often tilt their heads in order to see more clearly, resulting in strabismus. Astigmatism can be corrected and can be restored. People with high astigmatism often squint when looking at distant objects, creating pinhole and slit effects to improve vision. Seeing through a pinhole or slit can reduce the impact of astigmatism on your vision.
Reports on the incidence of astigmatism in the modern ophthalmic literature vary widely. Generally speaking. Congenital astigmatism is common, while acquired astigmatism is rare. Research has found that congenital astigmatism is very common, and up to 90% of astigmatic eyes can be found clinically. The incidence of significant astigmatism is 7.5%---75%, depending on the purpose of the study and the standards set. About 44% of people have astigmatism of more than 0.50 diopters, 10% of people have astigmatism of more than 1.00 diopters, and 8% of people have 1.50 diopters of astigmatism, astigmia
produced in the optical system of the eye Astigmatism. If the curvature of the refractive surface (mainly the cornea) is different due to the meridian direction, the light from the light spot cannot converge on a focus, and two focal lines in the front and back are produced, thus hindering clear vision.
If when looking at an astigmatism chart with many radial straight lines drawn, it cannot be adjusted simultaneously to make all the straight lines clear, astigmatism can be detected. This type of astigmatism is called positive astigmatism or regular astigmatism (astigmatismus regularis). The radial line of maximum curvature (strong main radial line) and the minimum curvature radial line (weak main radial line) are generally orthogonal, and the strong main radial lines are mostly in vertical positions. This is called regular astigmatism or straight astigmatism. In addition, there is abnormal astigmatism or irregular astigmatism (astigmatismus irregul-aris) caused by irregular concavities and convexities on the corneal surface. Whether there is any deformity on the corneal surface can be directly observed with a Placido keratoscope. Even a normal eye with corneal curvature may have mild straight astigmatism (physiological astigmatism), but it does not hinder clear vision. Astigmatism is expressed as the difference between vertical refractive power and horizontal refractive power. Eyes below 0.5 diopter (D) are still emmetropic. Positive astigmatism can usually be corrected with cylindrical lenses, while incorrect astigmatism can be corrected with contact lenses. In addition, the light beam incident obliquely to the refractive plane will produce a regular astigmatism even in normal eyes, but because the posterior wall of the eyeball has a certain inclination, it plays a correction role.
Astigmatism
Due to the different refractive powers of each diameter of the eye's refractive system, a refractive state in which parallel light rays entering the eye cannot form a focus is called astigmatism.
Cause:
Regular astigmatism is mostly caused by congenital abnormal changes in the cornea, and lens astigmatism may also exist.
Irregular astigmatism is mainly caused by the uneven refractive surface of the cornea, such as corneal ulcers, scars, keratoconus, pterygium, etc.
Performance:
◆The degree of vision loss varies greatly due to factors such as the nature of astigmatism, diopter level, and axis direction. Astigmatism within the physiological range usually has no impact on near and distance vision. , high degree of astigmatism, mostly due to combined radial linear amblyopia or other abnormalities, obvious vision loss, and it is difficult to obtain good corrected vision.
◆Visual fatigue In order to improve vision, patients with mild astigmatism often use methods such as changing accommodation, squinting, and torticollis to correct themselves. Continuous adjustment tension and efforts can easily cause visual fatigue. Eyes with high astigmatism cannot improve their visual acuity due to subjective efforts, and the symptoms of visual fatigue are not obvious.
◆Because the meridians of the cornea and the lens have different curvature sizes, the difference in curvature of the horizontal and vertical meridians is usually the largest.
◆ Caused by corneal crystal disease such as keratoconus, corneal clouding, early senile cataracts, etc.
Symptoms:
1. Vision: It is difficult to see clearly at distance or near, as if there is a double image.
2. Eye fatigue: eye swelling, headache, tearing, nausea and vomiting.
3. Fundus: Sometimes the optic disc appears in a vertical oval shape with blurred edges, and the fundus cannot be seen clearly with glasses.