Myopia&Hyperopia&Astigmatism

Myopia

Global myopia problem
The incidence of myopia varies in different regions of the world
The incidence of myopia in some Asian countries is very high and on the rise
High myopia can cause damage to the internal structures of the eye, such as the retina and vitreous

What is myopia
After passing through the refractive system of the eye, parallel rays do not focus on the retina, but instead focus in front of it, which is called myopia.

Myopia manifestations
When looking at distant objects, the eyes cannot focus clearly, but within a certain range, the near vision is very clear. After wearing glasses for correction, the image on the retina shrinks

Why is myopia caused
The reason is not fully understood, but it is related to the following factors:  
Genetics,
outdoor exercise time
time spent with eyes in close proximity

Time of myopia occurrence
Tends to occur in adolescence, with myopia extending rapidly during school age. 

What kind of lenses are used to correct myopia?
Myopia is caused by the eyeball being too long or the eye focusing intensity being too high, requiring a reduction in the overall refractive power of the eye in order for the object image to be focused on the retina.
Whether myopia is caused by excessive refractive power or a long axial length, negative lenses can be used to correct myopia in the eyes.

The degree of myopia
≤ -3.00D is mild myopia
-3.25D to -6.00D is moderate myopia
Greater than -6.00D indicates high myopia

Hyperopia

What is hyperopia
Parallel rays entering the refractive system of the eye do not focus on the retina, but instead focus behind it, which is called hyperopia.

Manifestations of hyperopia
Mild hyperopia allows for clear vision of distant objects, but can lead to fatigue and discomfort when looking up close
After a period of time, close range vision will become blurred
Often experiencing headaches or eye fatigue
Relatively speaking, farsightedness is not as common as myopia

Why is farsightedness?
The reason is not yet clear, but there are issues with changes in eye length or weak eye focusing ability

What kind of lenses are used to correct farsightedness?
Need to increase focusing ability to help the object image focus on the retina
Using a positive lens to correct hyperopia

Mild hyperopia is very common - more common than we imagine
In fact, mild hyperopia is considered a normal phenomenon - the eyes can be easily adjusted
A degree of hyperopia of 0+1.50D or above can cause visual impairment where it is difficult to see both far and near clearly

Classification of Hyperopia Degree
Low hyperopia: ≤+ 3.00D
Moderate hyperopia:>+ 3.00D and ≤+5.00D
High hyperopia:>+ 5.00D
This level of grading should also be analyzed in conjunction with the specific adjustment ability of far sighted customers

Astigmatism

What is astigmatism?
The image formed by parallel rays passing through the refractive system of the eye is not a focal point, but rather in the retina or anterior or posterior regions
A refractive state in which two focal lines and the minimum diffuse circle between the focal lines are formed at different positions

The manifestation of astigmatism
Blurred or fatigued vision in both distant and nearby areas

Reasons for astigmatism
The reason is not yet clear, but it is related to the change in corneal shape. After passing through the refractive system of the eye, an object cannot be seen
A focal point is formed on the retina, but two focal lines are formed in the front and back, resulting in unclear vision

Correction of astigmatism:
Astigmatism is easily corrected
Both myopia and hyperopia may be accompanied by astigmatism
Rx. -3.25/-1.25X95 (prescription for myopia and astigmatism)
Rx.+2.25/-0.50X10 (prescription for hyperopia and astigmatism)
When you see prescriptions such as -1.25X95 or -0.50X10, this customer usually suffers from astigmatism

Astigmatism can alter or distort the shape of an object
Regular astigmatism can be easily corrected by wearing glasses