What does eye diopter mean?

There are many problems with people's eyes. For example, many people now have myopia, a small number of people have hyperopia, and the elderly are prone to presbyopia, etc. When you go to the hospital to check your eyes, or go to a professional eyewear store to get glasses, you will come into contact with the term eye refractive power. Many people don't know what eye refractive power means specifically. Let's learn more about it below.

What does eye diopter mean?

Diopter is the unit of refractive power, expressed in D. It means that when parallel light passes through the refractive material and forms a focus at 1 meter, the refractive power of the refractive material is 1 diopter or 1D. The reciprocal of the focal length of the lens is the diopter. A convex lens with a focal length of 10 cm means a lens diopter of 10D, which means that a 10D convex lens can focus parallel light at 10 cm. The refractive power of the eye is generally measured through methods such as retinal shadowing, computer optometry, and comprehensive ophthalmometer.

Eye refractive problems include myopia, hyperopia, astigmatism and presbyopia. Myopia is the most common and most troubling problem for both adults and children. Below is an analysis of eye refractive problems by contact lens experts.

Hyperopia - congenital and genetic factors

"The main cause of hyperopia is that the eye axis is too short, causing the image to focus behind the retina. It is related to congenital and genetic factors." Contact lens experts reveal the cause of hyperopia in one sentence. "Among full-term babies, 99% are farsighted. After 1 or 2 years old, they gradually develop mild farsightedness, and after 8 or 9 years old, they become non-metropial, and even start to become nearsighted later." Contact lens experts emphasize that farsightedness will disappear with age. It is worth noting that some children with high farsightedness, in order to make the image clear, use their ability to adjust their vision, which causes the medial rectus muscle of the eye to over-contract. Over time, they develop esotropia and amblyopia, which require treatment by a professional ophthalmologist.

Myopia in this section - the degree is easy to increase

In contrast to the cause of hyperopia, myopia is caused by an excessively long eye axis, which causes the image to focus in front of the retina and is closely related to improper eye use. "If you overuse your eyes or write too close, it is easy to increase your myopia. The younger the child, the faster the increase. Therefore, it is very important to take care of the eyes of children before the age of 10." The myopia rate among young children is rising year by year. How to delay the age of myopia is the main goal of young children's eye care.

"Myopia can only increase, not decrease." A contact lens expert puts forward an important concept, "Applying medicine can only temporarily stop the degree from rising, but it cannot restore the already lengthened eye axis to its original state. The best way to prevent myopia is to develop correct eye habits from an early age and engage in more outdoor sports." said the contact lens expert.

Astigmatism in this section - Everyone has it

Astigmatism, also known as stray eyesight, is mostly caused by the cornea not being far enough. In fact, everyone has slight astigmatism, with a degree of less than about 50 degrees, but the degree of astigmatism changes with age. "According to statistics, about 40% of babies are born with 100 degrees of astigmatism, and 20% of children aged 5 or 6 still have more than 100 degrees of astigmatism. This is mainly because babies are born with farsightedness and hyperopic astigmatism, but as they age, the degree of hyperopia decreases and the degree of astigmatism also decreases." Experts say that this common astigmatism problem is usually related to incorrect eye posture and abnormal upper eyelid pressure on the eyeball. As myopia increases, the degree of astigmatism will also increase.