Controlling the progression of myopia

Myopia is an eye condition where vision is clear up close, but blurred far away. In myopia, images of distant objects are formed in front of the retina rather than on it.

Myopia is a major cause of vision loss worldwide. It's not new, but it's becoming a growing concern for us today, as the percentage of those affected is increasing. Over the past 50 years, the number of myopic patients has doubled in many countries, with Asian countries being the most affected. The number of myopic patients is increasing, so we must have a thorough understanding and up-to-date information to address this refractive error.

When we talk about myopia control we refer to the control of the progression of myopia

Control doesn't mean cure. We can't eliminate myopia in patients who are already myopic, but we can act on its progression. This is the message I want to convey: we can do something to prevent it, even before it appears, and if it's already present, we can control its progression.

Currently, the management of myopia is approached differently, taking into account several aspects. It's no longer just a matter of refraction and prescription for glasses with conventional lenses, and perhaps refractive surgery later on. It also includes the possibility of fitting special contact lenses, orthokeratology treatment (Ortho-K lenses), or even atropine. But the important thing is to try to do something to prevent or prevent myopia progression.

How do we know that myopia will appear?

We need to understand the child's ocular development. That is, we have information about the evolution and development of the eye at a certain age and whether or not this development is as expected. If this development doesn't progress toward emmetropization, a neutral value, which would be the physiological evolution, it can be a factor that predisposes to myopia, or pre-myopia. This means a physiological state of the eye that is on the path to full-blown myopia.

Children are born with hyperopia and mild astigmatism. As they grow and their eyeball develops, this astigmatism disappears, and hyperopia decreases until it reaches zero or neutral, around the age of 6-8. This is the physiological process of emmetropization, the development of the child's visual system. If this doesn't occur, it may indicate that something is wrong and that the physiological process isn't occurring.

In other words, if optometrists find that at a young age there is no mild hyperopia, this finding may indicate that the patient has low or relatively recent myopia, but it has already developed. And when it has already developed to high levels, such as 4-5 diopters, it requires very careful monitoring.

Why should we seriously consider myopia control?

Currently, the number of myopic individuals in our society is increasing at an ever-increasing rate, and myopia is increasingly appearing at younger ages. The prevalence of myopia is increasing and is cumulative, resulting in an ever-increasing number of myopic individuals. This is a reality, and it is becoming a public health problem.

Myopia is increasing dramatically. In just two generations, it has gone from 10% to 15% to 40% to 45%. Around 35% of current university students in Europe are myopic, and it's also becoming more common at younger ages.

We are not only concerned about the progression of myopia, but if it increases excessively, that is, if it increases by 6 diopters or more (pathological myopia), the risk of suffering from eye diseases that are associated with myopia increases, such as: retinal detachment, early cataracts, glaucoma, myopic retinopathy, myopic maculopathy.
All of this damage can irreversibly impair vision. The cumulative risk increases with age. People with myopia won't see the results of their myopia until they are 40 or 50 years old. It's at this age that eye health problems are likely to begin, hence the importance of having myopia screening performed early.

Optometrists, as healthcare professionals, must inform their patients when they detect this abnormal progression or development. It is essential to provide information with the best and most appropriate solution for each case and recommend the best treatment, in order to address the rate of myopia progression. In this way, prevention can provide benefits both now and in the future, and avoid the risk of developing pathologies.

Where and how should optometrists and ophthalmologists act?

The key is to understand how the eye develops and grows in a myopic patient, that is, to understand the growth of its axial length, the evolution in diopters, and accommodation.

Age correlates with the axial length of the eye. If we have a myopic patient, this measurement must be performed along with the refraction. If the axial length grows excessively, that is, more than 0.10 mm per year, the patient will be increasingly likely to develop high myopia and, consequently, vision loss.

An eye at birth has an axial length of 17 mm, and it reaches 23-24 mm by age 6-8. Also, from birth, the power of the lens decreases. That is, the axial length increases and the optical power of the lens decreases. The cornea plays little role in emmetropization.

Physiologically, until the age of 6, the eye increases its axial length by approximately 0.10 mm per year. But when this increase per year is greater, that is, it grows more than 0.10 mm, myopization begins to derail.

Therefore, it is important that the axial length does not grow excessively, in an abnormal way.

We'll also look at the increase in diopters of myopia, which usually correlates with the increase in axial length. We'll also consider the accommodative value, which is also affected. Myopic patients have a greater accommodative lag. In this situation, light is focused behind the retina in near vision, which could signal increased eye growth and therefore induce myopia.

Starting at age 50, patients with high myopia—more than 6 dp or more than 26 mm in axial length—are at increased risk of mild to severe vision loss. They are more likely to develop myopic maculopathy or retinal detachment.

By preventing and monitoring children and young people as early as possible, we are investing in the future. Currently, given the age of these patients, they don't consider it important; they have no symptoms, and they see well with glasses or contact lenses. But it's important to inform parents about prevention, the benefits they can have in the future, and, above all, to avoid the risk of developing pathologies.
Eye care professionals have an ethical obligation to inform myopic children and their families about the risks of myopization and the options available for its treatment and prevention of its progression.

Which patients should be treated for myopia control?

• Myopia is a major problem, the earlier it appears the faster it progresses.
• Myopia is more likely to appear earlier and progress more rapidly in patients whose parents are both myopic, compared to those who do not have myopia.
• Refraction is also important, that is, if a child at a certain age does not have Hyperopia or is emmetropic (neutral)
• The intense work on close vision, the number of hours with electronic devices and screens
• Environmental factors also influence, that is, the less time they spend outdoors and the less exposure to natural daylight, the greater the risk of developing myopia.

“If you have a significant genetic makeup, if your refractive error at age 6-8 is less than +0.75 dp (hyperopia) and you spend little time outdoors, you are very likely to become myopic.”

When would it be appropriate to have myopia checked?

We need to act as soon as possible. There's a narrow age range, a small window of opportunity for myopia control, and that's where it's best to act.

As previously discussed, we know that in emmetropic patients, the axial length of the eye grows 0.10 mm per year, but in myopic patients, for example, with 4 diopters, it grows 0.20 mm per year, double.

When we talk about controlling the progression of myopia, it's very important to know how that eye is developing. What we need to know is whether it's growing as an emmetropic eye or abnormally. If we can slow this axial length progression to 0.10 mm instead of 0.20 mm, we reduce the elongation and possibly the myopia that will develop in adulthood and, therefore, the risk of disease. We can't eliminate myopia, but we can control it.

If myopia appears very early, at 5 or 6 years of age, it is a window of opportunity for action, as the condition is still growing, and we can respond more easily than if it were already stabilized. Ninety-five percent of the population who developed myopia in childhood see their growth stabilize around age 25.

"We must address myopia control as early as possible, during the growth phase."

"Myopia should be monitored from the onset phase, between ages 5 and 8, until the age of 25, when it shows complete stabilization."

There are different age ranges in which myopia typically appears. If it appears very early, between 5 and 6 years of age, myopia progresses very rapidly until 14 and 16 years of age, and then stabilizes. There is another, narrower and later age range, between 10 and 12 years of age. Finally, there is an even later age range, the pre-university stage. This range is very narrow, progresses rapidly, and stabilizes. Around the age of 25, 95% of cases of myopia in the childhood and adolescent phase stabilize.

This determines where we need to act, that is, in the phase where myopia is still developing, where it hasn't stabilized. Since the process can't be reversed, intervention is required, such as myopic containment or retention.

We cannot know for sure what would happen if we did nothing, but we do know from the many scientific studies that exist today that if we act during this growth phase of myopia, if we intervene with myopia control strategies during a sufficiently long phase of this abnormal eye growth process, there will be less progression of myopia and the potential benefit we will have will be greater.

Treatment should be started as early as possible, when myopia appears and is progressing. And we should stop treating it as late as possible, when myopia has stopped progressing, when it has already stabilized.

“Between 5-8 years, when myopia appears and progresses, until 20-25 years when it shows complete stabilization”

Isabel Sánchez
Optometrist No. 4394

REFERENCES:
2013- Jessie Charm, Pauline Cho. High myopia-partial reduction orthokeratology (HM-PRO): Study design Jessie Charm∗, Pauline Cho.- School of Optometry, The Hong Kong Polytechnic University, Hong Kong

2013- Jessie Charm, Pauline Cho. High myopia-partial reduction orthokeratology: A2- Year Randomized Study

2016- Efficacy Comparison of 16 Interventions for Myopia Control in Children A Network Meta-analysis, Jinhai Huang, MD,1,2,* Daizong Wen, MD,1,3,* Qinmei Wang, MD,1,2,* Colm McAlinden, MB BCh, PhD,1,4,5,* Ian Flitcroft, FRCOphth, DPhil,6,* Haisi Chen, MD,1,2 Seang Mei Saw, PhD,7 Hao Chen, MD,1 ,Fangjun Bao, MD,1,2 Yune Zhao, MD,1,2 Liang Hu, MD,1,2 Xuexi Li, MD,3 Rongrong Gao, MD,1,2 Weicong Lu, MD,1,2 Yaoqiang Du, MD,1 Zhengxuan Jinag, PhD,8 Ayong Yu, PhD,1,2 Hengli Lian, MS,9 Qiuruo Jiang, MD,1,2 Ye Yu, MD,1,2 Jia Qu, MD, PhD1,2

2019- IMI – Myopia Control Reports Overview and Introduction. James S. Wolffsohn; Daniel Ian Flitcroft; Kate L. Gifford; Monica Jong; Lyndon Jones; Caroline C. W. Klaver; Nicola S. Logan; Kovin Naidoo; Serge Resnikoff; Padmaja Sankaridurg; Earl L. Smith, III; David Troilo; Christine F. Wildsoet Author Affiliations & Notes Investigative Ophthalmology & Visual Science February 2019, Vol.60, M1-M19. doi:https://doi.org/10.1167/iovs.18-25980 https://iovs.arvojournals.org/article.aspx?articleid=2727310