What is Childhood Myopia and Ocular Development?
Myopia, also known as nearsightedness, is a condition where you have difficulty seeing distant objects. This happens when light rays are focused in front of the retina, the inner back part of the eye, instead of directly on it, when your eye is in a relaxed state. The occurrence of myopia is increasing globally. In 2010, it was understood that roughly 27% of the world’s population, or about 1.45 billion people, were affected. Experts predict that by 2030, half of the world’s population will be dealing with myopia.
Myopia can be broadly categorized into two types: pathological myopia and spontaneous onset childhood myopia. Pathological myopia is often a result of a rapid increase in the length of the eye, usually requiring strong vision correcting lenses with more than six units of corrective power, known as diopters.
This fast surge in myopia can lead to many damaging changes in the eye’s retina, choroid (the layer containing blood vessels), and sclera (white outer layer of the eyeball). Hence, it’s called pathological myopia. On the other hand, school-age myopia, which is the most common type, progresses slowly and generally settles down by the age of 20.
What Causes Childhood Myopia and Ocular Development?
Myopia, also known as nearsightedness, happens when the images we see form in front of the light-sensing cells in the back of our eyes.
There are a few types of myopia based on how it develops:
* Axial myopia happens when the length of the eye grows too quickly. For every small unit of increase in myopia, the length of the eye increases by 0.35 millimeters.
* Curvature myopia happens when the clear front surface of the eye, called the cornea, becomes too curved. Consequently, the image isn’t focused properly on the back of the eye but forms in front of it. Each millimeter change in the curve of the cornea makes the myopia six units worse.
* Lenticular myopia occurs when the clear lens inside our eye becomes too strong or powerful.
Sometimes, myopia can come from the crystalline lens (the clear lens inside our eye) moving towards the front of the eye. Sudden occurrences of myopia can be caused by various conditions. For instance, a fluid build-up behind the eye, or a forward movement of the part of the eye made up of the clear lens and colored ring, often due to certain medications like topiramate.
Risk Factors and Frequency for Childhood Myopia and Ocular Development
Myopia, also known as nearsightedness, is becoming a major public health concern. It’s on the rise due to factors like less outdoor activity, more screen time, and long periods of close-up work, all of which have been particularly prevalent during the COVID-19 pandemic. This condition is common in young kids, with varying rates in different countries.
- It affects approximately 20 to 30% of children aged 6 to 7 in Singapore.
- In China, between 5.7 to 78.4% of children aged 5 to 15 are myopic.
- Asian children are more often affected than their European counterparts, who have a lower prevalence rate of 17.8-23.5%.
- In the United States, Myopia ranges from 4.6% to 28% in children aged 6 to 12 years old.
- The prevalence in India varies between 8.5 to 15% among urban children aged 5 to 15 years old.
Signs and Symptoms of Childhood Myopia and Ocular Development
Kids with myopia, commonly known as short-sightedness, often experience difficulty seeing faraway things clearly. For instance, they might have trouble reading the blackboard at school. They might also complain about other issues such as eyestrain, headaches, and forehead pain. It’s important for these children to undergo a comprehensive eye exam to rule out any changes in the back part of their eye due to myopia.
Testing for Childhood Myopia and Ocular Development
In order to accurately assess potential nearsightedness (myopia) up until the age of 20, eye doctors may use a process known as cycloplegic refraction. This method helps to avoid overestimation of myopia. To perform the process, doctors employ certain agents that numb the eye and allow it to stay focused on a single point while being examined. Some common agents used are Atropine 1%, Homatropine 2%, Cyclopentolate 1%, Tropicamide 1%, and a combination of Tropicamide 0.8% and Phenylephrine 5%. The most effective agent, Atropine 1%, can stay active for up to 14 days.
Cyclopentolate is the agent of choice for children aged 5 to 13 to test for vision issues. For children above 13, Tropicamide is used primarily to dilate pupils, making it easier to examine the interior of the eye, especially in cases of suspected nearsightedness.
Special care must be taken when applying Atropine ointment to avoid side effects like facial redness, fever, and rapid heart rate. The American Academy of Ophthalmology provides guidelines for prescribing glasses in children with myopia that vary depending on the age and degree of vision issue.
After having their vision tested, patients should have a complete examination of their eye’s front part and an evaluation of their retina, the light-sensitive tissue layer at the back of the eye. This is particularly important for patients with severe myopia to identify any signs of damage. Some conditions that may be spotted during this check-up include degenerative changes, thin areas of the retina, retinal holes, certain bumpy changes on the retina, cracks, macular holes, and abnormal bulging of the eye (staphyloma).
Treatment Options for Childhood Myopia and Ocular Development
When managing childhood myopia (nearsightedness), the most common option is to prescribe glasses. These glasses are precisely designed to correct the individual’s degree of vision blur. It’s crucial to consider factors such as the fit and weight of the glasses to encourage kids to wear them regularly. However, access to glasses remains a significant challenge in resource-poor areas and developing countries.
Contact lenses can also be used to correct nearsightedness. However, evidence does not suggest that using contact lenses can slow down the worsening of nearsightedness.
Drug treatments to control myopia progression are currently being studied but are not approved by the US Food and Drug Administration (FDA). One promising candidate is atropine 0.01%, which seems to be safe and effective with few side effects. Atropine works by affecting acetylcholine receptors, which are involved in eye growth. It may also stimulate the production of a substance involved in the firmness and flexibility of the eye and regulate the growth of the eye.
Other drugs like pirenzepine, a certain class of drug that block specific types of receptors, and 7-Methylxanthine, a derivative of a substance found in coffee and chocolate, are also being tested for myopia management. Some medications that decrease pressure within the eye have also been explored to stop the worsening of myopia.
Spending more time outdoors can also help reduce the risk and progression of myopia. Increasing outdoor activities to 14 hours a week can lower the risk of nearsightedness development by a third. This benefit might be linked to the release of dopamine, a chemical that inhibits eye growth, and the visual stimulation provided by outdoor environments.
Other approaches to control myopia progression include using bifocal or multifocal glasses, as these optical devices could relax the eye’s focusing system. Some specialized types of eyeglass lenses also help control eye growth and slow the worsening of nearsightedness by inducing a certain focus arrangement. Special soft contact lenses and overnight contact lenses that temporarily reshape the cornea are also used.
Other experimental therapies are being explored in the management of myopia, and these include various surgical techniques and procedures, drug treatments, and even the use of stem cells. However, further research is needed to confirm their safety and effectiveness.
What else can Childhood Myopia and Ocular Development be?
When examining children with low vision, doctors should also check for other potential causes. These might consist of:
- Keratoconus (a condition where the cornea thins and bulges out)
- Childhood cataracts (cloudy spots in the eye’s lens)
- Microspherophakia (an unusual small spherical lens in the eye)
- Childhood glaucoma (increased pressure in the eye that can cause vision loss)
- Eye injuries
- Irido-fundal coloboma (a hole in parts of the eye)
- Nystagmus (involuntary eye movement)
- Birth defects of the optic nerve
- Unusual grouping of nerve fibers covering the fovea (center of the retina)
- Retinal abnormalities at birth, like pigmentary retinopathy (a breakdown of cells in the back of the eye)
Medical professionals should also look at the child’s birth history, whether the child received laser treatment for retinal issues, if the child had delayed crying at birth, or if they stayed in an intensive care unit. Myopia (short-sightedness) can be linked with Down syndrome, happening in 8 to 41% of cases.
Conditions like Marfan syndrome and Stickler syndrome can cause pseudomyopia. This is where it looks like a child is short-sighted because of their excessive eye accommodation, but they are not. So, if testing for myopia is done without eye-muscle relaxation (cycloplegia), it might overestimate the condition by -1 to -2 power (diopters).
What to expect with Childhood Myopia and Ocular Development
School-aged children who develop nearsightedness (also known as myopia) at a young age typically have longer eyeballs and a bigger discrepancy in their vision. However, in children who were born with severe nearsightedness (diagnosed as having more than -5 D of myopia before six years old), the progression of the condition is different. In a study by Shih and his colleagues, they found that nearsightedness progresses more quickly in children with less severe myopia, between 5.0 to 7.75 D, than in those with more severe myopia (up to 11.0 D).
In people with pathological myopia – a severe form of nearsightedness, the thinning out of a layer in the back of the eye called the choroid, or the presence of posterior staphyloma, which is an outward bulge of the back of the eye, they may have worse vision in the long run.
Possible Complications When Diagnosed with Childhood Myopia and Ocular Development
Pathological myopia, or severe shortsightedness, can lead to several complications in the retina, a layer at the back of the eye that senses light and sends signals to the brain. These complications can include the retina detaching, tension or pulling at the back of the eye (myopic macular traction), holes forming in the macula (the central part of the retina that provides detailed central vision), and the formation of abnormal blood vessels underneath the retina (choroidal neovascular membrane formation). Individuals with severe shortsightedness may also have loose lenses in their eyes (subluxated lenses) and risk developing a type of eye disease called primary open-angle glaucoma.
List of Complications:
- Retinal detachment
- Myopic macular traction
- Macular hole
- Choroidal neovascular membrane formation
- Subluxated lenses
- Primary open-angle glaucoma
Preventing Childhood Myopia and Ocular Development
Myopia, or nearsightedness, can be influenced by many factors. Spending too much time in front of screens or staying indoors for too long are often pointed out as causes for the onset and worsening of myopia. Encouraging activities outside, using treatments like atropine 0.01% eye drops every night in both eyes, and wearings contact lenses could help slow down its progression.
Parents must fully understand the importance of eyeglasses and the risks associated with the worsening of myopia. Regular comprehensive eye exams should be carried out to monitor the condition. Oftentimes, myopia is overlooked in children because they find it difficult to articulate their vision problems. It is usually spotted accidentally during routine check-ups. Therefore, improving school visual testing programs is crucial, especially so in developing nations, to ensure that needed eyeglasses can be provided.
