專家教學

Myopia

Author: Vanessa Thai
Developmental and Behavioural Optometrist
Central Health Southside – Child Development Team

What Is It?

Myopia, also known as shortsightedness or nearsightedness, is a refractive error where near objects are seen more clearly than distant ones. Myopia occurs when there is an imbalance between the length of the eye being excessively elongated and the refractive power of the cornea, causing light to focus in front of the retina, rather than on it, leading to blurred images.

Risk Factors

Family History

Genetic factors play a role in myopia development. Research shows that children are 3 times more likely to develop myopia if one parent is myopic, and 6 times more likely if both parents are myopic. Worse, the Chinese University of Hong Kong states that children of 2 myopic parents have 12 times the risk of developing it compared to those with nonmyopic parents.

Environment

Researchers link the rise of myopia prevalence to the modern environment in which our children are raised. Excessive time doing close-distance activities like reading and device use, coupled with limited outdoor play, is believed to contribute to the surge in childhood myopia. Studies suggest that up to 80 percent of the population in some East Asian countries is myopic. Furthermore, it is estimated that half of the world’s population will be myopic by 2050.

Signs and Symptoms

Headaches and eyestrain can occur when myopia goes undiagnosed, as it causes blurred distance vision. Children with myopia may display certain behaviours, including squinting to see distant objects, experiencing difficulty recognising familiar faces from afar, adopting poor posture while doing near tasks such as colouring or drawing, eye rubbing, increased blinking, and displaying decreased interest in outdoor activities.

Treatment Options

Myopia is a progressive and irreversible condition. Children who suffer from myopia at a young age are at an increased risk of high myopia later in life. This not only increases dependency on corrective prescriptions but high myopia poses risks of sight-threatening complications including cataract, glaucoma, macular degeneration, and retinal detachment.

Wearing glasses or undergoing laser refractive surgery cannot correct the issue of elongated eyeballs, and therefore, the risk of complications cannot be mitigated. As a result, it is important to prioritise the prevention or delay the onset of myopia.

Outdoor Time

While genetic predisposition cannot be changed, it is never too soon to establish positive habits with ample outdoor time, particularly in early childhood. It appears that sunlight has a restraining effect on the elongation of the eyes, and a lack of sunlight during the early years seems to increase the risk of developing myopia. Therefore, 90 minutes to 2 hours of daily outdoor time is recommended.

Visual Hygiene

Implementing the 20-20-20 rule as part of visual hygiene and to avoid eye strain. That is, take a 20-second break every 20 minutes of near work and look at something in the distance at least 20 feet away.

Glasses

While traditional treatment options such as single vision distance glasses correct the distance blur, they do not slow the progression of myopia caused by the lengthening of the eyeball. Specific myopia control technology such as Highly Aspherical Lenslet Target (H.A.L.T.) or Defocus Incorporated Multiple Segments (D.I.M.S.) spectacle lenses are recommended to slow the progression of myopia. Vision therapy may also be recommended.

Contact lenses

Specially designed rigid and soft contact lenses are available for myopia management. Orthokeratology (also known as ortho-K or OK) involves using a rigid contact lens overnight to reshape the cornea, providing clear vision during the day without glasses or contact lenses. However, overnight lens wear increases the risk of eye infections. Studies have shown that ortho-K lens wear can slow eyeball elongation and myopia progression. Children as young as 6 years of age can be successfully fitted with ortho-K lenses.

Convenient and safe, soft contact lenses that incorporate myopia control technology in MiSight and NaturalVue lenses present an alternative treatment option. Their ease and flexibility of use allow children to switch between wearing glasses and soft daily disposable lenses on different days of the week.

Atropine Eye Drops

Atropine is used for relaxing the focusing muscles of the eye and dilating (widening) pupils yielding excellent results in slowing myopia progression with minimal side effects. They have also been studied to have success in prophylactic use in delaying the onset of myopia. Atropine may also be used in conjunction with other treatment options such as with glasses or contact lenses.

Repeated Low-Level Red Light (RLRL)

This is a new treatment modality for myopia control in children. Repeated low-level red light therapy stimulates blood flow and strengthens the retinal layers thus regulating the lengthening of eyeballs and slowing myopia progression. The treatment involves light therapy for 3 minutes, twice a day, 5 days a week, with a minimum 4-hour gap between sessions, and is suitable for children as young as 3 years of age.

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