Which are the causes of High Myopia?

High myopia, defined as a refractive error of -6.00 diopters or more or an axial length of 26.5 mm or greater, is primarily caused by a combination of complex genetic predispositions and environmental factors that lead to excessive elongation of the eyeball. While the exact etiology is still being researched, it is understood as a multifactorial condition where internal genetic blueprints interact with external visual habits to alter the structure of the eye.

What are the primary causes of High Myopia?

The core mechanism behind High Myopia is axial elongation—the eye grows too long from front to back. Imagine the eye like a camera; if the camera body is too long, the light rays focus in front of the film (the retina) rather than directly on it, resulting in blurred distance vision. In High Myopia, this elongation is not just a minor variation but a significant structural change that stretches the delicate tissues of the retina, choroid, and sclera, increasing the risk of sight-threatening complications.

Is High Myopia hereditary?

Yes, genetics play a significant role in the development of High Myopia. Research suggests that if both parents have High Myopia, the likelihood of their children developing the condition increases substantially. Geneticists have identified over 200 genetic loci associated with refractive error. Mutations in genes such as LRPAP1, CTSH, and ZNF644 have been linked to early-onset or syndromic forms of the condition. However, for most patients, it is a polygenic trait, meaning many small genetic variations work together to increase susceptibility rather than a single "myopia gene."

What role do environmental factors play?

While genetics provide the foundation, environmental triggers act as the catalyst for High Myopia. The rapid global increase in myopia prevalence suggests that modern lifestyle factors are accelerating eye growth. Key risk factors include:

• Near-work intensity: Prolonged periods of reading, screen time, or close-range tasks without breaks.


• Lack of outdoor time: Exposure to natural daylight is thought to trigger the release of dopamine in the retina, which helps regulate eye growth and prevents excessive elongation.


• Urbanization: Studies indicate that children living in urban environments often have higher rates of myopia compared to those in rural areas, likely due to differences in visual environment and light exposure.

Are there metabolic or structural mechanisms involved?

The sclera—the tough, white outer wall of the eye—is the primary site of failure in High Myopia. In healthy eyes, the sclera maintains a rigid shape. In patients with High Myopia, the extracellular matrix of the sclera undergoes remodeling, essentially becoming weaker and more "stretchy." This structural weakening allows the internal pressure of the eye to push the walls outward, causing the eye to grow longer. Researchers are currently investigating how metabolic signaling pathways, particularly those involving collagen synthesis and tissue repair, contribute to this scleral thinning.

How is research evolving to understand the etiology?

Current research is focused on distinguishing between "causes"—the biological drivers—and "risk factors"—the behaviors that trigger them. Scientists are using large-scale genomic studies to identify markers that predict who is at the highest risk of progressing from mild to High Myopia. By understanding these biological triggers, the medical community hopes to develop pharmacological interventions, such as specialized eye drops or lifestyle protocols, to stop the eye from elongating during childhood and adolescence.

Next steps

• Schedule a comprehensive eye exam with an optometrist or ophthalmologist to monitor axial length and retinal health.


• Join the DiseaseMaps.org community to connect with the 78 members currently sharing their experiences with High Myopia.


• Implement the "20-20-20" rule: every 20 minutes, look at something 20 feet away for at least 20 seconds to reduce eye strain.


• Discuss myopia management strategies, such as orthokeratology or multifocal contact lenses, with your eye care specialist.

Medical disclaimer: This content is for informational purposes only and does not constitute professional medical advice, diagnosis, or treatment; always seek the advice of your physician with any questions regarding a medical condition.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Myopia.


• Orphanet: High myopia - retinal detachment syndrome.


• OMIM (Online Mendelian Inheritance in Man): Myopia, High-Grade; MYP.


• PubMed: "The genetics of high myopia: a review of current knowledge."