MYOPIA

MYOPIA - THE DISEASE

Myopia, also commonly referred to as ‘near-sightedness’ or ‘short-sightedness’, is a common eye condition which causes blurred distance vision. In myopic eyes, the eyeball is either longer than normal, or the cornea is too curved, both causing some images to be blurry1 The word Myopia is derived from a Greek term “muopia” which means to close the eyes. Myopia manifests itself as blurred distance vision, hence it is popularly known as “near-sightedness”2

Signs and Symptoms3, 4

People suffering from Myopia often have trouble-seeing whiteboard, movie screen, television set or other distant objects.

The most common symptoms of Myopia include:

  1. Headache
  2. Eyestrain
  3. Squinting
  4. Frequent blinking and rubbing of eyes
  5. Head tilt or abnormal head posture while watching TV
  6. Reading books by placing very close to the eyes
  7. Difficulty seeing distant objects, such as highway signs

Classification

The various ways adopted to classify are based on etiological dichotomies such as hereditary vs. environmental, physiological vs. pathological, structural vs. functional, or axial vs. refractive. Paradoxically, such a classification, being devoid of etiological assumptions, may help to make possible a better understanding of the etiology of the various categories of Myopia5. Several classifications have been postulated6:
Degree of Myopia
  • Low (-0.50 D and less than -3.00 D)
  • Moderate (-3.00 D and -6.00 D)
  • High (-6.00 D or more)
Presumed etiology
Axial, benign, component, correlational, curvature, index, lenticular, physiologic, physiological, refractive, school, simple, syndromic.
Age at onset
Childhood, congenital, acquired, juvenile onset, youth onset, school, adult, early adult onset, late adult onset.
Progression pattern of Myopia
Permanently progressive, progressive, progressive high, progressive high degenerative, stationary, temporarily progressive.
Amount of Myopia
Low, medium, intermediate, moderate, high, pathologic, pathological, physiologic, physiological, severe, simple.
Structural complications
Degenerative, degenerative high, malignant, pathologic, pathological, pernicious, progressive, progressive high, progressive high degenerative.

Etiology/Causes7-10

The evidence suggests that Myopia is more likely to result from the combined and interacting effects of hereditary and environmental factors7. Some of these risk factors include:
Parental Myopia7
The incidence of Myopia is higher in children with myopic parents. As per the results of a published study, the proportions of Myopia were 6.3% in schoolchildren aged 13.7±0.5 years whose both parents are emmetropic, 18.2% in children with one myopic parent, and 32.9% in children who’s both parents are myopic.
Socioeconomic factor7
Myopic children were also found to have a stronger parental history of Myopia in families with higher parental level of education, higher income, and white collar or professional occupations.
Near-work7
Near-work such as reading, writing, using mobile phones, compute use, and playing video games, have been suggested to be possibly responsible for the remarkable increase in the prevalence of Myopia.
Ethnicity8
Higher odds of Myopia were found in children of East Asian than those of European Caucasians in the same population.
Education9
The level of education is suggested to cause Myopia. A very significant study showed that higher levels of school and post-school professional education are associated with a more myopic refraction. The epidemiological surveys have consistently found a higher prevalence of Myopia in well-educated population thus proving the workload from formal education system. Studies conclude that Myopia typically developed in children of younger age are gradually increased both in prevalence and in severity from grade school throughout graduation.
Income10
As per the results of a study from China, Myopia was twice as prevalent in middle class students than poor students. According to the data from the American Academy of Ophthalmology (AAO), Myopia afflicts an 80 to 90% of people in Asia and about 40% in the US.

Myopia Mechanism

Available evidence suggests that genetic and environment factors play a crucial role in the development of juvenile-onset Myopia. Though the manners in which both these factors interact and lead to the pathogenesis of Myopia remain inconclusive, several studies report that near work plays a pivotal role in the development of Myopia. Adenosine through its receptors modulate the ocular growth related functions and may regulate the growth of the eye by cell proliferation and scleral thinning which lead to axial elongation and myopia progression.11


In addition, experimental studies suggest that refractive errors could be induced through form deprivation and lens-induced defocus. Every literate individual across the globe regularly does near work, however only a certain percentage of the population develops Myopia. This furthermore warrants the involvement of genetic factors in those individuals11.

Complications 12

Myopia happens to be one of the most common causes of visual deterioration and blindness. Most often people with myopia suffer from various eye pathologies

  • Retinal detachment
  • Glaucoma
  • Macular hemorrhage / degeneration
  • Cataracts

References

  1. Myopia (Nearsightedness). Available At: Https://Www.Aoa.Org/Healthy-Eyes/Eye-And-Vision-Conditions/Myopia?Sso=Y. Last Assessed On 25th August 2022
  2. Binu J, Et Al. International Journal Of Health Sciences & Research. 2016;6(6):30-38
  3. Myopia (Nearsightedness). Available At: Https://Www.Nei.Nih.Gov/Learn-About-Eye-Health/Eye-Conditions-And-Diseases/Nearsightedness-Myopia. Last Assessed On 11th August 2022
  4. Myopia (Nearsightedness). Available At: Http://Bc.Doctorsofoptometry.Ca/Myopia-Nearsightedness/. Last Assessed On 11th August 2022.
  5. Grosvenor T. Am J Optom Physiol Opt. 1987;64(7):545-54.
  6. Flitcroft DI, Et Al. Investigative Ophthalmology & Visual Science February. 2019;60:M20-M30.
  7. Foster PJ, Et Al. Epidemiology Of Myopia.Eye. 2014;28:202-208.
  8. Ip JM, Et Al. Invest Ophthalmol Vis Sci. 2007;48(6):2520-8.
  9. Mirshahi A, Et Al. Ophthalmology. 2014;121(10):2047-52.
  10. American Academy Of Ophthalmology (AAO). “Lower-Income Students In China Found To Have Better Vision Than Middle-Class Peers.” ScienceDaily. ScienceDaily, 5 February 2015. <Www.Sciencedaily.Com/Releases/2015/02/150205082922.Htm>.
  11. Congdon N, Et Al. Community Eye Health. 2019;32(105):7-8.
  12. Francisco BM, et al. Oxid Med Cell Longev. 2015;2015:750637