What are the different types and causes of myopia?

Most of us are familiar with myopia word. If you need minus power glass in the young age that means you have myopia. Myopia also called short-sightedness. As an optometrist when I advised starting wearing glass to any child, many parents told that excessive using mobile, tablets are the causes of myopia.

Myopia means you need a pair of glasses to see distance object clearly. The exact causes of myopia are unknown. But myopic patient’s eyeball is too long (Longer than normal emmetropic people) or Cornea is too curved. Due to this reasons the light rays fall into the eye can’t reach to the retina (Through retina image signals pass to brain)

Causes of myopia - Too long eyeball

Depends on the age myopia can be divided into two categories:-

  • Juvenile onset myopia
  • Adult onset myopia

Juvenile onset myopia:-

Juvenile myopia has seen between 7-16 years of age. In this age, myopia occurs due to increase the axial length of the eye. That means increasing the size of the eyeball. The increase of minus power is rapid in this age. Minus power can increase yearly 1.00D or more in this age. For that reason, optometrist or ophthalmologist suggested for a regular eye check up in 6 months interval or depends on refractive error change. Mostly myopia begins at the age of 9-10 years for girls and 11-12 years of age in boys. The progression of myopia is very less if myopia starts after 16 years of age.

Adult onset myopia:-

It begins about 18-20 years of age. Excessive near work especially works with a visual display unit (VDU) like a computer, mobile etc are the causes of this type myopia. But this is computer and electronics era. Kids and children are always busy with mobile or computer for educational purpose or gaming purpose. That’s why it may be one of the causes of myopia for kids and children as well. Last year a study published about the prevalence of myopia. As per the study, approximately 5 billion people may need spectacle by 2050 and excessive using of mobile and computer is the main culprit. After that study, many parents are worried about their children eyesight. Low hyperope and emmetrope patient can be shifted to low myopia.

                                                             

When myopia progression will stop?

Clinically and pathologically myopia is divided into two types – Simple myopia and Pathological myopia.

Most of the cases myopia progression stops at the 18 years of age or before. Generally, simple myopia progression stops at the age of 15-18 years in girls and 18-20 years in boys as the growth of the body height stop. But few cases myopia progression continues after 20 years age also. The condition is known as pathological myopia. Pathological myopia is 2.5 times more common in females than males. Mostly pathological myopia exceeds more than -10.0D and it may progress 20-25D. High and pathological myopia associated with pathological changes in the retina like retinal hole, retinal tear, Retinal detachment. So regular retina check up is very important in the case of pathological myopia.

                                                           

Clinically myopia can be divided into 4 types:-

  • Congenital Myopia
  • Simple Myopia
  • Pathological Myopia
  • Acquired Myopia

Congenital Myopia:-

Congenital myopia detects at the age of 2-3 years old. It may present since birth. Most of the cases congenital myopia associated with premature birth, Marfan’s syndrome, homocystinuria etc.

Simple Myopia:-

Simple myopia also is known as developmental myopia. It begins between 7-10 years of age. It is the most common type of myopia. The progression of simple myopia arrest at the age of 18 years (Most of the cases). The axial length of myopia eye is longer than the normal eye.

Infographic: Myopia Facts

Pathological Myopia:-

Read above about pathological myopia. Pathological myopia id hereditary. The growth of retina and increase the axial length of the eye not stop after the age of 18 years old. This type of myopia not common and genetic factors play the major role to progress myopia.

Acquired Myopia:-

Acquired myopia occurs due to cataract, diabetes, excessive accommodation, spasm of accommodation etc. 

Treatment:-

Myopia can be treated by spectacles, contact lenses and refractive surgery.

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Krishnendu Mandal
Optometrist, Blogger, Blogging since Jan 2016

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