Myopia

Myopia


MYOPIA

  • Also called short-sightedness.
  • It is a type of refractive error in which parallel rays of light coming from infinty are focussed in front of retina when accomodation is at rest.
  • Short-sightedness implies that patient has difficulty seeing object far away (distinct object), such as road signs or a blackboard at school, while objects near to eye can be seen properly.
  • The patient sequeezes his eye in order to reduce the inherent accomodative tone (by relaxing ciliary muscles) which helps him see better.
  • Symptoms are headache, eye strain & sometimes lacrimation.
  • Black spots floating in front of eye & flashes of light may also be seen.

Pathophysiology of myopia

  • In myopia the image is formed in front of the retina.
  • Patient can see near objects more clearly but are unable to see objects properly that are far from him.
  • This is because myopic eyes have problem in focusing the light on retina from an object that is far & the light is focused in front of the retina.
  • If objects is placed near to the eye, the point at which light focuses properly will shift backward on the retina.
  • Far point & near point come nearer.

Examination findings

  • On examination following findings are seen:
  1. Large prominent eyeball & cornea.
  2. In early cases of myopia fundus is normal.

Later there may be myopic crescents, Foster’s fusch’s spot at the macula, peripheral retinal (lattice & Snail track) degeneration,vitreous liquefaction & opacities, posterior vitreous detachment (Weiss reflex).

Types of Myopia

  •  Simple (developmental) myopia: Mild & nonprogressive. Complications are rare.
  • Pathological (Progressive or degenerative) myopia: Rapidly progressive & is frequently associated ith complications.

TREATMENT

1. NON SURGICAL

  • Most commonly used method for treatment of myopia is correction by concave (divergent or minus) lens.
  • These may be spectacles (most commonly used method for low myopia i.e.

2. REFRACTIVE SURGERY:

  • Most common procedures are performed with an excimer laser.
  • LASIK is the most commonly used procedure.

3. ORTHOKERATOLOGY: 

  • Non-Surgical procedure where special contact lenses are worn that slowly reshape the cornea over time to correct myopia.

High myopia is defined as myopia>-6D.

  • Treatment of choice for high myopia is contact lens.
  • LASIK is an alternative.

COMPLICATIONS

  • Macular degeneration & retinal detachment are the most common complications.
  • Other complications are complicated cataract, strabismus fixus convergence & vitreous & choroidal haemorrhage.
Exam Question
 
  • In senile nuclear cataract Index myopia is seen.
  • Maximum correction of myopia can be done by LASIK.
  • Retinal detachment is the most common complication of high myopia.
  • Haemorrhage at macular spot in high myopia is called Foster-Fuchs fleck.
  • Radial keratotomy corrects myopia by causing Flattening of cornea.
  • Posterior staphylomas are commonly seen in patients with high myopia.
  • Refractive surgery most commonly performed for myopia is  LASIK.
Don’t Forget to Solve all the previous Year Question asked on Myopia

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