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Sunday, February 17, 2013

LASIK - Laser Assisted In Situ Keratomileusis

LASIK (Laser Assisted In Situ Keratomileusis) :

LASIK is a type of eye surgery done to correct refractive errors of the eye.

Refracrive error is based on two factors:

1.     Anterior-Posterior length of the eyeball (normally 23 mm)

·        Increased A-P length of the eyeball = myopia
·        Decreased A-P length of the eyeball = hypermetropia

2.     Corneal curvature:
a.      Steep corneal curvature > More bending / refraction > Image will form in front of retina > Myopia (refractory power is more)

b.     Flat cornea > Decreased bending > Image will form behind retina > Hypermetropia (refractory power is less)

c.      If corneal curvature is unequal > 2 images will be formed > Astigmatism

Principles of LASIK:

Reshaping of cornea (alter shape of cornea):

·        In myopia > make cornea flat

·        In hyper metropia > make cornea more steep

How much correction is possible?
·        Myopia > up to 16 D

·        Hypermetropia > up to 7 D

·        Astigmatism > up to 7 D

Procedure of LASIK:

Procedure of LASIK
1.     Make a thin corneal flap with automated microkeratome, attached at one end

2.     Treat bed with Excimer laser. Ablate Bowmen’s layer and stroma with laser > precisely cur tissue without disturbing surrounding structure.

3.     Reposition of flap

For 10µm ablation = correction of 1D myopia.
eg if you need 5 D correction = 50 µm tissue has to be ablated.

Note: Before LASIK, asses corneal thickness by pachymetry.
·        Normally centre = 0.56 mm
·        Periphery = 1.00 mm

Complication of LASIK:

1.     Wrinkling
2.     Decentration
3.     Cellular proliferation in between interface = becomes hazy
4.     Overcorrection or under-correction
5.     Ectesia (procedure not done in center, but to one side)

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1 comment:

  1. Really really informative. Many custom lasik phoenix companies will surely enjoy this wonderful and informative blog you have shared. Thanks a lot.


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