The Ablation Depth Of Cornea For LASIK And The Amount Of Correction Needed

Laser vision correction changes the corneal contour by removing small amounts of tissue. As a result, the cornea is thinned. The average corneal thickness is 0.540 mm, and the absolute minimum of residual thickness is 0.250 mm.

The Ablation Depth Of Cornea For LASIK And The Amount Of Correction Needed

If the depth of the ablation leaves less than 0.250 mm of residual corneal tissue, the risk of the cornea shape ectasia, or blowing out is greatly increased. Most surgeons of LASIK choose a flap depth between 0.120 mm and 0.180 mm and leave 0.270 mm - 0.275 mm of residual cornea in order to provide a safety margin to allow for retreatment of LASIK.

Ablation Depth Of Cornea Is Proportional To Amount Of Correction Needed

Ablation Depth Cornea = Ablation Squared Diameter X Correction Diopter

Required Correction Ablation Depth of Cornea (mm)
Diopters Diameter 5mm Diameter 6mm Diameter 7mm
– 1.00 – 0.0083 – 0.0120 – 0.0163
– 2.00 – 0.0167 – 0.0240 – 0.0327
– 3.00 – 0.0250 – 0.0360 – 0.0490
– 4.00 – 0.0333 – 0.0480 – 0.0653
– 5.00 – 0.0417 – 0.0600 – 0.0817
– 6.00 – 0.0500 – 0.0720 – 0.0980
– 7.00 – 0.0583 – 0.0840 – 0.1143
– 8.00 – 0.0667 – 0.0960 – 0.1307
– 9.00 – 0.0750 – 0.1080 – 0.1470
– 10.00 – 0.0833 – 0.1200 – 0.1633
– 11.00 – 0.0917 – 0.1320 – 0.1797
– 12.00 – 0.1000 – 0.1440 – 0.1960