Hollis Lasik

Hollis Nomogram for the Medlogics the ML-7 (90 micron flaps)

Use an 8 ring for corneas 11.5 and down, yields an average 9.3 mm flap diameter

Use an 8.5 ring for corneas 12 and up, yields an average 9.5 flap diameter

Central Pachy Blade_________________________________

<470 Do PRK

471-530 Plus 20

531-560 Plus 10

561-590 Neutral

591-620 Minus 10

>621 Minus 20

1) Thicker corneas give thicker flaps and vice versa. This is the main determination of flap thickness if the microkeratome translation speed across the cornea is kept constant.

2) Higher vacuum pressures give thicker flaps, but this is usually fixed. We raise the vacuum on the second eye to make for the thinner flap from the duller blade, dull from being used on the first eye.

3) Larger rings gives slightly larger flaps but very minimal.

4) Flat corneas gives a larger diameter flap but has little effect on flap thickness.

5) 525 is used on the first eye and 575 on the second. If the flap is much thicker than the target 90 microns, leave the vacuum at 525 on the second eye.

6) If the first flap is too thin, then increase vacuum or increase ring size to get a thicker flap on the second eye.

7) Flaps may be 70 on the thinner corneas and I consider that a perfect flap, my target is 70 to 105, with 90 considered the target. Anything less than 70 is not good. A 60 micron flap will give a superior temporal haze. The epethelium is thinner in the superior temporal cornea.

8) I have lifted hundreds of thin flaps with none of the expected problems with handling such a thin flap. Striae can be a problem so positioning is more important with the thin flap.

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