Under normal circumstances, consider the following patients as candidates:

A. Planning PKP but cornea is clear centrally
B. Extreme Topography (Mean K greater than 50 diopters)
C. Experience CL problems throughout or for part of the day
D. Multiple CL refits in the last 24 months
E. Motivated for refractive but showing signs of potential KC

Swanson’s three principles of cornea architecture modification for Keratoconus:

• Principle 1
  Steep Axis incision to control Astigmatism

Incision on the steep axis aids in reducing and or eliminating both regular and irregular astigmatism.

• Principle 2
  Tight 10-0 nylon suture left in for 2 months

The tight suture at the incision site maintains the hoop stress in the 7 mm optical zone.

• Principle 3
  Intacs placement in the flat (most elevated) meridian normally

Intacs create a second limbus adding structure at the 7 mm optical zone. 

Conclusion:

The tight 10-0 suture on the steep meridian and the Intacs on the Flat meridian work together to create a "hoop" Stress (a term coined by David Schanzlin, M.D.) Intacs act as a second limbus.  As such, the corneal stresses are harnessed within the 7 mm optical zone; thereby restructure an abnormal corneal lamallae to a more normal prolate aspericity.