The skin incision is made just below the eyelashes. Subsequent to the skin incision there are three optional pathways for the dissection down to the orbital rim:
- Deep to the orbicularis oculi muscle
- Step dissection or layered Converse technique
Subcutaneous dissection produces an extremely thin skin flap predisposed to scar contracture and hence a high incidence of ectropion. For access to the infraorbital rim the orbicularis muscle and the periorbita must be split below the infraorbital rim.
The path of dissection deep to the orbicularis oculi muscle includes the pretarsal orbicularis muscle in the elevated skin muscle flap if the skin incision is placed across the tarsus. Motor denervation can critically reduce lower lid tone and diminish vertical lid support.
The step incision starts with a skin flap leaving the pretarsal muscle portion intact before the suborbicularis plane is entered by muscle transsection.
In options 2 and 3 the integrity of the orbital septum has to be meticulously preserved, otherwise there is a risk of vertical lid shortening. The incision through the periosteum for entry into the floor of the orbit is made beneath the infraorbital rim.
The step dissection outlined here is technically easier than the other two methods. It preserves pretarsal fibers of the orbicularis oculi, thereby limiting scarring at the eyelid margin.
Common complications associated with options 1 and 2, such as skin buttonholes, darkening of the skin, ectropion, and occasionally entropion are minimized.
The advantages of the step dissection technique are the imperceptible scar and the ease of extending laterally for additional exposure of the entire lateral orbital rim.