I thought this was interesting as it explains the open and closed procedures of LIS and Corsicas question about the cut being equal to the length of the anal fissure.
Lateral internal sphincterotomy
This is the current surgical procedure of choice. The procedure can be performed with the patient under general or spinal anesthesia. (Local anesthesia may even be used in the cooperative patient, although this is not always recommended). The purpose of an internal sphincterotomy is to cut the hypertrophied internal sphincter, thereby releasing tension and allowing the fissure to heal.
When first described, the sphincterotomy was performed in the posterior midline at the site of the fissure with or without a fissurectomy. However, the incision for the sphincterotomy usually did not heal for exactly the same reason that the fissure did not heal. Now, sphincterotomies are normally performed in the lateral quadrants (right or left, depending on the comfort or handedness of the surgeon). In a properly performed lateral internal sphincterotomy, only the internal sphincter is cut; the external sphincter is not cut and must not be injured.
The sphincterotomy can be performed in either an open or a closed manner. In a closed sphincterotomy, a No. 11 blade is inserted sideways into the intersphincteric groove laterally. It is then rotated medially and drawn out to cut the internal sphincter. Care is taken to not cut the anal mucosa because this could result in a fistula. After the knife is removed, the anal mucosa overlying the sphincterotomy is palpated, and a gap in the internal sphincter can be felt through it. The sphincterotomy is extended into the anal canal for a distance equal to the length of the anal fissure.
In an open sphincterotomy, a 0.5- to 1-cm incision is made in the intersphincteric plane. The internal sphincter is then looped on a right angle and brought up into the incision. The internal sphincter is then cut under direct visualization. The 2 ends are allowed to fall back after being cut. A gap can then be palpated in the internal sphincter through the anal mucosa, as in the closed technique. The incision can be closed or left open to heal.
In the treatment of chronic anal fissures, the surgeon may choose to excise the fissure in conjunction with the lateral sphincterotomy. Take care to not include a piece of the internal sphincter with the excision. More simply, instead of excising the fissure along with the sphincterotomy and worrying whether it will heal, the surgeon can excise the hypertrophied papillae and the skin tag and leave the fissure to heal on its own. Sometimes, long-standing chronic fissures do not heal, even with an adequate sphincterotomy, and an advancement flap must be performed to cover the defect in the mucosa. This can be performed either at the time of the sphincterotomy if the surgeon does not think the fissure will heal or as a second procedure if the fissure does not heal.
http://emedicine.medscape.com/article/196297-treatment

Oh, my God - that was heavy Tabby and usefu! I will have to read it again - heavy English....
I did not understand this one: "The sphincterotomy is extended into the anal canal for a distance equal to the length of the anal fissure"
Corsica

I think that means they just cut as far back as the fissure extends into the booty.
Thanks for posting that Tabby. When I see the CRS tomorrow, should I refer to my bumcakes as my bootychops?

My heavens! If this is true I belive that some with ulcers instead of fissures my need repeated surgery. Half of my anus where torn to pieces because of the ulcer. If they had cut 2 cm(length of my ulcer) into my internal sphincter I think that maybe it could be damaged.

Lars,
What is the difference between an AF and an ulcer? Did your CRS explain the difference between the two??
Cheryl

An ulcer is a very big, deep and wide chronic fissure. It isn`t just a cut in the mucous membrane. It is a wound that goes from the anus opening and through linea dentata(the end of the anus with no nerves). So over half of my anus were torn to pieces. Mine was also down to the internal sphincter.