The external approach is best done using a "seagull-shaped" incision to reduce the likelihood of the scar webbing. Having found and diathermied the angular vein and dissecting down on to the periosteum, the anterior lacrimal crest should be found and then a sub-periosteal dissection done posteriorly, staying on the bone of the medial part of the orbit. This will stop orbital fat prolapsing and getting in the way, so it is important to stay in the right plane. It is often surprising to those who are not familiar with the procedure how far back the anterior ethmoid artery is. It can be seen approximately 2.4 cm from the anterior lacrimal crest as what looks like a firm attachment of the orbital periosteum, but in fact it is simply where the anterior eth-moidal artery is going through the periosteum, tenting it as it goes into the anterior ethmoid foramen. The periosteum is mobilized to expose enough of the artery to allow it to be clipped or diathermied.
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