In this operation the bony outer wall of the orbit is divided above and below, and turned outwards so as to expose the orbital contents without interfering with the globe; the bony wall, being kept attached to the overlying tissue, can be replaced subsequently without fear of necrosis.
Indications. The operation is performed in cases of a suspected tumour of the orbit, which, if small and non-malignant, can be removed, the eye being left in situ. If doubt exists as to the nature of the tumour a piece can be removed and examined microscopically, either at the time of the operation or later. It is especially suitable for tumours of the optic nerve and for orbital cysts behind the globe.
Instruments. Scalpel, dissecting forceps, artery forceps, scissors, periosteum detacher, chisel and hammer, or preferably, a motor rotary saw, and retractors.
Operation. Performed under a general anæsthetic.
First step. A slightly curved incision with the convexity forwards is made so as to expose the outer margin of the orbit and carried down to the bone. The periosteum is separated from the inner surface of the outer wall of the orbit by means of a periosteum detacher and divided horizontally, the finger is inserted, and the orbit explored. If a small tumour or cyst be found it can sometimes be shelled out through this incision without enlarging the wound further.
Second step. The eye and orbital contents are carefully protected with a large flat retractor. The bone is first divided above, by means of either a chisel or a saw. The upper incision should pass through the base of the external angular process of the frontal bone, and run backwards and slightly downwards to the posterior end of the spheno-maxillary fissure. The lower incision should run directly backwards from the lower orbital margin into the spheno-maxillary fissure. The triangular wedge of bone attached by its outer surface to the soft tissues in the temporal fossa is then forced outwards. In doing this care must be taken not to fracture the orbital wall anteriorly, otherwise the space to work in will be much reduced.
Third step. Consists in the removal of the tumour. Care must be taken to displace the external rectus to one side so as to avoid injury to it as much as possible. If the case should be one of an optic nerve tumour, for which the operation is most frequently performed, the optic nerve is divided close behind the globe. The tumour is freed from the surrounding ciliary nerves and the ophthalmic artery and brought up into the wound as much as possible. The optic nerve is then divided at the apex of the orbit and the tumour removed. The wound in the periosteum of the outer wall of the orbit is closed with a catgut suture, the bone, together with the soft parts, replaced in position and the skin wound closed by sutures. A drainage tube should be inserted for at least twenty-four hours.
Complications. 1. Proptosis. The operation is liable to be followed by great proptosis as the result of hæmorrhage into the orbit. If the optic nerve has been removed, the globe may be dislocated forwards between the lids and come in contact with the dressings.
2. Corneal ulceration. As the cornea is frequently anæsthetic from division of the ciliary nerves, ulceration is very liable to follow. It is, therefore, desirable in many cases to stitch the lids together after closing the skin wound.
3. Defective outward movement in the globe is of frequent occurrence, owing either to injury of the external rectus or the sixth nerve, or to involvement of them in the scar tissue. Stitching the periosteum together obviates the latter to a certain extent.