Surgical rehabilitation of the patient with dysthyroid eye disease

Severe conjunctival chemosis is self-perpetuating due to the "throttling" effect of the lower eyelid on the prolapsed conjunctiva and will, in some patients, prevent eyelid closure (Figure 11.3a). After subconjunctival injection of local anaesthetic with adrenaline, drainage of subconjunctival fluid and placement of Frost sutures in the upper and lower eyelids will typically allow closure of the eyelids under an occlusive dressing, with topical application of a steroidal ointment (Figure 11.3b). This typically produces a dramatic improvement within 12 hours (Figure 11.3c), allows the cornea to rehydrate and gives time for systemic antiinflammatory therapy to act.

Orbital decompression is necessary if visual function deteriorates despite the use of highdose systemic steroids (Figure 11.1b). As compression of the optic nerve occurs mainly at the orbital apex, decompression for visual failure must include removal of the posterior part of the medial wall (Figure 11.4); in a few patients the most posterior part of the medial wall being the lateral wall of the sphenoid sinus. Pre-operative CT is required to confirm the diagnosis (especially with unilateral disease), to exclude underlying sinus disease and to detect any cranio-facial anomalies, such as a midline encephalocoele.

Although Olivari has described reduction of proptosis by meticulous excision of orbital fat from the intraconal and extraconal spaces, most orbital decompressions involve removal

Conjunctival Chemosis

Figure 11.3 (a) Severe conjunctival chemosis preventing any movement of the right eyelid and causing dehydration of the right cornea. After drainage of the chemosis under local anaesthesia and placement of multiple eyelid traction sutures (b), the eyelid was padded closed for 12 hours with a dramatic improvement in the clinical state (c).

Figure 11.3 (a) Severe conjunctival chemosis preventing any movement of the right eyelid and causing dehydration of the right cornea. After drainage of the chemosis under local anaesthesia and placement of multiple eyelid traction sutures (b), the eyelid was padded closed for 12 hours with a dramatic improvement in the clinical state (c).

of a combination of the medial wall, floor and lateral wall of the orbit. Removal of the medial wall is necessary for relief of optic neuropathy (Figure 11.5), removal of the floor adds the

Compressive Optic Neuropathy

Figure 11.4 Patient referred with persistent compressive optic neuropathy on the left side, due to the failure to remove the posterior half of the left medial orbital wall.The right side had successful relief of optic neuropathy after a complete ethmoidectomy reaching the orbital apex.

Figure 11.4 Patient referred with persistent compressive optic neuropathy on the left side, due to the failure to remove the posterior half of the left medial orbital wall.The right side had successful relief of optic neuropathy after a complete ethmoidectomy reaching the orbital apex.

Ethmoidal Arteries
Figure 11.5 The medial orbital wall, showing the lamina papyracea with the foramina for the anterior and posterior ethmoidal arteries in relation to the optic canal.

most to reduction in proptosis and removal of the lateral wall allows reduction of lacrimal gland prolapse and reduces the deleterious effect of medial wall decompression on ocular muscle balance. Decompression requires adequate hypotensive general anaesthesia and a reverse Trendelenburg positioning of the patient to reduce bleeding during this complex surgery.

Other surgery for dysthyroid eye disease

Upper eyelid retraction in thyroid eye disease occurs due to a combination of primary factors (adrenergic stimulation, inflammation and fibrosis) and secondary retraction due to inferior rectus fibrosis - with secondary overaction of the superior rectus/levator complex. If secondary upper eyelid retraction is present, the restriction of ocular motility should be addressed first, with inferior rectus recession. Primary upper eyelid retraction is treated by one of the several techniques for graded levator tenotomy (Chapter 7), but with all methods it is particularly important to completely divide the lateral horn of the levator aponeurosis and to maintain a levator action on the medial part of the upper eyelid.

Lower lid displacement, with excessive scleral show below the lower limbus, is due to proptosis and is almost always corrected by adequate orbital decompression - which should probably be considered in any patient with exophthalmos of 24 mm or more. True lower lid retraction, due to an overaction of the retractor fascia in the lower lid, probably occurs only after inferior rectus recession. Lower lid retraction may require surgery to elevate the eyelid using an implant of sclera, hard palate mucosa or ear cartilage.

Lateral tarsorrhaphy invariably stretches with time and, with appropriate surgery to address the other position of the globe and upper eyelid, there is almost no indication for this rather disfiguring procedure in the patient with dysthyroid eye disease. Likewise, skin-reduction blepharoplasty should be used with caution, as removal of anterior lamella in these patients may risk exacerbation of exposure keratopathy.

Methods for bone-removing orbital decompression

Orbital decompression can be achieved through several approaches: transnasal or transantral endoscopic decompression leaves no external incision, but can provide only a limited decompression (of the medial wall and medial part of the floor); likewise, the post-caruncular transconjunctival incision also provides access for medial wall decompression, but can present some surgical difficulty due to the presence of unrestrained orbital fat in the operative field. The lateral canthotomy approach provides the most aesthetic approach for decompression of up to three walls, which may be required where exophthalmos is greater than 25 mm (Figure 11.6).

Although the use of a bicoronal flap for orbital decompression has been widely reported in the past, there is no advantage to the use of this large-incision approach. Likewise, the Lynch incision of the external ethmoidectomy approach often leaves an unsightly scar and gives only limited access - to the medial wall and medial part of the orbital floor.

Lynch external ethmoidectomy approach

A gently curving incision is placed from the medial end of the brow, past the attachment of the medial canthal tendon, towards the orbital floor (Figure 11.7). After securing haemostasis within the orbicularis muscle, the periosteum is opened in front of the anterior lacrimal crest and the lacrimal sac and medial orbital periosteum raised from the bone. The anterior ethmoidal artery may be exposed, cauterised and divided, although this should not be necessary as the artery provides a key landmark to the level of the cribriform plate -the upper limit of decompression.

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