How to Treat – Eyelid and lacrimal disorders
from previous page but can be associated with weight fluctuation, fluid influxes from renal disease, thyroid eye disease and blepharochalasis, as well as from connective tissue disorders.
The marginal reflex distance( see ptosis section) is positive and usually 2mm or greater. When the marginal reflex distance is reduced, zero or negative, a ptosis is diagnosed. Ptosis and dermatochalasis may often coexist, but dermatochalasis is more common in the author’ s experience.
Corrective surgery for dermatochalasis is a blepharoplasty, removal of excess skin, sometimes removal of a conservative strip of orbicularis oculi muscle, removal or re-draping of prolapsed fat and recreation of skin creases. Incisions are placed in natural skin lines. Orbital fat herniation can protrude because of weakening of the orbital septum— the hammock that holds the orbital fat pads back.
Ptosis The term ptosis is derived from the Greek for falling. Ptosis, with reference to upper eyelids, refers to a low-positioned upper eyelid( see figure 4). Ptosis interferes with superior vision and sometimes central vision.
The severity of ptosis is often assessed by measurement of the marginal reflex distance, the distance between the upper-eyelid margin and central corneal reflex. This is measured while stabilising the brows in the relaxed non-elevated state, while the patient gazes straight ahead. Patients with ptosis and severe dermatochalasis chronically use their frontalis muscles to elevate their brows to enhance their superior vision. They may tire in the evenings when they notice their ptosis is more marked, and they may develop headaches.
The muscle elevating the eyelid is the levator palpebrae superioris, which originates from the posterior bony orbit just above the optic foramen. It spans and thins peripherally and becomes the levator aponeurosis. This inserts into both the upper-eyelid skin( and is thought to give rise to the skin crease) and the fibrous tarsal plate. It is a skeletal muscle and is intimately related to the Müller’ s muscle: a smooth muscle on its undersurface. The levator palpebrae superioris is innervated by the oculomotor nerve( third cranial nerve) and the Müller’ s muscle by the sympathetic nervous fibres. Both muscles contribute to eyelid elevation.
While ptosis is usually an involutional( or ageing) change, with dehiscence or stretching of the levator palpebrae superioris, it can be a sign of a subarachnoid haemorrhage from an aneurysm, causing a third cranial nerve palsy, or a tumour compressing the sympathetic pathway, causing Horner’ s syndrome. The causes of ptosis are listed in table 1 and key diagnoses to exclude in Box 4.
Of all eyelid malpositions, the assessment of ptosis requires the most careful evaluation. Determine if this is real or apparent / pseudo ptosis to ensure appropriate investigation and management. Ask about the duration of ptosis, variability
and presence of diplopia.
Ask about any systemic muscular fatigue. Assess fatigability of the levator muscle by asking the patient to view a target in upgaze for a prolonged period. An ice test may lead to temporary cessation of the ptosis if there is a concern that myasthenia gravis is the cause. Then test for acetylcholine receptor and MUSK antibodies. Refer to a neurologist, who will be able to confirm the presence of myasthenia gravis. These patients will respond to medical treatment rather than surgical.
Examination of both pupils and extraocular motility is essential to exclude neurogenic and myogenic causes of ptosis. If motility is restricted in vertical or medial gaze, or a dilated pupil is found, this may herald a third cranial nerve palsy from a stroke, tumour or aneurysm, especially if there is pupillary involvement.
It is imperative to evert the eyelids in all cases of ptosis, particularly in children. Severe allergic eye disease with giant papillae( see figure 5) or a foreign body can present with a ptosis. In these cases, address the cause. Lastly, exclude masqueraders. It is imperative to ensure that proptosis or displacement of the globe from a mass lesion is not the cause of a ptosis( see figure 1).
A patient may often present with a unilateral ptosis; however, on lifting the ptotic eyelid, the contralateral upper eyelid drops, indicating a masked bilateral ptosis. This is an important examination that an oculoplastic surgeon will perform before determining if unilateral or bilateral surgery should be undertaken. It occurs as a result of Hering’ s law, whereby both levator muscles receive innervation from a single central cerebral nuclear input. 5
History will usually elucidate a congenital ptosis, with an absent skin crease, poor levator muscle excursion and an upper eyelid slow to move down on downgaze( lid hangup). Because of poor levator function, surgical management is different from traditional ptosis surgery and usually involves resection of the levator or the use of slings( silicone or autogenous).
Ptosis surgery traditionally Figure 4. Ptosis, more marked on the left side.
Figure 5. Patient presenting with bilateral ptosis, with bilateral giant papillary conjunctivitis. The ptosis improved with topical steroid treatment.
A
Causes
Aponeurotic: defect or dehiscence in the levator aponeurosis
Neurogenic: due to an innervational defect
Myogenic: myopathy of levator palpebrae superioris muscle or impaired transmission of impulses at neuromuscular junctions
Mechanical: pseudoptosis
Table 1. Causes of ptosis
Features
Often found in ageing, eye-rubbing, contact lens wear, recurrent eyelid oedema( such as blepharochalasis) or following intraocular surgery Often manifests with an absent or high skin crease in a thin eyelid Ptosis usually constant but can worsen when the frontalis muscle fatigues later in the day
Third cranial nerve palsy Horner’ s syndrome: mild ptosis in the presence of a miosed pupil Other rarer causes: Marcus – Gunn jaw-winking syndrome, third cranial nerve misdirection
Myasthenia gravis: ptosis, which may fluctuate and may coexist with variable diplopia Myotonic dystrophy: limited motility Ocular myopathy: chronic progressive external ophthalmoplegia: limited ocular motility Congenital: simple congenital or blepharophimosis syndrome
Dermatochalasis Foreign body or retained contact lens caught under the upper eyelid Tumours: haemangioma, neurofibroma Oedema or inflammation of the upper eyelid( eg, chalazion, allergic eye disease, post-traumatic oedema) Anterior orbital lesions: lymphangioma, mucocoele Scarring
Figure 6. A. Patient with a right-sided blepharospasm. Note the low upper eyelid and the high lower eyelid. B. Blepharospasm responds to injections of botulinum toxin A.
B
20 | Australian Doctor | 24 November 2017 www. australiandoctor. com. au