Eyelid position

Summary

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Eyelid malposition is the abnormal positioning of the eyelids. In this article, we will describe ptosis, ectropion and entropion.

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Ptosis

nPtosis is an abnormally low position of the upper eyelid.

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Measurements

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• Margin reflex distance (MRD): MRD1 is the measurement in mm from the light reflex on the patient’s cornea to the level of the centre of the upper-eyelid margin. Normal: 4-5mm. MRD2 instead measures from the corneal light reflex to the central portion of the lower eyelid.

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• Palpebral fissure height: distance between the upper and lower lid margins, measured in the pupillary plane. The upper lid margin normally rests about 2 mm below the upper limbus and the lower 1 mm above the lower limbus. Ptosis may be graded as mild (up to 2 mm), moderate (3 mm) and severe (4 mm or more)

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• Upper lid crease: The vertical distance between the lid margin and the lid crease in downgaze.

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• Pretarsal show: The distance between the lid margin and the skin fold with the eyes in the primary position

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• Levator function measurement: With the eyes in downgaze, a thumb is placed against the patient’s brow to limit frontalis muscle action (and isolate levator function). The patient is then instructed to look up as far as possible and the amount of excursion is measured with a ruler.

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,Marcus Gunn jaw-winking syndrome

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Marcus Gunn Jaw winking syndrome is a congenital condition (complicating around 5% of all cases of congenital ptosis) which results in movement of the upper lid upon jaw mastication as a result of a congenital aberrant connection between the motor branches of the trigeminal nerve controlling the muscles of mastication, and the superior division of the oculomotor nerve innervating levator palpebrae superioris.

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,Oculomotor synkinesis

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Oculomotor synkinesis, also known as aberrant regeneration of the third nerve, is an inappropriate response to third nerve stimulation, resulting in a paradoxical co-contraction of muscles. It occurs as a result of failure to fully recover following injury to the nerve. After injury to the oculomotor nerve, fibres grow to supply muscles other than their original terminal muscle (a process termed as aberrant regeneration), leading to co-contraction of these muscles (lid, extraocular muscles, or pupil) on firing of the nerve. This can result in an involuntary movements of the upper lid.

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Be aware of ‘pseudoptosis’ – a false impression of ptosis may occur with a hypotropia squint, brow ptosis, dermatochalasis, a reduced orbital volume (e.g. in enophthalmos, artificial eye or phthisis bulbi) or a lid retraction in the other eye.

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Ectropion

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Ectropion is outward turning of the eyelid margin. In most cases, definitive management is surgery. Four main types of ectropion exist:

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• Involutional
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  • This usually affects the lower lid of elderly people

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  • Results in epiphora, and can exacerbate ocular surface disease

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• Cicatricial
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  • Shortening of the anterior lamella (comprised of the skin + orbicularis muscle)

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  • Secondary to scarring and contracture of the tissues

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• Paralytic
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  • Caused by ipsilateral facial nerve palsy

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  • Also associated with retraction of the upper and lower lids and brow ptosis

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  • Complications include exposure keratopathy due to lagophthalmos, and epiphora

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  • Treatment can be temporary measures if facial nerve function is expected to return (e.g. lubrication of the ocular surface, botulinum toxin injection) or permanent surgical treatment

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• Mechanical
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  • Tumours or swellings on the lid margin that mechanically evert the lid

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Entropion

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• Involutional
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  • Mainly affects the lower lid

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  • Can be problematic as in longstanding cases, eyelashes constantly rub against the ocular surface resulting in punctate epithelial erosions and ulceration in severe cases

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  • Temporary solutions include lubricants, taping, bandage contact lenses and denerveration of the orbicularis muscle with botulinum toxin

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  • Surgical management is definitive

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• Cicatricial
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  • Scarring of the palpebral conjunctiva may result in rotation of the upper or lower lid margin towards the globe

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  • Causes include cicatrizing conjunctivitis, trachoma, trauma and chemical injuries

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References

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1. Salmon, John F., and Jack J. Kanski. Kanski’s Clinical Ophthalmology: A Systematic Approach. Ninth Edition, Elsevier, 2020

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2. Demirci H, Frueh BR, Nelson CC. Marcus Gunn Jaw-Winking Synkinesis Clinical Features and Management. Ophthalmology 2010;117:1447–1452

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