INTRODUCTION

Ptosis is a drooping or an abnormally low position of the upper eyelid(s) which may be congenital or acquired. Depending on the severity of the condition, droopy upper eyelids can block or greatly reduce vision depending on how much it obstructs the pupil.

EPIDEMIOLOGY

There are no substantial differences in prevalence between men and women or between ethnicities. However, it’s most common in older adults because of the natural aging process. The levator muscle is responsible for lifting the eyelid. As you age, that muscle can stretch and as a result cause the eyelid to fall. Sometimes, it could be a sign of an underlying medical condition, especially if the issue affects both eyelids. If just one of your eyelids droops, it may be a result of a nerve injury or a chalazion. Routine LASIK or cataract surgery is sometimes to blame for the development of ptosis, as a result of the muscle or tendon being stretched.

SIGNS AND SYMPTOMS OF PTOSIS

Important signs of ptosis include: drooping of upper eyelid(s) with impaired elevation on up-gaze, recruitment of brow muscles with brow furrows, higher lid crease and smaller eye on ptotic side, chin up position when bilateral, high astigmatism or lagophthalmos in congenital ptosis. Sometimes, ptosis is associated with a weakness of the extra-ocular muscles, particularly those concerned with the elevation of the eye. The degree of ptosis is variable. Usually it is largely a cosmetic defect concern because it is not marked enough to affect vision. However, in severe cases the affected eye is likely to develop a stimulus deprivation amblyopia as a result of its disuse. This is avoided in bilateral cases because of the necessity to tilt the head backwards to achieve some of vision.

Non-specific symptomology may include fatigue, headache (from chronic compensatory contracture of the frontalis muscle), blurred vision or even pain. Examination of the patient with acquired ptosis reveals a narrowed palpebral aperture and notable lid droop. The condition may be unilateral or bilateral. The laterality may be indicative of the underlying aetiology. Unilateral ptosis often stems from neurologic or mechanical disease, while bilateral ptosis is typically associated with generalised muscle disorders or aging. Associated signs may also help to identify the specific disorder. For example, Horner’s syndrome involves a unilateral ptosis with a miotic pupil. A third nerve palsy demonstrates a ptosis with restriction of both up-gaze and adduction. Additionally, the pupil may be dilated and unresponsive to light. Pain and swelling of the lid may point to an inflammatory or neoplastic disorder involving the lid, such as dacryocystitis or preseptal cellulitis. When ptosis is variable and intermittent, myasthenia gravis is often the cause.

PATHOPHYSIOLOGY

Congenital ptosis is usually the result of developmental failure of the levator muscle of the lid, alone or in association with anomalies of the superior rectus (most frequent) or complete external ophthalmoplegia (rare). It may be transmitted as a dominant characteristic. Acquired ptosis can be considered in 5 main categories:

Mechanical factors: Abnormal weight of the lids may make it difficult for a normal levator muscle to elevate fully. This may be due to acute or chronic inflammatory oedema or swelling, tumour, or an extra fold of fatty material as in xanthelasma or dermatochalasis.

Myogenic factors (for example, muscular dystrophy, myasthenia gravis, blepharophimosis syndrome, simple congenital, ocular myopathy). Ptosis of one or both lids is often the first sign of myasthenia gravis and occurs eventually in over 95% of cases. The essential defect in myasthenia gravis seems to be in the humoral transmission at the myoneural junction.

Neurogenic (paralytic) factors. There is interference with the pathways of the portion of the third cranial nerve supplying the levator muscle at any level from the oculomotor nucleus (midbrain) to the myoneural junction. Other examples of neurogenic factors include Horner syndrome, Marcus Gunn jaw-winking syndrome and third nerve syndrome.

Aponeurotic factors. Aponeurotic factors include involutional and post-operative conditions. Aponeurotic ptosis is caused by a defect in the levator aponeurosis.

Miscellaneous. Although elderly patients are primarily affected, younger patients can  develop this condition as a result of trauma, severe lid swelling, blepharochalasis, prior ocular surgery or long-term contact lens wear.  

MANAGEMENT OF PTOSIS

A simple inspection of the eyelid is the obvious first step. Secondly, an assessment of the degree of the levator function demands the prevention of any upwards movement of the eyebrow by pressing firmly on it with the finger so that the frontalis muscle is not allowed to exert an indirect elevating influence on the eyelid.

Clinically, the severity of ptosis is graded by measuring the marginal reflex distance (MRD), bearing in mind that the upper eyelid covers approximately 1.5mm to 2mm of the cornea.

• Mild ptosis = 2mm or less.
• Moderate ptosis = 3mm
• Severe ptosis = 4mm or more.

Levator function is assessed by measuring the upper lid excursion. It is graded as follows:

• Good = 12mm or more
• Fair = 6-11mm
• Poor = 5mm or less

Without question, the most important aspect of managing a patient with acquired ptosis is determining the underlying cause. A thorough history is crucial: time of day when worst, associated symptoms such as generalised fatigue, breathing problems, diplopia.The clinician must consider laterality and check associated motility function and pupillary responses. Pseudoptosis—any condition that gives the appearance of a drooped lid but actually involves no lid dysfunction in the involved eye must be ruled out. Some examples of pseudoptosis include patients with small globes (e.g., microphthalmos, phthisis bulbi), enophthalmos, blowout fracture, contralateral lid retraction and ipsilateral hypotropia.

Mechanical aetiologies are the simplest to remedy, in principle: Removal of the cause creating the resistance should render improvement. In cases of extensive scarring from long-standing disease, a surgical consultation may be advised.

Aponeurogenic ptosis may be treated by a variety of methods. Procedures such as levator resection and aponeurosis tightening are principle considerations. All surgical patients should be followed closely for the development of secondary lagophthalmos and exposure complications. The use of a prosthetic ptosis crutch attached to the spectacle frame can provide relief from some of the major symptoms encountered by these patients. The ptosis crutch is a nonsurgical option that involves adding an attachment to the frames of spectacles. This attachment, or crutch, prevents drooping by holding the eyelid in place. There are two types of ptosis crutches: adjustable and reinforced. Adjustable crutches are attached to one side of the frames, while reinforced crutches are attached to both sides of the frames. Crutches can be installed on nearly all types of spectacles, but they work best on metal frames.

The principle advantage of this modality is diminished cost without the risks of surgical intervention. Of course, surgery offers a more consistent and long-term solution for patients with ptosis. Ptosis that is neurogenic or myogenic in nature is best managed by a specialist with advanced training in neuro-ophthalmology. Such cases generally require imaging and other specialised testing (e.g. Tensilon® in myasthenia gravis) for confirmatory diagnosis.

CLINICAL PEARLS

• Congenital ptosis is immediately evident and is occasionally observed to be associated weakness of other EOMs.
• Pseudoptosis may be due to prosthesis, microphthalmos, phthisis bulbi, ipsilateral hyoptropia, contraleral lid retaction and enophthalmos.
• Consider the lid crease when differentiating congenital ptosis from acquired ptosis. Acquired ptosis will maintain a lid crease; congenital ptosis will not. A high lid crease often heralds an aponeurogenic ptosis.
• Old photographs of the patient may also often help to differentiate mechanical ptosis resulting from trauma to the lid.
• The laterality of a ptosis can help determine its aetiology. In general, unilateral ptosis may be due to Horner’s syndrome, third nerve palsy, inflammation, trauma or infiltrative disease. Bilateral ptosis suggests damage to the supranuclear pathways of the brain or ocular myopathies. Age-related (senile or involutional) ptosis is typically bilateral but may be unilateral or asymmetric. A ptosis that is variable is highly suggestive of myasthenia gravis.
• Ptosis is usually the initial and most common complaint in myasthenia gravis. To confirm suspicions, clinicians can test sustained upgaze and/or conduct the “sleep or ice-pack test.” Tensilon® testing confirms a diagnosis of systemic myasthenia.
• Third nerve palsies are variable in presentation and may or may not show pupillary involvement. Associated ipsilateral motility problems may be very subtle and are often overlooked. Remember that upgaze and adduction are affected most commonly. Third nerve palsies are unilateral except in cases involving the third nerve nucleus. In the latter, patients present with bilateral ptosis.
• The ideal time to operate congenital ptosis is between ages 3 and 4. Treatment is by levator resection assuming there is simple congenital ptosis and is not associated with jaw-winking phenomenon.
• During ptosis surgery, the levator muscle is tightened. This will lift the eyelid up into the desired position. Another alternative is a “sling” operation, in which the forehead muscles are used to elevate the eyelids. Assess levator function to determine aetiology and treatment plan. If there is minimal to absent levator function (<4mm), consider a frontalis suspension procedure. If there is reasonable levator function, consider a levator aponeurosis advancement of a muscle resection. Minimal ptosis can be corrected by conjunctival Mullerectomy or Fasanella-Servat procedure.

CONCLUSION

Ptosis may be congenital or acquired, but those with the acquired form are typically the patients who present symptomatically. Most individuals with congenital ptosis develop adaptations early in life, making their concerns primarily cosmetic. The most common symptoms associated with acquired ptosis involve an inability to fully open the involved eye, decreased vision and superior loss of field due to lid obstruction.The aetiological cause should be identified before planning treatment.

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