Traditionally, ptosis has been divided into either the congenital or acquired category. In the literature there have been publications reporting a 90% preponderance of congenital ptosis versus acquired ptosis; and yet there have also been papers reporting that acquired ptosis constituted the majority of cases. Obviously, the reported incidence will depend heavily on the type of patients profiled by the observers, their training and subspecialty inclination, their referral pattern, and even the town that they practice in (whether it is a younger population). This method of classification does not immediately yield any clue as to the origin of the particular type of ptosis, although it tends generally to fall into those with poor to fair levator function (congenital ptosis), and those with good levator function (acquired ptosis). In this classification, the most prevalent form of ptosis to be encountered in a clinical ophthalmologist’s practice would be involutional ptosis (‘senile’ ptosis) within the acquired ptosis group. The etiology of this form of ptosis would include aging, stretching of the levator aponeurotic complex, as well as postsurgical.

A more informative etiological classification deriving from the above is to categorize ptosis into the following groups:

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  aponeurotic ptosis (from levator aponeurotic dehiscence or rarefaction);

  
  
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  myogenic ptosis;

  
  
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  neurogenic ptosis; and

  
  
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  mechanical ptosis.

In this scheme, the traditional ‘acquired ptosis’ would fall into the involutional aponeurotic dehiscence type, while ‘congenital ptosis’ would be part of the myogenic group.

Aponeurotic ptosis would include involutional ptosis seen in elderly patients, where the levator aponeurosis ( Fig. 12.1 ) may have undergone rarefaction or partial dehiscence along the superior tarsal border, resulting in elongation of the length of the muscle and a ptotic upper lid margin.

Surgeon’s open-sky view of levator aponeurosis and Whitnall’s suspensory ligament, right upper lid.

Clinical findings in involutional ptosis may include mild to moderate ptosis, a high lid crease, and a good to excellent levator function (greater than 10mm). The clinician may be able to see the outline of the cornea through the upper lid skin when the patients close their eyelids. Intraoperatively, one may see fatty infiltration and degenerative changes of the levator aponeurosis, partial dehiscence of the medial portion of the levator muscle ( Fig. 12.2 ), and lateral shifting of the tarsal plate ( Fig. 12.3 ).

Dehiscence and fatty degeneration of the medial portion of the levator muscle in a left upper eyelid.

Lateral migration of the tarsi in an elderly woman.

Other causes include surgical trauma (ocular surgery, vitreoretinal surgery, enucleation, and evisceration), repeated subclinical injury to the upper lids (including contact lens wear and recurrent periorbital swelling), and actual traumatic injury.

Myogenic ptosis includes the broad category of congenital ptosis, congenital ptosis with superior rectus weakness (double elevator palsy), Marcus Gunn jaw winking ptosis, blepharophimosis, myasthenia gravis, chronic progressive external ophthalmoplegia, and rarer entities like muscular dystrophy.

Congenital ptosis typically presents at birth ( Fig. 12.4 ). It is thought to be an isolated dystrophy of the levator muscle, at times manifesting as a hypoplasia of the muscle. On clinical examination the patient may present with mild to severe ptosis, and levator function in the poor (0–5mm) to fair (5–10mm) range. The eyelid typically shows absence of lid crease and may manifest lagophthalmos on downgaze. There is frequently a history from the parent that the child’s eyelids do not approximate at night during sleep, although the cornea may be rolled up from an intact oculocephalic reflex (Bell’s phenomenon). It may be unilateral or bilateral, with asymmetric involvement.

Congenital ptosis of the right upper lid. Note absence of crease on affected lid.

Marcus Gunn jaw winking ptosis ( Fig. 12.5A ) is a peculiar condition where the patient’s ptosis appears to be lessened when the subject moves his or her lower jaw to the opposite side of the involved eyelid ( Fig. 12.5B ). For example, a patient who has ptosis of the right upper lid may reduce his ptosis when his jaw is moved laterally to the left side, or the patient may show fluctuation of his upper lid’s ptotic position as he is having his meals (activating his masticatory muscles innervated by the fifth nerve). It is thought to be an aberrant innervational connection between the levator and the fifth nerve, although the exact location is unclear.

(A) Marcus Gunn jaw winking ptosis.

(B) When the jaw is moved to the opposite side, the ptosis is relieved.

Blepharophimosis is typically an autosomal dominant trait and includes the findings of congenital ptosis, telecanthus, epicanthus inversus, phimosis, and lateral displacement of the inferior punctum. For patients with significant telecanthus, ptosis repair usually follows repair of the telecanthus by way of transnasal wiring. This is then followed by frontalis suspension.

Patients with myasthenia gravis are thought to have an immunological blockage at the level of the neuromuscular junction, resulting in an effective lack of acetylcholine. The ptosis is often severe, with poor levator function. Diplopia may be present. The evaluation consists of appropriate diagnostic assays for neuroreceptor blocking antibodies, the Tensilon (edrophonium chloride) test and muscle biopsy, followed by therapeutic use of systemic medications (Mestinon) to see if the ptosis can be improved. Significant ptosis that is functionally disabling can be treated with frontalis suspension utilizing an adjustable 1mm silastic rod. It has been reported in the literature that approximately 5–10% of myasthenia patients have Graves’ disease. Ptosis may occur in hyperthyroidism and therefore patients with Graves’ disease who manifest ptosis with poor levator function should be screened for myasthenia gravis.

Chronic progressive external ophthalmoplegia may have a myogenic as well as neurogenic origin. The patient may present with bilateral, severe ptosis and absence of extraocular movements to a varying degree in each eye, but typically does not report diplopia. The pupillary reflexes are typically normal. The levator function is poor. Some of these patients may have associated involvement of the periorbital orbicularis muscles, and some even have paresis of the frontalis muscles of the forehead. Since these patients have absent Bell’s protective eye movement due to their absent extraocular movement, with a poor orbicularis function causing poor eyelid closure, treatment of ptosis is best managed using an adjustable technique like the frontalis suspension with a 1mm silastic rod.

Among the neurogenic ptosis category, one would include Horner’s syndrome as well as third nerve palsy. Horner’s syndrome can occur with involvement of the primary, secondary, or tertiary fibers of the sympathetic nervous system. The most often mentioned causes include tumors (e.g. Pancoast tumor of the lung), trauma, aneurysms, and iatrogenically from surgery. The manifestation includes mild ptosis with excellent levator function, relative miosis of the pupil, anhidrosis, and a greater degree of anisocoria in dark as compared with light setting. Third nerve palsy may occur with diabetes, orbital trauma, tumors, vascular episodes, infections, as well as neurologic emergencies. The manifestation includes severe ptosis with poor levator function and paralysis of the superior rectus, inferior rectus, medial rectus, and inferior oblique. The ptotic upper lid when lifted shows an eye in a downward and out-turned position, due to the remaining actions of the lateral rectus and the superior oblique muscles. Cases that do not resolve after at least 6 months may be treated with strabismus correction followed by ptosis repair in the form of adjustable frontalis suspension, preferably using a 1mm silastic rod.

Mechanical ptosis, as the name implies, may include aging-related dermatochalasis, fatty prolapse, presence of abnormal tissues (hemangiomas), tumors as in plexiform neuroma of von Recklinghausen’s syndrome (neurofibromatosis), and patients with floppy eyelid syndrome (pachydermoperiostosis – constellation of sebaceous hyerplasia, recurrent blepharitis, and meibomitis; thickened, engorged, and elastic upper tarsi, and spontaneous out-turning of the tarsal plates, especially during sleep). Mechanically, scar bands may occur following surgery, trauma, or idiopathic conditions like ocular pemphigoid and Stevens–Johnson syndrome. Cicatricial reaction along the skin as well as within the middle lamella (orbicularis, orbital septum, preaponeurotic fat, levator muscle) can cause a mechanical tethering of the levator muscle, resulting in ptosis.