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Ptosis

 

IV. PTOSIS

Definition:-

Drooping down of the upper lid to cover more than 1/5 of the cornea. It may be congenital or acquired.

A. Congenital ptosis:-

 It is the commonest type and characterized by:

- Dated since birth.

- Usually (but not always) bilateral.

- May be accompanied by other anomalies as epicanthus, S.R. weakness or blepharophemosis syndrome.

- Causes:-

* The commonest is dystrophy of LPS (i.e; myogenic defect).

* Congenital agenesis of  third nerve nucleus.

* Rare cases occur due to abnormal connection between oculomotor and trigeminal nerves. This rare condition is called "jaw-winking reflex" because opening of the lids occurs with movements of the jaw as mastication and yawning (also called Marcus Gunn's phenomenon).

* Blepharophemosis syndrome: It is bilateral ptosis that is inherited as an autosomal dominant feature. Ptosis is also associated with lateral displacement of medial canthi and epicanthus inversus. Congenital ectropion of lower lid may occur.

B. Acquired ptosis:

It occurs at any age and it is usually unilateral. Its common causes are:

1. Paralytic ptosis:

a. LPS paralysis due to oculomotor nerve paralysis (causes of nerve paralysis are mention with paralytic squint). Complete oculomotor paralysis is characterized by:

- Complete ptosis.

- Dilated fixed pupil.

- Loss of accommodation.

- Outward deviation of the eye with crossed diplopia when the lid is lifted by fingers.

b. Paralysis of Muller's muscle causes minimal ptosis. It occurs in cases of:

- Horner's syndrome: It is manifested by ptosis, anhydrosis, pseudo-enophthalmos and miosis. It occurs due to injury of the sympathetic supply of the eye. It may occur due to a preganglionic lesion (as in cases of carcinoma of the apex of the lung) or due to a postganglionic lesion.

- Toxic paralysis of Muller's muscle in cases of trachoma (the sleeping eyes appearance).

2. Mechanical ptosis:

It occurs due to increased weight of upper lid as in cases of:

- Edema either inflammatory or allergic (e.g.; palpebral spring catarrhal).

- Hematoma of upper lid.

- Tumours of the upper lid.

3. Traumatic ptosis:

Due to either or both: - Injury of LPS and/or its nerve supply.

                                  - Lid hematoma.

4. Myogenic ptosis:

a. Myasthenia gravis:-

It occurs most commonly in females between 20 - 40 years due to an autoimmune disease of myoneural junction. It is manifested clinically by:

- Ptosis by the end of the day. It can not be compensated by occipito-frontalis muscle.

- Diplopia by the of the day.

- Difficulty in swallowing by the end of the day.

- Immediate  improvement  by  injection of edrophonium which is a short acting choline esterase inhibitor (tensilon test).

- It is treated medically by long acting choline esterase inhibitors as neostigmine.

b. Myotonic dystrophy.

5. Senile ptosis:

It occurs due defects in the insertion of levator aponeurosis. It characterized by being a bilateral ptosis in an old patient.

6. Hysterical ptosis:

It occurs in young adult girls with emotional troubles. It is bilateral and sudden.

NB. Pseudo-ptosis:

- Lid retraction of the other eye.

- Atrophic and enophthalmic eyes.

 

Evaluation of a case of ptosis:-

Symptoms:

- Cosmetic disfigurement.

- Visual impairment if  ptosis is complete.

History taking is very important to identify congenital ptosis or if there is an underlying cause as trauma, diabetes, neurological disease or previous surgery.

Examination:

1. Assessment of the degree of ptosis:

a. The upper lid position:-

Normally the upper lid covers 2 mm (1/6) of the cornea. The degree of ptosis depends on how many mm upper lid drops beyond its normal site as following:

- In mild ptosis ---> 1 - 2 mm drop.

- In moderate ptosis ---> 3 mm drop.

- In severe ptosis ---> 4 mm drop or more.

b. The margin reflex distance (MRD):-

A source of light is held in front of the patient. The distance between the corneal reflection and lid margin is measured. Normally it is about 4 mm The more severe the ptosis, the smaller the MRD. In severe ptosis, the corneal reflection is not seen because the lid covers the centre of the cornea.

2. Assessment of the degree of LPS action (the thumb test):

It is done by measuring the amount of upper lid movement from the maximal down gaze to the maximal up gaze while the brow is fixed by the thumb (to eliminate frontalis action). The amount of LPS action is classified into:

- Normal action = 15 - 18 mm.

- Good action = 10 - 14 mm.

- Fair action = 5 - 9 mm.

- Poor action = less than 5 mm.

3. Compensatory mechanisms:-

To compensate for ptosis the patient tries to expose his visual axis by the following mechanisms:

- Over action of frontalis muscle leads to elevation of the brows (astonished look) and wrinkling of forehead.

- Compensatory head and vertebral column posture:

* Lordosis  and head retraction in bilateral cases.

* Scoliosis and torticollis in unilateral cases.

4. Diagnosis of the cause of ptosis:-

The age of onset, duration of ptosis and old photos are very important (Mention the characteristics of each type of ptosis).

Complications of ptosis:-

1. Visual complications (amblyopia):

- Squint in unilateral cases.

- Nystagmus in bilateral congenital complete ptosis.

2. Skeletal complications:

- Torticollis and scoliosis in unilateral cases.

- Head retraction and lordosis in bilateral cases.

N.B. Complications occur with the higher degrees of ptosis not in mild ptosis.

NB. Visual complications are more common in unilateral cases (amblyopia and squint), while skeletal complications are more common in bilateral cases.

Treatment of congenital ptosis:-

I. Timing of surgery:

* In mild ptosis (1 - 2 mm.) without complications, we wait to the age of 3 years or more. It gives better results because we work on a well developed LPS.

* In severe ptosis we interfere as early as possible for fear of amblyopia and skeletal deformity.

II. The choice of surgery:

1. If ptosis is due to Muller’s muscle paralysis we do tarso-mullerectomy from the conjunctival side (Fasanella operation).

2. In moderate or severe ptosis with fair levator action (5-9 mm) we strengthen the LPS by partial resection and advancement of its aponeurosis. Partial tarsectomy can be added to decrease the weight of the lid. It can be done by 2 techniques:

a. Through the skin side (Everbusch operation).

b. Through the conjunctival side (Blaskovic's operation).

   N.B. Each 5 - 6 mm resection corrects 1 mm of ptosis.

3. In severe or complete ptosis with poor levator action we do:

a. Frontalis sling operation:

- The action of frontalis muscle is transmitted to the lid margin by a strip of fascia lata (Crowford operation) or a synthetic material.

b. Mustarde operation:

* We shorten the lid by a split level resection.

4. If ptosis is due to levator aponeurosis dehiscence, we repair it.

For ptosis operations we have to note the following:

1. If epicanthus is present it should be corrected at first.

2. Contraindications of ptosis operations are:

- Corneal anaesthesia in cases of trigeminal nerve lesions.

- Marcus Gunn phenomenon.

- In cases of oculomotor paralysis we have to correct squint before correction of ptosis, otherwise diplopia will occur after surgery.

- Myasthenia gravis.

- Dry eye syndrome.

- Absent Bell's phenomenon.

 

 

Complications of ptosis operations:-

1. Over correction leading to abnormally wide palpebral fissure.

2. Lagophthalmos.

3. Undercorrection & recurrence.

4. Hess operation causes astonished look.

5. Hemorrhage and infection

 

Treatment of acquired ptosis:

1. Paralytic ptosis due to oculomotor nerve paralysis:

- Neurological treatment is given for 6 months aiming at spontaneous improvement, then ptosis is corrected only after correction of squint.

2. Mechanical ptosis is treated by treatment the etiology as removal of the masses.

3. Traumatic ptosis: Wait for 6 months to give chances for nerve regeneration and complete healing of tissues. Then the residual ptosis is corrected.

4. Myasthenia gravis:-

- Mainly medical treatment by choline esterase inhibitors as neostigmine.

- Steroids are given because it is an autoimmune disease.

- Irradiation or excision of the thymus may help the treatment.

5. Patients with hysterical ptosis are referred to psychiatrist.