In a normal eye, the upper lid covers one-sixth of the cornea that is about 2 mm and the lower lid just touches the limbus. Cornea is a transparent membrane that covers brown and black of the eye that is the iris and pupil. Iris can off course be different colors but in normal Indian population, iris is brown, so cornea is the transparent covering this iris which if of different colors in different people and the black pupil of the eye and the upper eyelid covers one sixth of this cornea in a normal eye.
Elevation of upper eyelid is caused be levator palpebrae superioris muscle (which is a muscle of the eyelid and will be dealt in the structure of the eyelid). This function is also assisted by other muscles like frontalis muscle and muller’s muscle.
Palpebral aperture: It is the elliptical space between the upper and the lower eyelid, that is, it is the amount of space measured as the part of eyeball that is visible to us when the eye is open. Normally it measures 10-11 mm vertically in the centre and 28-30 mm horizontally.
What is drooping eyelid
Drooping Eyelid can be defined as the abnormal falling of the upper eyelid. That means the upper eyelid covers more than one sixth of the cornea or more than 2 mm of the cornea.
Drooping eyelid is of two types i.e Congenital and Acquired, and is further divided into subtypes.
- Simple Ptosis
- Complicated Ptosis
- Neurogenic Ptosis
- Myogenic Ptosis
- Aponeurotic Ptosis
- Mechanical Ptosis
Causes of drooping eyelid or ptosis
1. Congenital Ptosis
It is the commonest form of ptosis. It is mostly bilateral and should be confirmed by photographs taken in childhood. It is due to congenital weakness of levator palpebrae superioris muscle or say due to the defective development of the muscle. As this muscle is responsible for elevation of the upper eyelid, its weakness leads to the drooping of the upper eyelid or ptosis.
a. Simple ptosis: If it is not associated with any other defect. It is just the congenital weakness of the LPS muscle, it is called simple ptosis.
b. Complicated ptosis: It is the congenital ptosis in which along with the weakness of LPS muscle there are other defects of the surrounding structures are associated. These are:
1. Extraocular muscle weakness: Congenital weakness of LPS muscle can be associated with weakness of Superior rectus muscle. An inability to move the eyes in upward direction is the commonest congenital defect associated and is due to the weakness of extrinsic muscles.
2. Blepharophimosis syndrome: Simple congenital ptosis can be accompanied with blepharophimosis syndrome. The Blepharophimosis syndrome is:
- Congenital ptosis
- Blepharophimosis: Palpebral fissure is decreased horizontally. It appears shortened or contracted at the outer canthus.
3. Congenital synkinetic ptosis (Marcus Gunn jaw-winking ptosis): In this condition, when the patient moves his jaw or with the jaw movements the ptotic lid retracts or moves upward. This also occurs on moving the jaw to the opposite side. This phenomenon is due to stimulation of the pterygoid muscle of the same side as of the ptotic lid.
2. Acquired Ptosis
It is mostly unilateral,can be bilateral too. It is of following types:
a. Neurogenic ptosis: It is caused due to involvement of third cranial nerve (oculomotor nerve) or branches supplying the LPS muscle. The involvement can be due to wounds or fractures by the direct injury or any palsies.
The common cause of neurogenic ptosis can also be Horner’s syndrome due to reduction in sympathetic innervation and includes:
- Mild ptosis: Which is due to the paralysis of Muller’s muscle.
- Miosis: That is decrease in size of the pupil or contraction of the pupil which is due to paralysis of dilator pupillae muscle
- Anhidrosis: Reduced sweating on the side of the ptotic lid.
- Loss of ciliospinal reflex.
- Other less common causes of neurogenic ptosis are ophthalmoplegic migraine and multiple sclerosis.
b. Myogenic ptosis: It occurs due to defect in the levator palpebrae superioris muscles but the defect is not congenital but acquired due to various diseases involving the myoneural junction like :
Myasthenia gravis, dystrophia myotonica, ocular myopathy, etc.
The ptosis is usually bilateral and symmetrical in myotonic dystrophy and asymmetrical in myasthenia gravis.
Myogenic ptosis usually develop gradually over years.
c. Aponeurotic ptosis: In this kind of acquired ptosis, usually the levator muscle function is normal but the aponeurosis of the LPS muscle is not inserted properly to the anterior part of the tarsal plate. The diagnostic feature of this is presence of a high lid fold and good levator action. It is usually seen in old age, also called involutional or senile ptosis.
Other causes of aponeurotic ptosis are: Postoperative ptosis( rare), traumatic disinsertion of the aponeurosis.
d. Mechanical ptosis: As the name says, it is due to the mechanical effect of the tumors or the inflammation which weighs down the upper lid and cause ptosis.
So the causes would be:
- Lid tumors
- Lid oedema
Examining the drooping eyelid
1. Observation or inspection
- Whether the ptosis or drooping is in one eye or in both the eyes.
- Whether the lid crease is present or not.
- Whether the person can close eyes properly or not that is examining the function of orbicularis oculi muscle.
- Whether the person is able to do the upward movements of the eye or not that is examining the function of superior rectus and other extraocular muscles.
- Whether the jaw winking phenomenon is present or not.
- Whether the Bell’s phenomenon (up and out rolling movements of the eye on forceful closure) is present or not.
2. Measurement of the degree of ptosis: It is measuring the amount of the ptosis or drooping. It can be done as follows:
In unilateral ptosis or drooping of the eyelid of one eye-take the vertical height of the palpebral fissures of both the eyes. The next step is to subtract the vertical heights of the palpebral fissures of both the eyes. This will indicate the degree of the ptosis.
As told upwards, the normal vertical height of palpebral fissure is 10-11 mm. So in drooping the vertical height would decrease and subtracting this from the normal height in the other eye would give the degree or the amount of the drooping.
In bilateral ptosis or drooping of the upper eyelid in both the eyes-measure the amount of cornea covered by the drooping eyelids and subtract 2 mm from it as normally the upper lid covers 2 mm of the cornea in a normal eye. This will give the amount of ptosis or drooping.
- Mild ptosis: 2 mm
- Moderate ptosis: 3 mm
- Severe ptosis: 4 mm
3. Assessing Margin Reflex Distance (MRD): It is defined as the distance between the the centre of the upper lid and the corneal light reflex (pen torch held in front, on which patient looks). The difference between MRD’s of normal and the drooping eyelid gives the amount of ptosis or the degree of drooping.
- Normal MRD IS 4-5mm.
4. Assessment of levator function: It is done with the help of Burke’s method, the basic principle behind which is lid excursion which is caused by the action of LPS muscle. The patient is asked to look down and the thumb of one hand is placed firmly against the eyebrow of the patient to block the action of the frontalis muscle. The patient is asked to look up and the amount of lid excursion that is the degree of lid elevation is measured with the ruler by the examiner.
- Normal: 15 mm
- Good: 8mm
- Fair: 5-7 mm
- Poor: 4 mm or less
5. Ruling out pseudoptosis: Pseudoptosis is a condition in which ptosis is actually not present but on visualising the patient’s eye it seems that there is drooping of the eyelid. Thus pseudoptosis must be ruled out and it is seen in the following conditions:
- Phthisis bulbi
- Brow ptosis
- Eyelid retraction the other eye
- High myopia in the other eye
- Proptosis in the other eye
Treatment of Drooping eyelid
1. For congenital ptosis: Surgery is the treatment for choice and should be done as early as possible, to prevent sensory deprivation amblyopia. The type of surgery depends upon degree of ptosis, associated defects or complicated ptosis and levator function. The surgeries are:
- Fasanella servat operation or Tarso Conjunctivo- mullerectomy- indicated for mild ptosis 1.5 – 2 mm, with good levator function and good lid fold.
- Levator resection: Indicated in cases of moderate to severe degree of ptosis with a moderate levator action.
- Frontalis sling operation: Indicated in cases of severe ptosis with no elevator action.
2. Acquired ptosis: Treatment of the underlying cause is done.
1. A.K Khurana, MD “Ophthalmology” (New Age International Publisher, Inc 2012) p325-327.
2. Drooping eyelid image used on this page is copyright to EyePtosis (www.eyeptosis.com).