The eyelids protect the eyes, spread the tear film over the eyeball, and help in drainage of the tears. The two eye lids meet at medial and lateral canthi. With open eyes, upper eye lid covers about ⅙th (2 mm) of the cornea and the lower eyelid just touches the limbus. Therefore, the palpebral aperture, with open eyes, measures approximately 10 mm (normal corneal diameter being 12 mm) vertically and 28 to 30 mm horizontally.
The lids are covered anteriorly by skin and posteriorly by conjunctiva. The margin or free edge of the lid between anterior and posterior borders is called intermarginal strip. Other important features of lid margin are as follows:
•Anterior border is rounded.
•The sharp posterior border lies in contact with the globe.
•Intermarginal strip is covered by stratified squamous epithelium and divided into anterior and posterior part by a gray line. The eyelashes originate anterior to the gray line. The ducts of the Meibomian glands open in a single row posterior to the gray line. The gray line is important as the lid is split at this level.
■Structure of Eyelid
Eyelids contain muscle, glands, blood vessels, nerves and connective tissue. The eyelid is made up of several layers (superficial to deep) which are as follows (Fig. 20.1):
4.Fibrous layer (consisting of tarsal plate and orbital septum).
5.Lid retractors of upper and lower eyelids.
6.Retroseptal pad of fat.
The skin of eyelids is the thinnest of the body, covered with finer hairs, and contain sebaceous and sweat glands. The upper eye lid skin crease (8–11 mm superior to the eyelid margin) is formed by the superficial insertion of levator aponeurotic fibers into the skin. At the margins, the eyelashes are arranged in two or more rows.
The subcutaneous tissue is absent over the medial and lateral palpebral ligaments, where the skin adheres to the underlying fibrous tissue. The fat is very sparse in preseptal and preorbital skin and is absent from pretarsal skin. The loose attachment of skin permits accumulation of edematous fluid or blood.
Orbicularis oculi is divided into:
Orbital portion: It extends in circular fashion around the orbit.
Palpebral portion: It is divided into preseptal and pretarsal portions. The preseptal portion overlies the orbital septum. The fibers from the upper and lower lid join laterally to form the lateral palpebral raphe, which is attached to the overlying skin. The pretarsal portion lies anterior to the tarsus, with a superficial and deep head of origin. The palpebral portion is used in blinking and voluntary winking, while the orbital portion is used in forced closure. Its function involves closing the eyelids.
It is supplied by temporal and zygomatic branches of the facial nerve. Therefore, facial nerve palsy results in inadequate closure of eyelid and exposure keratitis.
Submuscular Areolar Tissue
This layer is deep to orbicularis oculi and contains nerves and vessels of eyelid. Therefore, anesthetic agents are injected in this layer.
It consists of tarsal plate and orbital septum. The tarsal plates are composed of dense fibrous tissue. Each tarsus is approximately 29 mm long and 1 mm thick. The superior tarsus is crescentric with 10 mm in vertical height centrally and narrows medially and laterally. The inferior tarsus is rectangular and 3.5 to 5 mm in height at the eyelid center. Each tarsus encloses approximately 25 sebaceous Meibomian glands that secrete sebum. These glands are directed vertically and opened by a single duct on the lid margin, posterior to gray line and just anterior to the mucocutaneous junction. The medial and lateral ends of the tarsi are attached to the orbital rims through medial and lateral palpebral ligaments. The medial palpebral ligament attaches the tarsi to the lacrimal crest, while the lateral palpebral ligament attaches to the Whitnall tubercle.
The orbital septum represents the anatomic boundary between the lid tissue and the orbital tissue. It is a connective tissue structure that attaches peripherally at the periosteum of the orbital margin and fuses with the lid retractors near the lid margins, thus acting as a diaphragm that retains the orbital contents.
There are two lid retractors: upper and lower. Upper lid retractors include levator palpebrae superioris (LPS) and Muller’s muscle, while fascial extension from tendon of inferior rectus muscle forms the lower lid retractor. It inserts on the inferior border of the inferior tarsus (Fig. 20.2).
Levator Palpebrae Superioris
Origin: It originates from the lesser wing of the sphenoid bone at the orbital apex.
Course: It proceeds anteriorly and ends in an aponeurosis which changes direction from a horizontal to a more vertical direction. Laterally and medially, aponeurosis forms lateral and medial horns. The medial horn attaches to the posterior lacrimal crest. The lateral horns divide the lacrimal gland into orbital and palpebral lobes.
Insertion: The levator aponeurosis spreads anteriorly to insert into the skin of upper eyelid and superior tarsal plate.
Nerve: Oculomotor nerve (superior division).
Action: Retracts or elevates upper eyelid.
Müller Muscle (Superior and Inferior Tarsal Muscles)
The superior tarsal muscle originates from the under surface of LPS and travels inferiorly between the levator aponeurosis and conjunctiva to insert on the superior margin of tarsus. The inferior tarsal muscle lies below the inferior rectus and is inserted into the lower tarsus. These are innervated by the sympathetic nerves.
The part of conjunctiva lining the lids is called palpebral conjunctiva. The palpebral conjunctiva starts at the mucocutaneous junction of the lid margin and is firmly attached to the tarsal plates (tarsal conjunctiva). It continues as forniceal conjunctiva.
The eyelid is supplied by three cranial nerves (CNs) (III, V, and VII) and a sympathetic nerve (Fig. 20.3).
Sensory Nerve Supply
•The upper lid is supplied by the ophthalmic division of the trigeminal (V) nerve through the supraorbital nerve, supratrochlear nerve, and lacrimal nerve.
•The lower lid is supplied by the maxillary division of the trigeminal (V) nerve through the infraorbital (from V2) and medial aspect from the infratrochlear nerve (V1).
Motor Nerve Supply
•LPS is supplied by the 3rd nerve.
•Orbicularis oculi is supplied by the 7th nerve.
•Muller muscles are supplied by sympathetic nerves.
The eyelids drain into preauricular and submandibular lymph nodes as depicted in Fig. 20.4.
The internal and external carotid arteries contribute to lid arterial supply. Internal carotid artery gives off ophthalmic artery (medially) and lacrimal artery (laterally). Ophthalmic artery gives off supraorbital, supratrochlear, dorsal nasal, and two medial palpebral arteries, while lacrimal artery gives off two lateral palpebral arteries. External carotid artery gives off the following three arteries:
•Facial artery which continues as angular artery (it anastomoses with the dorsal nasal artery from the ophthalmic artery).
•Superficial temporal artery.
•Infraorbital artery (anastomose with vessels of the lower eyelid).
The two medial palpebral arteries arise as superior marginal vessel (supplying the upper lid) and inferior marginal vessel (supplying the lower lid), which pass horizontally as marginal arcades lying on the anterior tarsal surface 4 mm from the upper lid margin and 2 mm from the lower lid margin. In the upper lid, a peripheral arcade arises from the marginal arcade and lies on the anterior surface of the Muller muscle, just above the superior tarsal border. In the lower lid, no peripheral arcade exists. The two lateral palpebral arteries from the lacrimal artery pass medially to the upper and lower eyelids and anastomose with the marginal arcades (Fig. 20.5).
■Glands of the Eyelids
There are five glands in the eyelids as described below (Fig. 20.6):
•Meibomian glands (tarsal glands): These are modified sebaceous glands located in the tarsal plate. There are approximately 30 glands in each lid, which are vertically directed and open by a single duct on the margin of the eyelids. Each gland consists of a central duct with multiple acini. The Meibomian glands synthesize lipids (meibum) that form the outer layer of the precorneal tear film.
•Glands of Zeis: They are the modified sebaceous glands associated with the eyelash follicles.
•Glands of Moll: These are modified sweat glands near the margin of the lid immediately behind the hair follicle. Their ducts open into the duct of Zeis glands or hair follicles. These do not open directly onto the surface of skin as elsewhere.
•Gland of Wolfring: The accessory lacrimal glands of Wolfring are present near the upper tarsal border.
•Sebaceous (holocrine) glands: These are located in the caruncle and within eyebrow hairs.
■Disorders of Eyelid
•Edema of the lids.
•Inflammation of lids.
•Inflammation of lid glands.
•Deformities of eye lashes.
•Disorders of lid margins and palpebral aperture.
•Tumors of lid.
•Congenital anomalies of lid.
▃Edema of the Eyelids
Edema of the lids is common, owing to looseness of the tissues. Eyelid swelling can be unilateral or bilateral. It may be asymptomatic or accompanied by itching or pain.
There are numerous causes of a swollen eye including:
•Inflammation (inflammatory edema).
•Fluid overload (passive edema).
Pain, redness, warmth, and tenderness suggest inflammation or infection. Painless, pale swelling suggests allergic edema (angioneurotic edema).
It is due to the inflammation of lid itself or of neighboring structures. It may be due to:
•Inflammation of lids, for example, dermatitis, stye and hordeolum internum.
•Inflammation of conjunctiva, for example, acute conjunctivitis.
•Inflammation of lacrimal sac, for example, acute dacryocystitis.
•Inflammation of lacrimal gland, for example, acute dacryoadenitis.
•Inflammation of the eye ball, for example, endophthalmitis and panophthalmitis.
•Inflammation of the orbit, for example, orbital cellulitis.
•Inflammation of paranasal sinus, for example, maxillary sinusitis.
Eye allergies occur when our immune system overreacts to an allergen. Pollen, dust, cosmetics, insect bite, certain eye drops, and contact lens solutions are some of the most common eye allergens. The eyes release chemical “mediators” to protect the eyes from allergens, with the most common being histamine, which causes blood vessels in the eyes to dilate and swell, mucous membranes to itch, and eyes to become red and watery.
It is due to circulatory obstruction and is a common feature of:
•Local conditions, for example, cavernous sinus thrombosis.
◊Congestive heart failure.
Any trauma to the eye including eyelid contusion or surgical trauma can cause lid edema.
▃Inflammation of the Lids (OP2.1, 2.2, 2.3)
Anterior blepharitis may be of two types: seborrheic or squamous blepharitis and ulcerative or infective blepharitis. Difference between the two forms are listed in Table 20.1.
Table 20.1 Difference between squamous and ulcerative blepharitis
Infection commonly due to Staphylococcus aureus
On removal of crusts from lid margin
The underlying surface is found to be hyperemic but not ulcerated
Leaves small ulcer which bleed easily
Replaced without distortion
Often not replaced
Punctate epithelial erosions
May be present
Seborrheic (Squamous) Blepharitis
Seborrheic blepharitis is often associated with generalized seborrhea of scalp. It is essentially a metabolic disorder. The neutral lipids in secretions of Zeiss glands are split into free fatty acids by some bacterial lipases. These free fatty acids irritate the lid margins and conjunctiva.
Accumulation of white dandruff-like scales among the lashes at the lid margins. If the scales are removed the underlying surface is found to be hyperemic but not ulcerated (Fig. 20.7). Falling of eye lashes which are replaced without distortion. It is associated with irritation, itching, and watering.
It rarely causes complications but irritation due to free-fatty acids may cause chronic papillary conjunctivitis (Fig. 20.8) and punctate epithelial erosions of cornea.
•Removal of scales after softening with lukewarm solution of 3% sodium bicarbonate.
•Application of corticosteroid–antibiotic ointment at the lid margins after removing the scales.
•Treatment of associated seborrheic dermatitis and dandruff by medicated shampoo.
Ulcerative (Infective) Blepharitis
It is an infective condition of the anterior lid margin and is a common cause of irritation and ocular discomfort. (Fig. 20.9). It is commonly due to Staphylococcus aureus.
Symptoms include redness of lid margins, itching, irritation, watering, photophobia, and falling of eyelashes. Important presenting signs are as follows:
•Yellow crusts are seen around the bases of the lashes.
•Eyelashes are glued together due to these crusts. The removal of crusts leaves small ulcers which bleed easily.
If infective blepharitis is not treated properly, it becomes chronic and causes (Flowchart 20.1).
•Madarosis: The lashes fall out and often not replaced. The condition is known as madarosis. Eyelashes may be replaced by small and distorted cilia.
•Trichiasis (misdirection of eyelashes).
•Tylosis (thickening of lid margin).
•Ectropion leading to epiphora.
•Punctate epithelial erosions in the lower part of cornea (marginal keratitis).
•Removal of scales after softening with lukewarm solution of 3% sodium bicarbonate.
•Application of antibiotic ointment at the lid margins after removing the scales (b.i.d or t.ds. for 2–3 weeks).
•Systemic tetracycline or doxycycline may be useful.
•Topical steroids are very effective in papillary conjunctivitis and marginal keratitis, as steroids control the hypersensitivity reaction.
•Tear substitutes as eyes with blepharitis show the associated tear film instability.
◊Daily swabbing of lid margin after elimination of infection.
◊Rubbing of lids is completely avoided.
It is also called Meibomian blepharitis or meibomitis and caused by Meibomian gland dysfunction. Posterior blepharitis produces abnormal oil secretions. Bacterial lipases may result in the formation of free-fatty acids, increasing the melting point of the meibum.
Oil droplets are seen at the Meibomian gland orifices. Pressure on the lid margin results in expression of Meibomian secretion that is turbid or toothpaste-like. In severe cases, expression is impossible due to inspissated secretions. Blockage of ducts may result in cystic dilatation of Meibomian ducts. The tear film is oily and foamy. The condition may result in papillary conjunctivitis and inferior corneal punctate epithelial erosions.
Treatment modalities include:
•Topical antibiotics and steroids.
Systemic tetracyclines (doxycycline or minocycline) for 6 weeks are the mainstay of treatment. Tetracyclines block the Staphylococcal lipase production.
The crab louse Phthirus pubis can cause blepharitis. It is adapted to living in pubic hairs and may be transferred to another hairy area such as chest, axillae, or eyelids in an infected person. The infestation of lashes (Pthiriasis palpebrum) is common in children living in poor hygienic conditions.
It causes chronic irritation and itching of lids. The lice are anchored to the lashes with the claws. Presence of nits (ova) are seen as oval, opalescent pearls at the root of the eyelashes (Fig. 20.10).
Treatment modalities include the following:
•Mechanical removal of lice and nits with forceps.
•Topical yellow mercuric oxide (1%) is applied to the lashes.
•Delousing of the patient to prevent recurrences.
▃Inflammation of Lid Glands
(OP2.1, 2.2, 2.3)
■Hordeolum Externum (Stye)
It is a suppurative inflammation of a Zeiss gland.
It is often caused by Staphylococcus aureus. It is more common in children and young adults with eye strain due to refractive error or muscular imbalance.
The following conditions are usually associated with stye:
•Rubbing of eyes.
Painful, tender swelling is present in the lid margin with a lash at the apex of swelling (Fig. 20.11). Soon an abscess forms, and a pus point in relation to the affected cilia is visible on the lid margin. The lid is edematous. Occasionally, multiple lesions are present.
Treatment involves the following measures:
•Systemic antibiotics and anti-inflammatory drugs.
•When the abscess is formed and the pus point is formed, epilation of the associated lash is done or a small incision is made over the pus point.
In recurrent stye, diabetes mellitus must be excluded and the patient is asked to stop rubbing of eyes. The patient must be examined for the presence of refractive errors.
It is the suppurative inflammation of the Meibomian gland (Fig. 20.12). It may be due to secondary infection of a chalazion with Staphylococcus aureus. The inflammation is more violent than stye due to the larger size of the gland. The pus point appears through the conjunctiva and may burst through the Meibomian duct or the conjunctiva. An incision may be required to evacuate the pus.
■Chalazion (Meibomian Cyst)
It is also known as tarsal cyst. In fact, it is not a cyst but a chronic granulomatous inflammation caused by retained sebaceous secretions in Meibomian gland (Fig. 20.13).
The granular tissue shows the granulomatous inflammatory reaction containing epitheloid cells, giant cells, plasma cells, and lymphocytes.
These are more common in adults than in children. They are often multiple. The patient presents with painless, round or oval nodule in either lid. On eversion of the lid, the conjunctiva is red or gray over the nodule. The spontaneous resolution seldom occurs. Sometimes, the granulation tissue may form in the duct of the gland and the nodule is located on the lid margin (marginal chalazion).
A chalazion may be treated by:
•Intralesional injection of triamcinolone acetonide is given through conjunctiva. It is preferable for smaller chalazion and lesions close to the lacrimal puncta to avoid the damage during surgery. The success rate is approximately 80%. The second injection, if needed, can be given two weeks later. Local skin depigmentation may occur with the injection.
•Incision and curettage: If the chalazion is large or does not dissolve with intralesional injection, it should be incised and curetted. Steps of curettage include the following:
◊The eye is anesthetized with surface anesthesia by instillation of 4% xylocaine or proparacaine.
◊Infiltration of anesthesia with 2% xylocaine is given in the area of chalazion.
◊A chalazion clamp is applied and the eyelid is everted.
◊A vertical incision (to avoid damage to adjacent Meibomian glands) is made through palpebral conjunctiva. If the chalazion is subcutaneous, it can be incised through the skin side by horizontal incision (for the scar to be invisible).
◊The contents and the walls of cavity are curetted by a chalazion scoop.
◊A clamp is released and the eye is bandaged for a few hours.
Postoperatively, antibiotic eye drops and ointment are prescribed along with oral anti-inflammatory drugs.
In patients with recurrent chalazion in old age, the histopathological examination (biopsy) must be done to rule out adenocarcinoma of Meibomian gland.
It is caused by a double-stranded DNA poxvirus. It presents as a small, multiple, white, and umbilicated swellings near the lid margin. It produces severe conjunctivitis and superficial keratitis (Fig. 20.14).
The lesion should be incised and the substance resembling sebum is expressed.
The interior of the lesion is cauterized with tincture of iodine or pure carbolic acid.
▃Deformities of Eye Lashes
■Trichiasis (OP2.1, 2.2, 2.3)
It is a condition in which cilia are misdirected backward and rub against the cornea (Fig. 20.15). It may occur in isolation or as a result of scarring of lid margin secondary to the following conditions:
•Trachoma (Fig. 20.16).
•Injuries (mechanical or surgical).
•Herpes zoster ophthalmicus.
There is posterior misdirection of lashes rubbing the cornea which cause punctate epithelial erosion, vascularization of cornea, and corneal ulceration.
Following are the treatment modalities used for trichiasis:
•Epilation is a simple and temporary method of pulling out the misdirected eyelashes with forceps. It must be repeated every few weeks due to recurrences.
•Electrolysis is useful for few isolated lashes. In electrolysis, a fine needle is inserted into the root of eyelash and the follicle of eye lash is destroyed by passage of electric current of 2 mA. Then, the eye lash is removed. In diathermy, a current of 30 mA is applied for 10 seconds. The electrolysis is painful and tedious; therefore, local anesthesia can be injected into the lid margin.
•Cryotherapy is effective in eliminating many lashes. A cryoprobe at -20 degree C is applied after injecting local anesthesia, and the double freeze-thaw technique is applied. Cryotherapy may lead to depigmentation of the lid, skin necrosis, and damage to Meibomian gland which may affect the tear film.
•Argon laser ablation is useful for few scattered lashes and is less effective than cryotherapy.
•Surgery is undertaken if many cilia are displaced and resistant to other methods of treatment. The operative procedures are similar to that for entropion.
In districhiasis, an extra row of lashes emerge at or is slightly behind the Meibomian gland orifices. These lashes are often directed posteriorly, rubbing the cornea. It may be congenital or acquired (associated with chemical injury Stevens–Johnson syndrome and ocular cicatricial pemphigoid). These are treated with cryotherapy or electrolysis (Fig. 20.17).