Eyelid Coloboma

Etiology

The exact cause of an eyelid coloboma is unknown but is thought to be a form of facial cleft. Any intrauterine factors such as amniotic band, inflammation, decreased placental circulation, mechanical influences, and abnormal vascular system have been hypothesized, but all remain unproven. The precise etiology of eyelid coloboma is uncertain, though it is thought to result from a type of facial cleft. Various intrauterine factors, including amniotic bands, inflammation, reduced placental circulation, mechanical influences, and abnormal vascular systems, have been proposed as potential causes, yet none have been conclusively established.

Eyelid colobomas are classified within the spectrum of facial cleft disorders, ranging from complete cryptophthalmos to minor notches in the eyelid margin. In a case review, Nouby established a 5-level grading system for eyelid colobomas with cryptophthalmos, with Grade 1 representing the mildest form (coloboma alone) and Grade 5 signifying the most severe presentation involving cryptophthalmos with nose and lip deformities.[1]

Eyelid colobomas can be an isolated finding or associated with various syndromes mentioned below:

• Fraser syndrome: This rare condition is characterized by cryptophthalmos, syndactyly, ear malformations, urinary tract dysgenesis, ambiguous genitalia, laryngeal/tracheal stenosis. The condition is autosomal recessive with mutations of FRAS1, GRIP1, and FREM2 genes.[2][3]
• Goldenhar syndrome: A classical triad of (1) mandibular hypoplasia with facial asymmetry; (2) ocular and auricular malformations-periauricular tags, epibulbar dermoid, microphthalmia, eyelid coloboma; and (3) vertebral anomalies, such as scoliosis and hemivertebra, characterizes Goldenhar syndrome. [4]
• Treacher Collins syndrome (mandibulofacial dysostosis): Antimongoloid slant, colobomas of lateral lower eyelids, cataracts, microphthalmos, and atresia of lacrimal passages.[5] Typically intellect is normal; 50% develop conductive deafness due to malformation of ossicles—mutation of TCOF1 (over 80% of cases), POLR1C, and POLR1D genes seen.
• CHARGE syndrome: Coloboma, heart defects, choanal atresia, growth retardation, genital abnormalities, and ear abnormalities[6]
• Frontonasal dysplasia: Orbital hypertelorism, bifid nose, and medical facial cleft
• Delleman-Oorthuys (oculocerebrocutaneous) syndrome: Agenesis of the corpus callosum, cerebral/cerebellar cysts, orbital cysts, and periorbital/facial tags, punched-out defects of the lip with philtrum[7]
• Nasopalpebral lipoma coloboma syndrome: Upper eyelid and nasopalpebral lipoma, both eyelid coloboma, telecanthus, and maxillary hypoplasia. It is autosomal dominant with full penetrance[8]
• Manitoba oculotrichoanal (MOTA) syndrome: Unilateral upper eyelid coloboma or cryptophthalmos, anophthalmia/microphthalmia, triangular growths of hair extending from scalp to eyebrow, bifid nose, omphalocele, and anal atresia/stenosis. It has autosomal recessive inheritance and mutation of the FREM1 gene[3] 

Epidemiology

Eyelid coloboma is estimated to occur in approximately 1 in 10,000 births, with no gender predilection.[9] Eyelid coloboma does not exhibit racial predisposition, except for the Manitoba oculotrichoanal syndrome, which is specific to the aboriginal population of northern Manitoba.[10] One study found bilateral eyelid coloboma in 44.4% of cases.[11] Goldenhar syndrome is strongly associated with eyelid coloboma and occurs in about 1 in 5600 births.[12] 

Eyelid coloboma is estimated to occur in approximately 1 in 10,000 births, with no gender predilection. 

Eyelid coloboma does not exhibit racial predisposition, except for the Manitoba oculotrichoanal syndrome, which is specific to the aboriginal population of northern Manitoba. Bilateral eyelid coloboma is found in 44.4% of cases.

Notably, Goldenhar syndrome is strongly linked to eyelid coloboma and occurs in about 1 in 5,600 births.

History and Physical

A careful history is vital to confirm the diagnosis of eyelid coloboma. Since it is a congenital defect, the absence of eyelid tissue has to be present at birth. Traumatic damage to the eyelid tissue must be ruled out. Colobomas of the eyelid are generally rare and associated with systemic and ocular abnormalities. A complete review of symptoms should be asked, and medical records should be reviewed. 

The physical exam should include an examination for dermoids, lipo-dermoids, keratoconus, coloboma of the iris, and micro-ophthalmia. There will be a shortage of conjunctiva, tarsal plate, orbicularis oculi muscle, and skin seen in patients with eyelid colobomas. The eyelid defect leaves the cornea exposed, leading to exposure keratopathy and secondary bacterial infections, so the cornea should be examined for epithelial breakdown and corneal ulcers.[13]

In any patient with an eyelid coloboma, a complete eye exam should be performed. This includes assessing visual acuity, a pupil exam, checking intraocular pressure, a dilated fundus examination, assessing for ocular misalignment, and cycloplegic refraction.

Evaluation

Further ophthalmic testing that can be considered includes corneal topography, visual field testing, external/fundus photos, and optical coherence tomography. Measurement involving the coverage of the cornea as well as the movement of the eyelid should also be performed.[14] Outside of the complete eye exam, the patient's primary care provider needs to perform a complete physical exam because of the high association of an eyelid coloboma with syndromic conditions. If systemic abnormalities are suspected, imaging may be necessary to detect the deformities. Imaging techniques include x-ray, computed tomography, magnetic resonance imaging, and ultrasound.

Treatment / Management

Medical management: Corneal protection and amblyopia management is the primary goal of medical treatment. Artificial tears and ointment, moist chamber optical bandages, and bedtime patching will help protect the cornea. Arrange for an interprofessional evaluation to rule out systemic deformities. Amblyopia should be anticipated in all patients with lid coloboma, as astigmatism is common. Epibulbar dermoids seen in Goldenhar syndrome induce astigmatism and can obstruct the pupillary axis and cause amblyopia.

Surgical management: The surgical technique and timing of the surgery depend upon the size of the defect and the presence of corneal exposure, and the general well-being of the infant in terms of fitness for general anesthesia. If the defect is small with no corneal exposure or obstruction of the visual axis, the surgery can be delayed until 3 or 4 years of age. Moreover, there could be contraindications for general anesthesia due to defects in the palate or poor general conditions to thrive.[15][16] Defects are graded as small (less than 25% of the length of lid margin), moderate (25%-50% defect), and severe (more than 50%). In severe defects, both cosmetic and functional results are difficult to obtain.(B3)

Surgical Management

1) Upper eyelid reconstruction

Small defects: Direct appositional closure, direct appositional closure with lateral cantholysis, direct appositional closure with Tenzel’s semicircular flap

Moderate defects: Direct appositional closure with Tenzel semicircular flap, Mustarde lid switch flap, and Cutler-Beard reconstruction

Severe defects: Cutler-Beard method and Mustarde lid switch flap[17]

2) Lower Eyelid Reconstruction: 

Small defects: Same as upper eyelids         

Moderate Defects

• Posterior lamella: Hughes tarsoconjunctival flap
• Anterior lamella: Advancement of cheek skin, full-thickness skin graft, Tripier flap unipedicle

Large Defects

• Posterior lamella: Chondromucous graft, palatal mucoperiosteal flap
• Anterior lamella: Mustarde cheek rotation flap, nasolabial flap, medial forehead flap, lateral temporal flap  

Surgical Principles of Commonly Used Surgical Techniques

Direct closure: Direct closure is the choice for small defects. The defect is closed in layers and is especially useful in upper eyelid congenital simple colobomas. Cantholysis of the upper crux of the lateral canthal tendon helps relieve sutural tension. Tense lids interfere with lid movement and can cause entropion/ectropion, depending on the repair.[18]

1. Tenzel “semicircular” flap: For central defects that cannot be closed directly, a superiorly/inferiorly based semicircular flap can be transposed from the lateral canthal area.[19]
2. Cutler-Beard “bridge flap” procedure: First described in 1955, it is used to repair full-thickness upper eyelid defects. The principle is to bring full-thickness lower eyelid tissue, harvested from 4 mm below the lower eyelid margin, over the cornea to fill the upper eyelid defect. Around 1 month postoperatively, the full-thickness flap is divided into 2 at the level of the upper eyelid margin. The disadvantages are the long time lag required for lid separation, so it is not useful for monocular patients and is amblyogenic. Other disadvantages are the risk of entropion and loss of eyelashes.[20]
3. Hughes “tarsoconjunctival" flap: In 1937 Dr. Wendel Hughs described this procedure to repair full-thickness lower eyelid defects involving more than 50% of the lid length. It is a two-stage procedure, with the first stage involving the advancement of tarsoconjunctival flap from the upper eyelid and the second stage involving the reconstruction of the posterior lamella of the lower eyelid. The flap width should be less than the defect size. Reconstruction of the lower lid anterior lamella is done using a skin-muscle advancement flap, local skin, or free full-thickness skin graft. In the second stage of the procedure, severance of the flap is done 3 to 4 months after the initial stage. The modified Hughes procedure includes sparing of the marginal (4 mm) upper lid tarsus (as it provides stability to upper eyelid margin) and removal of the levator muscle aponeurosis from the tarsoconjunctival flap.[21]
4. Mustarde cheek rotation flap: This flap is particularly useful for reconstruction involving larger, especially vertical defects of the lower lid. Lower eyelid defects involving the entire lower eyelid may be reconstructed using a Mustarde cheek rotation flap. A large skin muscle flap is rotated from the cheek to repair large lower eyelid defects. The posterior lamella can undergo reconstruction with tarsoconjunctival, nasal cartilage, or mucous membrane grafts.[22]
(B3)

Differential Diagnosis

If there is an absence of eyelid tissue, trauma to the tissue should be considered on the differential and ruled out. If the defect has been present at birth, it is most likely a coloboma. The clinician must consider the following syndromes and investigate if they establish the diagnosis of an eyelid coloboma.

1. Fraser syndrome
2. Goldenhar syndrome
3. Treacher Collins syndrome (mandibulofacial dysostosis)
4. CHARGE syndrome
5. Frontonasal dysplasia
6. Delleman-Oorthuys (oculocerebrocutaneous) syndrome
7. Nasopalpebral lipoma coloboma syndrome
8. Manitoba oculotrichoanal (MOTA) syndrome
9. Anophthalmia and micophthalmia[23]

Prognosis

Prognosis is good for small and moderate defects in terms of anatomical reconstruction of the defect and functionality of the lid. Achieving a good cosmetic outcome in severe defects may be more challenging. Associated astigmatism and eye coverage in lid-sharing surgeries could cause amblyopia and decrease visual acuity. In one case series, all 21 patients that received surgical intervention for eyelid colobomas had acceptable cosmetic outcomes, and visual acuity compared to the other eye was similar, indicating a good prognosis in patients with eyelid colobomas that undergo early surgical intervention.[22]

Complications

Complications with eyelid colobomas often cause decreased vision in the affected eye. Exposure keratopathy develops because the corneal surface cannot stay lubricated without eyelid coverage, and the tear film evaporates away. This can cause corneal epithelial breakdown, allowing for infectious keratitis. The abnormalities in the eyelid can lead to an alteration in the corneal curvature, causing astigmatism. If the astigmatism is not corrected, amblyopia can develop.[24]

Amblyopia is highly associated with strabismus, which can also commonly be seen with eyelid coloboma.[25] Lastly, the absence of eyelid tissue can lead to cosmetic disfigurement.