Eyelid Colobomas – Causes, Symptoms. Treatment

Eyelid Colobomas result in a full-thickness defect of the eyelid: although the coloboma may occur anywhere on the eyelids, the most common site is at the junction of the medial and middle third of the upper eyelid. Eyelid colobomas are classified as traumatic (accidents, surgery) or congenital. Congenital colobomas may be isolated or may occur in the presence of other facial deformities and syndromes. In eyelid colobomas, corneal protection is paramount. Topical lubricating drops and ointment are applied and moisturizing chambers may be used. Patching is sometimes necessary. Surgical repair to improve corneal coverage is undertaken as necessary. The size and location of the defect will determine the exact surgical procedure used. Direct closure may be performed in defects up to 25% of the eyelid. In defects larger than 25% and up to as much as 60%, lateral mobilization with canthotomy, cantholysis, and multiple “Z” plastics allow direct closure of the coloboma. When the defect is larger, lid-sharing procedures like the Hughes procedure for lower lid reconstruction and the Cutler-Beard procedure for upper eyelid closure may be necessary, together with the use of skin grafts.

Iris colobomas affect the inferonasal quadrant and are caused by the failure of the embryologic optic fissure to close during the fifth gestational week. This results in a typical keyhole-shaped pupil. On occasion, a bridge of iris may be present in the coloboma, giving rise to a type of coloboma called a “bridge coloboma”. Iris colobomas are frequently bilateral and associated with a pyriform corneal shape. When the corneal shape is normal, one must look for a surgical cause of coloboma.

Iris colobomas may be associated with colobomas of the ciliary body, choroid, retina or optic nerve. Glaucoma, nystagmus, or strabismus may be seen in the presence of iris colobomas.

Causes of Eyelid Colobomas

In normal eye development, the neuroectoderm approaches the surface ectoderm and forms the optic vesicle. The optic vesicle invaginates to form an optic cup dorsally and proximally and the optic fissure ventrally and distally. The most proximal portion of the vesicle forms the optic stalk. The margins of the optic fissure grow toward each other until they fuse, leaving a small opening, the optic disc, for the hyaloid artery. The optic fissure begins to close in the fifth week of fetal development and is completed by about the seventh week. Partial or complete failure of closure of the optic fissure results in colobomas. Since the optic fissure closes ventrally last, the location of the colobomas is usually ventral. The extent of visual impairment caused by a coloboma ranges from asymptomatic to complete loss of vision, depending on the size and location of the defect. The inheritance pattern can be a defect in any of the 39 genes associated with colobomas or more commonly sporadic.[rx]

Diagnosis of Eyelid Colobomas

History and Physical

Failure of retinal pigment epithelial development in the area of a region-choroidal coloboma may lead to hypoplasia of the choroid and sclera with the formation of a staphyloma. If the fovea is involved, vision may be significantly affected. On the other hand, even with large chorioretinal colobomas, if the fovea is not involved, vision is relatively preserved.

Children who have symptomatic unilateral optic disc abnormalities generally present during the preschool years with sensory esotropia. Visual acuity may be unaffected as in optic disc pit, or optic disc drusen. Optic nerve colobomas have been associated with microphthalmos, iris coloboma, ciliary coloboma, lens notching, retinal detachment, neovascular membranes, and macular holes. Rhegmatogenous retinal detachments can develop secondary to breaks in the thin membrane that overlies the coloboma.[rx] Pal et al. showed that vitrectomy with silicone oil had a success rate in patients with optic disc coloboma and retinal detachment.[rx]

Evaluation

Colobomas are seen in

• The Treacher Collins syndrome (autosomal dominant with variable penetrance)
• In association with cryptophthalmos (absence of eyelid formation)
• Cat eye syndrome is a chromosome 22 abnormality with vertical iris colobomas
• Patau syndrome (trisomy 13)
• Fraser syndrome
• Manitoba Oculotrichoanal syndrome (seen in Northern Manitoba Aboriginal patients), Goldenhar syndrome
• First arch syndrome.
• Franceschetti syndrome
• Amniotic band syndrome
• The CHARGE syndrome is composed of coloboma, heart defects, choanal atresia, growth retardation, genital abnormalities and ear abnormalities. Microphthalmia may also be seen.
• Other associated conditions include renal coloboma syndrome, Aicardi syndrome, Solomon syndrome, and Noonan syndrome.[rx]

In the presence of a congenital coloboma involving any of the eye structures, it is wise to perform a complete ophthalmic examination, looking specifically for the following:

• Eyelids: trichiasis, dermoid, lipodermoid
• Eyebrows: defect
• Conjunctiva: symblepharon, caruncle abnormalities
• Cornea: exposure keratopathy, pyramidal cornea, corneal scarring
• Sclera: epibulbar dermoid
• Lacrimal system: punctal or canalicular obstruction
• Lens: anterior polar cataract, subluxation
• Iris: coloboma
• Choroid: coloboma
• Optic Disc: coloboma

Central visual acuity in children born with colobomas involving the optic nerve correlates with the development of normal foveal anatomy, regardless of the size of the coloboma. Olsen et al. studied optic nerve colobomas of 23 eyes. Two graders masked to patients’ visual acuities were asked to rate coloboma size, optic nerve color, foveal development, and subfoveal retinal pigment epithelial changes. Increased relative coloboma excavation (ratio of coloboma depth to axial length) was significantly associated with an increased risk of retinal detachment. A relative coloboma excavation more than 0.15 was associated with a 52% increased risk of retinal detachment, compared to those with a relative coloboma excavation less than 0.15 (23%, P = 0.014). The presence of any structural abnormality or retrobulbar cyst were associated with an increased risk of retinal detachment and severe visual impairment of worse than 20/200. An increased coloboma depth, width, volume, and relative coloboma excavation were not associated with an increased risk of severe visual impairment.[rx]

On a typical funduscopic exam, clinicians see large optic nerve excavations usually inferiorly. Defects occur both unilaterally and bilaterally at equal rates. Patients may have microphthalmia or optic nerve cysts that communicate with the subarachnoid space. Cysts rarely expand to cause compressive optic neuropathy.

Optic coherence tomography (OCT) of the optic nerve can help elucidate the different optic nerve anomalies that look similar on fundoscopy alone. OCT of optic nerve coloboma shows the retinochoroidal-scleral excavation of the nerve. On follow up examinations, OCT is used to monitor for peripapillary CNVs. OCT angiography could be used to distinguish between morning glory syndrome, which has a dense peripapillary network, and optic nerve pits and optic nerve colobomas that do not have a radial peripapillary network.[rx]

Treatment of Eyelid Colobomas

Head imaging should be obtained in all patients with bilateral ONC, as they are more likely to have midline brain defects.[rx] Additional management in these patients includes the use of sunglasses to reduce the photophobia and treatment for anisometric amblyopia in cases of low visual acuity.[rx] Ophthalmologists should assess the possibility of a chromosomal disorder or malformations of the central nervous system (CNS) in patients who have colobomatous microphthalmia along with developmental delay or any other malformations.[rx] The literature confirms the finding of systemic anomalies in the CNS, urogenital, skeletal, and other systems in patients with ocular coloboma. Van Dalen et al. found systemic anomalies almost exclusively in patients with bilateral ocular colobomatous changes.[rx]