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Choroidal Colobomas: Etiology, Complications, Management

Title: Choroidal Colobomas: Etiology, Complications, Management

Authors: Aileen G. MacLachlan, MS4, Eileen S. Hwang, MD, PhD

Date: August, 2025

Coloboma Overview

Ocular colobomas are the result of failure of the embryonic optic fissure to close during development. Colobomas can be located in both the anterior and posterior segments of the eye. The former results from failure of anterior fissure closure, causing iris, ciliary body, and lens colobomas.^1,2 The latter results from failure of posterior fissure closure, causing chorioretinal and optic nerve colobomas.^1,3 Coloboma size is widely variable and patients often develop both anterior and posterior colobomas concurrently.^2,4 Ocular colobomas can be sporadic, inherited or associated with systemic syndromes and chromosomal abnormalities. Recent research is investigating the possible role of environmental insults on the formation of colobomas.^5,6,7

Choroidal Colobomas

In choroidal colobomas, the choroid and retinal pigment epithelium are absent within the coloboma and the overlying retinal layer is termed the intercalary membrane.⁸ Patients with choroidal colobomas are at significant risk for vision-threatening complications such as retinal detachment and choroidal neovascularization.⁹

Image 1: Choroidal coloboma, not involving the macula or optic disc.

Associated Findings

Choroidal colobomas are associated with amblyopia, strabismus, nystagmus, microphthalmia, refractive errors, and non-choroidal colobomas.^4,10 Hyperpigmentation is a common finding, usually located at the margins of the choroidal coloboma.² There is limited data detailing the etiology of hyperpigmentation in association with colobomas, but it may be the result of reactive hyperplasia of the retinal pigment epithelium.¹¹ Although generally benign, this finding requires careful examination to rule out vision-threatening pathologies including subretinal hemorrhage, choroidal neovascularization, retinal detachment, and melanoma.¹

Image 2: Hyperpigmentation at the choroidal coloboma margin.

Genetic Associations

Ocular colobomas are often associated with systemic disorders. CHARGE syndrome is the most common with an incidence between 12-20% of patients with ocular colobomas.¹⁰ One study specifically evaluated pediatric patients with chorioretinal and optic nerve colobomas, finding that 60% had comorbid systemic disorders, of which CHARGE syndrome comprised 20%.⁴

The following genetic disorders have also been associated with ocular colobomas:¹²

• Trisomy 13 or 18
• Cat eye syndrome
• Jacobsen syndrome
• Goldenhar syndrome
• Meckel syndrome
• Morning glory anomaly
• Rubinstein-Taybi syndrome
• Warburg syndrome
• SOX2-related eye disorders
• Joubert syndrome

Complications

Retinal detachment is the most common vision-threatening complication of choroidal colobomas with rates from 2.4-42%.^4,13 In addition, the rate of recurrent detachment after repair is as high as 63.3%.⁴ Retinal detachment often presents with acute or acute on chronic vision loss, but can also be mild enough that vision is not affected.⁹

Choroidal neovascularization is another complication found in 13.7% of patients with choroidal colobomas and typically occurs near the margin of the coloboma.⁹ It can be found incidentally on exam or manifest as a reduction in vision.⁹

Image 3: Choroidal coloboma with a retinal detachment.

Image 4: Sub-retinal hemorrhage due to choroidal neovascularization.

Image 5: Fluorescein angiography showing leakage from choroidal neovascularization and blockage from the resulting sub-retinal hemorrhage.

Patient presentation

Choroidal colobomas can be asymptomatic and incidentally discovered during routine exams.⁴ In some cases, the caretaker of a pediatric patient notices associated anomalies such as microphthalmos, nystagmus, leukocoria, or iris coloboma which prompt an ophthalmology clinic visit. In the absence of gross anomalies, vision changes can be a presenting symptom of colobomatous eyes. Choroidal colobomas involving the macula or optic disc cause , chronic poor vision. Acute or acute on chronic vision loss may be a symptom of complications such as retinal detachment, sub-foveal choroidal neovascular membranes, or choroidal neovascularization.^1,9

Diagnosis and imaging

Most choroidal colobomas are diagnosed during fundus exams. When located outside of the optic disc, colobomas appear as well-circumscribed, whitened areas, sometimes with scalloped edges and pigmentation at the margins. Optic disc colobomas have variable appearances from physiologic cupping to clear involvement of the surrounding retina.^1,2 All ocular colobomas, including choroidal colobomas are typically located in the inferonasal quadrant which is the physiologic location of optic fissure closure during embryogenesis.^1,2

With high rates of vision-threatening conditions including retinal detachment and choroidal neovascularization, early identification of complications is key to preserving vision. Patients should be educated on the importance of regular ophthalmology follow-up, common signs of complications, and can be advised to perform home monocular vision checks. For pediatric patients, an exam under anesthesia may be necessary when there is concern for complications or baseline images cannot be obtained in clinic.

Fundus photography can provide a baseline image of the coloboma for monitoring purposes. Optical coherence tomography imaging has been helpful in identifying subclinical retinal detachment and choroidal neovascularization.¹⁴ Fluorescein angiography is used to detect and identify the extent of choroidal neovascularization.⁹

Management

There is no treatment for choroidal colobomas, although some advocate prophylactic laser treatment to lower the risk of retinal detachment.¹⁵ Management primarily focuses on monitoring for and treating associated complications. For retinal tears that do not involve the coloboma, standard treatment is indicated. If a tear originates within or extends into the coloboma margin, it may be necessary to surround the entire coloboma with laser to prevent detachment of the structurally compromised intercalary membrane. For retinal detachment cases, vitrectomy with oil tamponade has been most successful.¹⁶ Choroid` al neovascularization is managed with intravitreal anti-VEGF injections. Other ocular abnormalities such as refractive errors and strabismus are managed with standard treatment.

Image 6: Laser treatment for a retinal tear at the anterior choroidal coloboma edge.

References:

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11. Olsen TW, Frayer WC, Myers FL, Davis MD, Albert DM. Idiopathic Reactive Hyperplasia of the Retinal Pigment Epithelium. Arch Ophthalmol. 1999;117(1):50-54. doi:10.1001/archopht.117.1.50
12. Genetic Disorders Clinical Update: Coloboma – American Association for Pediatric Ophthalmology and Strabismus. Accessed August 16, 2025. https://aapos.org/patient/patient-resources/genetic-info-patients/genetic-disorders-clinical-update-coloboma
13. Maumenee IH, Mitchell TN. Colobomatous malformations of the eye. Trans Am Ophthalmol Soc. 1990;88:123-135. Accessed August 26, 2025. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1298581/
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16. (PDF) SURGICAL OUTCOMES AND COMPLICATIONS OF RHEGMATOGENOUS RETINAL DETACHMENT IN EYES WITH CHORIORETINAL COLOBOMA: The Results of the KKESH International Collaborative Retina Study Group. ResearchGate. Published online August 7, 2025. doi:10.1097/IAE.0000000000001444