Unilateral macular Coloboma: a rare finding

Introduction

Macular colobomas are rare congenital defects, occurring in 0.5 to 0.7 per 10.000 births [1]. Clinically, they are associated with significant central vision loss, often due to foveal involvement. Although frequently isolated, macular colobomas may also be associated with other ocular anomalies, such as retinal detachment or anterior segment disorders [2]. These colobomas may result from various causes, including defect in ocular development distinct from the failure of choroidal fissure closure, abnormalities in optic cup cell differentiation, primary mesodermal disorders affecting the ectoderm, or pathological processes such as infections occurring before or after birth [3]. This case highlights a unique presentation of unilateral macular coloboma in a pediatric patient.

Case report

Patient information

A 10-year-old boy presented with significant visual impairment in the left eye.

Clinical finding

The best corrected visual acuities were 20/20 in the right eye and 20/400 in the left eye. Anterior segment examination was unremarkable. Fundoscopic examination of the left eye revealed an atrophic macular lesion, oval-shaped, sharply demarcated, with exposed large choroidal vessels at the base (Fig. 1a). The lesion measured approximately four-disc diameters (DD) in width and two DD in height. The patient had no other congenital anomalies or family history of genetic diseases.

Figure 1.

Unilateral macular Coloboma of the left eye. (A) Color fundus photograph of the left eye, showing an atrophic macular lesion, oval-shaped, sharply demarcated, with exposed large choroidal vessels at the base. These findings are consistent with macular coloboma, a congenital defect in the retina. (B) Optical coherence tomography of the left macula revealing a crater-like depression, atrophic neurosensory retina, and absence of retinal pigment epithelium. These structural alterations confirm the diagnosis of macular coloboma and illustrate the characteristic retinal and pigmentary changes associated with this.

Diagnostic assessment

Optical coherence tomography (OCT) of the right macula showed no abnormalities. However, OCT of the left macula revealed a crater-like depression with an atrophic neurosensory retina and an absence of the retinal pigment epithelium (RPE) (Fig. 1b). General examination was unremarkable, and family screening revealed no abnormalities.

It is essential to differentiate congenital macular coloboma from post-inflammatory macular scars associated with ocular toxoplasmosis or cytomegalovirus, as well as from retinal dystrophies. Laboratory analyses revealed negative serum IgG and IgM titers for Toxoplasma, rubella, cytomegalovirus, and simplex herpes. Furthermore, the severity of visual loss, associated signs, and the ophthalmoscopic appearance of the lesion helped distinguish this condition from Leber congenital amaurosis.

Therapeutic intervention

Glasses were prescribed, and regular follow-up was recommended to monitor visual function and identify potential complications.

Discussion

Coloboma is a rare congenital anomaly resulting from incomplete optic fissure closure during the 5th to 7th gestational weeks [4]. Retinochoroidal (RC) coloboma, the most prevalent form, accounts for 60%–70% of cases, with visual outcomes varying depending on macular involvement [4]. Macular coloboma, a rare subtype resulting from defective arcuate bundle development, predisposes patients to retinal detachment from the persistent inner retinal layers [5]. Commun complications include progressive loss of visual acuity, photophobia, and an increased risk of retinal detachment, necessitating regular monitoring [5].

In these situations, establishing an accurate diagnosis is essential, as many conditions can mimic a macular coloboma, requiring different therapeutic approaches. Among these conditions are Leber congenital amaurosis, central choroidal atrophy, advanced cone dystrophy, posterior staphyloma, and macular scars secondary to infectious choroiditis [3]. These pathologies must be excluded before confirming a macular coloboma.

The management of macular coloboma is primarily symptomatic, focusing on optimizing residual visual function. Low-vision rehabilitation, combined with optical aids and orthoptic therapy, can improve visual performance [6]. Prophylactic laser photocoagulation may be considered for colobomas that do not affect the macula or the papillomacular bundle [7]. However, its effectiveness remains controversial, and its impact on vision preservation is limited [7]. In most cases of retinal detachment associated with coloboma, the posterior vitreous remains attached, although partial liquefaction is observed in front of the lesion. Inducing posterior vitreous detachment can be challenging, often requiring the systematic injection of triamcinolone to facilitate the process. A simple fluid-air exchange, without attempting to eliminate the subretinal fluid, has also shown good results [8].

The presence of a macular coloboma necessitates not only ophthalmological assessment and management, but also a multidisciplinary approach to identify and address potential associated anomalies. Regular follow-up is essential, including a dilated fundus examination at each consultation [7].

This case of unilateral macular coloboma, rarely reported in the literature, presented with deep foveal involvement, significantly affecting central visual acuity. This underscores the importance of comprehensive ophthalmologic and systemic evaluations to exclude associated conditions and confirm the isolated nature of the coloboma through thorough investigative procedures.

Ethical Approval

This study was conducted in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Ethical approval for this study was obtained from the Ethics Committee of Hassan II University Hospital of Fez.

Conflict of interest

The authors declare no conflict of interest.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Consent

Informed consent was obtained from the parent of the child included in the study.

The parent has consented to the submission of the case report and images of the child for publication in this journal.

Guarantor

Pr. MOUTEI Hassan assumes full responsibility for the integrity of the study and the final manuscript. He guarantees that all aspects of the work are accurate and have been duly investigated and resolved.