MORNING GLORY SYNDROME IN A NIGERIAN - A CASE REPORT

Abstract

Morning glory syndrome is an uncommon congenital excavated optic disc anomaly that can impair vision and may be associated with ocular and non-ocular abnormalities. It has a characteristic fundoscopic appearance which consists of a large excavated disc with radial vessels and a central turf of glial tissue situated within a funnel shaped excavation of the posterior fundus. It is more common in Caucasians than in blacks. We report a case of this uncommon congenital anomaly of the optic disc in a Nigerian male.

Introduction

Morning glory syndrome is an uncommon congenital anomaly of the optic disc in which there is an excavation of the posterior globe which encloses and includes the optic disc1. It is typically a unilateral anomaly but bilateral cases have been documented in the medical literature2^-4; and it is more common in females1 It can impair vision and has also been associated with a number of ocular and non-ocular abnormalities2^-7. The prevalence of morning glory syndrome is unknown, however, a recent study reports a prevalence of 2.6/100,000 in Stockholm, Sweden2. Morning glory syndrome is more common in Caucasians and uncommon in African Americans1. We report a case of this uncommon congenital anomaly of the optic disc in a Nigerian male.

Case report

A 35-year old Nigerian male presented to the eye clinic with a history of diminished vision in the right eye since childhood. He also had a history of hallux valgus but no history of facial clefts. There was no family history of ocular disease or congenital anomalies. On examination, he had no facial abnormalities and the neurologic examination was normal. The best corrected visual acuity was count finger at 0.5metres in the right eye and 6/5 in the left eye. Refraction was -12.25DS-4.00DC X 062^o in the right eye and plano- 0.75 X 090^o in the left eye. There was no nystagmus, but a 15^o exotropia with normal ocular motility and a relative afferent pupillary defect in the right eye. Anterior segment examination was unremarkable in that eye. Fundoscopy of the right eye showed a large excavated disc with a central turf of glial tissue and peripapillary chorioretinal pigmentation. The blood vessels were supernumerary and fanned out from the disc in a radial fashion (Fig. 1). The examination of the left eye was unremarkable. The intraocular pressures were 14mmHg and 10mmHg in the right and left eye respectively. B-scan ultrasound scan showed an axial length of 25.7mm right eye and 23.3mm in the left eye. There were floating echogenic strands in the right vitreous humour but no retinal detachment (Fig. 2). The left eye was sonographically normal. The vision in the right eye was not improved with optical correction.

Fig. 1. Fundus photographs showing A) excavation of the optic disc with peripapillary pigmentation and radiating vessels in the right eye, B) normal fundus left eye.

Fig. 2. B-Scan ultrasonography showing A) excavated optic disc and echogenic strands in the vitreous of the right eye, and B) normal scan left eye.

Discussion

Morning glory syndrome is one of the congenital excavated optic disc anomalies apart from optic disc coloboma and peripapillary staphyloma. Morning glory syndrome is non-hereditary and genetic defects associated with it are not yet established7. Altun et al 8 reported a case of morning glory syndrome in a patient with Down syndrome but no other genetic abnormality was detected apart from the trisomy of chromosome 21 which is associated with Down syndrome. The exact pathogenesis of morning glory syndrome is not well established. The excavation is thought to result from either an insufficient closure of the embryonic fissure, and therefore may be a variant of optic nerve coloboma, or it may be a primary mesenchymal abnormality resulting in scleral defect, central glial tuft and vascular abnormalities1.

Morning glory syndrome can be diagnosed clinically by its characteristic appearance on fundoscopy. There is a funnel shaped excavation of the posterior fundus which encloses and includes the disc. The disc is large and excavated with a central area of white glial tissue and peripapillary chorioretinal pigmentation. The blood vessels are supernumerary, fan out in a radial manner from the periphery of the disc and it is hard to distinguish between arterioles and venules1.

The visual acuity in eyes with morning glory syndrome is variable from no light perception to normal vision, but in most cases it is impaired1. The refractive error in eyes with morning glory syndrome is commonly myopic2. Our patient had poor vision, high myopic astigmatism and impaired vision in the eye with morning glory syndrome. There was no history of treatment of amblyopia in childhood in our patient. The poor vision in patients with congenital structural (organic) abnormality may be attributable to a superimposition of functional amblyopia on the organic defect9. Functional amblyopia refers to poor vision caused by deprivation of pattern vision or abnormal binocular interaction in an eye which appears normal on physical examination10 , whereas organic amblyopia refers to poor vision caused by structural abnormality of the eye or brain that is independent of sensory input such as structural abnormalities of the visual pathway11. Although organic amblyopia is traditionally believed to be irreversible, some authors have reported cases in which there were improvements in visual acuity with amblyopia therapy in children with morning glory syndrome2, 12. Cavazos-Adame et al12 reported improvement in visual acuity from count finger at 0.3metre in a 3.8month old child with unilateral morning glory syndrome to 20/100 after 5 years of amblyopia therapy.

Ocular associations that have been reported with morning glory syndrome include strabismus, nystagmus, retinal detachment, persistent hyperplastic primary vitreous (PHPV), cataract, microphthalmia, corneal leucoma and optic nerve glioma2,3,5,6. Our patient had strabismus (exotropia). Strabismus associated with morning glory syndrome is of the horizontal deviation (exotropia or esotropia) commonly but few vertical deviations have been recorded7. Non-ocular associations of morning glory syndrome include basal encephalocele, corpus callosum agenesis, capillary hemangiomas, cerebrovascular anomalies such as carotid artery stenosis and moyamoya disease, pituitary gland abnormalities and facial abnormalities such as median cleft lip and palate2,4,7.

Optic disc coloboma is a differential diagnosis of morning glory syndrome. In morning glory syndrome, the whole disc is excavated unlike in optic disc coloboma in which the excavation is contained within the optic disc usually in the inferior aspect of the disc and the superior neuroretinal rim is recognizable13. Another differential diagnosis in our patient who also had high myopia is posterior staphyloma. In posterior staphyloma there is excavation of the posterior fundus surrounding the optic disc; the optic disc is usually flat, without a central tuft and the retinal vasculature is normal1, 13, 14. Posterior staphyloma is unlikely in our patient because the posterior fundus as well as the disc was excavated and there was a central tuft of tissue on the disc with abnormal retinal vasculature.

Conclusions

In conclusion morning glory syndrome is a vision threatening, uncommon congenital excavated optic disc anomaly that may be associated with ocular and non-ocular features.