Morning glory disc anomaly

DEFINITION/OVERVIEW AND ETIOLOGY

The morning glory disc anomaly is a congenital, funnel-shaped excavation of the posterior fundus that incorporates the optic disc.20

The etiology is uncertain, but it possibly arises from a failure of posterior scleral development during gestation.

CLINICAL PRESENTATION

The disc is enlarged, orange or pink in color, and situated within a funnel-shaped excavation (218). A white tuft of glial tissue often overlies the central portion of the disc. The blood vessels appear increased in number and arise from the periphery of the disc. The retinal vessels are abnormally straight and tend to branch at acute angles. Arterioles may be indistinguishable from venules. The fundus excavation is often surrounded by an elevated annular zone of retinal epithelial pigmentation. The macula may be incorporated into the excavation. The morning glory disc anomaly was named by Kindler (Kindler 1970) because of its resemblance to a morning glory flower.21

Visual acuity is generally less than 20/200, although it may range from 20/20 to no light perception. Most cases are unilateral although bilateral cases have been reported.22 Morning glory discs occur more frequently in females and in Caucasians.23 Serous retinal detachments occur in 26–38% of eyes with morning glory discs and often involve the peripapillary retina.20 The source of the subretinal fluid is unknown. Contractile movements of the optic disc have been documented. These may occur from fluctuations in subretinal fluid volume and the degree of retinal separation within the excavation.20

218

218 Morning glory disc anomaly,right eye.Note central glial tuft,peripapillary retinal pigment epithelial changes,and peripheral origin of disc vessels.

DIAGNOSIS

Neuroimaging may show a funnel-shaped enlargement of the distal optic nerve at its junction with the globe.22,24 In addition, morning glory optic discs are associated with basal encephaloceles in patients with midfacial anomalies (hypertelorism, cleft palate, cleft lip, depressed nasal bridge, midline upper lid notch).22 Therefore, children with morning glory discs and midfacial anomalies should be evaluated by MRI in order to detect associated basal encephaloceles.

MANAGEMENT/TREATMENT

With unilateral cases in young children, amblyopia therapy may be indicated to ameliorate nonorganic visual loss.

Optic disc coloboma

DEFINITION/OVERVIEW AND ETIOLOGY

The term ‘coloboma’ is used to describe any congenital notch, gap, or fissure of the ocular structures. Optic disc colobomas occur bilaterally in approximately 50% of patients. All ocular colobomas may occur sporadically or with autosomal dominant (AD) inheritance.25 Colobomas occur from incomplete coaptation of the embryonic fissure.

CLINICAL PRESENTATION

An optic disc coloboma appears as a white, bowl-shaped excavation that occurs in an enlarged optic disc. The excavation is decentered inferiorly such that the superior neuroretinal rim is relatively spared. In cases of complete excavation of the entire disc, the excavation is deeper inferiorly. The defect may extend inferiorly to involve the adjacent choroid and retina (219). Chorioretinal colobomas are associated with microphthalmia.26 Iris and ciliary body colobomas often coexist (220).

Visual acuity impairment may be mild or severe and is difficult to predict from the optic disc appearance. Visual acuity has been associated with the appearance of the fovea.27 Optic disc colobomas are associated with serous macular detachments. In addition, rhegmatogenous retinal detachments may occur with retinochoroidal colobomas.28 Retinal detachments may require surgical treatment.

DIAGNOSIS

Ocular colobomas may be accompanied by multiple systemic abnormalities and conditions such as the CHARGE association, Walker– Warburg syndrome, Goldenhar sequence, and linear sebaceous nevus syndrome.29 Therefore, children with ocular colobomas should be evaluated for associated genetic syndromes. Family members should have an ophthalmologic evaluation to identify subclinical ocular colobomas and establish AD inheritance.

219

219 Coloboma that involves the optic nerve, choroid and retina.

220

220 Iris coloboma,left eye.

Peripapillary staphyloma

DEFINITION/OVERVIEW AND ETIOLOGY

Peripapillary staphyloma is a generally sporadic, rare, usually unilateral optic disc anomaly in which a deep fundus excavation surrounds the optic disc. A peripapillary staphyloma is usually an isolated finding. There are typically no associated ocular or systemic abnormalities.

CLINICAL PRESENTATION

The disc, which is generally normal appearing, is at the bottom of the excavated defect (221). The walls and margin of the excavated defect may show atrophic pigmentary changes in the retinal pigment epithelium and choroid. In contrast to the morning glory disc, there is no central glial tuft overlying the disc and the retinal vascular pattern is normal.

Visual acuity may be mildly or severely decreased. Affected eyes usually have mild myopia, although high myopia has been reported.30 Peripapillary staphylomas are associated with basal encephalocele in patients with midfacial anomalies.31 Therefore, MRI is indicated for children with peripapillary staphylomas and midfacial anomalies.

Congenital tilted disc

DEFINITION/OVERVIEW AND ETIOLOGY

Congenital tilted disc is known as the nasal fundus ectasia or a Fuch’s coloboma, occurring in 1–2% of the population. The congenitally tilted optic disc is a generally sporadic anomaly. It most likely arises from partial nonclosure of the embryonic fissure and is a variant of a colobomatous defect.

CLINICAL PRESENTATION

The superotemporal optic disc is elevated and the inferonasal disc is posteriorly displaced. The optic disc appears oval with the long axis obliquely oriented (222, 223). The tilted optic disc is accompanied by situs inversus of the retinal vessels and thinning of the inferonasal retinal pigment epithelium (RPE) and choroid. The optic disc appearance occurs from posterior

ectasia of the inferonasal fundus and optic disc. The fundus ectasia results in myopic astigmatism in affected patients.

DIAGNOSIS AND MANAGEMENT/TREATMENT

Patients with tilted optic discs may have an artifactual bitemporal hemianopia that does not reflect chiasmal dysfunction.32 The bitemporal hemianopia is typically incomplete and involves the superior quadrants. This visual field defect occurs partially from a refractive scotoma, secondary to regional myopia in the inferonasal retina. Therefore, placement of a −3.00 lens over the patient’s glasses will often eliminate the visual field abnormality, confirming the refractive nature of the deficit. In some cases, retinal sensitivity may be decreased in the area of ectasia, so that the defect persists despite appropriate refractive correction.33 Unlike the visual field loss accompanying chiasmal lesions, the visual field defects associated with tilted disc do not respect the vertical meridian and mostly affect the medium-sized isopters, owing to the marked ectasia of the midperipheral fundus.

Children with tilted optic discs and visual field deficits that do not respect the vertical meridian do not require neuroimaging. However, tilted discs have been reported in patients with suprasellar tumors.34–36 Therefore, intracranial MRI is indicated in a child with tilted disc syndrome and a bitemporal hemianopia that respects the vertical meridian. Tilted discs have also been associated with X-linked congenital stationary night blindness in patients with nystagmus.37 Therefore, children with tilted discs and nystagmus should be evaluated with an electroretinogram.

In unilateral cases, amblyopia therapy may improve nonorganic visual loss.