The examination is performed with the patient supine. Real-time linear array transducer with Doppler capability is used. The eye is studied in axial and sagittal planes while images are recorded and analysed with cine-loop. Sedation or general anaesthesia is rarely necessary.

Anophthalmia is rare and readily demonstrated with sonography. The axial length of the globe increases until 8 years of age. The most rapid growth occurs during the first 40 weeks of postnatal life. Microphthalmos is diagnosed when the axial length is less than 21mm in an adult, or less than 19mm in a 1-year-old child. Microphthalmia results from insult after outgrowth of the optic vesicle and found isolated or associated with anomalies including congenital rubella and persistent hyperplastic primary vitreous (PHPV). In PHPV, the intraocular foetal vascular system extending from the optic nerve head to the lens fails to resorb, resulting in a vascularized plaque on the posterior lens. It is usually unilateral and nonhereditary. When bilateral, Warburg's syndrome or Norrie's disease should be considered. Sonographic features of PHPV consist of unilateral microphthalmia and presence of the embryonic hyaloid vessel transversing the triangular retrolental vitreous mass that is attached to the optic disc. The lens is commonly cataract and ovoid with decreased anterior chamber width. Macrophthalmia is associated with axial myopia, congenital glaucoma, Sturge-Weber syndrome, and neurofibromatosis.

Optic nerve colobomas are found both in normal-sized and microphthalmic eyes, occasionally associated with retinal detachment. Coat's disease is a congenital, non-familial, idiopathic, vascular disease of the retina, primarily caused by a defect of the endothelial cells, causing leakage of fluid into the vessel wall and perivascular spaces. Sonographically, there is an echogenic vitreous mass with increased vascularity and retinal detachment. Optic nerve head drusen are benign with occasional autosomal dominant inheritance. There are calcified spherical concretions buried within the substance of the nerve head, usually anterior to the lamina cribrosa. Sonography allows early detection. Congenital cataract is found in 1:4000-1:10,000 live-born infants and may be unilateral or bilateral. It can be isolated or part of a systemic disease, including chromosomal aberrations, multisystem syndromes, metabolic disease or acquired. Retinoblastoma is the commonest congenital malignant eye tumour. It is usually asymptomatic at birth but ocular involvement and metastasis may be present. The differential diagnosis includes retinal hamartoma and medullary epithelioma. Incomplete canalisation of the nasolacrimal duct with a persistent membrane at the inferior end forms a nasolacrimal mucocoele.

In conclusion, ocular sonography is technically easy to perform in children and diagnostic for most paediatric congenital ocular pathologies. It should be used as first study of choice with MRI and CT reserved as supplementary studies.

Reference

Outcomes in persistent hyperplastic primary vitreous
Hunt A, Rowe N, Lam A, Martin F
Br J Ophthalmol 2005 Jul: 89(7): 859-63