Microphthalmia indicates reduction in volume of the eye and is generally characterized by a corneal diameter of less than 10 mm or an anteroposterior globe diameter of less than 20mm. There may be marked variation in the severity of the lesion. Occasionally posterior microphthalmia can occur with normal corneal dimensions, conversely, microcornea can be found in the absence of microphthalmia. There may be associated cataract, coloboma of the iris, choroid and/or optic nerve. The pathogenesis of microphthalmia is unclear. Absence of expansive forces within the eye, due to a defect in the formation of the secondary vitreous, may lead to microphthalmia; alternatively it may occur secondary to degeneration of the optic vesicle. Colobomatous microphthalmia may result from failure of closure of the fetal fissure of the invaginated optic vesicle. Occasionally, microphthalmia may accompany a choristoma, frontal cephalocele or orbital tumour. The incidence of microphthalmia/clinical anophthalmia is 0.22 per 1000 births. Approximately 1% of blind adults, and between 3 and 11% of blind children, have microphthalmia. Microphthalmia may be isolated, familial or part of a number of malformation syndromes. It has been estimated that 15 to 30 % of cases with microphthalmia/coloboma are related to the CHARGE association; 15% are recessive; 22% are dominant; the remainder are sporadic.


Although orbital imaging is not routine in most centres, and is not included in the AIUM guidelines for obstetrical sonography, the bony orbits are reliably imaged on scanning the fetal face after the twelfth week. At 15 weeks the lenses and hyaloid arteries are recognized. Care must be taken to avoid tangential cuts through the orbits. In general, microphthalmia is found in association with normal inner orbital distance, the outer orbital distance and the globe diameters are usually below the third centile. With the head in an occipitotransverse position, the transducer can be placed in two possible planes, firstly, in a coronal plane, approximately 2 cm posterior to the glabella-alveolar line, or secondly, in a transverse plane along the orbitomeatal line, approximately 2 to 3 cm below the level of the biparietal diameter. In both these views, the midline, orbital rings, nasal processes, and portions of the maxilla can be demonstrated. The inner and outer orbital diameters are measured from the leading edge to falling edge: outer diameters from the lateral border of one bony orbit to lateral border of the other bony orbit; inner diameters from medial border to medial border. Occasionally, when the head is in this position, it is difficult to define accurately the distal orbital margin because of acoustic shadowing from the nose. With the head in an occipitoposterior position, a biparietal diameter cannot be obtained. However, the orbits can be identified and measured with the transducer placed in a plane that transects the occiput, orbits and nasal processes. Measurements should only be obtained when the fetal face is perpendicular to the uterine wall, since measurements in an oblique plane may be unreliable. The optimal view of the fetal eyes on transvaginal sonography is on a transverse section of the fetal skull at the level of the orbit. The eyes within the bony orbits are detected as bilateral hypoechoic circles superolateral to the nasal bones. In addition to the bony orbital dimensions discussed above, direct measurement of the vitreous and lens circumferences can be performed, utilising transvaginal ultrasonography until 17 weeks gestation and a transabdominal approach thereafter. The lenses and the hyaloid arteries are easily recognized at 15 weeks. The eye is evaluated in a plane with the probe positioned lateral to the orbit. The probe orientation is adjusted until the lens appears as an annular structure within the anterior portion of the orbit, and a maximal diameter of the vitreous is found. The transverse and superoinferior diameters are measured from inner edge to inner edge, while the lens diameter is measured from outer edge to outer edge. Microphthalmia may be associated with structural brain abnormalities, especially midline defects such as agenesis of the corpus callosum or absence of the septum pellucidum. Accompanying hypophyseal/hypothalamic dysfunction may cause growth deficiency.

Differential Diagnosis

Microphthalmia can accompany cryptophthalmia, where the palpebral fissures are absent and the globe hidden. Eyelids are closed before 25 weeks gestation; their border appears as a thick sonolucent line.

Sonographic Features

Reduction in any or all of the following dimensions:

Inner and outer orbital diameter

Vitreous circumference

Lens circumference

Look for associated cerebral anomalies such as absence of the septum pellucidum or agenesis of the corpus callosum.

Associated Syndromes

  • Aicardi
  • Beals
  • Branchio-oculo facial
  • Cerebro-oculo facial
  • Chromosomal Abnormalities
  • Fraser
  • Goldenhar
  • Goltz
  • Gorlin
  • Hallerman-Streiff
  • Isolated
  • Lenz
  • Lowe
  • Maternal disease
  • Meckel-Gruber
  • Microphthalmia with cataract
  • Microphthalmia with ectopia lentis
  • Microphthalmia with mental retardation
  • Microphthalmia with myopia
  • Microphthalmia with retinal detachment
  • Oculo-dento digital
  • Rubinstein-Taybi
  • Sjogren-Larsson
  • Teebi-Shaltout
  • Teratogens
  • Waardenburg anophthalmia
  • Walker-Warburg


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