From the Dipartimento di Oftalmologia e ORL, Università di Bari – Policlinico, Bari, Italy.
The authors have no financial or proprietary interest in the materials presented herein.
Address correspondence to M. Leozappa, Dipartimento di Oftalmologia e ORL, Università di Bari – Policlinico, P.zza G.Cesare 11, 70124 Bari, Italy.
Microphthalmia and anophthalmia are rare disorders characterized by, respectively, incomplete or absent development of one or both eyes.
Causes of these conditions include genetic and/or chromosomal mutations.
Other risk factors, such as exposure to X-rays, chemicals, drugs, pesticides, toxins, radiation, or viruses, had been reported.
Most cases of achiasmia or chiasmal hypoplasia are due to acquired abnormalities due to chiasmal compression, trauma or inflammation.
The absence of optic chiasm (chiasmal agenesia) may be associated with several abnormalities: microphthalmia, optic nerve hypoplasia/aplasia, optic tracts hypoplasia, skull base encephalocele, optic septum displasia, hypopituarism, corpus callosum agenesia, microgiria. Chiasmal hypoplasia can be associated with sub-clinical epilectiform activity, with Aspergen syndrome, and with multiple deformities including hemi-facial microsomia, esophageal atresia, and hydronephrosis.
We present a 15-year-old boy who had bilateral severe microphthalmia, optic nerve hypoplasia, optic chiasm, optic tracts aplasia, and hypogenitalism, but no other neurological abnormalities were associated.
A 15-year-old boy underwent neurological and ophthalmological evaluation.
He was born at term; mother’s pregnancy had been normal and the delivery was uneventful.
At birth, patient showed severe bilateral microphthalmia, micropenis, and scrotal hypoplasia.
Current ophthalmologic examination showed right anophthalmia (with ocular prothesis) and severe left microphthalmia, associated with micro-cornea and total cataract; the patient had bilateral hypoplastic orbits well formed, but rudimentary eyelids and brows. Ultrasonographic orbital examination showed in right side a microcystic structure, in left side a hyper-reflectivity posterior to lens, due to the presence of primitive hyperplastic vitreous. Radiological examination showed normal orbital and skull structures. Flash visual-evoked potentials were elicited from the patient, but no response was recorded. Audiometric examination and electroencephalogram were normal. There was no mental retardation. The chromosomal examination was normal.
The boy’s examination was also negative for toxoplasma, citomegalovirus, and rubella virus infections. He was accepted as a case of an isolated congenital microphthalmia.
Magnetic resonance imaging (MRI), with sequences T1- and T2-weighted, revealed the absence of the right eye which was replaced by soft and isointense tissue.
The left eye was microphthalmic and showed little calcifications inside.
Both optic nerves were hypoplastic; the optic chiasm and the optic tracts were absent. The lateral ventricles were normal and the corpus callosum was present (Figs. 1 and 2).
Figure 1. Magnetic Resonance Imaging Scan Showing Right Anophthalmia with Ocular Prothesis, Left Eyeball’s Atrophy and Small Vitreo-Retinic Granular Calcifications; Optic Nerve is Slightly Reduced in Thickness, Agenesia of Optic Chiasm and Optic Tracts. (T1-Weighted, Axial Image).
Figure 2. Magnetic Resonance Imaging Scan Showing Agenesia of Optic Chiasm and Optic Tracts (A: T1-Weighted, Sagittal Image; B: T1-Weighted Coronal Image).
Eye development begins at fourth week of pregnancy, at the cranial end of the embryo, in the forebrain region. The optic nerve is formed by more than a million nerve fibers that grow into the brain and decussate through the primitive chiasmal commissura. An abnormality of embryogenesis within the first 8 weeks of gestation can cause anophthalmia or microphtalmia. If the pathogenous stimulus occurs till 4 weeks of pregnancy it will produce bilateral anophthalmia, intracranial abnormalities interesting the optic nerve, the chiasm, the optic tracts, and the corpus callosum. If the pathogenous stimulus occurs between the fourth and the eight week, it will cause a degeneration of already grown elements of the eye, producing unilateral anophthalmia or microphthalmia with unilateral craniofacial abnormalities.
Various factors have been reported to cause this extremely rare abnormality.
Traumatic factors, such as, diagnostic amniocentesis, or congenital infections (toxoplasmosis, cytomegalovirus, rubella virus) have been reported to cause congenital anophthalmia. In our case, there was no history of this procedure and/or congenital infections. Most cases of anophthalmia are sporadic and have a multifactorial aetiology. Anophthalmia and optic pathways abnormalities are present in several syndromes and chromosomal abnormalities: in the Mattew–Wood syndrome anophthalmia is associated with pulmonary hypoplasia, diaphragmatic defects, and facial deformity; in Delleman syndrome (oculocerebro-cutaneus syndrome) anophthalmia is associated with cerebral abnormalities and skin defects; in Waandenburg (ophthalmo-acromelic) syndrome, anophthalmia is associated with limb abnormality, deafness, and partial albinism; in De Morsier syndrome anophthalmia is associated with optic nerve and septum pellucidum agenesia; in Fryns syndrome, anophtalmia is associated with protrusion of part of the stomach and/or small intestines into the chest cavity (diaphragmatic hernia), abnormalities of the head and face areas (craniofacial region) and underdevelopment of the ends of the fingers and toes, hypoplasia of the lungs, cleft palate, cardiac defects, and varying degrees of mental retardation. In Hallermann Streyff Françoise (oculomandibulo-facial) syndrome, microphthalmia is associated to dyscephaly, parrot nose and mandibular hypoplasia, and nanism. Microphthalmia is also found in Aicardi, Meckel–Gruber and Walker–Warburg syndromes. Chromosomal abnormalities (trisomy 13 and 18) are also often associated to microphthalmia. In the literature, there are few cases of isolated malformation of the optical pathways. Some authors reported similar cases of microphthalmia/anophthalmia and aplasia of optical pathways in healthy subjects.1–3
Pearce4 et al. described a case of achiasmia associated with polymicrogiria, epilessy, mental retardation, and focal neurological symptoms
The case we reported showed anophthalmia/microphthalmia, optic nerve ipoplasia, optic chiasm, optic tracts aplasia, and micropenis, not associated to other congenital abnormalities. Moreover, the parental medical history was negative for cases of anophthalmia. The patient not showed epilessy or focal neurological symptoms. None of the mentioned factors could explain the optical pathways (hypoplasia/aplasia).
- Benezra D, et al. Bilateral anophthalmia and unilateral microphthalmia in two siblings. Ophthalmologica. 1989;198:140–144.
- Albernaz SA, et al. Imaging findings in patients with clinical anophthalmos. AJNR Am J Neuroradiol. 1997;18:112–113
- Scott IU, et al. Bilateral aplasia of the optic nerve s, chiasm, and tracts in a otherwise healthy infant. Am J Ophthalmol. 1997;124:409–410.
- Pearce WG, et al. Primary anophthalmos. Histological and genetic features. Can J Ophthalmol. 1974;9:141–145.