Optic nerve manifestations of human congenital cytomegalovirus infection

Review of Evidence for Environmental Causes of Uveal Coloboma

Uveal coloboma is a condition defined by missing ocular tissues and is a significant cause of childhood blindness. It occurs from a failure of the optic fissure to close during embryonic development,and may lead to missing parts of the iris, ciliary body, retina, choroid, and optic nerve. Because there is no treatment for coloboma, efforts have focused on prevention. While several genetic causes of coloboma have been identified, little definitive research exists regarding the environmental causes of this condition. We review the current literature on environmental factors associated with coloboma in an effort to guide future research and preventative counseling related to this condition.

Optic Nerve Hypoplasia: A Review of the Literature

This paper reviews the literature concerning optive nerve hypoplasia, including septo-optic dysplasia. It examines the cause and pathogenesis of optic nerve hypoplasia and analyzes the data from a total of 189 cases taken from three recent studies. General information, maternal history and subject characteristics are examined. Because of an apparent increase in the frequency with which this syndrome occurs, resulting in visual impairment and associated with midline defects, it is recommended that research which emphasizes behavioral and learning characteristics be conducted.

Optic Nerve Aplasia, Chorioretinal Hypoplasia, and Microcornea After In Utero Infection With Cytomegalovirus

Optic nerve aplasia (ONA) is a rare phenomenon characterized by absence of the optic nerve, retinal blood vessels, and retinal ganglion cells. The authors report a case of optic nerve aplasia in association with congenital cytomegalovirus (CMV) infection, conveyed through multimodal imaging including color fundus photography, fluorescein angiography, and B-scan ultrasonography. Furthermore, the authors review the common ocular findings and previously reported cases of ONA in congenital CMV infection. Screening and counseling can be performed to advise parents about the potential risks and severity of this rare clinical manifestation. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:e171-e175.].

Prenatal determinants of optic nerve hypoplasia: review of suggested correlates and future focus

Optic nerve hypoplasia (ONH), a congenital malformation characterized by an underdeveloped optic nerve, is a seemingly epidemic cause of childhood blindness and visual impairment with associated lifelong morbidity. Although the prenatal determinants of ONH are unknown, early case reports have led to a longstanding speculation that risky health behaviors (e.g., prenatal use of recreational drugs, alcohol) are a likely culprit. There has yet to be a systematic review of the epidemiology of ONH to assess the common prenatal features that may help focus research efforts in the identification of likely prenatal correlates. A review of the past 50 years of epidemiologic research was conducted to examine the prenatal features linked with ONH and provide direction for future research. There are select prominent prenatal features associated with ONH: young maternal age and primiparity. Commonly implicated prenatal exposures (recreational or pharmaceutical drugs, viral infection, etc.) were rare or uncommon in large cohort studies of ONH and therefore unlikely to be major contributors to ONH. Familial cases and gene mutations are rare. The preponderance of young mothers and primiparity among cases of ONH is striking, although the significance is unclear. Recent research suggests a potential role for prenatal nutrition, weight gain, and factors of deprivation. With the rapidly increasing prevalence of ONH, future research should focus on investigating the relevance of young maternal age and primiparity and exploring the recently suggested etiologic correlates in epidemic clusters of ONH.

Optic nerve hypoplasia syndrome: a review of the epidemiology and clinical associations

OPINION STATEMENT

BACKGROUND

Optic nerve hypoplasia (ONH) has developed into a leading cause of congenital blindness. The frequently associated features of hypopituitarism and absent septum pellucidum were felt to have embryonic linkage as "septo-optic dysplasia" or "de Morsier's syndrome." More recent studies have suggested these associations are independent of one another. This review provides an assessment of the historical and recent evidence linking neuroradiologic, endocrinologic and developmental morbidity in patients with ONH. The prenatal risk factors, heritability, and genetic mutations associated with ONH are described.

RESULTS

Recognition of the critical association of ONH with hypopituitarism should be attributed to William Hoyt, not Georges de Morsier. De Morsier never described a case of ONH or recognized its association with hypopituitarism or missing septum pellucidum. Hypopituitarism is caused by hypothalamic dysfunction. This, and other more recently identified associations with ONH, such as developmental delay and autism, are independent of septum pellucidum development. Other common neuroradiographic associations such as corpus callosum hypoplasia, gyrus dysplasia, and cortical heterotopia may have prognostic significance. The predominant prenatal risk factors for ONH are primiparity and young maternal age. Presumed risk factors such as prenatal exposure to drugs and alcohol are not supported by scrutiny of the literature. Heritability and identified gene mutations in cases of ONH are rare.

CONCLUSION

Children with ONH require monitoring for many systemic, developmental, and even life-threatening problems independent of the severity of ONH and presence of brain malformations including abnormalities of the septum pellucidum. "Septo-optic dysplasia" and "de Morsier's syndrome" are historically inaccurate and clinically misleading terms.

Reappraisal of the optic nerve hypoplasia syndrome

BACKGROUND

Optic nerve hypoplasia (ONH) has been described as an increasingly prevalent cause of congenital blindness. Its association with hypopituitarism and absent septum pellucidum has been recognized for more than 40 years as "septo-optic dysplasia" or "de Morsier syndrome." More recent studies have suggested that these associations are independent of one another. This review was designed to assess the historical and recent evidence for associations of neuroradiologic, endocrinologic, and developmental problems in patients with ONH.

EVIDENCE ACQUISITION

Historical and contemporary literature review.

RESULTS

The medical literature does not support the notion that Georges de Morsier ever described a case of ONH or recognized its association with hypopituitarism or missing septum pellucidum. Recognition of the critical association of ONH with hypopituitarism should be attributed to William Hoyt. Hypopituitarism and other more recently identified associations with ONH, such as developmental delay, hypothalamic dysfunction, and autism, are independent of septum pellucidum development. Other common neuroradiographic associations, such as corpus callosum hypoplasia, gyrus dysplasia, and cortical heterotopia, may have prognostic significance.

CONCLUSIONS

Children with ONH need to be monitored for many systemic, developmental, and even life-threatening problems independent of the status of the septum pellucidum. "Septo-optic dysplasia" and "de Morsier syndrome" are historically inaccurate and clinically misleading terms that should be abandoned.

Optic nerve hypoplasia in North America: a re-appraisal of perinatal risk factors

PURPOSE

The purpose of this study is to describe and clarify the birth and prenatal characteristics of a large cohort of children with optic nerve hypoplasia.

METHODS

This is a descriptive report of 204 patients aged

RESULTS

Birth characteristics were unremarkable for birthweight and gestation, but significant for increased frequency of caesarean delivery and fetal and neonatal complications. Young maternal age and primaparity were dominating maternal features. Preterm labour, gestational vaginal bleeding, low maternal weight gain and weight loss during pregnancy were prevalent.

CONCLUSIONS

These findings confirm young maternal age and primaparity as associated risk factors, challenge many other suggested factors such as alcohol and drug abuse, and introduce potentially significant prenatal characteristics such as maternal weight loss and early gestational vaginal bleeding as aetiological correlates.

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Key Words

• aetiology
• de morsier syndrome
• optic nerve hypoplasia
• perinatal
• prenatal
• septo-optic dysplasia

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MESH Headings

• Birth Weight
• Child, Preschool
• Eye Abnormalities/epidemiology
• Female
• Gestational Age
• Humans
• Infant
• Infant, Newborn
• Infant, Premature
• Male
• Maternal Age
• North America/epidemiology
• Optic Nerve/abnormalities
• Parity
• Pregnancy
• Prospective Studies
• Registries/statistics & numerical data
• Risk Factors
• Sweden/epidemiology

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Grants

• M01 RR000043-44 NCRR NIH HHS
• UL1 RR031986 NCRR NIH HHS
• M01 RR00043 NCRR NIH HHS
• UL1 RR031986-01 NCRR NIH HHS
• M01 RR000043 NCRR NIH HHS

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Affiliation(s)

Pamela Garcia-Filion The Vision Center at Childrens Hospital Los Angeles, and Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, California 90027, USA.
Cassandra Fink
Mitchell E Geffner
Mark Borchert

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Unilateral optical nerve hypoplasia in a Beagle dog

Unilateral (left eye) optic nerve hypoplasia was detected in a six-month-old male Beagle dog. Vision testing indicated that the left eye had poor vision and testing the pupillary light reflex showed the left eye to have an absence of the afferent pathway of the reflex but it had a normal efferent pathway. Ophthalmoscopy revealed a small-sized optic disc, winding retinal artery and dilated retinal vasculature in the left globe. Electroretinography showed no abnormal findings even in the left globe. Histopathologically, the left optic nerve was markedly hypoplastic and was composed of sparse neural elements and a moderate amount of connective and glial tissues. In the retina of the left globe, the nerve fibre layer and the ganglion cell layer were reduced in thickness, although a small number of ganglion cells were still present. There were no abnormal findings detected in the right globe and the right optic nerve. The brain appeared normal macroscopically.

Ocular coloboma: a reassessment in the age of molecular neuroscience

Congenital colobomata of the eye are important causes of childhood visual impairment and blindness. Ocular coloboma can be seen in isolation and in an impressive number of multisystem syndromes, where the eye phenotype is often seen in association with severe neurological or craniofacial anomalies or other systemic developmental defects. Several studies have shown that, in addition to inheritance, environmental influences may be causative factors. Through work to identify genes underlying inherited coloboma, significant inroads are being made into understanding the molecular events controlling closure of the optic fissure. In general, severity of disease can be linked to the temporal expression of the gene, but this is modified by factors such as tissue specificity of gene expression and genetic redundancy.

Visually impaired children with posterior ocular malformations: pre- and neonatal data and visual functions

AIM

To analyse pre- and neonatal data and ocular findings in children with visual impairment caused by posterior ocular malformations.

METHODS

Medical records were scrutinized, dried blood spot cards were analysed for virus DNA and ophthalmological assessments were performed in 28 children with optic nerve hypoplasia (ONH) and 10 with optic/chorio-retinal coloboma.

RESULTS

Prenatal exposure to possible teratogens was documented in 5/28, herpes simplex virus type 1 DNA was identified in the dried blood spot cards of 1/26 children and neonatal hypoglycaemia in 12/28 children with ONH. The time delay from ocular to endocrinological diagnosis and treatment was 3 years. Children with ONH and severe visual impairment had endocrinopathy more often (11/13) than ONH children with better visual functions (5/15). Prenatal exposure to teratogens or neonatal hypoglycaemia was not identified in any of the children with coloboma.

CONCLUSION

Neonatal hypoglycaemia was common in children with ONH. Severe visual impairment predicted endocrinopathy. Analysis of dried blood spot cards could serve as an additional diagnostic tool in children with ocular malformations.

Ocular colobomata

Ocular colobomata present diagnostic and therapeutic challenges in patients of all ages, but especially in young children. The "typical" coloboma, caused by defective closure of the fetal fissure, is located in the inferonasal quadrant, and it may affect any part of the globe traversed by the fissure from the iris to the optic nerve. Ocular colobomata are often associated with microphthalmia, and they may be idiopathic or associated with various syndromes. Types and severity of complications vary depending on the location and size of the colobomata. This article reviews the pathogeneses, categorization, genetic bases, differential diagnoses and management of ocular coloboma.

Developmental changes in the optic nerve related to ethanol consumption in pregnant rats: analysis of the ethanol-exposed optic nerve

Visual impairment is one of the most common ophthalmic abnormalities in fetal alcohol syndrome. Pathologic changes in optic nerve development related to alcohol consumption could be involved in this dysfunction. In order to assess the consequences of pre- and postnatal exposure to alcohol on the developing optic nerve, we administered an ethanol-containing liquid diet (5% w/v) before and during gestation and throughout lactation to rats and their offspring. A group of control animals were kept on a pair-fed isocaloric diet. The optic nerves were obtained at key stages from fetuses (21 days of gestation) and pups (4, 7, 14, 21 and 28 postnatal days). Samples of the optic nerve cross-section, behind the eyeball, were processed for analysis of gliogenesis, myelinogenesis, axonal growth, and remodelling events, using light and electron microscopy. Qualitative, morphometric, and immunocytochemical analyses, alternatively using anti-GFAP and anti-MBP antibodies, were carried out. Optic nerve cross-sections from prenatal and postnatal alcohol-exposed rats showed a decrease in size. Ultrastructural alterations and retarded development in macroglial cells, optic axons, and myelin sheath were also observed. The most prominent abnormalities were: damage of cytoplasmic organelles and disorganization of cytoskeleton in astrocytes; a decrease in free ribosome density and nuclear membrane inclusions in oligodendrocytes; and fragmentation of lamellae, aberrant myelin sheaths and intralamellar inclusions in myelin. These findings suggest that alcohol abuse during pregnancy is teratogenic to the optic nerve and closely related to the altered visual function.

Systemic viral infections and their retinal and choroidal manifestations

Viruses are one of the most common causes of infections involving the posterior segment of the eye. Such infections can occur either on a congenital or an acquired basis, and may affect primarily the retina or the choroid. Congenital cytomegalovirus (CMV) and rubella infections may result in retinitis. CMV retinitis is also the most common cause of acquired viral retinitis, primarily because of the acquired immunodeficiency syndrome (AIDS). Other types of viral retinitis, such as those caused by herpes simplex or herpes zoster, can occur in immunocompromised or immunocompetent individuals. Retinitis or choroiditis caused by viruses such as measles, influenza, Epstein-Barr virus, and Rift Valley fever virus, typically occurs subsequent to an acute viral systemic illness. The systemic and ocular manifestations, as well as the histopathology, laboratory tests, differential diagnoses, and treatment regimens for each of the individual viruses are discussed in detail.

Aplasia of the retinal vessels combined with optic nerve hypoplasia, neonatal epileptic seizures, and lactic acidosis due to mitochondrial complex I deficiency

A newborn male with mitochondrial complex I deficiency suffered from neonatal epileptic seizures, which later developed into infantile spasms. The infant was blind due to aplasia of the retinal vessels and hypoplasia of the optic nerve. There was congenital lactic acidosis, which persisted in later life. The boy was microcephalic and retarded. Muscular hypotonia later shifted to spasticity. Succinic acid was increased in urine. We assume that the aplasia of the retinal vessels is due to damage of the retinal ganglion cells caused by the mitochondrial disease in the first 3 to 4 months of pregnancy.

Abnormalities of the visual system in infants exposed to cocaine

The authors describe 13 cocaine-exposed infants with optic nerve abnormalities, delayed visual maturation, and prolonged eyelid edema. Prolonged and potentially vision-threatening eyelid edema is a new clinical entity. The pharmacology of cocaine, its easy access to fetal circulation, and its neurotropic characteristics can be used to explain optic nerve abnormalities and delayed visual maturation. In infants with any of these eye abnormalities, a careful investigation for cocaine abuse is advisable.

Lethal cytomegalovirus infection in preterm infants: clinical, radiological, and neuropathological findings

Fifteen premature infants with lethal congenital cytomegalovirus infection were studied to determine the clinical, neuroradiological, and neuropathological characteristics of the disease in this population. Nine infants were liveborn but died at a postnatal age of 18 +/- 21 days; 6 infants were stillborn. Clinical findings in liveborn infants included microcephaly (77%), seizures (55%), hypotonia (33%), and multiple contractures (18%). Ophthalmological findings included chorioretinitis, optic atrophy, and corneal opacities. Neuroradiological findings included the postnatal evolution of periventricular calcification in 1 infant, and cerebellar hypoplasia diagnosed by magnetic resonance imaging in 1 infant. Neuropathological findings included periventricular necrosis and calcification (12), associated diffuse calcification frequently involving the convexity of the gyri (6), cerebellar hypoplasia (5), periventricular leukomalacia (2), intraventricular hemorrhage (2), hydrocephalus (2), and porencephalic cyst (1). Intranuclear inclusion bodies within the brain were observed in 4 infants, whereas systemic inclusion bodies were present in all infants. These data indicate several atypical findings in preterm infants rarely reported in term infants, including hypotonia, multiple contractures, periventricular leukomalacia, and optic atrophy.

Ocular teratology

The principles of teratology are described, and animal models for research in abnormal ocular development and clinical studies of human teratogens are surveyed. A review is made of presumed ocular teratogenic agents: radiation; external environmental teratogens; maternal conditions such as infections, diabetes, and epilepsy; alcohol and drugs such as thalidomide, retinoic acid, and coumarin anticoagulants; and other agents, such as cigarettes.

Optic nerve hypoplasia, encephalopathy, and neurodevelopmental handicap

Abnormalities of the central nervous system are frequently described in optic nerve hypoplasia. In a longitudinal study of 46 consecutive children (32 term, 14 preterm) with bilateral optic nerve hypoplasia 32 (69.5%) had associated neurodevelopmental handicap. Of these, 90% had structural central nervous system abnormalities on computed tomographic brain scans. Neurodevelopmental handicap occurred in 62.5% of the term and 86% of the preterm infants respectively. Term infants had a greater incidence of ventral developmental midline defects and proportionately fewer maternal and/or neonatal complications throughout pregnancy, while encephaloclastic lesions were commoner among the premature infants. An association of optic nerve hypoplasia with the twin transfusion syndrome and prenatal vascular encephalopathies is described.

Optic nerve hypoplasia in children

Optic nerve hypoplasia (ONH) is characterised by a diminished number of optic nerve fibres in the optic nerve(s) and until recently was thought to be rare. It may be associated with a wide range of other congenital abnormalities. Its pathology, clinical features, and the conditions associated with it are reviewed. Neuroendocrine disorders should be actively sought in any infant or child with bilateral ONH. Early recognition of the disorder may in some cases be life saving.

Localising patterns of optic nerve hypoplasia--retina to occipital lobe

Six cases are presented which provide clinical evidence that optic nerve hypoplasia can occur as a result of a lesion at any site in the developing visual system. The mechanisms of hypoplasia are discussed in the light of recent understanding of optic nerve development.

Optic nerve hypoplasia

Optic nerve hypoplasia is an easily overlooked, nonprogressive developmental anomaly which results in a wide range of visual deficits. It is frequently associated with clinically significant central nervous system and endocrine abnormalities. Maternal substance abuse is increasingly recognized in many cases. A supranormal regression of optic nerve axons in utero, rather than a primary failure of differentiation, is proposed as the pathogenesis.

Antiviral therapy with ganciclovir for cytomegalovirus retinitis and bilateral exudative retinal detachments in an immunocompromised child

A child with bilateral cytomegalovirus (CMV) retinitis, vitritis, and exudative retinal detachments, who was in remission from stage IV neuroblastoma and status post-chemotherapy and autologous bone marrow transplantation, was treated with ganciclovir. The drug is a new acyclic nucleoside antiviral drug with potent antiCMV activity. There was bilateral retinal reattachment, clearing of vitritis and regression of retinal exudates and hemorrhages, with concomitant resolution of viral shedding in urine and blood, on ganciclovir 7.5 mg/kg per day. There was recurrence of exudative detachments, vitritis and retinitis when the dose was reduced to 2.5 mg/kg per day, and regression of these findings when the dose was again increased to 7.5 mg/kg per day. Despite continued therapy at this dose, a relapse occurred. When the dose of drug was doubled to 15 mg/kg per day, there initially was a partial therapeutic response, followed by a subsequent relapse. No further response was seen when the dose was increased to 19.5 mg/kg per day. This patient was treated with ganciclovir for a total of 192 days. No adverse reactions to ganciclovir were seen. On the last day of drug administration, there were persistent bilateral exudative retinal detachments and progressive optic nerve head involvement with optic disc pallor, despite quiescence of the retinitis.

Optic nerve hypoplasia: changing perspectives

Optic nerve hypoplasia, having once been regarded as exceedingly rare, is now regarded as one of the major causes of visual loss in infancy. Recognition of subtle forms and segmental forms of optic nerve hypoplasia are important in explaining the evaluation of subnormal vision, and have an added significance in the recognised associations of central nervous system anomalies including abnormalities of the endocrine system. These changing clinical perspectives are reviewed, together with a discussion of the pathogenesis of optic nerve hypoplasia in the light of cell death and nerve fibre degeneration seen in normal development of the neural visual system.

Optic nerve hypoplasia: a review

Optic nerve hypoplasia is a developmental anomaly of the retina and optic nerves in which there is a reduction in the number of ganglion cells in the retina and of their centripetal fibers projecting through the optic nerve to the lateral geniculate body. The condition may be unilateral or bilateral and is frequently misdiagnosed as optic atrophy. In about 25% of cases, bilateral optic nerve hypoplasia is associated with a variety of cerebral malformations of which the commonest single disturbance is absence of the septum pellucidum (septo-optic dysplasia). Cerebral malformations and their endocrine accompaniments are also seen, though less frequently, in unilateral hypoplasia. The endocrine disturbances that may accompany optic nerve hypoplasia include growth hormone deficiency, adrenal insufficiency, hypothyroidism, and disturbances of antidiuretic hormone production. Precocious puberty and hypogonadism have also been observed. The prognosis of optic nerve hypoplasia depends upon the severity of the changes in the optic nerves and especially the degree of associated cerebral malformation. The finding of optic nerve hypoplasia should lead to thorough ophthalmologic, neurologic, and endocrinologic evaluation of the patient.

Maternal age and congenital optic nerve hypoplasia: a possible clue to etiology

The maternal age of two groups of children with congenital handicaps, cerebral palsy and fetal alcohol syndrome (FAS), were examined and compared with a group of mothers of children with congenital optic-nerve hypoplasia (CONH). The maternal age of children with CONH was significantly less than for the cerebral-palsied children which, in turn, was significantly less than for the FAS children. In addition, about one-half of the children with CONH had associated handicaps which clustered into four progressively more severe combinations. Maternal age and the occurrence of endocrine problems did not differ significantly among the clusters.

Syndrome of septo-optic-pituitary dysplasia: the clinical spectrum

Septo-optic-pituitary dysplasia is a syndrome characterized by abnormalities of midline brain structures, optic nerve hypoplasia, and congenital hypothalamic-pituitary insufficiency. Four infants, diagnosed as having clinical variations of this disorder, are described. The first had agenesis of the septum pellucidum and corpus callosum, partial hypothalamic insufficiency, and normal optic nerves. The second had a structurally normal brain, bilateral optic nerve hypoplasia, and panhypopituitarism. The third had bilateral agenesis of the cerebral cortex, bilateral optic nerve hypoplasia and partial hypothalamic insufficiency. The fourth had a structurally normal brain, unilateral optic nerve hypoplasia and panhypopituitarism. A review of the recent literature revealed 191 patients with bilateral optic nerve hypoplasia who were examined for possible existence of this syndrome. Of the 178 patients who had radiographic imaging of the brain, 60% were found to have structural abnormalities. Of the 145 patients evaluated for pituitary function, 62% had evidence of insufficiency. Approximately 30% of fully evaluated patients had evidence of all three components of the syndrome. Because of high incidence of structural abnormalities of the brain and congenital hypopituitarism in patients with optic nerve hypoplasia, we conclude that full evaluation is indicated in patients with any of the three components of the syndrome.

The disc that really isn't (hypoplastic disc syndrome)

A nine-and-one-half month old boy with poor visual function was found to have bilaterally small optic discs. He subsequently demonstrated a retarded growth pattern. A series of photographs revealing part of the spectrum of optic disc hypoplasia are included. Associated structural and endocrine defects as well as various opinions concerning the appropriate approach to these patients are discussed.

Clinical spectrum of congenital optic nerve hypoplasia: review of 51 patients

Fifty-one patients with congenital optic nerve hypoplasia (CONH) were reviewed. It was found that the risk of having an affected child is higher in an adolescent mother, and that maternal alcohol or drug abuse may be important factors. Frequently the disorder is associated with other neuropsychiatric handicaps, and with neuro-endocrine abnormalities. The findings suggest that CONH probably is not a homogeneous group of disorders; some may be caused by primary failure of differentiation of the retinal ganglion cells, while others may be the product of an acquired transsynaptic degeneration of optic-nerve fibres.

Clinical anophthalmia associated with congenital cytomegalovirus infection

Three cases of congenital clinical anophthalmia associated with congenital cytomegalovirus infection were diagnosed by positive viral cultures and immunologic studies. Ultrasonography in one infant with clinically detected anophthalmia showed the presence of severe microphthalmia with cyst. These findings suggest that maternal infection occurred within the first trimester of gestation.

Complex sporadic colobomata

Sporadic colobomata may be associated with a variety of secondary changes, and these have been classified and discussed with special reference to unusual findings published during recent years. Clinically some cases may appear to be neoplastic, and pathological examination may be important in demonstrating their true nature. A malformation apparently not previously reported is described.

Spectrum of optic nerve hypoplasia

Optic nerve hypoplasia is a non-progressive condition characterised by subnormal vision and a subnormal number of optic nerve axons. It may be unilateral or bilateral, isolated or combined with other defects. Analysis of fundus photographs from a series of 7 patients with a stationary abnormality of different degrees showed that the functional defects could be closely correlated with defects in the retinal nerve fibre layer. Our observations show that the condition has a wide range of both functional and anatomical defects and that a subnormal diameter of the optic disc is not a requisite for the diagnosis. Presumably, there is also a wide variety of causes, not only a primary failure of development of retinal ganglion cells. We suggest that optic nerve hypoplasia can be viewed as a non-specific manifestation of damage to the visual system, sustained any time before its full development.