Light, dark, and melatonin: emerging evidence for the importance of melatonin in ocular physiology

Melatonin is a hormone, which is mainly produced by the pineal gland, a vestigial eye. Rather than the rods and cones, it is a newly discovered subgroup of photosensitive retinal ganglion cells, which is responsible for mediating the light-dark cycles, thus regulating melatonin's secretion. One of the correlates of the circadian rhythm of melatonin release is the habitual sleep pattern. Patients with circadian rhythm sleep disorders, including some blind patients with no light-induced suppression of melatonin, benefit from melatonin treatment. Melatonin is synthesized in the retina, lens, ciliary body as well as other parts of the body. In this review, we discuss the physiological roles of melatonin in the eye, as well as the potential therapeutic avenues currently under study.

Melatonin replacement therapy in a child with a pineal tumor

The case report of a child with the diagnosis of a pineal tumor and severe, chronic sleep disorder is reported. Due to treatment of her lesion, the nighttime melatonin secretion was markedly suppressed. For 4(1/2) years, she has been receiving oral melatonin, which has greatly improved her sleep, without any adverse effects. Sleep difficulties should be considered in the management of pineal lesions. Melatonin replacement therapy is beneficial for those patients who have deficient melatonin synthesis.

Visual impairment due to a dyskinetic eye movement disorder in children with dyskinetic cerebral palsy

Neurological lesions that cause dyskinetic cerebral palsy (CP) commonly involve ocular movements. This report describes a group of 14 children (nine males, five females) whose CP is associated with severe dyskinetic eye movements. Ages ranged from 4 months to 13 years (mean 6.9 years). Clinical features of this eye movement disorder are discussed and defined. The visual function of these children is slow, variable, and highly inefficient. They are often misdiagnosed as blind, due to cortical visual impairment. Early recognition of dyskinetic eye moment disorder and appropriate developmental and educational management are important.

Clinical trials of controlled-release melatonin in children with sleep-wake cycle disorders

This is the first study to examine effective doses of controlled-release (CR) melatonin in children with chronic sleep wake cycle disorders. All 42 subjects had severe neurodevelopmental difficulties. Initially, a randomized double-blinded cross-over design was used in 16 children, comparing the effectiveness of fast-release (FR) and CR melatonin. In the remainder of the patients, the CR melatonin was studied on a clinical basis. The effectiveness of treatment was assessed by sleep charts and clinical follow-up. Emphasis was placed on the judgement of the parents, who had guidance from the physicians. The average final CR melatonin dose in the 42 patients was 5.7 mg (2-12 mg). The studies showed that the FR melatonin was most effective when there was only delayed sleep onset, but CR formulations were more useful for sleep maintenance. Children appeared to require higher doses than adults.

Cortical visual impairment in children with infantile spasms

BACKGROUND

Infantile spasms are often associated with cortical visual impairment.

METHOD

We report a series of 10 patients with infantile spasms, hypsarrhythmic electroencephalograms, and developmental delay, (ie, West syndrome), who presented with severe visual inattention despite a normal ocular examination.

RESULTS

At follow-up (14 months to 6 years), 5 patients (50%) had no improvement in their visual behaviour. Although some degree of improvement was observed in the others, their visual function remained abnormal. All patients had moderate or severe mental retardation.

CONCLUSIONS

The clinical features of West syndrome are reviewed, and the cause of the associated cortical visual impairment is discussed. Cortical visual impairment with infantile spasms is an important association, which pediatric ophthalmologists should recognize.

Melatonin treatment of non-epileptic myoclonus in children

Oral melatonin (MLT) has been used by our Vancouver research group in the treatment of paediatric sleep disorders since 1991; slightly over 200 children, mainly with multiple disabilities, who frequently had seizures, have been treated. Three children with markedly delayed sleep onset due to recurring myoclonus were also referred for MLT treatment: two had non-epileptic, and one had epileptic and non-epileptic myoclonus. Low doses of oral MLT (3 to 5 mg) unexpectedly abolished their myoclonus and allowed them to sleep. There were no adverse effects. It appears that certain types of myoclonus, which might be resistant to conventional anticonvulsant medications, may respond to MLT but the mechanism of action is unclear. Further research on this novel treatment is urgently needed.

Neurologic abnormalities associated with persistent hyperplastic primary vitreous

BACKGROUND

Persistent hyperplastic primary vitreous (PHPV) is usually a unilateral ocular abnormality not associated with other systemic findings. We describe 16 patients, 7 with unilateral and 9 with bilateral PHPV, in whom significant neurologic abnormalities were identified.

METHODS

The clinical records of 16 children referred to the Visually Impaired Program at a university-affiliated children's hospital in Vancouver were studied from 1970 to 1996. Further investigations, including electroencephalography, computed tomography and pediatric neurologic evaluation, were performed to ascertain neurologic deficits.

RESULTS

Neurologic abnormalities were identified in three of the children with unilateral PHPV (hemiparesis, impaired coordination and homonymous hemianopia) and seven of the children with bilateral PHPV (ataxia, impaired coordination, hypotonia, spastic quadriplegia, microcephaly and deafness).

INTERPRETATION

The possibility of underlying neurologic abnormality should be considered in patients with PHPV, particularly those with bilateral disease. Referral to a pediatric neurologist may be appropriate.

Unilateral alpha reactivity: an electroencephalographic finding in albinism

Persons with various forms of albinism frequently have misrouting of their optic nerve fibers. Visual evoked potential (VEP) studies can confirm this because monocular stimulation tends to result in asymmetrical rather than symmetrical occipital response. This type of decussation abnormality is associated only with albinism. In the electroencephalogram (EEG) of normal subjects, unilateral eye opening or closing does not affect the frequency, reactivity, regulation, and symmetry of alpha rhythm. In contrast, in our study, 6 of 19 persons with oculocutaneous and ocular albinism responded to unilateral eye opening with contralateral disappearance or significant attenuation of their alpha rhythm. The most likely explanation of this phenomenon is that the visual pathway misrouting is complete or nearly complete in some children with albinism so that one rather than both occipital lobes receive visual information from each eye. This type of alpha behavior, like VEP studies, supports the diagnosis of albinism, and such testing can be easily performed during a routine EEG recording.

Speech, cognition, and imaging studies in congenital ocular motor apraxia

Detailed neurological, speech and language, psychological, and neuroimaging studies were carried out in eight children with the diagnosis of congenital ocular motor apraxia. The neurological examination showed clinical evidence of cerebellar vermis abnormality (hypotonia and truncal ataxia) in all cases. Neuroimaging studies suggested that the site of neuropathological disturbance of congenital ocular motor apraxia was the inferior vermis. Half of the subjects had associated speech apraxia. The most likely location of brain disturbance, which was responsible for the speech apraxia, was also an as yet undefined area of the vermis. Psychological testing consistently revealed visual-spatial difficulties. These may have been secondary to cerebellar pathology or to developmentally inappropriate sensory input caused by the abnormal saccades. Children with speech apraxia appear to be slightly more affected neurologically than those with normal speech.

Congenital ocular motor apraxia: imaging findings

PURPOSE

To determine the frequency of cerebellar and cerebral abnormalities on brain imaging studies in children with congenital ocular motor apraxia.

METHODS

Brain imaging studies were performed in 19 children with typical congenital ocular motor apraxia who were in the care of a visual impairment program at a children's hospital. Independent clinical review categorized the subjects as having partial (n = 10) or expanded (n = 9) congenital ocular motor apraxia on the basis of extent of associated speech or neurodevelopmental problems. Fifteen CT studies and 13 MR examinations of the brain performed in these children were reviewed independently by two pediatric neuroradiologists. Radiologic findings were agreed on by consensus.

RESULTS

Cerebellar abnormalities were found in 12 of 19 cases. The cerebellar vermis was small in 10 children. A small cerebellar vermis was the only abnormality in five of 10 children with partial congenital ocular motor apraxia and in two of nine children with expanded congenital ocular motor apraxia. Among seven children with a small vermis examined with high-resolution MR imaging, the inferior portion of the vermis was preferentially involved in each case. Of these seven subjects, none of four with partial congenital ocular motor apraxia but two of three with expanded congenital ocular motor apraxia had an abnormality of the superior portion of the vermis. Miscellaneous supratentorial lesions affecting both gray and white matter were found in six subjects. Five of the 19 children had normal imaging findings.

CONCLUSION

Inferior vermian hypoplasia is the most common abnormality in children with congenital ocular motor apraxia.

Use of melatonin in the treatment of paediatric sleep disorders

A group of Vancouver health professionals, including the authors, have studied the use of oral melatonin in the treatment of chronic sleep disorders in children with disabilities since the Fall of 1991. This review article is based on the first 100 patients, half of whom were visually impaired or blind. Children with neurological, neuropsychiatric, and developmental disabilities are predisposed to chronic sleep-wake cycle disturbances. Disorders such as blindness, deaf-blindness, mental retardation, autism, and central nervous system diseases, among others, diminish the ability of these individuals to perceive and interpret the multitude of cues for synchronizing their sleep with the environment. Melatonin, which benefitted slightly over 80% of our patients, appears to be a safe, inexpensive, and a very effective treatment of sleep-wake cycle disorders. The oral dose of fast release melatonin taken at bed-time ranged from 2.5 mg to 10 mg. Side effects or the development of tolerance have not been observed. Since the causes of sleep difficulties are extremely variable, not all children are candidates for treatment. For successful melatonin treatment, clinical experience is required, and the influences of other health problems and medications need to be considered. Further clinical and laboratory research in this field is imperative because melatonin treatment offers enormous health, emotional, social, and economic benefits to society, especially since multidisabled children with chronic sleep difficulties do not respond well to current therapeutic regimes.

Visually impaired children with sensory defect nystagmus, normal appearing fundi and normal ERGS

The differentiation of congenital motor nystagmus (CMN) from sensory defect nystagmus (SDN) in early life is a common diagnostic problem, since their wave forms are indistinguishable. A diagnosis of SDN is made when fundal or ERG abnormalities are present. CMN is generally diagnosed by exclusion. This approach can lead to late or incorrect diagnosis, and to the overlooking of important genetic implications. In addition, the classification of congenital nystagmus into pure motor and sensory types is inadequate. The authors present case reports illustrating this problem and suggest strict criteria for a diagnosis of CMN. They also point out that a miscellaneous group of rare disorders of the macula tend to be overlooked and misdiagnosed.

Familial paroxysmal kinesigenic choreo-athetosis in a child with visual hallucinations and obsessive-compulsive behaviour

A teenage male is described, in whom Tourette Syndrome was suspected, which was later replaced by attacks of paroxysmal kinesigenic choreo-athetosis. He also exhibited bizarre, episodic perceptual distortions of his visual environment and manifestations of an obsessive-compulsive disorder. Carbamazepine treatment not only completely eliminated the recurring attacks of his choreo-athetosis but also, contrary to expectations, the visual disturbances and even the symptoms of his obsessive-compulsive disorder. Obsessive compulsive disorder should be searched for by direct questioning in all patients with basal ganglia disorders.

Eye-poking

Eye-poking, -rubbing and -pressing are often incorrectly grouped together because of the assumption that they represent variations of the same self-stimulating behaviour. This prospective study of 21 children shows that eye-poking is a distinct, chronic, stereotyped, self-injurious act seen mainly among severely mentally disabled individuals, who may or may not be visually impaired. Eye-poking, which leads to intense, self-induced pain, is a harmful behaviour because it can result in permanent visual loss and even in total blindness. The cause is unclear, although it is probably multifactorial. The treatment is exceedingly difficult. Further studies are needed to develop specific management techniques to prevent eye-poking, which adds to the physical and emotional burden on the caregivers.

The septum pellucidum and spatial ability of children with optic nerve hypoplasia

Animal studies suggest that spatial skills are dependent on an intact septum pellucidum. This theory was tested by comparing patients who were visually impaired due to bilateral optic nerve hypoplasia: 13 with a septum pellucidum were compared with six children without a septum pellucidum. There was no difference in spatial ability. The finding of an absent septum pellucidum may only indicate the timing of a congenital brain insult, and it cannot be used to predict specific clinical, neuroendocrinological, cognitive or spatial abnormalities.

Rapid cycling in severely multidisabled children: a form of bipolar affective disorder?

A debilitating, regularly recurring, biphasic disorder is described in 6 severely multidisabled children. It was characterized by several days of lethargy, withdrawal, loss of abilities, irritability, and hypersomnolence followed or preceded by a high-energy state for several days during which the children slept very little, at times were euphoric, had improved mental ability, and were hyperactive. These cyclic episodes had been present for years but unexpectedly disappeared in one child. The etiology is unknown, in spite of detailed neurologic, metabolic, and endocrine investigations. All patients had family histories positive for affective disorder. Melatonin treatment helped to regulate the coexisting chronic sleep disorders of 3 children but failed to eliminate the cycles. Antiepileptic drug treatment, lithium, sedatives, stimulants, tranquilizers, and light therapy were largely ineffective. The children's symptoms and signs fit the diagnostic criteria of a bipolar affective illness, as it was modified for patients with associated neurologic disability; therefore, the patients appeared to have a unique disorder that closely resembles or is a variant of rapid cycling affective disorder.

The treatment of sleep disorders with melatonin

Fifteen children (most of whom were neurologically multiply disabled) with severe, chronic sleep disorders were treated with 2 to 10mg of oral melatonin, given at bedtime. Nine had fragmented sleep patterns, three had delayed sleep onset and three others had non-specific sleep disturbance of unclear aetiology; all had failed to respond to conventional management. Nine patients had ocular or cortical visual impairment. The health, behavioural and social benefits of treatment were significant, and there were no adverse side-effects. While the response was not always complete, the study clearly showed that melatonin has an important role in the treatment of certain types of chronic sleep disorders.

Cortical visual impairment in children

Cortical visual impairment (CVI) in children is most commonly caused by peri- or post-natal hypoxia-ischemia, but may also occur following other insults, e.g., trauma, epilepsy, infections, drugs or poisons, and certain neurologic diseases. The disorder differs considerably in etiology, physical findings, and, perhaps, prognosis, from the cortical blindness seen in adults. The same event that causes CVI by damaging the geniculate and/or extrageniculate visual pathways may also damage other areas of the brain, or the retina, optic nerves, or chiasm. Thus, children with CVI often have other neurological problems. Diagnosis may require the participation of a multidisciplinary team and the use of special visual testing techniques. Due to the uncertainty concerning the prognosis in CVI, clinicians should remain optimistic about the child's potential for some vision recovery.

Monocular nystagmus caused by unilateral anterior visual-pathway disease

The authors examined five young children with monocular vision loss who developed monocular nystagmus. The nystagmus was of fast frequency and small amplitude in all fields of gaze. In four children, successful treatment of the cause of the vision loss resulted in cessation of the nystagmus. No child showed signs of spasmus nutans, or of optic nerve or chiasmal tumor. The evaluation of the young child with unilateral nystagmus should begin with a careful eye examination.

Oculocerebral hypopigmentation syndrome associated with Bartter syndrome

We describe a 20-year-old man with tyrosinase-negative oculocutaneous albinism, mental retardation, epilepsy, sensorineural deafness, ataxia, and Bartter syndrome. When combined, these neurocutaneous and renal findings form a previously unreported combination. The neurological and cutaneous manifestations of this case are distinctly different from those of the syndrome first reported by Cross et al. [1967]. The literature is reviewed and an attempt is made at classifying the oculocerebral hypopigmentation syndromes.

Photophobia and cortical visual impairment

Photophobia, or intolerance of light, is not completely understood as a symptom. It has been divided into ocular and central types. This study shows that persistent, usually mild, photophobia occurs in about one-third of children with cortical visual impairment (CVI). When the CVI is congenital the photophobia is present from birth, and when it is acquired the sensitivity to light appears immediately after the brain insult. The intensity of photophobia tends to diminish with time and occasionally it may even disappear. The pathophysiology is unclear, as in all other neurological disorders associated with photophobia.

Acquired ocular visual impairment in children. 1960-1989

OBJECTIVE

To describe the causes, sites, and types of eye anomaly and associated handicaps in children identified in the last 30 years with ocular visual impairment of 20/200 (6/60) or worse in the better eye with correction.

DESIGN

Trend study.

STUDY POPULATION

Children in British Columbia younger than 19 years with visual loss diagnosed between January 1960 and December 1989 who were referred for multidisciplinary assessment.

RESULTS

The incidence of acquired ocular visual impairment has decreased from 0.6 to less than 0.2 per 10,000 people aged 19 years or younger during the last 30 years. The most common cause was a genetic cause, followed by tumor, injury, infection and autoimmune disorders. Optic nerve atrophy and retinal disorders together resulted in more than 90% of all ocular lesions. Gender distribution revealed more males than females to be affected. Sixty-six percent of children had enough sight to read. The percentage of affected children with neurologic disabilities has increased overall in the last 30 years because more children with profound brain damage have survived.

CONCLUSIONS

Acquired ocular visual impairment is rare. The incidence of such impairment has been reduced by two thirds in the last 30 years. This decline has had little impact, however, because most cases of blindness are due to congenital conditions. The number of cases of acquired blindness is only one fourth that of congenital blindness, which has begun to increase again owing to the reemergence of retinopathy of prematurity.

Ataxia-telangiectasia in a child with vaccine-associated paralytic poliomyelitis

Vaccine-acquired poliomyelitis developed in a nonimmunized 10-month-old boy. At age 4 years, ataxia-telangiectasia was recognized. We conclude that the occurrence of vaccine-related poliomyelitis warrants a detailed assessment of immunity, and that, in patients with ataxia-telangiectasia, the use of live vaccines may be hazardous, even in those with apparently normal immunity.

Visual hallucinations after acute visual loss in a young child

A four-year-old boy developed complex visual hallucinations consisting of moving figures, animals and other familiar objects one week after becoming totally blind. This followed a six-month period of gradually deteriorating vision and was precipitated by the debulking of a large optic nerve glioma. Although visual hallucinations are well recognised in adults with visual loss, secondary to both ophthalmological and neurological causes, they have not been reported in young children.

Neurodevelopmental criteria in the classification of congenital motor nystagmus

Congenital motor nystagmus (CMN) can be familial or non-familial. The expressivity of CMN is so variable that in one affected member of the family the oscillations are obvious, while in the others the nystagmus could be overlooked even by the patients themselves. In spontaneous cases the proof of heredity might be discovered by an ophthalmological examination or eye movement recordings of other family members. Our multidisciplinary studies of 27 children with CMN suggests that a neurodevelopmental assessment can also be valuable in establishing a diagnosis of heredity. Our studies suggest that the hereditary form of CMN is free from neurodevelopmental problems, while the non-familial form is not. Therefore, children with spontaneous CMN could be referred for neurodevelopmental evaluation in order to establish a more accurate diagnosis.

Hepatic dysfunction in Alström disease

Alström disease is a rare disorder; less than 20 cases have been reported. An 11-year-old girl is described with this condition. She has pigmentary retinopathy, sensory neural deafness, obesity, Type II diabetes mellitus, hyperlipidemia, and acanthosis nigricans. However, in addition she developed hepatic dysfunction, pathologically similar to chronic active hepatitis. This may be a further, previously undescribed systemic manifestation of Alström disease.

Rapid recovery from cortical visual impairment following correction of prolonged shunt malfunction in congenital hydrocephalus

Three children with congenital hydrocephalus are described in whom increased intracranial pressure was associated with severe, long-lasting cortical visual impairment. Following shunt revisions or reconstructive craniotomies, visual improvement began within hours. It is speculated that increased intracranial pressure can occasionally result in chronic hypoperfusion of the parietal-occipital lobes, either due to posterior cerebral artery compromise secondary to transtentorial pressure gradient or to direct compression of cerebral tissues.

Head shaking by visually impaired children: a voluntary neurovisual adaptation which can be confused with spasmus nutans

Rapid, horizontal, pendular head oscillations were observed in 18 visually impaired children with nystagmus during intense visual fixation, and the characteristics of this behaviour were analysed. Head tilting and eye deviations also occurred in 14 of the children. Their symptoms and signs resembled spasmus nutans. Head shaking appeared to be a voluntary, learned, neurovisual adaptation to improve visual acuity. Accurate simultaneous recordings of eye and head movements are required to understand the pathophysiological significance of these head oscillations.

Light-gazing by visually impaired children

This study assessed the prevalence and characteristics of light-gazing by all visually impaired children referred during a 2 1/2-year period. Light-gazing (compulsive staring into lights) is one of the many clinical signs of cortical visual impairment (CVI), and in the present study it occurred in 60 per cent of children with CVI. The authors believe that light-gazing by any child with ocular lesions indicates some degree of CNS involvement. Visually impaired children who flicker their fingers in front of their eyes against a light source demonstrate an extension of this compulsive behaviour. This and other studies suggest that blind mannerisms have specific neuropathological substrata and therefore are useful clinical signs.

Computed tomography of the brains of children with cortical visual impairment

Computed tomography (CT) of the brains of 70 children with permanent cortical visual impairment (CVI) and of 25 children who recovered from their cortical visual loss were analysed and the findings were correlated with clinical signs and symptoms. The 70 children with CVI were divided into groups depending on the known or suspected pathophysiology of CVI. Asphyxia caused permanent CVI in 34 children, of whom 16 were preterm, 17 were term and one lost vision later in life. Congenital brain malformations were the second largest group, followed by trauma, infections and shunt failure. 25 children recovered their visual acuities, but six of them were left with homonymous hemianopia. The results identified various clinical characteristics of the groups. CT scanning was helpful in understanding the pathophysiology of CVI, and provided useful information for the prognosis of visual recovery.

Delayed diagnosis of optic nerve glioma: a preventable cause of visual loss

Optic nerve glioma is a rare but important cause of visual impairment during childhood. The presenting symptoms and signs usually are visual, but are commonly misinterpreted. We report 18 children with visual loss secondary to optic nerve glioma. Thirteen of these patients presented with failing vision; only 3 had a correct initial diagnosis. The errors in diagnosis resulted in many years of treatment delay with consequent further visual impairment or no improvement in vision and a possible reduced efficacy of treatment. This delay may explain some of the controversy surrounding the role of radiotherapy in the management of these tumors. The diagnosis of optic nerve glioma must be considered in any child who presents with failing vision, optic atrophy, and/or nystagmus, in whom there is no demonstrable intraocular cause.

Neurological and developmental findings in children with cataracts

Ninety-seven children who were born between 1954 and 1986 and presented to the Visually Impaired Program of British Columbia's Children's Hospital, Vancouver, Canada, with a primary ophthalmologic diagnosis of cataracts, were assessed neurologically, ophthalmologically, audiologically, and developmentally. Causal factors included prenatal infection (35 cases), hereditary cataracts (22 cases), various syndromes and metabolic disorders (9 cases), trauma (1 case), and unknown (30 cases). Ninety children were diagnosed to have congenital cataracts while 7 acquired them. Findings indicated that prenatal infection continues to be a cause of infantile cataracts, despite rubella immunization; that prematurity is not, as has been stated in the past, a cause of infantile cataract; and that careful neurological, audiological, and developmental examination is vital in the assessment of likely causes of this condition.

Joubert's syndrome associated with congenital ocular fibrosis and histidinemia

We describe a 16-month-old girl with Joubert's syndrome (JS), congenital ocular fibrosis, and histidinemia. Abnormal respiration, ptosis, and minimal eye movements were observed in the neonatal period. Intraoperative examination of the eyes later demonstrated severely restricted eye movements and abnormal insertions and fibrosis of the extraocular muscles. Computed tomography of the head revealed absence of the corpus callosum and brain stem. Histidine levels were elevated in the blood, urine, and cerebrospinal fluid. The patient was ataxic and developmentally delayed. To our knowledge, the association of JS with congenital ocular fibrosis has not previously been described. This report indicates that jerky eye movements are not an invariable finding in JS.

Quantitative VEP analysis in children with cortical visual impairment

Children with cortical visual impairment (CVI) usually have a typical clinical presentation. However, in some cases, it may be useful to have confirmatory evidence based on objective electrophysiologic information. To achieve this, we examined some mathematically derived parameters constructed from 20 channel visual evoked potential (VEP). A group of 30 children diagnosed with CVI by clinical and CT findings was compared to a normal control group of 52 children. Each recorded VEP was mathematically transformed using Hjorth's source derivation, to reduce reference contamination and enhance local features. The area under the response curve, computed for each channel within a fixed time window, was used as a measure of the response activity at that channel. These areas were then used to construct several parameters ("R values") describing ratios of activities between different recording electrode areas. Some of these ratios provided good separation between patient and control groups, especially for children older than 5 years of age; in particular CVI patients were found to have a low occipital-to-parietal activity ratio. This finding, together with the observed age independence of the R values in the normal population, their ease of computation and possible physiological interpretability, suggest that R values could be used as confirmatory diagnostic measures.