Hereditary nystagmus in early childhood

Monocular and Binocular Temporal Visual Perception of Infantile Nystagmus

Contrast sensitivity is mostly used as a tool for testing aspects of visual functions. Infantile nystagmus is a pathological phenomenon that affects the spatial-temporal visual functions due to spontaneous oscillating movements of the eyes. We examined the spatial-temporal aspects of nystagmus perception, aiming to investigate the mechanisms underlying the deterioration of their visual performance. We tested the monocular and binocular contrast sensitivity of nystagmus and normally sighted subjects by measuring contrast detection of a Gabor target with spatial frequencies slightly above the cutoff threshold of each subject (nystagmus ~3; controls = 9cpd; presentation times 60–480 ms). The dominant eye of nystagmus revealed large differences over the non-dominant eye, highlighting the superiority of the dominant over the non-dominant eye in nystagmus. In addition, binocular summation mechanism was impaired in majority of the nystagmus subjects. Furthermore, these differences are not attributed to differences in visual acuity. Moreover, the visual performance in nystagmus continue to improve for longer presentation time compared with controls and was longer in the poor eye. Since the results are not due to differences in eye movements and strabismus, we suggest that the differences are due to developmental impairment in the visual system during the critical period.

Assisting people with Nystagmus through image stabilization: Using an ARX model to overcome processing delays

Pathological Nystagmus is characterized by an unintended and involuntary eye-movement, which tends to impact on visual acuity. Today only view therapies (for instance medication or surgeries) to treat nystagmus are at hand and the existing therapies only show partial improvement. Only general Assistive Technology (AT) solutions like glasses, screen magnifiers, speech output, display adaptation and concepts holders are at hand to support daily living. More specific ATs to reduce the impact of nystagmus are missing. This paper presents conceptual research and feasibility studies with the attempt to reduce the impact of nystagmus by stabilizing the image on the retina (digital Retinal Image Stabilization) by moving the digital image synchronal with the unintended eye movement using gaze contingent display technology. Further an identification and validation process using recorded eye-movements is presented since the synchronization approach relies on predicting eye-movements to reduce the impact of delays due to processing time.

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.

A gene for X-linked idiopathic congenital nystagmus (NYS1) maps to chromosome Xp11.4-p11.3

Congenital nystagmus (CN) is a common oculomotor disorder (frequency of 1/1,500 live births) characterized by bilateral uncontrollable ocular oscillations, with onset typically at birth or within the first few months of life. This condition is regarded as idiopathic, after exclusion of nervous and ocular diseases. X-linked, autosomal dominant, and autosomal recessive modes of inheritance have been reported, but X-linked inheritance is probably the most common. In this article, we report the mapping of a gene for X-linked dominant CN (NYS1) to the short arm of chromosome X, by showing close linkage of NYS1 to polymorphic markers on chromosome Xp11.4-p11.3 (maximum LOD score of 3.20, over locus DXS993). Because no candidate gene, by virtue of its function, has been found in this region of chromosome Xp, further studies are required, to reduce the genetic interval encompassing the NYS1 gene. It is hoped that the complete gene characterization will address the complex pathophysiology of CN.

Value of the ERG in congenital nystagmus

A group of 64 children with poor vision and early onset nystagmus were investigated retrospectively by the electroretinogram (ERG). Fifty-eight of these children also underwent analysis of the visual evoked potential (VEP), and 40 underwent colour vision analysis. Seventeen children were found to have complete congenital achromatopsia (rod monochromatism), being identified by their total colour blindness, reduced visual acuity, and reduced or absent photopic and flicker (30 Hz) ERGs. Two children with incomplete X-linked congenital achromatopsia were also found. This study identified the need to investigate children with nystagmus by means of the ERG and suggested that the ERG was useful where the diagnosis was uncertain, particularly at early school age. The incidence of congenital achromatopsia in a group of otherwise undiagnosed children with early onset nystagmus was high (29%), with 40% being classified as having congenital idiopathic nystagmus.

Fast-phase instabilities in normally sighted relatives of congenital nystagmus patients--autosomal dominant and x-chromosome recessive modes of inheritance

Verification of inheritance in congenital nystagmus (CN) is only possible through the identification of more than one affected member in a family since in a single case there are no accurate clinical differentiations between "spontaneous" and inherited CN. We performed electronystagmographic examinations (ENG) to search for abnormal involuntary eye movements as a sign of heredity in seemingly unaffected members of CN families. ENG registrations were performed under three test conditions: (1) with the subject fixating a target, (2) with the room lights off and (3) with closed eyes. Fifty normally sighted individuals (group (a] underwent the test procedure to provide a baseline of normality. Five CN families (three dominant, two sex-linked recessive) were tested as group (b). The eye movement recordings were analysed in terms of nystagmus intensity (amplitude x frequency of the involuntary saccade). In every one of the five families, abnormalities in seemingly non-affected members could be demonstrated: in four families, fast-phase instabilities, in the fifth family a true (CN) (slow-phase instability). All certain gene carriers were diagnosed correctly by the ENG. These findings indicate a method for detecting slightly affected members in dominant pedigrees and female gene carriers in sex-linked mode of transmission.

Congenital nystagmus: a clinical perspective in infancy

In a series of 152 patients with congenital nystagmus, 119 had sensory nystagmus while 13 had pure motor nystagmus. The most common diagnoses in the sensory group were optic nerve hypoplasia. Leber's amaurosis, and oculocutaneous or ocular albinism. Eight of the patients in the motor group had a similarly afflicted parent. Diagnostic features in infants and preverbal children were reviewed. This study supports the continued clinical classification of congenital nystagmus into sensory and motor subtypes.

Nystagmus and other abnormal ocular movements in children

This article at first reviews the normal maturation of the ocular system in infants and then progresses to a discussion of the ways that this system can vary and produce nystagmus and nystagmus-like disorders.

Vertical nystagmus in infants with congenital ocular abnormalities

In a series of 131 patients with congenital nystagmus, nine patients initially presented with vertical nystagmus associated with congenital ocular abnormalities. Four patients initially presented with upbeating nystagmus. All four of these patients had Leber's amaurosis. The upbeating nystagmus became horizontally directed in three of the four patients prior to one year of age. The other patient is now eight years old and upbeating nystagmus persists. CT scanning reveals cerebellar vermis hypoplasia in this patient. Five patients with albinism in this series presented initially with seesaw nystagmus. In two cases this resolved to one year of age, but in the other three cases, it is still intermittently seen in children ranging in age from two and a half to five years old. Vertically directed nystagmus may be associated with some ocular abnormalities in infancy and is not always a sign of isolated neurologic disorders.

Essential tremor, nystagmus and duodenal ulceration. A "new" dominantly inherited condition

The familial occurrence of essential tremor combined with (congenital) nystagmus, duodenal ulceration and a narcolepsy-like sleep disturbance caused by an autosomal dominant gene with high penetrance and fairly uniform expressivity is reported in a family of Swedish-Finnish ancestry. Twelve of 17 affected family members had essential tremor which began between 30-40 years of age and which could be controlled temporarily by alcohol; this resulted in alcoholism in several affected individuals. The most severly affected persons showed cerebellar signs which may reflect a possible pathogenetic relationship of the syndrome to the genetic cerebellar atrophies. Nystagmus, observed in 12 of 17 affected family members (eight of whom were also affected with tremor) usually was congenital and accompanied by refractive errors. Duodenal ulcers occurred almost exclusively in individuals with the neurological syndrome, and preceded its onset in some cases. The ulcer disease therefore seems to be a component manifestation of the syndrome and is interpreted as a pleiotropic effect of the gene which also causes the nystagmus, tremor and sleep disturbance.