Gaze evoked amaurosis in neurofibromatosis type II.
Explore the source record for details and available documents.
Blindness↗
Biomedical subjects
A Kriss
Publications and source records attributed to A Kriss.
Sequential pattern-onset, -reversal and -offset VEPs: comparison of effects of checksize.
The effects of checksize on individual components of half-field pattern-onset, -reversal and -offset VEPs were studied by presenting these three modes of stimulation sequentially in a single recording epoch so as to provide near identical recording and subject conditions. Components on the side of the scalp ipsilateral and contralateral to the stimulated half-field were measured so as to separate the macular and paramacular contributions. Ten checksizes were used (6'-110'). MANOVA showed a significant effect of checksize: small checksizes enhanced onset ipsilateral CII and contralateral P105, as well as all ipsilateral reversal components and offset N85 component, suggesting they are reflecting macular function. Onset CI, and contralateral reversal N105 and offset N115 components increased in amplitude with increasing checksize, suggesting they are predominantly of paramacular origin. The morphology of the contralateral onset P105 component was checksize dependent: small checks (< 35') produced a sharply defined positivity (macular sub-component), whereas larger checks produced a broadened/bifid waveform, suggesting the emergence of a later paramacular sub-component.
Adult↗
Vision in patients with leber congenital amaurosis.
Explore the source record for details and available documents.
Blindness↗
Interocular interaction assessed by VEPs to pattern-onset, -reversal, and -offset in normally sighted and amblyopic subjects.
The extent of interocular interaction reflected in sequentially averaged VEPs to checkerboard onset, reversal and offset stimulation was investigated to assess the relative efficacy of the three modes of pattern stimulation. Thirty-one controls and 18 amblyopic children were studied. Components on the side of the scalp ipsilateral and contralateral to the stimulated left half-field were measured for checksizes 12', 20', 50' and 80'. Binocular:monocular amplitude ratios for normals were compared with 'binocular:good eye' amplitude ratios for amblyopes. The reversal P100 ratio was found to differ significantly between normals and amblyopes for 12', 20' and 50' checks. Ipsilateral (CII) and contralateral (P105) onset components also differed significantly but for the smallest 12' checks only. In controls, onset components (P105 and CIII) and, reversal components (N80 and P100) showed significantly shorter binocular as compared with monocular latencies. These latency differences were not found in amblyopes. Our results show that interocular interaction in normals is best shown by potentials which predominantly reflect macular pathway activation, and are most conspicuous for reversal N80 and P100 components. Similarly, these components demonstrated the clearest differences when comparing binocular interaction effects between controls and amblyopic subjects.
Adolescent↗
Delayed visual maturation in infants: a disorder of figure-ground separation?
Delayed visual maturation (DVM) is characterised by visual unresponsiveness in early infancy, which subsequently improves spontaneously to normal levels. We studied the optokinetic response and recorded pattern reversal VEPs in six infants with DVM (aged 2-4 months) when they were at the stage of complete visual unresponsiveness. Although no saccades or visual tracking with the eyes or head could be elicited to visual objects, a normal full-field rapid buildup OKN response occurred when viewing biocularly or during monocular stimulation in the temporo-nasal direction of the viewing eye. Almost no monocular OKN could be elicited in the naso-temporal direction, which was significantly poorer than normal age-matched infants. No OKN quick phases were missed, and there were no other signs of "ocular motor apraxia." VEPs were normal in amplitude and latency for age. It appears, therefore, that infants with DVM are delayed in orienting to local regions of the visual field, but can respond to full-field motion. The presence of normal OKN quick-phases and slow-phases suggests normal brain stem function, and the presence of normal pattern VEPs suggests a normal retino-geniculo-striate pathway. These oculomotor and electrophysiological findings suggest delayed development of extra-striate cortical structures, possibly involving either an abnormality in figure-ground segregation or in attentional pathways.
Attention↗
The role of ERG/VEP and eye movement recordings in children with ocular motor apraxia.
Ocular motor apraxia (OMA) is characterised by an intermittent inability to initiate voluntary saccades, and a failure to produce optokinetic and vestibular quick phases. Some patients have no other abnormalities (idiopathic OMA), whereas in others it appears associated with a variety of neurological conditions which may affect the sensory visual pathway. Electroretinograms (ERGs), flash and pattern visual evoked potentials (VEPs) and eye movements were assessed in 53 children with OMA (age range 17 days to 14 years) to determine their efficacy in helping to distinguish between idiopathic and non-idiopathic cases. Seven patients (13.2%) had idiopathic OMA and the remaining 46 (86.8%) had other associated clinical conditions. All patients had episodes of absent quick phases ('lock up') during optokinetic nystagmus (OKN) and/or vestibular testing. Flash ERGs were abnormal in only 7 patients (13.2%); 6 had syndromes involving a pigmentary retinopathy (Joubert's, Bardet-Biedl, infantile Refsum's, Kearns-Sayre's), and the seventh had a cone dystrophy with vermis hypoplasia. VEPs were normal in all 7 patients with idiopathic OMA. Thirty-three (72%) patients with OMA in association with neurological conditions had abnormal VEPs and 13 had normal VEPs (28%). There was a significant positive correlation between VEP abnormality and poor OKN gain. VEP/ERG testing and eye movement studies are useful when OMA is suspected as they help in distinguishing isolated idiopathic cases from those with more widespread neurological abnormalities.
Adolescent↗
Severe microcornea with anterior segment malformation in a mother and her son.
A male infant with microcornea, anterior segment dysgenesis and congenital cataracts, but with a normal ocular posterior segment is reported. His mother also had extreme microcornea, no useful vision from birth, but had globes of grossly normal size.
Adult↗
Achiasmia in a case of midline craniofacial cleft with seesaw nystagmus.
Explore the source record for details and available documents.
Craniofacial Abnormalities↗
Visual acuity in unilateral cataract.
BACKGROUND: Patching the fellow eye in infancy is a well recognised therapy to encourage visual development in the lensectomised eye in cases of unilateral congenital cataract. The possibility of iatrogenic deficits of the fellow eye was investigated by comparing the vision of these patients with untreated unilateral patients and binocularly normal controls. METHODS: Sweep visual evoked potentials (VEPs) offer a rapid and objective method for estimating grating acuity. Sweep VEPs were used to estimate acuity in 12 children aged between 4 and 16 years who had had a congenital cataract removed in the first 13 weeks of life. The acuities of aphakic and fellow phakic eye were compared with the monocular acuities of similarly aged children who have good binocular vision, and with children with severe untreated uniocular visual impairment. Recognition linear acuities were measured with a linear Bailey-Lovie logMAR chart and compared with the sweep VEP estimates. RESULTS: A significant difference was found between Bailey-Lovie acuity of the fellow eye of the patient group and the right eye of binocular controls, and the good eye of uniocular impaired patients (one way ANOVA, p < 0.01). However, this was not evident for a similar comparison with sweep VEP estimates. There was no significant difference between the right and left eye acuities in binocular controls measured by the two techniques (paired t test). CONCLUSION: A loss of recognition acuity in the fellow phakic eye of patients treated for unilateral congenital cataract has been demonstrated with a logMAR chart. This loss was not apparent in children who have severe untreated uniocular visual impairment and may therefore be an iatrogenic effect of occlusion. An acuity loss was not apparent in the patient group using the sweep VEP method. Sweep VEP techniques have a place for objectively studying acuity in infants and in those whose communication difficulties preclude other forms of behavioural test. The mean sweep VEP acuity for the control groups is 20 cpd--that is, about 6/9. When acuities higher than this are under investigation--for example, in older children, slower transient VEP recording may be more appropriate, because higher spatial frequency patterns are not as visible at higher temporal rates (for example, 8 Hz used in sweep VEP recordings).
Adolescent↗
The optokinetic response differences between congenital profound and nonprofound unilateral visual deprivation.
BACKGROUND: The occurrence of monocular naso-to-temporal optokinetic nystagmus (OKN) asymmetry, as a reflection of the immature oculomotor system in infants, and its persistence with early onset monocular visual deprivation, is well known. This asymmetry has been linked with poor binocular function and attributed to disruption of the development of binocular cortical projections to the pretectum. Optokinetic nystagmus symmetry in patients with congenital uniocular total pattern vision deprivation has not been fully investigated. METHODS: The authors compared the optokinetic responses in six children with "profound" uniocular visual deprivation, who were born with untreated conditions (microphthalmos and persistent hyperplastic primary vitreous), with ten aphakic children treated early for congenital unilateral cataracts (nonprofound unilateral visual deprivation). Eye movements were recorded using dc-electro-oculography, and OKN was elicited using a full-field patterned curtain. Flash and pattern visual-evoked responses were also measured in each subject. RESULTS: Latent nystagmus was present in six children in the nonprofound group, whereas none was detected in the profound group. All children in the nonprofound group showed statistically significant monocular naso-to-temporal asymmetry for either eye. Subjects in the profound group had symmetric OKN. CONCLUSIONS: The authors conclude that unequal input from the two eyes and interocular rivalry lead to OKN asymmetry. Their results suggest that if vision from one eye is so negligible that it does not compete with the neuroanatomic connections of the fellow eye, then the input from this eye remains undisturbed, and OKN remains symmetric.
Adolescent↗
Modulation of amblyopia therapy following early surgery for unilateral congenital cataracts.
BACKGROUND: Stimulus deprivation amblyopia is the principal cause of visual impairment in infants with unilateral congenital cataract. Even if lensectomy is undertaken at an early age, intensive postoperative occlusion of the phakic eye is essential for the development of useful vision in the aphakic eye. Despite this, the optimum method of regulating occlusion therapy is uncertain. METHODS: Interocular acuity differences identified using clinical preferential looking techniques (Keeler cards) were used to regulate target levels of phakic eye occlusion in a prospective evaluation of 10 systemically, metabolically, and neurologically normal infants in whom dense unilateral cataract was diagnosed before 8 weeks of age, and operated upon by 10 weeks. Actual occlusion levels were recorded each day by parents in a diary. The development of preferential looking acuity in the phakic and aphakic eye were compared with prediction intervals derived from observations on 43 normal children. RESULTS: Aphakic eye preferential looking acuities were within the normal range at last review in all but one infant. Interocular acuity differences were < or = 0.5 octave in all children older than 1 year of age at last review, and > or = 1 octave in three of four children less than 1 year old at last review (Fisher exact p = 0.033). Phakic eye acuities were within the normal range in all infants at all visits. CONCLUSION: Within the first 2 years of life, normal preferential looking acuity may be achieved in both eyes of infants undergoing early surgery for unilateral congenital cataract if occlusion therapy is modulated according to interocular acuity differences quantified by clinical preferential looking techniques.
Amblyopia↗
Visual evoked potentials in phenylketonuria: association with brain MRI, dietary state, and IQ.
At separate institutions, pattern reversal visual evoked potentials (VEPs) were recorded in children and older patients with phenylketonuria and compared with MRI of the brain. In nine patients aged less than 14 years, who were still on a diet low in phenylalanine, VEPs were clearly abnormal in only one and the abnormalities seen on MRI were mild. In 27 patients aged 14-31 years VEPs were abnormal in more than 80%, with significant reduction of amplitude and prolongation of latency despite the general absence of visual symptoms and abnormalities on routine neuro-ophthalmological examination. Among the older patients there was no significant correlation between VEP measures and plasma phenylalanine or tyrosine concentrations; neither was the incidence of VEP abnormalities dependent on whether or not the patients were still on a low phenylalanine diet. Some VEP amplitude measures were inversely correlated with the MRI lesion score, perhaps reflecting the severity of white matter abnormalities in the parieto-occipital region. In the older patients the amplitude of VEPs to stimulation of the central 8 degrees of the visual field was significantly correlated with IQ. The study confirms the high incidence of subclinical visual pathway involvement in older children and adults with phenylketonuria, and suggests the possibility of a link between the abnormal appearance of subcortical white matter on MRI and a physiological index of function of the CNS. As there was no evidence of general intellectual decline, it is suggested that the correlation between central field VEP amplitude and IQ may reflect abnormal development during infancy. Abnormalities on MRI, on the other hand, seem to be more closely related to current dietary state and phenylalanine concentration.
Adolescent↗
Skin ERGs: their effectiveness in paediatric visual assessment, confounding factors, and comparison with ERGs recorded using various types of corneal electrode.
Comparison of scotopic and photopic ERGs recorded using a variety of ERG electrodes show that contact lens electrodes produce the largest ERGs, and these are about 30-50% larger compared with those recorded with foil or thread electrodes, which contact a smaller part of the cornea. Flash ERGs recorded from infra-orbital skin electrodes are about one eighth the size of those recorded with contact lens electrodes, and around one quarter the size of those recorded with foil or fibre corneal electrodes. Reliable ERGs can be obtained in young children from infra-orbital electrodes sited centrally, within 1 cm of the rim of the eyelid, when signal averaging is used. Stimulation under fully darkened laboratory conditions with red and dim blue flashes permit assessment of cone and rod function, respectively. Factors such the recording electrode position, electrode derivation, upward rotation of the eye, eyelid closure and markedly constricted pupils can degrade the skin ERG. There are strong diagnostic advantages in recording the VEP concurrently with the skin ERG, particularly in young children. Examples of recordings in Leber's amaurosis, delayed visual maturation, albinism, optic nerve hypoplasia, achromatopsia add X-linked congenital stationary nightblindness are shown to demonstrate how ERG/VEP recordings can help in distinguishing between these conditions.
Child↗
An electrophysiological study on children and young adults with Alport's syndrome.
Alport's syndrome is characterised by progressive haematuric nephritis and high tone sensorineural hearing loss. Ocular signs are variable, the most consistent findings being anterior lenticonus and retinal flecks in the macula and mid peripheral areas. Previous electrophysiological studies on patients with Alport's syndrome have mostly been on adult patients undergoing haemodialysis, or after renal transplantation. A group of young patients with Alport's syndrome were studied to assess if early electrophysiological changes were detectable. A total of 20 patients (15 males and five females) between the ages of 3.5 and 22 years (mean 12.7 (years) were examined and compared with control subjects. Visual evoked potentials and electroretinograms were obtained following flash and pattern reversal stimulation. Electro-oculograms were also recorded. No significant electrophysiological changes were found in any of the 20 patients, including four who had visible fundus changes.
Adolescent↗
Concordance and recessive inheritance of Leber congenital amaurosis.
Pedigrees were obtained on 43 patients with confirmed Leber congenital amaurosis, a rare form of blindness caused by congenital dysfunction of the retina. All of the pedigrees were consistent with autosomal recessive inheritance and the segregation frequency using classical segregation analysis was 0.24 +/- 0.07. Six of the 7 affected sib pairs were concordant in regards to systemic abnormalities. Despite previous reports that Leber congenital amaurosis can be inherited either as an autosomal dominant or recessive condition, our findings support only an autosomal recessive inheritance of this disorder.
Adolescent↗
A comparison of flash electroretinograms recorded from Burian Allen, JET, C-glide, gold foil, DTL and skin electrodes.
Single flash scotopic and photopic electroretinograms (ERGs) were recorded from the same subjects using six types of corneal electrode, in order to assess their relative effectiveness. In addition, the ERG from a lower eyelid skin electrode was recorded to give an indication of the degree of attenuation to be expected from a skin electrode. On average, the scotopic ERG recorded from the Burian Allen electrode measured 471 microV (100%), and relative to this the b-waves recorded using other electrodes were as follows: JET (89%), C-glide (77%), gold foil (56%), DTL (46%) and skin (12%). Under photopic conditions the order was the same and the interelectrode proportions similar. The b-wave amplitude recorded using the Burian Allen electrode was 125 microV (100%), and with other electrodes was as follows: JET (93%), C-glide (78%), gold foil (60%), DTL (60%) and skin (14%).
Adult↗
Eye movement and electrophysiological findings in an infant with hemispheric pathology.
A visually unresponsive infant had a normal ophthalmological examination. Eye-movement studies using electro-oculography revealed asymmetrical binocular smooth pursuit, binocular optokinetic nystagmus and vestibulo-ocular reflex. Electrophysiological testing showed markedly asymmetrical occipital flash and pattern visual evoked potentials. Both investigations suggested a posterior right-hemispheric problem, which was confirmed with cranial ultrasound. This case study illustrates the usefulness of non-invasive techniques in neuro-ophthalmological investigations of young children.
Brain Diseases↗
Congenital third nerve palsy associated with mid-trimester amniocentesis.
Explore the source record for details and available documents.
Amniocentesis↗