Management of nystagmus in children: a review of the literature and current practice in UK specialist services

Nystagmus is an eye movement disorder characterised by abnormal, involuntary rhythmic oscillations of one or both eyes, initiated by a slow phase. It is not uncommon in the UK and regularly seen in paediatric ophthalmology and adult general/strabismus clinics. In some cases, it occurs in isolation, and in others, it occurs as part of a multisystem disorder, severe visual impairment or neurological disorder. Similarly, in some cases, visual acuity can be normal and in others can be severely degraded. Furthermore, the impact on vision goes well beyond static acuity alone, is rarely measured and may vary on a minute-to-minute, day-to-day or month-to-month basis. For these reasons, management of children with nystagmus in the UK is varied, and patients report hugely different experiences and investigations. In this review, we hope to shine a light on the current management of children with nystagmus across five specialist centres in the UK in order to present, for the first time, a consensus on investigation and clinical management.

An audit of the outcome of amblyopia treatment: a retrospective analysis of 322 children

BACKGROUND/AIMS

Little is known about the effectiveness of occlusion therapy in hospital settings. A retrospective analysis was conducted to assess modalities, outcome and hospital costs of children treated for amblyopia with patching in a UK clinic.

METHODS

Notes of 322 children with amblyopia discharged after occlusion treatment were selected consecutively and reviewed. Data collated included age at presentation, amblyopia type, visual acuity (VA; before/after occlusion and at discharge), number of prescribed hours of occlusion, duration of patching treatment, number of glasses prescribed and number of visits attended or failed to attend. Hospital treatment costs were estimated.

RESULTS

Mixed amblyopes were prescribed the longest amount of patching (mean 2815 h over 23 months) followed by strabismic (1984 h) and anisometropic (1238 h) amblyopes. 319 amblyopes received glasses and five atropine treatment. The percentage of patients reaching VA of 6/12 was best in the anisometropic and strabismic groups (>75%) and worse in mixed amblyopia (64%). Average hospital costs were estimated at pound1365.

CONCLUSION

Although the mean duration of treatment was long, involving many hospital visits, the visual outcome was variable, unsatisfactory (<6/9) and more expensive than necessary. As compliance has been identified as a major problem methods to improve amblyopia treatment are needed, possibly by using educational/motivational intervention.

Nystagmus characteristics in congenital stationary night blindness (CSNB)

AIM

To analyse nystagmus characteristics in patients with congenital stationary night blindness (CSNB) for differentiation from other forms of early childhood nystagmus.

METHODS

Horizontal and vertical eye movements of 10 patients (6-46 years, mean 17.1 years, median 12.5 years) with CSNB (eight with CSNB1, two with CSNB2) were recorded with the scleral magnetic search coil technique or by electro-oculography. Nystagmus characteristics such as the amplitude, frequency, conjugacy and intermittency were analysed.

RESULTS

All patients had continuous, pendular, oblique and mostly dysconjugate nystagmus of high frequency and low amplitude. In seven cases, a large horizontal or vertical jerk nystagmus with increasing, decreasing or constant velocity was superimposed. Jerk nystagmus was mostly intermittent and conjugate. Head nodding was found not to be compensatory.

CONCLUSIONS

Eye-movement recordings of CSNB patients disclosed specific nystagmus characteristics, such as an oblique direction, superimposed waveforms and dysconjugate eye movements. These features may help to distinct nystagmus in CSNB from other forms of early infancy nystagmus, such as congenital idiopathic nystagmus, latent nystagmus and spasmus nutans. We found nystagmus in CSNB to be similar to the nystagmus reported in blue-cone monochromatism and rod monochromatism, and in patients with a severe sensory defect. The nystagmus characteristics described should prompt electroretinographic investigation in cases of uncertain diagnosis.

Mutations in FRMD7, a newly identified member of the FERM family, cause X-linked idiopathic congenital nystagmus

Idiopathic congenital nystagmus is characterized by involuntary, periodic, predominantly horizontal oscillations of both eyes. We identified 22 mutations in FRMD7 in 26 families with X-linked idiopathic congenital nystagmus. Screening of 42 singleton cases of idiopathic congenital nystagmus (28 male, 14 females) yielded three mutations (7%). We found restricted expression of FRMD7 in human embryonic brain and developing neural retina, suggesting a specific role in the control of eye movement and gaze stability.

Why is compliance with occlusion therapy for amblyopia so hard? A qualitative study

OBJECTIVE

To explore parents' perceptions and experiences of occlusion (patching) therapy for treatment of amblyopia in children.

METHODS

Qualitative study involving semistructured interviews with 25 families of a child with amblyopia being treated at a specialist clinic. Interviews were tape recorded and transcribed verbatim. Data analysis was based on the constant comparative method, assisted by qualitative analysis software.

RESULTS

Parents of children prescribed patching treatment found themselves obliged to manage the treatment. This involved dilemmas and tensions, with many parents describing children's distress, particularly in the early stages of patching treatment. Parents were highly sensitive to the credibility of the treatment, but were sometimes confused by information given in the clinic or did not see clinic staff as authoritative. There was evidence that parents were likely to abandon or modify treatment if no improvement could be detected or if the child continued to suffer socially or educationally. Parents described a range of strategies for facilitating patching, including explanation; normalisation; rewards; customising the patch; establishing a routine; and enlisting the help of others. Whatever their practices in relation to patching, parents were keen to defend their behaviour as that of a "good parent".

CONCLUSIONS

Interventions that aim to improve compliance should take account of the difficulties and tensions experienced by parents, rather than simply treating non-compliance as resulting from information deficits. Practical support that builds on strategies described by parents is likely to be of benefit.

Survey of management of acquired nystagmus in the United Kingdom

PURPOSE

To determine the current management of acquired nystagmus by ophthalmologists and neurologists.

METHODS

Questionnaires were sent to ophthalmologists (850) and neurologists (434) in the United Kingdom. Estimated numbers of patients seen with acquired nystagmus, treatment options used, and the results of treatment of the patients were collected.

RESULTS

Response rate was 37% for ophthalmologists and 34% for neurologists. The most common causes of acquired nystagmus were estimated to be multiple sclerosis and stroke. 58% of ophthalmologists and 94.5% of neurologists reported seeing patients with nystagmus. The most commonly used medical treatment was gabapentin and baclofen. Other drugs used were clonazepam, carbamazepine, benzhexol, ondansetrone, buspirone, memantine, and botulinum toxin (n=3). Eleven ophthalmologists and 52 neurologists noted symptomatic improvement with medical treatment. Eleven ophthalmologists and 44 neurologists noted improvement in visual acuity (VA). Occurrence of side effects noted with baclofen and gabapentin treatments were similar.

CONCLUSION

A variety of drugs are used to treat acquired nystagmus in the UK. Baclofen and gabapentin are the drugs most commonly used and are reported to cause significant improvement in symptoms and VA. Better knowledge of the action of drugs in nystagmus is needed to establish guidelines and to give patients wider access to treatment.

The effects of gabapentin and memantine in acquired and congenital nystagmus: a retrospective study

BACKGROUND

Pharmacological treatment has been successful in some forms of acquired neurological nystagmus. However, drugs are not known to be effective in idiopathic infantile nystagmus or nystagmus associated with ocular diseases.

METHODS

The authors retrospectively analysed Snellen visual acuity (VA), subjective visual function, and eye movement recordings of 23 patients with nystagmus (13 secondary to multiple sclerosis, three associated with other neurological diseases, two idiopathic infantile, and five with associated ocular diseases) treated with gabapentin or memantine.

RESULTS

With gabapentin, 10 of 13 patients with nystagmus secondary to multiple sclerosis (MS) showed some improvement. Memantine improved the VA in all three patients with MS who did not improve on gabapentin. There was no change of nystagmus in other neurological disorders. Patients with congenital nystagmus showed reduction of nystagmus and their VA changes depended on the ocular pathology.

CONCLUSION

Gabapentin and memantine may be effective in acquired nystagmus secondary to MS. To the authors' knowledge this is the first series of patients showing that gabapentin is effective in improving nystagmus in congenital nystagmus/nystagmus associated with ocular pathology. Memantine may be useful as an alternative drug in treating patients with nystagmus.

Social and visual function in nystagmus

AIM

To investigate the influence of nystagmus on visual and social function and determine if parents are able to assess visual and social function in children with nystagmus.

METHOD

A postal questionnaire comprising 14 questions related to visual function (VF-14) and questions pertaining to social function were sent to all 1013 members of the Nystagmus Network-a UK based organisation for nystagmus sufferers and their families. Visual and social function scores were compared by regression analysis.

RESULTS

180 adult, 233 parent, and 124 child questionnaires were returned. Idiopathic nystagmus was the most common cause. In adults the mean VF-14 score indicated very low visual function, in the same range as patients assessed in low vision services. Children's visual function scored better than adults, between scores of patients with age related macular disease and corneal grafts. There was a strong correlation between perceived visual and social function for adults (p<0.001) and parental assessment of their children (p<0.001), but not between child self assessment of visual and social function. There was strong correlation between parental and child assessment of visual and social function (p<0.001, p<0.001)

CONCLUSION

Questionnaires indicated that nystagmus is associated with very low visual function. There is a strong correlation between visual and social impairment. The authors have shown for the first time in an ophthalmic disease that parents are able to estimate the impact of nystagmus on their child both in terms of visual and social functioning, although they underestimate the impact of nystagmus on emotional aspects of wellbeing.

Asymmetry of the Optokinetic Nystagmus in Lesion of the Central Nervous System

BACKGROUND

Unilateral lesions of the central nervous system (CNS) may be associated with a reduction of the optokinetic nystagmus (OKN) slow component in the direction of the lesion. The aim of our study was to assess the role played in these cases by the direct injury of the OKN pathways and/or by a possible associated visual field defect.

METHODS AND PATIENTS

Monocular OKN was elicited with black and white stripes moving temporally-to-nasally (TN) or nasally-to-temporally (NT) at velocities of 15, 30, 45 and 60 degrees /s. Patients with cortical or chiasmal lesions associated with visual field defects were investigated. OKN was considered asymmetrical if the gain difference between TN and NT stimulation was not within 2 standard deviations of an age-matched control group (n = 86).

RESULTS

We examined 12 patients with cortical lesions and 4 patients with chiasmal lesions. Asymmetric OKN gain was measured in 7 patients with cortical lesions associated with a visual field defect, and in 2 patients with chiasmal compression and bitemporal hemianopia. In 2 patients with isolated occipital lesions, OKN asymmetry was explained by the associated visual field defect.

CONCLUSION

The interpretation of OKN asymmetry in patients with CNS lesions should not only consider a direct lesion of the OKN pathways but also a sensory deficit due to a visual field defect.

Look and Stare Optokinetic Nystagmus in Healthy Subjects and in Patients with No Measurable Binocularity. A Prospective Study

BACKGROUND

The aim of our study was to assess the difference between look and stare optokinetic nystagmus (OKN) in healthy subjects and in patients with early onset strabismus and no measurable binocularity.

METHODS AND PATIENTS

OKN was elicited monocularly with black and white stripes moving horizontally or vertically at 15, 30, 45 and 60 degrees /s. Subjects were instructed either to follow individual stripes across the screen (look OKN) or to fixate stripes in the centre of the screen (stare OKN). We examined 20 healthy subjects (mean age 29 years; range 21 - 39), and 10 patients with no measurable binocularity (mean age 12.7 years; range 5 - 37). OKN gain was measured with photo-oculography.

RESULTS

In both groups and at stimulation with the higher velocities gains for look OKN were significantly better than for stare OKN, and gains with horizontal stimuli were significantly better than with vertical stimuli (p < 0.05). In the group with no measurable binocularity horizontal look and stare OKN answers were significantly better for temporal-to-nasal stimulation than for nasal-to-temporal stimulation (p < 0.05).

CONCLUSIONS

The performance of look or stare OKN influences the gain in healthy subjects and in patients with no measurable binocularity. Data about both modes of OKN stimulation are helpful to better interpret OKN responses especially in subjects with poor cooperation.

Serum uric acid levels in optic neuritis

Uric acid, an antioxidant, is reduced in multiple sclerosis (MS). Patients with gout have a reduced incidence of MS. Optic neuritis (ON), often the first manifestation of MS, is not known to be associated with reduced uric acid. Patients with recent onset of ON were investigated to determine whether uric acid levels were reduced at presentation. Twenty-one patients with ON were included, 17 females and 4 males. The mean (SD) serum uric acid in the ON female group was 184.4 ( +/-55.1) micromol/L (range, 116-309 micromol/L), whilst in the control group it was 235.2 (+/- 50.2) micromol/L (range, 172-381 micromol/L). The difference was statistically significant (chi2 = 8.93, P = 0.003). In the small male cohort, mean (SD) serum uric acid was 305 (+/- 52.1) micromol/L, whilst in the control group it was 328 (+/- 80.4) micromol/L. These differences were not statistically significant. Reduced antioxidant reserve is possibly an early pathogenic mechanism in inflammatory demyelination, and raises the possibility that low uric acid levels could be an indicator of disease activity. Since optic neuropathies of other causes were not investigated, future research needs to determine whether low uric acid represents a unique feature of optic neuritis or is seen in other optic neuropathies.

Age related change of optokinetic nystagmus in healthy subjects: a study from infancy to senescence

BACKGROUND

Optokinetic nystagmus (OKN) gain is asymmetrical between temporal to nasal (TN) and nasal to temporal (NT) stimulation in infancy and decreases at older ages. The age at which OKN gain becomes symmetrical and decreases is debated. The aim was to investigate OKN over the whole lifespan in a large sample of healthy subjects.

METHODS

In a prospective, cross sectional study OKN was tested monocularly using TN and NT small field stimulation. Stimulation velocity was 15 degrees /s and 30 degrees /s for children aged under 1 year (n = 97), and 15 degrees /s, 30 degrees /s, 45 degrees /s, and 60 degrees /s for older subjects (1-9 years, n = 66; 10-89 years, n = 86). Gain was measured using infrared oculography.

RESULTS

Significant OKN gain asymmetry in favour of TN versus NT stimulation was found during the first 5 months of life (p<0.05). Only at 11 months of age was OKN symmetrical in 100% of the subjects. The percentage of children with symmetrical OKN decreased with increasing stimulus velocity. OKN gain increased in the second and third years (p<0.05 for 15 degrees /s), remained stable until 50 years of age, and showed a small but significant decrease afterwards for the tested velocities (between 6% and 18%, p<0.05).

CONCLUSIONS

Infrared oculography is an accurate method to assess OKN, especially in children. Knowledge about change of OKN in healthy subjects could be helpful to interpret OKN in patients with abnormal binocular vision or lesions of the central nervous system.

Torsional optokinetic nystagmus: normal response characteristics

BACKGROUND/AIMS

Few studies have investigated normal response characteristics of torsional optokinetic nystagmus (tOKN). The authors have investigated the effect of stimulus velocity and central/peripheral stimulation on tOKN.

METHODS

Torsional OKN was elicited using a sinusoidal grating rotating at velocities of 3 degrees /s to 1000 degrees /s in clockwise and anticlockwise directions. To investigate the effect of central stimulation, stimulus size was varied from 2.86 degrees to 50.8 degrees. An artificial scotoma placed over a 50.8 degrees stimulus was varied from 2.86 degrees to 43.2 degrees to investigate peripheral stimulation. Eight subjects participated in each experiment and torsional eye movements were recorded using video-oculography. The mean slow phase velocity (MSPV) and gain were calculated.

RESULTS

The maximum gain occurred in response to 8 degrees /s stimulation. The MSPV increased up to a stimulus velocity of 200 degrees /s achieving a maximum of 3 degrees /s in both directions. MSPV was linearly correlated with the log of stimulus velocity. The smallest field size, rotating at 40 degrees /s, evoked 10% of the gain elicited by the largest display. When the most peripheral stimulus was used, the gain was maintained at 50% of the gain evoked when the full display was used.

CONCLUSIONS

A wide range of stimulus velocities can elicit tOKN and peripheral field stimulation contributes significantly to its response.

Role of the stimulus size in the generation of optokinetic nystagmus in normals and in patients with retinitis pigmentosa

BACKGROUND

To find out the smallest stimulus size still able to elicit optokinetic nystagmus (OKN). To discuss the differences in the generation of OKN between normals and patients with tunnel vision.

METHODS AND PATIENTS

OKN was elicited monocularly with black and white stripes of 2 degrees moving on a screen temporally-to-nasally or nasally-to-temporally at velocities of 15, 30, 45, and 60 degrees /s. In healthy subjects (n = 10) the size of the stimulus was gradually increased from minimal 8 degrees x 0.5 degrees to maximal 48 degrees x 10 degrees. OKN was elicited in retinitis pigmentosa (RP) patients (n = 2) with visual field reduced to the central 10 degrees. OKN gain was measured using infrared oculography. OKN response was considered as normal if it was within 2 standard deviations of the mean OKN of age-matched control groups (n = 29).

RESULTS

In healthy subjects the size of the stimulus necessary to elicit normal OKN gain was smaller at low velocity of 15 degrees /s (16 degrees x 1 degrees ) than at higher velocities of 30, 45, and 60 degrees /s (16 degrees - 24 degrees x 3 degrees ). Normal OKN gain was measured in the RP patients only at the low velocity of 15 degrees /s.

CONCLUSIONS

Small stimuli are sufficient in normals to elicit good OKN answers. Therefore, poor OKN gain in RP patients may not be explained by their tunnel vision only. We postulate that in these patients the reduction of gain is due to a multifactorial decrease of their visual perception related to disorders of the visual field, the visual acuity, and the contrast sensitivity.

Differences in the management of amblyopia between European countries

BACKGROUND

Amblyopia treatment is not standardised and differences between centres and countries have not been systematically investigated. This survey compares the different patterns of orthoptic treatment of amblyopia in the United Kingdom (UK) and three German speaking countries (GSC).

METHODS

Questionnaires were sent to orthoptists in the UK and the GSC asking for their preferred choices of treatment of amblyopia between the ages of 6 months to 10 years.

RESULTS

The following significant differences in management of amblyopia were found: (1) the number of hours of occlusion per week was higher in the GSC, p<0.0001, (2) orthoptists in the GSC treat amblyopia up to an older age. Orthoptists in the GSC and in the UK predicted similar treatment outcomes.

CONCLUSION

Orthoptists in the GSC usually treat patients more intensively and for longer, while the prediction of visual outcome does not differ significantly between countries. These results highlight the lack of standardisation in the treatment of the various types of amblyopia.

Possible role of corticosteroids in nervous system plasticity: improvement in amblyopia after optic neuritis in the fellow eye treated with steroids

OBJECTIVE

Amblyopia consists of reduced visual function in the absence of organic disease, caused by deficient visual stimulation, most commonly due to squint or refractive error. Amblyopia is thought to be reversible up until the age of approximately 8 years (critical period) and is usually treated with occlusion of the fellow eye. There is recent evidence for visual system plasticity extending beyond the critical period, supported by reports of improvement in visual acuity in the amblyopic eye after loss of vision in the contralateral eye. This suggests that the adult visual system exhibits sufficient plasticity to allow such improvement. We describe here improvement in visual acuity in three amblyopic patients after they received high-dose intravenous glucocorticoids for optic neuritis in the contralateral eye.

METHODS

Clinical and neurological evaluation added.

RESULTS

In all cases, the improvement was sustained, even after the recovery from the optic neuritis.

CONCLUSIONS

Because steroids affect neural plasticity, we hypothesize that they facilitate and enhance visual improvement in amblyopia, a quality that may be tested in future controlled trials.

Nystagmus

This article reviews the recent literature on nystagmus and various aspects of the pathophysiology of congenital idiopathic nystagmus and nystagmus treatment. One paper shows a new classification of latent/manifest latent nystagmus based on eye movement recordings. Nystagmus associated with complex syndromes and with onset in childhood represents the subject of several important recent articles, as does acquired nystagmus. Nystagmus as a manifestation of the toxicity of pharmacological agents is becoming increasingly recognized. Important contributions have been made to the genetics of various forms of nystagmus that represent an essential feature of retinal diseases, such as congenital stationary night blindness, albinism, blue cone monochromatism, and achromatopsia.

Optokinetic nystagmus in patients with central scotomas in age related macular degeneration

BACKGROUND

Reports on the impact of a loss in the central field of vision on optokinetic nystagmus (OKN) are varied. A study was therefore undertaken to reassess the role of the central retina in the generation of OKN in a large group of patients with age related macular degeneration.

METHODS

Four groups of 20 patients were examined: a control group without scotoma and three groups with absolute central scotomas measuring 1 degrees--10 degrees, 11 degrees--20 degrees, and 21 degrees--30 degrees. OKN was elicited with black and white stripes moving nasally to temporally or temporally to nasally on a screen subtending 54 degrees x 41 degrees at four velocities (15, 30, 45, and 60 degrees /s). OKN gain was measured using infrared oculography.

RESULTS

There was no significant difference in OKN gain between the control group and those with scotomas of 1 degrees--10 degrees and 11 degrees--20 degrees. A significant difference in OKN gain was found between the group with scotomas of 21 degrees--30 degrees and all other groups at stimulus velocities of 30, 45, and 60 degrees/s (p<0.05). OKN gain significantly diminished with increasing stimulus velocity (p<0.05). No statistically significant difference was found in OKN gain between stimuli moving temporally to nasally and nasally to temporally.

CONCLUSION

Abnormalities of OKN gain were noted only in patients with large scotomas. An intact macula is therefore not necessary for the generation of OKN.

Periodic alternating nystagmus in two children with a similar, unusual phenotype

The report describes two unrelated male children, aged 6 and 8 years, respectively, with congenital periodic alternating nystagmus, congenital strabismus, microcephaly with cortical and cerebellar hypoplasia, mental retardation, low stature, and bat ears. Karyotypes were normal. Neuropediatric and ophthalmologic examinations, radiologic imaging of the brain, and laboratory analyses were performed to exclude other causes of periodic alternating nystagmus, such as ataxia-telangiectasia, acquired disease of the caudal brainstem or the cerebellum, albinism, or loss of vision resulting from cataract or vitreous hemorrhage. The similar morphologic and clinical features of both patients raise the possibility that they have an identical syndrome.

Nystagmus

This report reviews the recent contributions to the field of pathologic nystagmus. The classification and nomenclature of nystagmus with onset in infancy is controversial. Because there are differences in nystagmus forms between patients with idiopathic nystagmus and those with nystagmus associated with afferent sensory defects, a distinction between these two nystagmus types is proposed. The distinctions are also helpful for clinicians, because these separate entities imply different diagnostic evaluations and visual prognosis. Recent studies have confirmed that periodic alternating nystagmus is detected more easily if the patient is evaluated for a longer time period and occurs more commonly than previously thought. Psychophysical investigations indicate that extraretinal signals play an important role in suppression of oscillopsia in infantile nystagmus. Genetic analysis recently has allowed identification of genes of X-linked idiopathic nystagmus and achromatopsia.

Arnold-Chiari malformation and nystagmus of skew

The Arnold-Chiari malfomation is typically associated with downbeat nystagmus. Eye movement recordings in two patients with Arnold-Chiari malfomation type 1 showed, in addition to downbeat and gaze evoked nystagmus, intermittent nystagmus of skew. To date this finding has not been reported in association with Arnold-Chiari malfomation. Nystagmus of skew should raise the suspicion of Arnold-Chiari malfomation and prompt sagittal head MRI examination.

Rod monochromatism and blue cone monochromatism: pupillary, accommodative and convergence reactions to darkness

PURPOSE

To elucidate the mechanism of paradoxical pupillary constriction to darkness (PPCD) and the clinical characteristics facilitating this phenomenon.

METHODS

Six rod monochromats, three blue cone monochromats, with three obligate BCM carriers, and ten age matched controls were studied. Pupillary responses, refractions and eye positions were measured with an infrared refractometer, with and without background room lighting while being simultaneously recorded on VHS (infrared) video tape from onset of darkness.

RESULTS

Only rod monochromats displayed typical paradoxical pupillary responses. Blue cone monochromats and obligate BCM carriers showed reduced pupillary contraction, compared to controls, but no paradoxical pupillary reaction. Changes neither in accommodation nor convergence were found during paradoxical pupillary constriction to darkness in our rod monochromats.

CONCLUSIONS

Paradoxical pupillary constrictions to darkness were seen in rod monochromats but were found not to be age or gender related. This constriction was accompanied neither by accommodation nor convergence changes. No significant differences in pupillary responses to darkness were observed in BCMs nor their carriers, although pupillary dilation to darkness seemed slightly impaired as compared to normals.

Nystagmus mimicking spasmus nutans as the presenting sign of Bardet-Biedl syndrome

PURPOSE

To investigate the nystagmus of twin brothers presenting with spasmus nutans later diagnosed as Bardet-Biedl syndrome.

METHODS

The twins presented at the age of 14 months with a presumed diagnosis of spasmus nutans. They were followed clinically and with quantitative electro-oculographic eye movement recordings until the age of 6 years.

RESULTS

Polydactyly, truncal obesity, mild delay in cognitive development, visual acuity of 20/100, attenuated retinal vessels and pale disks, and bilaterally almost extinguished scotopic and photopic electroretinograms were found in both brothers. They had fine, fast, pendular, disconjugate, intermittent, oblique nystagmus. No head nodding was observed.

CONCLUSION

As described in patients with other retinal diseases such as achromatopsia and congenital stationary night blindness, nystagmus of patients with Bardet-Biedl syndrome can mimic spasmus nutans.

The detection, prevention, and rehabilitation of amblyopia

Some of the past year's important papers on amblyopia are reviewed. Preschool screening for amblyopia is still controversial in regard to its effectiveness, the best age, and the most cost-effective method. In Sweden, where screening for amblyopia is well established, the prevalence of deep and moderate amblyopia has been markedly reduced. Several studies in the past year underscored the importance of anisometropia as a risk factor for amblyopia. Clear evidence for the importance of early treatment of unilateral cataracts in the first 8 weeks of life has been shown. Cytidine-5'-diphosphocholine administration has been shown to positively influence amblyopia and represents, in addition to levodopa, another promising pharmacologic treatment.

Visual development in preterm and full-term infants: a prospective masked study

PURPOSE

To compare development of visual acuity and binocular vision in preterm and full-term infants in a prospective study that used testers masked to subject's gestational age.

METHODS

Seventy-nine healthy full-term infants, mean gestational age 40 weeks, and 18 low-risk preterm infants, mean gestational age 33 weeks, were examined biweekly between the 44th and 54th weeks of postmenstrual age. Ocular alignment, convergence, fusion, grating acuity, and onset of optokinetic nystagmus (OKN) were assessed at each examination.

RESULTS

The mean postnatal ages of onset of ocular alignment, convergence, fusion, grating acuity to 1.6 cycles per degree, and OKN from temporal to nasal and nasal to temporal were, respectively, 5, 7, 7, 11, 6, and 9 weeks for the full-term and 12, 13, 14, 18, 13, and 16 weeks for the preterm infants. The mean postmenstrual ages of onset for the corresponding parameters were 46, 48, 48, 51, 46, and 50 weeks for full-term and 46, 47, 48, 52, 47, and 49 weeks for preterm infants. The onset of all parameters was earlier in full-term infants than in preterm infants of the same postnatal age (P < or = 0.0001). However, no differences were found when the parameters were compared at postmenstrual ages.

CONCLUSIONS

Additional visual experience of preterm infants does not influence development of visual acuity or binocular vision during the first months of life as measured from the time of conception.

[Eye movement abnormalities as a sign for the diagnosis in Niemann-Pick disease type C]

BACKGROUND

Eye movement abnormalities in familial mental retardation syndrome should lead to the suspicion of a storage disorder, including Niemann Pick disease type C, Gaucher's disease, abetalipoproteinemia and Wilson's disease. The eye movement abnormalities in our two patients were suggestive of Niemann Pick disease type C, characterized by initial loss of voluntary vertical eye movements and subsequent loss of horizontal eye movements, with preservation of the vestibulo-ocular response. The characteristics of eye movements in storage disorders are different. In Gaucher's disease a progressive horizontal gaze palsy, in abetalipoproteinemia a particular type of internuclear ophthalmoplegia with nystagmus of the adducting eye and in Wilson's disease slowing of saccades may be observed.

PATIENTS

We evaluated two mentally retarded sisters with unclear diagnosis at the age of 34 and 27 years. At the age of 24 and 21 a vertical gaze palsy led to the diagnosis of Parinaud syndrome.

RESULTS

At the time of our examination both sisters were unable to perform voluntary horizontal or vertical saccades or pursuit eye movements. The vestibulo-ocular reflex was present in all directions. Optokinetic nystagmus and convergence were absent. This clinical picture led us to a suspicion of Niemann-Pick disease type C, confirmed by the presence of sea-blue histiocytes in the bone marrow biopsy.

CONCLUSION

These cases demonstrate that the pattern of eye movement disorders in some syndromes associated with mental retardation can give important clues in the determination of the diagnosis.

Nystagmus

This article reviews some of the past year's important papers, with emphasis on early onset and acquired neurological nystagmus. Advances in understanding the mechanisms of suppression of oscillopsia, the evolution of nystagmus, and the treatment of periodic alternating nystagmus and of nystagmus in albinism have been made in early-onset nystagmus. Successful pharmacological treatment for acquired neurological nystagmus has been demonstrated with the gamma aminobutyric acid agonist gabapentin and with memantine, a glutamate antagonist.

The development of visual pursuit during the first months of life

BACKGROUND

There are few previous investigations of smooth pursuit in infants. The aim of our study was to quantify visual pursuit in infants between 1 day and 16 weeks of age.

METHODS

Eye movements of 97 healthy infants between 1 day and 16 weeks of age were recorded one to seven times with infrared photo-oculography. For stimulation of visual pursuit a square of 9.4 deg of visual angle with vertical gratings moved horizontally at a constant velocity of 7.5 deg/s.

RESULTS

In the first 2 weeks of life, segments of smooth pursuit were measured with a maximum velocity of 7.93 deg/s, with a maximum gain of 1.06 and a maximal duration of 3.16 s. In sequential recordings no significant increases of velocity, gain or duration were found. However, the total time the subjects followed the stimulus with smooth plus saccadic pursuit increased significantly with age (from a median of 39.0% to a median of 61.5% of examination time).

CONCLUSION

This study clearly demonstrates that smooth pursuit is already present in the first week of life. We found no significant increase in velocity, gain and duration of smooth pursuit segments in the first 16 weeks of life with our recording technique. However, the total pursuit time, reflecting attention, increased with age. The ocular machinery to drive pursuit appears to be in place at birth and seems not to be influenced by increased attention in the first months of life.

A case of Erdheim-Chester disease with orbital involvement

The Erdheim-Chester disease is a rare idiopathic, systemic, histiocytic disorder. To our knowledge, ocular involvement has been reported in only 16 cases. We describe a 55-year-old man who had symmetrical exophthalmos and several skin nodules on the arms and trunk. A magnetic resonance imaging scan confirmed the presence of bilateral, intraconal, retrobulbar tumors. An examination of the histopathologic features of orbital and skin biopsy specimens revealed xanthogranulomatous infiltrate with Touton giant cells. Further systemic investigations showed bone and retroperitoneal involvement. Three years later, multiple eyelid xanthelasmas developed in the patient. These findings are consistent with the diagnosis of the Erdheim-Chester disease. The patient's condition is stable under therapy with low-dose corticosteroids. His survival is longer than usually described in the literature.

Infantile nystagmus. Development documented by eye movement recordings

PURPOSE

To report on the development of infantile nystagmus in a patient's first year of life.

METHODS

A case study using consecutive photo-oculographic and electro-oculographic eye movement recordings in the subject ranging between 1 and 12 months of age.

RESULTS

Although no nystagmus was present at 5 weeks of age, square-wave jerks were recorded at 7 weeks, and a small pendular nystagmus was recorded at 8 weeks. At 10 weeks of age, evaluation revealed predominantly larger jerk-type nystagmus with increasing and decreasing exponential velocities of the slow phase. After 14 weeks of age, the nystagmus became smaller and was predominantly pendular. Between 7 and 12 months of age, binocular electro-oculography recordings showed conjugate pendular nystagmus typical of infantile nystagmus.

CONCLUSION

This is the first report documenting that, at least in some forms of infantile nystagmus, eye movement abnormalities are not present at birth. Before the development of the typical pattern of infantile nystagmus waveforms (that is, conjugated pendular or jerk-type nystagmus with increasing exponential velocity slow phases), saccadic abnormalities (square-wave jerks) and jerk-type nystagmus with increasing as well as decreasing velocities were observed.