Interrelations between measures of visual acuity and parameters of eye movement in congenital nystagmus

The authors assessed relationships between visual acuity and the amplitude, frequency, intensity, and duration of foveation periods in a retrospective study of 32 patients. Twenty-four patients had congenital idiopathic nystagmus, and eight patients had nystagmus and albinism. Visual acuity was determined for Landolt ring optotypes and, as the extrapolated high-frequency cutoff of the contrast sensitivity function, for horizontal and vertical gratings. No significant correlation existed between acuity and any measured eye movement parameter; however, optotype acuity was related to the magnitude of astigmatic refractive correction, both in patients with idiopathic nystagmus and in albinos. In a subgroup of patients with idiopathic nystagmus whose astigmatic refractive error was -1.50 D or less, nystagmus intensity (amplitude x frequency) correlated significantly with acuity for optotypes (r = 0.71), but not for gratings. Although resolution for vertical gratings was correlated with astigmatic refractive correction, the ratio of resolution for gratings parallel and orthogonal to the meridian of nystagmus was not. Thus, the belief that poorer acuity in patients with substantial astigmatism is attributable to an optically induced meridional amblyopia is supported only partly by these results. The authors concluded that among patients with congenital nystagmus, the influence of eye motion on visual acuity is not readily predicted either from the parameters of nystagmus that they evaluated or from the comparison of resolution for horizontal and vertical gratings.     

Motor and sensory characteristics of infantile nystagmus

BACKGROUND/AIMS: Past studies have explored some of the associations between particular motor and sensory characteristics and specific categories of non-neurological infantile nystagmus. The purpose of this case study is to extend this body of work significantly by describing the trends and associations found in a database of 224 subjects who have undergone extensive clinical and psychophysical evaluations. METHODS: The records of 224 subjects with infantile nystagmus were examined, where 62% were idiopaths, 28% albinos, and 10% exhibited ocular anomalies. Recorded variables included age, mode of inheritance, birth history, nystagmus presentation, direction of the nystagmus, waveform types, spatial and temporal null zones, head postures and nodding, convergence, foveation, ocular alignment, refractive error, visual acuity, stereoacuity, and oscillopsia. RESULTS: The age distribution of the 224 patients was between 1 month and 71 years, with the mean age and mode being 23 (SD 16) years and 16-20 years respectively. By far the most common pattern of inheritance was found to be autosomal dominant (n = 40), with the nystagmus being observed by the age of 6 months in 87% of the sample (n = 128). 139 (62%) of the 224 subjects were classified as idiopaths, 63 (28%) as albinos, and 22 (10%) exhibited ocular anomalies. Conjugate uniplanar horizontal oscillations were found in 174 (77.7%) of the sample. 32 (14.3%) had a torsional component to their nystagmus. 182 (81.2%) were classed as congenital nystagmus (CN), 32 (14.3%) as manifest latent nystagmus (MLN), and 10 (4.5%) as a CN/MLN hybrid. Neither CN nor MLN waveforms were related to any of the three subject groups (idiopaths, albinos, and ocular anomalies) MLN was found in idiopaths and albinos, but most frequently in the ocular anomaly group. The most common oscillation was a horizontal jerk with extended foveation (n = 49; 27%). The amplitudes and frequencies of the nystagmus ranged between 0.3-15.7 degrees and 0.5-8 Hz, respectively. Periodic alternating nystagmus is commonly found in albinos. Albino subjects did not show a statistically significantly higher nystagmus intensity when compared with the idiopaths (p>0.01). 105 of 143 subjects (73%) had spatial nulls within plus or minus 10 degrees of the primary position although 98 subjects (69%) employed a compensatory head posture. Subjects with spatial null zones at or beyond plus or minus 20 degrees always adopted constant head postures. Head nodding was found in 38 subjects (27% of the sample). Horizontal tropias were very common (133 out of 213; 62.4%) and all but one of the 32 subjects with MLN exhibited a squint. Adult visual acuity is strongly related to the duration and accuracy of the foveation period. Visual acuity and stereoacuity were significantly better (p<0.01) in the idiopaths compared to the albino and ocular anomaly groups. 66 subjects out of a sample of 168 (39%) indicated that they had experienced oscillopsia at some time. CONCLUSIONS: There are strong ocular motor and sensory patterns and associations that can help define an infantile nystagmus. These include the nystagmus being bilateral, conjugate, horizontal uniplanar, and having an accelerating slow phase (that is, CN). Decelerating slow phases (that is, MLN) are frequently associated with strabismus and early form deprivation. Waveform shape (CN or MLN) is not pathognomonic of any of the three subject groups (idiopaths, albinos, or ocular anomalies). There is no one single stand alone ocular motor characteristic that can differentiate a benign form of infantile nystagmus (CN, MLN) from a neurological one. Rather, the clinician must consider a host of clinical features.     

102例眼球震颤儿童屈光状态分析

目的对儿童眼球震颤患者视功能、屈光状态分布进行分析,探讨儿童眼球震颤的屈光矫正时机与方式,从而促进患儿的视觉发育,提高视功能。方法回顾性病例研究。收集2002年1月至2013年2月在北京儿童医院就诊的102例眼球震颤患儿的视力、双眼视功能、屈光状态、眼球震颤相关检查资料,将患儿分为3组：特发性组81例,白化病组10例,其他原因组11例。对患儿等效球镜度、散光的类型以及散光度进行分析。结果眼球震颤的患儿平均裸眼视力为4．20±0．34,最佳矫正视力为4．45±0．27,最佳矫正视力大多在4．3至4．7之间。特发性组等效球镜度为（一0．25±3．36）D,白化病组为（＋0．24±3．25）D,其他原因组为（＋1．03±3．12）D。白化病组患儿主要表现为远视性屈光不正。眼球震颤患儿有着较大比例的散光．其中特发性眼球震颤组比例为86％．白化病及其他类型眼球震颤患儿为100％。其中顺规散光是其主要散光形式,顺规散光比例分别为55％、70％、64％。结论眼球震颤患儿常伴发屈光不正,应早期通过屈光矫正进行干预,促进视觉发育,提高视功能。     

Emmetropisation and the aetiology of refractive errors

The distribution of human refractive errors displays features that are not commonly seen in other biological variables. Compared with the more typical Gaussian distribution, adult refraction within a population typically has a negative skew and increased kurtosis (ie is leptokurtotic). This distribution arises from two apparently conflicting tendencies, first, the existence of a mechanism to control eye growth during infancy so as to bring refraction towards emmetropia/low hyperopia (ie emmetropisation) and second, the tendency of many human populations to develop myopia during later childhood and into adulthood. The distribution of refraction therefore changes significantly with age. Analysis of the processes involved in shaping refractive development allows for the creation of a life course model of refractive development. Monte Carlo simulations based on such a model can recreate the variation of refractive distributions seen from birth to adulthood and the impact of increasing myopia prevalence on refractive error distributions in Asia.     

Visual and perceptual consequences of congenital nystagmus

One way to assess the influence of retinal image motion on visual functioning in congenital nystagmus (CN) is to examine the effects of comparable image motion in observers with normal vision. A second approach is to evaluate visual functioning in subjects with CN when the retinal image motion is reduced. Using these approaches, we determined that spatial contrast sensitivity and visual acuity are not limited by the parameters of retinal image motion in some subjects with CN, but rather by a form of amblyopia. Clinical evidence from patients with bilateral refractive amblyopia suggests that a gradual improvement of visual acuity may be possible in persons with CN, if the optimal refractive correction is worn and parameters of the retinal image motion undergo long-term amelioration.     

Visual and Perceptual Consequences of Congenital Nystagmus

One way to assess the influence of retinal image motion on visual functioning in congenital nystagmus (CN) is to examine the effects of comparable image motion in observers with normal vision. A second approach is to evaluate visual functioning in subjects with CN when the retinal image motion is reduced. Using these approaches, we determined that spatial contrast sensitivity and visual acuity are not limited by the parameters of retinal image motion in some subjects with CN, but rather by a form of amblyopia. Clinical evidence from patients with bilateral refractive amblyopia suggests that a gradual improvement of visual acuity may be possible in persons with CN, if the optimal refractive correction is worn and parameters of the retinal image motion undergo long-term amelioration.     

先天性眼球震颤的临床特征

背景 先天性眼球震颤是严重影响患者视觉功能的眼科疾病,但目前对其临床特征完整描述的相关报道尚少见. 目的 分析先天性眼球震颤的临床特征. 方法 采用回顾性病例分析的方法,对2005年1月至2011年8月在河南省眼科研究所就诊的先天性眼球震颤患者376例的临床资料进行归纳分析,包括患者家系的系谱分析、眼球震颤类型观察、斜视度测定、视力检查、检影验光、立体视觉测定和对患者有无震动幻觉的调查.结果 本组患者就诊的年龄分布以＞5～ 10岁及＞15～20岁者最多,分别占24.73％和24.20％.本组患者中知觉缺陷型眼球震颤172例,运动缺陷型眼球震颤204例.先天性眼球震颤患者中最常见的遗传方式为常染色体显性遗传;水平眼球震颤为最常见的眼球震颤类型,占73.94％,其次为垂直眼球震颤,占10.11％.本组先天性眼球震颤患者中斜视的患病率为66.36％,知觉缺陷型患者与运动缺陷型患者间斜视的患病率差异无统计学意义(x2=3.048,P=0.081).先天性眼球震颤患者的双眼最佳矫正远视力均较差,知觉缺陷型患者双眼最佳矫正远视力明显低于先天性特发性患者(0.27±0.11 vs 0.50±0.13),差异有统计学意义(t=16.495,P=0.000).先天性眼球震颤患者屈光不正的患病率为77.62％,知觉缺陷型患者与运动缺陷型患者间屈光不正患病率的差异无统计学意义(x2=1.337,P=0.248);散光患病率为75.17％,显著高于近视和远视的患病率.65.18％的先天性眼球震颤患者无立体视觉或立体视觉值在3000”以上,运动缺陷型患者有立体视觉者明显多于知觉缺陷型患者,差异有统计学意义(x2=7.058,P=0.008).313例5岁以上的患者中36例有震动幻觉. 结论 先天性眼球震颤患者最常见的遗传方式为常染色体显性遗传;水平眼球震颤为其最常见的震颤类型;眼球震颤患者的斜视患病率高,视力和立体视觉较差,特别是知觉缺陷型患者;少数先天性眼球震颤患者有震动幻觉.     

X-linked infantile periodic alternating nystagmus

OBJECTIVE: To describe the clinical and electrophysiological characterization of four family members from three generations who have X-linked infantile periodic alternating nystagmus (XIPAN). METHODS: Complete clinical ophthalmological evaluation, pedigree analysis, electroretinograms (ERG), eye movement recordings (EMR), color vision, and fundus photography were performed on all subjects. RESULTS: Three males in two generations and one female were examined. Clinical examinations showed a jerk/pendular nystagmus with a latent component, strabismus, and a significant refractive error in the three affected males, while the female had only myopic astigmatism. ERG, color contrast, and fundus examinations were normal in all four family members. All four family members showed EMR abnormalities with infantile jerk/dual jerk and pendular nystagmus waveforms. The female had nystagmus present on EMR only and all patients showed (a)periodicity to their nystagmus. CONCLUSIONS: In this family with no other congenital visual sensory system disease, affected males had obvious periodic alternating nystagmus, strabismus, and refractive errors, while the female had clinically "silent" periodic nystagmus that is probably a marker for the carrier state.     

Stereothresholds in persons wtih congenital nystagmus and in normal observers during comparable retinal image motion.

Despite rapid oscillations of the eyes, visual acuity is close to normal in many observers with congenital nystagmus (CN). This study investigated whether binocular hyperacuity thresholds are also close to normal in observers with CN. To do so, we assessed stereothresholds for horizontally and vertically separated line targets in three normal observers and six observers with idiopathic horizontal CN. Stereothresholds in normal observers are better than in the observers with CN, especially for horizontally-separated targets and very small inter-line separations. Stereothresholds remain better in normal observers than in the observers with CN, even in the presence of conjugate retinal image motion simulating that in jerk nystagmus. However, when the simulated CN wave form also includes disconjugate position variability of the foveation periods, normal observers' stereothresholds become similar to those of approximately half of the observers with CN. We conclude that stereothresholds in observers with CN are degraded by the more-or-less constant motion of the retinal image, by excessive vergence instability and, in some observers, by a neural sensory deficit.     

CORNEAL TOPOGRAPHY OF HUMANS WITH CONGENITAL NYSTAGMUS

Abstract The refractive status of individuals with congenital nystagmus (albinos and idiopaths) has been examined. Our results indicate that there is a greater than normal incidence of high spectacle astigmatism. This is predominantly with-the-rule and corneal in origin (anterior surface). Partial neutralization by the against-the-rule residual astigmatism is frequent and does not differ significantly from that reported for normal populations. Topographical studies of the anterior cortical surface revealed that there was no significantly significantly difference in the mean shape factor values for the albino, idioparh and control populations. The aetiology of the astigmatism is discussed.     

Axial length and refractive error in X-linked retinoschisis

PURPOSE: To examine the relationship between axial length and refractive error in patients with X-linked retinoschisis. DESIGN: To determine whether the hypermetropia frequently found in patients with X-linked retinoschisis is axial hypermetropia. METHODS: The axial length and refractive error were measured in 29 right eyes of 29 patients. The patients were divided into two groups: a juvenile group with ages <13 years (12 eyes) and an adult group with ages > or =13 years (17 eyes). The axial length of the right eye of 30 adult men without eye diseases whose refractive error ranged from +/- 1.0 diopter served as controls. RESULTS: In the adult patient group, the refractive error was significantly more hypermetropic and the axial length was significantly shorter than was the normal adult group (P <.001). CONCLUSION: These results strongly suggest that the hypermetropia in patients with X-linked retinoschisis is axial hypermetropia.     

Sensitivity to temporal luminance modulation in congenital nystagmus.

Uniform field temporal contrast sensitivity functions were compared for 10 subjects with congenital nystagmus (seven idiopathic, three with albinism) and 10 normal observers. Sensitivity to luminance modulation did not differ significantly from normal at any temporal frequency tested except 0.5 Hz, at which the subjects with nystagmus had slightly higher sensitivity. In conjunction with other recent findings, their essentially normal temporal contrast sensitivity suggests that persons with nystagmus process retinal information continuously, rather than selectively during only only one phase of the nystagmus.     

Perception of a clear and stable visual world with congenital nystagmus.

Comparisons between the visual performance of persons with congenital nystagmus (CN) and normal observers under conditions of similar retinal image motion reveal the extent to which the nystagmus-induced image motion determines visual functioning and perception in CN. Visual acuity undergoes similar changes with the characteristics of retinal image motion in normal observers and persons with CN. However, acuity is poorer than expected on the basis of the image motion in some individuals with CN, suggesting an additional sensory deficit. When presented with visual stimuli that simulate the retinal image motion in CN, normal observers perceive substantial target movement and motion smear. In contrast, most individuals with CN perceive the visual world to be stable and relatively clear. These dramatic perceptual differences are attributed primarily to the visual consequences of extra-retinal signals, which have been shown to accompany the involuntary eye movements in CN as well as the voluntary and involuntary eye movements in normal observers. Adaptation to periodic motion of the retinal image may also contribute to the perception of stability in persons with CN. The data presented in this paper indicate that, on the whole, largely similar visual mechanisms are likely to underlie visual functioning and mediate perception in persons with CN and normal vision.     

Visual improvement in an albinotic patient with an alteration of congenital nystagmus

Biofeedback techniques were used to alter congenital nystagmus (CN) in an albino. In response to auditory cues, the patient was able to reduce the amplitude of the nystagmus by 50% or more. In response to a combination of auditory and visual cues, the patient was able to alter the waveform of the nystagmus in such a manner that progressively larger portions of each cycle of the nystagmus were spent with the eye relatively stationary. Presumably as a consequence of this alteration in waveform, the patient's visual acuity (VA) improved from 6/35 to 6/25. The results indicate that, although VA in albinos is limited ultimately by the presence of foveal hypoplasia, other components of the typical albinotic syndrome (such as the accompanying nystagmus) can add to the acuity reduction and should, therefore, be treated.     

近视眼后极部视网膜厚度与屈光度的相关性

目的：分析近视眼后极部视网膜厚度改变与屈光度的关系。方法：采用视网膜厚度分析仪(retinal thickness analyzer，RTA)测定48例(91眼)正常人和近视患者后极部视网膜厚度，研究其后极部不同区域视网膜厚度与屈光度的相关性。结果：近视眼后极部视网膜平均厚度与屈光度明显相关，与性别、年龄无关。黄斑区与黄斑周围区视网膜厚度差异有显著性。随着近视屈光度增加，后极部视网膜明显变薄，其中黄斑周围区视网膜变薄较黄斑区更明显。正常组、低中度近视组之间后极部视网膜平均厚度差异无显著性，而他们与高度近视组之间差异有显著性。结论：高度近视眼后极部视网膜较正常人、低度和中度近视眼明显变薄，其中以黄斑周围区更明显。     

Vision defects in albinism.

We have examined the possible presence of color vision anomalies in 9 individuals (17 eyes, 1 blind) with fundus findings suggesting ocular albinism using the Ishihara plates, the 28-hue Roth test, and the Davico anomaloscope. Results indicate that four of these individuals show no sign of the anomalies expected in an albino in either of the two eyes. Of the remaining cases, two are simple deuteranomals in both eyes, according to Pickford's classification criteria. The rest have protanomaly; however, in these the deviation toward red appears in both eyes in only one subject, whereas in the other two subjects it appears in only one eye, their binocular color vision being basically normal. Our study shows that a large proportion of these albinos have photophobia, pendular nystagmus, strabismus, noticeable refractive errors (astigmatism and high myopia), and poor visual acuity [usually less than 6/30 (20/100) with correction]. The measurement of contrast sensitivity function (CSF) indicates that the frequency of 12 cpd cannot be perceived, even in binocular vision.     

Eye movements of human albinos

Albino mammals are known to suffer from misrouted optic projections and there is a growing body of evidence suggesting that human albinos have similar aberrant anatomical pathways. The present study examined the possible consequences of such aberrant pathways on the oculomotor performance of five adult human albinos. Optokinetic nystagmus to drifting grating patterns and pursuit eye movements were measured. The subjects' congenital nystagmus was also measured under different conditions of gaze position and ambient room illumination. Two of the subjects showed clear instances of an inversion in the optokinetic response and there were probable inversions observed for a third subject. The magnitude of the optokinetic nystagmus was appropriate for the rate of pattern drift, but inverted in direction. In all cases smooth pursuit was severely impaired, but reversals of the appropriate direction of pursuit eye movements were not observed. Changes in the congenital nystagmus under conditions of light and darkness were found for four of the five subjects and varied greatly between subjects. The results suggest that human albinos share many of the oculomotor deficits found in other albino species.     

Visual and Refractive Status of Children With Down's Syndrome and Nystagmus

PurposeChildren with Down''s syndrome (DS) are known to have poorer visual acuity than neurotypical children. One report has shown that children with DS and nystagmus also have poor acuity when compared to typical children with nystagmus. What has not been established is the extent of any acuity deficit due to nystagmus and whether nystagmus affects refractive error within a population with DS.MethodsClinical records from the Cardiff University Down''s Syndrome Vision Research Unit were examined retrospectively. Binocular visual acuity and refraction data were available for 50 children who had DS and nystagmus and 176 children who had DS but no nystagmus. Data were compared between the two groups and with published data for neurotypical children with nystagmus.ResultsThe study confirms the deficit in acuity in DS, compared to neurotypical children, of approximately 0.2 logMAR and shows a deficit attributable to nystagmus of a further 0.2 logMAR beyond the first year of life. Children with both DS and nystagmus clearly have a significant additional impairment. Children with DS have a wide range of refractive errors, but nystagmus increases the likelihood of myopia. Prevalence and axis direction of astigmatism, on the other hand, appear unaffected by nystagmus.ConclusionsNystagmus confers an additional visual impairment on children with DS and must be recognized as such by families and educators. Children with both DS and nystagmus clearly need targeted support.     

Astigmatism in ocular neuromuscular nystagmus

BACKGROUND: Data on refraction of patients with congenital nystagmus are not available in the literature. PATIENTS AND METHODS: We have analysed the refractive errors in a cohort of 224 consecutive patients with congenital nystagmus, aged 1-57 years. RESULTS: Refractive errors, i. e., myopia, hyperopia (> 0.50 dioptres) and astigmatism (> 1.25 dioptres), were found in 179 patients (79.91 %). Of them 8 were myopic (4.46 %), 19 were hyperopic (10.61 %) and 152 were astigmatic (84.91 %). Mean astigmatism was of 2.44 dioptres for right eyes and 2.74 dioptres for left eyes. CONCLUSIONS: Astigmatism is extremely common in congenital nystagmus. Its presence is much higher than that found in normal populations. The amount of astigmatism found in nystagmus patients is noticeable. When considering he visual difficulties of patients with nystagmus, the astigmatic component should be taken in greatest consideration. Its presence should favour early surgery for anomalous head posture. Furthermore, refractive surgery should be considered as early as possible, for improving visual potential.     

Understanding ocular torticollis in children

Ocular abnormal head posture (AHP) or torticollis is a frequent sign in pediatric pathology The incidence is 5.6% in ophthalmological practice and 3.19% in pediatric ophthalmological practice. The abnormal head posture is adopted to improve visual acuity maintain binocular single vision, center residual visual field with the body or for cosmetic reasons. Face turn is the most frequent abnormal head posture in pediatric ophthalmology. The more common diseases causing face turn are Duane syndrome, congenital fibrosis of extraocular muscles, nystagmus, refractive errors, visual field defects. The most frequent ocular causes of head tilt in children are congenital nystagmus, superior oblique paresis, dissociated vertical deviation, Brown syndrome, refractive errors. Chin-up or chin-down abnormal head postures are most commonly caused by "A" and "V"-pattern strabismus, palpebral ptosis, nystagmus, refractive errors. Torticollis is not a diagnosis, but it is a sign of an underlying disease. There are ocular diseases which diagnosis is straightforward for general practitioner, pediatricians or pediatric surgeons (horizontal nystagmus, lateral rectus paralysis, ptosis, esotropia), but others less obvious (superior oblique paralysis, Duane syndrome, A and V-pattern strabismus, torsional nystagmus) because of the compensatory head posture, and these last disorders are predisposed to confusion with congenital AHP Interdisciplinary collaboration between ophthalmologist, pediatrician, pediatric surgeon, ENT specialist and neurologist is mandatory in establishing the etiology of AHP Every child with AHP must be examined by an ophthalmologist.