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Infantile nystagmus (IN) describes a regular, repetitive movement of the eyes. A characteristic feature of each cycle of the IN eye movement waveform is a period in which the eyes are moving at minimal velocity. This so-called “foveation” period has long been considered the basis for the best vision in individuals with IN. In recent years, the technology for measuring eye movements has improved considerably, but there remains the challenge of calibrating the direction of gaze in tracking systems when the eyes are continuously moving. Identifying portions of the nystagmus waveform suitable for calibration typically involves time-consuming manual selection of the foveation periods from the eye trace. Without an accurate calibration, the exact parameters of the waveform cannot be determined. In this study, we present an automated method for segmenting IN waveforms with the purpose of determining the foveation positions to be used for calibration of an eye tracker. On average, the “point of regard” was found to be within 0.21° of that determined by hand-marking by an expert observer. This method enables rapid clinical quantification of waveforms and the possibility of gaze-contingent research paradigms being performed with this patient group.

Background/AimsChildren with Down’s syndrome (DS) are known to have poorer visual acuity that 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 impacts on refractive error is 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 (DSN) 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 further deficit attributable to nystagmus of a further 0.2 logMAR beyond the first year of life. Children with DS and no nystagmus appear to have acuity that mirrors that of typical children with nystagmus, while children with both DS and nystagmus 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 appears unaffected by nystagmus.ConclusionNystagmus confers an additional visual impairment on children with Down’s syndrome and must be recognised as such by families and educators. Children with both DS and nystagmus clearly need targeted support.

It is widely recognised that children with Down syndrome have a broad range and a high prevalence of visual deficits and it has been suggested that those with Down syndrome are more likely to exhibit visual perception deficits indicative of cerebral visual impairment. This exploratory study aims to determine the prevalence of behavioural features suggestive of cerebral visual impairment (CVI) occurring with Down syndrome and whether the visual problems can be ascribed to optometric factors. A cohort of 226 families of children with Down syndrome (trisomy 21), aged 4–17, were invited to participate in a validated question inventory, to recognise visual perception issues. The clinical records of the participants were then reviewed retrospectively. A five-question screening instrument was used to indicate suspected CVI. The majority of the 81 families who responded to the questionnaire reported some level of visual perceptual difficulty in their child. Among this cohort, the prevalence of suspected CVI as indicated by the screening questionnaire was 38%. Only ametropia was found to have a significant association with suspected CVI, although this increased the correct prediction of suspected CVI outcome by only a small amount. Results suggest that children with Down syndrome are more likely to experience problems consistent with cerebral visual impairment, and that these may originate from a similar brain dysfunction to that which contributes to high levels of ametropia and failure to emmetropise. It is important that behavioural features of CVI are recognised in children with Down syndrome, further investigations initiated and appropriate management applied. V. Vinuela-Navarro and R. England were funded by Action Medical Research for Children GN2338.

Down syndrome (DS) is frequently associated with cataract, but there remains scant information about DS cataract morphology. Supra-nuclear cataracts in DS have been proposed as indicative of beta-amyloid (Aβ) aggregation and thus potential biomarkers for Alzheimer’s (AD). This study employed anterior segment OCT (AS-OCT) and slit-lamp (SL) photography to image the crystalline lens in DS, compared with adult controls. Lens images were obtained post-dilation. Using MATLAB, AS-OCT images were analysed and lens opacities calculated as pixel intensity and area ratios. SL images were classified using LOCS III. Subjects were n = 28 DS (mean ± SD 24.1 ± 14.3years), and n = 36 controls (54.0 ± 3.4years). For the DS group, AS-OCT imaging revealed the frequent presence of small dot opacities (27 eyes, 50%) in the cortex and nucleus of the lens, covering an area ranging from 0.2–14%. There was no relation with age or visual acuity and these dot opacities (p > 0.5) and they were not present in any control lenses. However, their location and morphology does not coincide with previous reports linking these opacities with Aβ accumulation and AD. Four participants (14%) in the DS group had clinically significant age-related cataracts, but there was no evidence of early onset of age-related cataracts in DS.

PURPOSE: Previous studies have reported that eye movements differ between good/average and poor readers. However, these studies have been limited to investigating eye movements during reading related tasks, and thus, the differences found could arise from deficits in higher cognitive processes involved in reading rather than oculomotor performance. The purpose of the study is to determine the extent to which eye movements in children with delayed reading skills are different to those obtained from children with good/average reading skills in non-reading related tasks.METHODS: After a screening optometric assessment, eye movement recordings were obtained from 120 children without delayed reading skills and 43 children with delayed reading skills (4 to 11 years) using a Tobii TX300 eye tracker. Cartoon characters were presented horizontally from -20° to +20° in steps of 5° to study saccades. An animated stimulus in the centre of the screen was presented for 8 seconds to study fixation stability. Saccadic main sequences, and the number and amplitude of the saccades during fixation were obtained for each participant. Children with delayed reading skills (n = 43) were unmasked after data collection was completed. Medians and quartiles were calculated for each eye movement parameter for children without (n = 120) and with (n = 43) delayed reading skills.RESULTS: Independent t-tests with Bonferroni correction showed no significant differences in any of the saccadic main sequence parameters (Slope, Intercept, A, n and Q ratio) between children without and with delayed reading (p > 0.01). Similarly, no significant differences were found in the number of saccades and their amplitude during the fixation task between the two groups (p > 0.05). Further, none of the gross optometric parameters assessed (visual acuity, refractive error, ocular alignment, convergence, stereopsis and accommodation accuracy) were found to be associated with delayed reading skills (p > 0.05).CONCLUSIONS: Eye movements in children with delayed reading skills are quantitatively similar to those found in children without delayed reading skills. These findings suggest that, in these children, delayed reading skills are not associated with eye movements and further question interventions targeted at improving eye movement control.

Purpose: It could be argued that current studies investigating smooth pursuit development in children do not provide an optimal measure of smooth pursuit characteristics, given that a significant number have failed to adjust their setup and procedures to the child population. This study aimed to characterize smooth pursuit in children using child-friendly stimuli and procedures.Methods: Eye movements were recorded in 169 children (4-11 years) and 10 adults, while a customized, animated stimulus was presented moving horizontally and vertically at 6°/s and 12°/s. Eye movement recordings from 43 children with delayed reading, two with nystagmus, two with strabismus, and two with unsuccessful calibration were excluded from the analysis. Velocity gain, proportion of smooth pursuit, and the number and amplitude of saccades during smooth pursuit were calculated for the remaining participants. Median and quartiles were calculated for each age group and pursuit condition. ANOVA was used to investigate the effect of age on smooth pursuit parameters.Results: Differences across ages were found in velocity gain (6°/s P < 0.01; 12°/s P < 0.05), as well as the number (12°/s P < 0.05) and amplitude of saccades (12°/s P < 0.05), for horizontal smooth pursuit. Post hoc tests showed that these parameters were different between children aged 7 or younger and adults. No significant differences were found across ages in any smooth pursuit parameter for the vertical direction (P > 0.05).Conclusions: Using child-friendly methods, children over the age of 7 to 8 years demonstrated adultlike smooth pursuit.Translational Relevance: Child-friendly procedures are critical for appropriately characterizing smooth pursuit eye movements in children.

Numerous research studies have demonstrated the scope and value of eye movement recording (EMR). There is now potential for EMR to be helpful in a range of clinical contexts and it could be developed as a routine part of the repertoire of clinical investigations offered by the NHS, at least in tertiary centres. We highlight potential uses and challenges below, as a prelude to further development and debate.

Our objective was to present the findings of an opt-in, school-based eye care service for children attending 11 special schools in England and use these findings to determine whether a vision screening programme would be appropriate for this population. Data from eye examinations provided to 949 pupils (mean age 10.7 years) was analysed to determine the prevalence and aetiology of visual deficiencies and reported eye care history. For 46.2% (n = 438) of pupils, a visual deficiency was recorded. 12.5% of all the children seen (n = 119) had a visual deficiency that was previously undiagnosed. Referral for a medical opinion was made for 3.1% (n = 29) of pupils seen by the service. Spectacle correction was needed for 31.5% (n = 299) of pupils; for 12.9% (122) these were prescribed for the first time. 3.7% (n = 11) of parents/carers of pupils needing spectacles chose not to use the spectacle dispensing service offered in school. Eye care history was available for 847 pupils (89.3%). Of the pupils for whom an eye care history was available, 44% (n = 373) reported no history of any previous eye care and10.7% (n = 91) reported a history of attending a community optical practice/opticians. Only one pupil from the school entry 4–5 age group (0.6% of age group n = 156) would have passed vision screening using current Public Health England screening guidelines. Children with a diagnosis of autism were significantly less likely to be able to provide a reliable measurement of visual acuity. This study supports previously published evidence of a very high prevalence of visual problems in children with the most complex needs and a significant unmet need in this group. It demonstrates routine school entry vision screening using current Public Health England guidelines is not appropriate for this group of children and very low uptake of community primary eye care services.

Background Visual acuity is known to be poorer in children with Down’s syndrome than in age-matched controls. However, to date, clinicians do not have access to norms for children with Down’s syndrome that allow differential discrimination of healthy from anomalous visual development in this population. Methods The Down’s Syndrome Vision Research Unit at Cardiff University has been monitoring visual development in a large cohort of children since 1992. Cross-sectional data on binocular visual acuity were retrospectively analysed for 159 children up to 12-years of age in order to establish binocular acuity norms. Longitudinal binocular acuity data were available for nine children who were seen regularly over the 12-years age-range. Monocular acuity was successfully recorded less often in the cohort, but analysis of scores for 69 children allowed assessment of inter-ocular acuity differences and binocular summation. Results In comparison with published norms for the various acuity tests used, binocular acuity was consistently poorer in children with Down’s syndrome from the age of three-years and stabilised at around 0.25 logMAR from the age of four-years. Inter-ocular acuity difference and binocular summation were both 0.06 logMAR, which is similar to the reported values in children without Down’s syndrome. Conclusions The study provides eye-care practitioners with the expected values for binocular acuity in children with Down’s syndrome and demonstrates the visual disadvantage that children with Down’s syndrome have when compared with their typically developing peers. The results emphasise the responsibility that practitioners have to notify parents and educators of the relatively poor vision of children with Down’s syndrome, and the need for classroom modifications.

Ricco’s area (the largest area of visual space in which stimulus area and intensity are inversely proportional at threshold) has previously been hypothesised to be a result of centre/surround antagonism in retinal ganglion cell receptive fields, but recent evidence suggests a sizeable cortical contribution. Here, Ricco’s area was measured in amblyopia, a condition in which retinal receptive fields are normal, to better understand its physiological basis. Spatial summation functions were determined at 12 visual field locations in both eyes of 14 amblyopic adults and 15 normal-sighted controls. Ricco’s area was significantly larger in amblyopic eyes than in fellow non-amblyopic eyes. Compared to the size of Ricco’s area in control eyes, Ricco’s area measured significantly larger in amblyopic eyes. Additionally, Ricco’s area in the fellow, non-amblyopic eye of amblyopic participants measured significantly smaller than in control eyes. Compared to controls, Ricco’s area was larger in amblyopic eyes and smaller in fellow non-amblyopic eyes. Amblyopia type, binocularity, and inter-ocular difference in visual acuity were significantly associated with inter-ocular differences in Ricco’s area in amblyopes. The physiological basis for Ricco’s area is unlikely to be confined to the retina, but more likely representative of spatial summation at multiple sites along the visual pathway.

Purpose. This study presents a two-degree customized animated stimulus developed to evaluate smooth pursuit in children\ud and investigates the effect of its predetermined characteristics (stimulus type and size) in an adult population. Then, the\ud animated stimulus is used to evaluate the impact of different pursuit motion paradigms in children.\ud Methods. To study the effect of animating a stimulus, eye movement recordings were obtained from 20 young adults while the\ud customized animated stimulus and a standard dot stimulus were presentedmoving horizontally at a constant velocity. To study the\ud effect of using a larger stimulus size, eye movement recordings were obtained from 10 young adults while presenting a standard\ud dot stimulus of different size (1- and 2-) moving horizontally at a constant velocity. Finally, eye movement recordings were\ud obtained from 12 children while the 2- customized animated stimulus was presented after three different smooth pursuit motion\ud paradigms. Performance parameters, including gains and number of saccades, were calculated for each stimulus condition.\ud Results. The animated stimulus produced in young adults significantly higher velocity gain (mean: 0.93; 95% CI: 0.90Y0.96;\ud P = .014), position gain (0.93; 0.85Y1; P = .025), proportion of smooth pursuit (0.94; 0.91Y0.96, P = .002), and fewer saccades\ud (5.30; 3.64Y6.96, P = .008) than a standard dot (velocity gain: 0.87; 0.82Y0.92; position gain: 0.82; 0.72Y0.92; proportion\ud smooth pursuit: 0.87; 0.83Y0.90; number of saccades: 7.75; 5.30Y10.46). In contrast, changing the size of a standard dot\ud stimulus from1- to 2- did not have an effect onsmooth pursuit in young adults (P 9.05). Finally, smooth pursuit performance did\ud not significantly differ in children for the different motion paradigms when using the animated stimulus (P 9 .05).\ud Conclusions. Attention-grabbing and more dynamic stimuli, such as the developed animated stimulus, might potentially be\ud useful for eye movement research. Finally, with such stimuli, children perform equally well irrespective of the motion\ud paradigm used.

Aims: To develop and validate a short questionnaire to assess self-reported visual ability in children and young people with a visual impairment. Methods: A list of 121 items was generated from 13 focus groups with children and young people with and without a visual impairment. A long 89-item questionnaire was piloted with 45 visually impaired children and young people using face-to-face interviews. Rasch analysis was used to analyse the response category function and to facilitate item removal ensuring a valid unidimensional scale. The validity and reliability of the short questionnaire were assessed on a group of 109 visually impaired children (58.7% boys; median age 13 years) using Rasch analysis and intraclass correlation coefficient (ICC). Results: The final 25-item questionnaire has good validity and reliability as demonstrated by a person separation index of 2.28 and reliability coefficient of 0.84. The items are well targeted to the subjects with a mean difference of −0.40 logit between item and person means, and an ICC of 0.89 demonstrates good temporal stability. Conclusion: The Cardiff Visual Ability Questionnaire for Children (CVAQC) is a short, psychometrically robust and a self-reported instrument that works to form a unidimensional scale for the assessment of the visual ability in children and young people with a visual impairment. Refereed/Peer-reviewed

Background: Down syndrome (DS) is a common chromosomal anomaly. People with this syndrome have recognisable physical characteristics and limited intellectual abilities. The aim of this study was to determine visual defects, especially refractive error and binocular anomalies, in a sample of Nepalese children with DS. Methods: Thirty-six children with DS (19 boys and 17 girls) from the Kathmandu valley, aged from four months to 18 years, underwent detailed optometric examination. Cycloplegic refraction was performed on all subjects. Vision on presentation of all the children was assessed with preferential looking cards, the Kay picture cards, the Bailey-Lovie logMAR chart or the Snellen chart. Binocular function was assessed with cover test, Hirschberg or Bruckner test. Results: Cycloplegic refraction of the children revealed that 80 per cent of the children had significant refractive error. Most of them had hyperopia (55 per cent), followed by astigmatism (44 per cent), myopia (25 per cent) and anisometropia (19 per cent). Only two (5.6 per cent) children were strabismic and both of them were alternating esotropes. Nystagmus was present in 10 (28 per cent). Other ocular findings were upward slanting palpebral fissures, blepharitis, congenital nasolacrimal duct obstruction, blepharoconjunctivitis, chalazion and lenticular opacities. Conclusion: Nepalese children with DS have a high prevalence of refractive error and nystagmus. Regular eye examinations are indicated for these children to enable early diagnosis and appropriate management of ocular disorders to improve their vision and quality of life.

PURPOSE. Down syndrome (DS) is associated with reduced visual acuity that cannot be explained by motivational or attentional factors. To isolate the contribution of optical factors to visual performance in DS, two types of resolution acuity were measured: grating resolution acuity, which is limited by optical quality, and interferometric acuity, which effectively bypasses the optics of the eye. METHODS. Twenty-nine children with DS (age range, 9 –16 years) were tested. Sixty-eight age-matched, developmentally healthy children acted as controls. All wore best refractive correction, and none had clinically significant ocular disease. Grating resolution and interferometric acuity were measured according to a two-alternative, forced-choice procedure. RESULTS. There was no change in grating resolution acuity or interferometric acuity with age in either group. Mean grating resolution acuities were – 0.12 log of the minimum angle of resolution (logMAR; SD 0.07) for the control group and 0.48 logMAR (SD 0.09) for the DS group. Mean interferometric acuities were – 0.11 logMAR (SD 0.08) for the control group and 0.004 (SD 0.06) for the DS group. In the DS group, the mean interferometric acuity was reduced by a factor of 1.3, whereas mean grating resolution acuity was substantially reduced, by a factor of 4.1, compared with controls. CONCLUSIONS. Grating resolution and interferometric thresholds are reduced in children with DS. However the discrepancy between developmentally healthy children and those with DS is greater for grating resolution acuity, suggesting that degradation in optical quality is a major contributor to poor visual performance in children with DS. (Invest Ophthalmol Vis Sci. 2007;48:3995– 4001) DOI:10.1167/iovs.06-1387

purpose. To determine the effect of visual demand on the nystagmus waveform. Individuals with infantile nystagmus syndrome (INS) commonly report that making an effort to see can intensify their nystagmus and adversely affect vision. However, such an effect has never been confirmed experimentally.\ud \ud methods. The eye movement behavior of 11 subjects with INS were recorded at different gaze angles while the subjects viewed visual targets under two conditions: above and then at resolution threshold. Eye movements were recorded by infrared oculography and visual acuity (VA) was measured using Landolt C targets and a two-alternative, forced-choice (2AFC) staircase procedure. Eye movement data were analyzed at the null zone for changes in amplitude, frequency, intensity, and foveation characteristics. Waveform type was also noted under the two conditions.\ud \ud results. Data from 11 subjects revealed a significant reduction in nystagmus amplitude (P < 0.05), frequency (P < 0.05), and intensity (P < 0.01) when target size was at visual threshold. The percentage of time the eye spent within the low-velocity window (i.e., foveation) significantly increased when target size was at visual threshold (P < 0.05). Furthermore, a change in waveform type with increased visual demand was exhibited by two subjects.\ud \ud conclusions. The results indicate that increased visual demand modifies the nystagmus waveform favorably (and possibly adaptively), producing a significant reduction in nystagmus intensity and prolonged foveation. These findings contradict previous anecdotal reports that visual effort intensifies the nystagmus eye movement at the cost of visual performance. This discrepancy may be attributable to the lack of psychological stress involved in the visual task reported here. This is consistent with the suggestion that it is the visual importance of the task to the individual rather than visual demand per se which exacerbates INS. Further studies are needed to investigate quantitatively the effects of stress and psychological factors on INS waveforms.

Purpose: This study was designed to investigate if the use of different target types or the RAF rule affected the measurement of near point of convergence (NPC). Methods: The subjects comprised three groups: (1) 20 children aged 6–9 years (2) 17 children aged 11–13 years (3) 14 adults aged 20–30 years. Five targets were used to measure the NPC: (1) pencil tip, (2) fingertip, (3) penlight, (4) N5 letter and (5) vertical line target on the RAF rule. Results: There was no significant difference in NPC measurements between the pencil tip, fingertip and N5 target in free space. The penlight resulted in significantly more remote NPC break and recovery points compared with the fingertip and pencil tip (p

Purpose: Infantile nystagmus (IN) consists of largely horizontal oscillations of the eyes that usually begin shortly after birth. The condition is almost always associated with lower than normal visual acuity (VA). This is assumed to be at least partially due to motion blur induced by the eye movements. Here, we investigated the effect of image motion on VA. Methods: Grating stimuli were presented, illuminated by either multiple tachistoscopic flashes (0.76 ms) to circumvent retinal image motion, or under constant illumination to subjects with horizontal idiopathic IN and controls. A staircase procedure was used to estimate VA (by judging direction of tilt) under each condition. Orientation-specific effects were investigated by testing gratings oriented about both the horizontal and vertical axes. Results: Nystagmats had poorer VA than controls under both constant and tachistoscopic illumination. Neither group showed a significant difference in VA between illumination conditions. Nystagmats performed worse for vertically-oriented gratings, even under tachistoscopic conditions (p < 0.05), but there was no significant effect of orientation in controls. Conclusions: The fact that VA was not significantly affected by either illumination condition strongly suggests that the eye movements themselves do not significantly degrade VA in adults with IN. Treatments and therapies that seek to modify and/or reduce eye movements may therefore be fundamentally limited in any improvement that can be achieved with respect to VA.

PURPOSE: Down syndrome (DS) is associated with reduced visual performance. Although poor optical quality has been implicated, no previous data are available regarding the contribution of cortical visual processes. The present study investigated Vernier performance for the first time in children with DS to evaluate the integrity of higher visual processing in this condition. METHODS: Participants were 29 children aged 9 to 16 years who had DS and 68 age-matched developmentally normal children acting as controls. All wore best refractive correction, and none had clinically significant ocular abnormalities. An out-of-phase test-pedestal Vernier stimulus was used to facilitate short test distances and optimize compliance with testing. RESULTS: Testing was successfully completed by 86% (n=25) of the DS group and 96% (n=65) of the control group. Vernier thresholds were invariant with age in both groups. Mean Vernier acuities were 39.8 arc seconds (SD+/-13.3) and 14.6 arc seconds (SD+/-4.7) in DS and control groups, respectively. When compared with control data, mean Vernier acuity was reduced by a factor of 2.7 in DS. CONCLUSIONS: Vernier thresholds were successfully measured in children with DS and were found to be reduced, indicating that cortical visual function is compromised. Impairment in cortical function in DS may be implicit, relating to histologic reports of differences in the DS brain, or they may result from abnormal experience during visual development. The magnitude of the cortical deficit demonstrated in DS in the present study is significant and should be considered along with previously reported poor optical quality.