Clinical Utility of 'Peekaboo Vision' Application for Measuring Grating Acuity in Children with Down Syndrome

Peekaboo Vision is an iPad grating acuity app built with typically developing children in mind. Given the ease of using this app in the pediatric age group, this study determined its clinical utility in children with Down syndrome. Two groups of participants (children with Down syndrome and age-matched controls) were included. Presenting binocular grating acuity was measured using Peekaboo Vision and Teller acuity cards II in random order. Parents' feedback about their child's engagement and time taken to complete each test was documented. Thirty-seven children with Down syndrome (males = 23; mean age = 8.1 ± 4.2 years) and 28 controls (males = 15; mean age = 8.71 ± 3.84 years) participated. Time taken to complete the tests was comparable (p = 0.83) in children with Down syndrome. Controls were significantly faster with Peekaboo Vision (p = 0.01). Mean logMAR acuities obtained with Peekaboo Vision (0.16 ± 0.34) and Teller acuity cards II (0.63 ± 0.34) were significantly different (p < 0.001) in children with Down syndrome (mean difference in acuities: -0.44 ± 0.38 logMAR (95% LoA: -1.18 to 0.3). For controls, the mean logMAR acuity with Peekaboo Vision (-0.13 ± 0.12) and Teller acuity cards II (0.12 ± 0.09) was also found to be significantly different (p < 0.001) (mean difference in acuities: -0.24 ± 0.14 logMAR (95% LoA: -0.51 to 0.03) Peekaboo Vision test can be used on children with Down syndrome. Peekaboo Vision and Teller acuity cards II can be used independently but not interchangeably. The differences in the acuity values between the two tests could be a result of the differences in the thresholding paradigms, different testing mediums and the range of acuities covered

Critical Immaturities Limiting Infant Binocular Stereopsis

PURPOSE. To determine what critical immaturity is responsible for the poor binocular stereopsis of human infants. METHODS. Infant and adult psychometric functions were measured for detection of stereoscopic depth in a random-texture display. A test stimulus defined by horizontal binocular disparity and a distracter stimulus defined by vertical disparity were used. Adults were tested by direct psychophysical methods at several contrast values, and infants by forced-choice preferential looking at 100% contrast. RESULTS. Infant stereoacuity matured from unmeasurable at age 12 weeks to 7.9 arc min at 20 weeks, which was still far from the nominal adult value of 5 to 10 arc seconds. In contrast, infant d-max (maximum disparity) was 86.8 minutes at 20 weeks, which was near the adult d-max of 110.6 minutes. The average maximum level of infant performance at 20 weeks was 77% correct, still far below adult performance. When the adult stereogram was low contrast, adult extrafoveal performance was similar to infant performance. Infant and adult stereo performance was predicted quantitatively, using infant and adult monocular performance in detecting the stereogram texture. Infant and adult stereopsis performance approached, but did not reach, the predicted values. CONCLUSIONS. The infantlike performance of adults tested at low contrast and the similarity of infant maximum percentage of correct data relative to the predicted values suggested that the critical immaturity limiting infant stereopsis is the well-known insensitivity of the infant visual system to contrast. This conclusion supports the clinical use of stereopsis as a screening test for bilateral monocular function in infants. (Invest Ophthalmol Vis Sci

Grasping isoluminant stimuli

We used a virtual reality setup to let participants grasp discs, which differed in luminance, chromaticity and size. Current theories on perception and action propose a division of labor in the brain into a color proficient perception pathway and a less color-capable action pathway. In this study, we addressed the question whether isoluminant stimuli, which provide only a chromatic but no luminance contrast for action planning, are harder to grasp than stimuli providing luminance contrast or both kinds of contrast. Although we found that grasps of isoluminant stimuli had a slightly steeper slope relating the maximum grip aperture to disc size, all other measures of grip quality were unaffected. Overall, our results do not support the view that isoluminance of stimulus and background impedes the planning of a grasping movement

Sinterability and mechanical properties of MnO2-doped Y-TZP: the effects of holding time variations

the effect of holding time variation and sintering temperature on the mechanical properties and sinterability of yttria stabilized tetragonal zirconia doped with 1 wt. MnO2 was investigated. Samples were sintered at 1150-1500 degrees C with holding times varying from 12 and 120 minutes. Comparing to the MnO2-doped Y-TZP, longer holding time resulted in enhanced densification of the undoped Y-TZP samples. In the case of MnO2-doped Y-TZP however, Bulk density, Young's modulus, Vickers hardness and fracture toughness results show the beneficial effect of MnO2 in enhancing the densification of Y-TZP ceramics

Sintering and densification behavior of ZnO-doped Y-TZP ceramics

The effect on densification and mechanical properties of 3 mol Y-TZP ceramics doped with zinc oxide (0.1 wt. to 1 wt.), has been investigated in this study. Green samples were compacted by uniaxial pressing and cold isostatically pressed at 200 MPa. All samples have been sintered over the temperature range of 1250 degrees C to 1500 degrees C with a ramp rate of 10 degrees C/ minute and 2 hours of holding time. In addition to that, the tetragonal phase stability of the samples was also studied in superheated steam at 180 degrees C/10 bar for up to 50 h. The sintered bodies were examined to determine the phase content, bulk density, Young's modulus, Vickers hardness and fracture toughness. The results showed that the addition of 1 wt. ZnO was effective in aiding densification (similar to 99 theoretical density). It also improved the matrix stiffness (similar to 208 GPa) and Vickers hardness (similar to 13 GPa), when the samples were sintered below 1300 degrees C comparing to the undoped Y-TZP sintered at the same temperature. In contrast, ZnO addition to the Y-TZP matrix displayed a tendency to change hydrothermal ageing behavior as it was noticed that the monoclinic content increased with increasing content of dopant. The undoped samples showed a better hydrothermal ageing behavior at 1300 degrees C compared to the doped samples

Manufacturing of high toughness hydroxyapatite produced by wet chemical method

Hydroxyapatite (HA) is among the leading ceramic materials for hard tissue replacement implants. Despite the excellent bioactivity of HA, low toughness has limited the application of these materials to non-load bearing areas. The sinterability of nanocrystalline hydroxyapatite (HA) powder via new heating profile for conventional pressureless sintering was studied. The starting nanocrystalline HA powder was synthesized by wet chemical precipitation method. After uniaxial pressing followed by isostatic pressing, HA powder compacts are sintered over the temperature range of 1000 degrees C to 1300 degrees C. Different holding time of 1 minute and 120 minutes was applied as a heating profile of HA samples. The results revealed that new heating profile was effective in producing a HA body with high density of 98 when sintered at 1200 degrees C. Subsequently, mechanical properties such as fracture toughness and hardness, of HA compacts increased with decrease in grain size. HA showed the highest hardness of 9.51 GPa and fracture toughness of 1.41 MPa.m1/2 when sintered at 1100 degrees C. XRD analysis indicated that decomposition of HA phase during sintering at high temperatures do not occur. Short holding time leads to finer microstructure of HA and subsequently better mechanical properties

Pressureless sintering of electro-conductive zirconia composites

In the present work, 3 mol Yttria-stabilized tetragonal zirconia (Y-TZP) composite containing 25 wt. of zirconium diboride (ZrB2) was prepared via pressureless sintering method in an inert atmosphere over the temperature range of 1350-1550 degrees C for one hour. The effect of zirconium diboride content in the zirconia matrix, as well as the sintering temperature on densification, phase stability and electrical properties of sintered samples have been studied. The results revealed that there was a significant increased in electrical conductivity of sintered samples when 25 wt. of ZrB2 is incorporated into Y-TZP matrix

Parent-Reported Visual Concerns in Children with Cerebral Visual Impairment Presenting to a Pediatric Neurology Clinic

PURPOSE: Children with cerebral visual impairment (CVI) present with delayed developmental milestones. Pediatricians and pediatric neurologists are usually the first point of contact, and eye exam largely remains referral based. This study documented the visual concerns reported by parents of children with CVI visiting a pediatric neurology clinic. Additionally, we investigated the association between visual concerns, functional vision measures and visual functions. PATIENTS AND METHODS: A cross-sectional study was undertaken in children with CVI (chronological age range: 7 months-7 years). Visual concerns reported by the parents/caregivers were documented as open-ended statements. Additionally, a functional vision assessment was conducted using the CVI Range instrument with phase 1, 2 and 3 indicating low, moderate and high visual functioning, respectively. Grating acuity and contrast sensitivity were measured using Teller acuity cards-II and Ohio contrast cards respectively. RESULTS: A total of 73 children (mean age of 2.84 ± 1.87 years) were recruited. Sixty-eight parents reported visual concerns that were broadly grouped into 14 unique concerns. Nineteen parents (27.9%) reported more than one visual concern. Difficulty maintaining eye contact and recognizing faces were the top two visual concerns in phases 1 and 2. Missing objects in the lower visual field was the top concern in phase 3. A larger number of visual concerns were reported in phase 1 (43%) than phase 2 (40.6%) and phase 3 (16.2%). Multiple regression analysis revealed that grating acuity, contrast sensitivity and chronological age were able to predict the functional vision, F (3, 55) = 63.0, p < 0.001, r2 = 0.77. CONCLUSION: Targeted questions enquiring about eye contact and face recognition can be included in history elicitation in children with CVI in pediatric neurology clinics. In the presence of visual concerns, it will be important to assess grating acuity and contrast sensitivity. A poor functional vision score requires referral for eye examination and vision rehabilitation services