Visual field asymmetries in visual word form identification.

Visual performance across the visual fields interacts with visual tasks and visual stimuli, and visual resolution decreases as a function of eccentricity, varying at isoeccentric locations. In this study, we investigated the extent of asymmetry and the rate of change in visual acuity threshold for visual word form (VWF) identification at horizontal and vertical azimuths across the fovea, and at eccentricities of 1°, 2°, 4°, 6° and 8° for 10%, 20%, 40%, and 80% contrast levels, to determine whether and how the eccentricities, meridians, and contrasts modulated the VWF identification acuity threshold. The stimuli were 16 traditional Chinese characters of similar legibility. Participants pressed a key to indicate the character presented, either monocularly or binocularly, at one of 21 randomly selected locations. A staircase procedure was used to determine the threshold, and a multiple linear regression model was used to fit the linear cortical magnification factor (CMF). We found that (1) the asymmetry was most pronounced on the vertical and superior azimuths, (2) the asymmetry between the right and left azimuths was not significant, (3) the CMF was significantly smaller on the vertical azimuth than on the horizontal azimuth, (4) the CMF was smaller on the superior vertical azimuth than on the inferior azimuth, and (5) monocular viewing and low contrast enhanced the CMF difference between azimuths. In conclusion, vertical and horizontal azimuths, location of eccentricity, contrast levels of word symbols, and monocular/binocular viewing have different effects on visual field asymmetry and cortical magnification factors.

The impact of visual function on staircase use performance in glaucoma.

OBJECTIVES: This cross-sectional study aimed to investigate the relationship between visual function and staircase use in glaucoma. METHODS: Overall, 181 patients with glaucoma with a best-corrected visual acuity ≥20/400 were classified into mild to moderate (mean deviation [MD] ≥ -12 dB) and advanced (MD < -12 dB) groups, according to 24-2 VF of the worse eye. Staircase use evaluation included stair descent and ascent time (SDT/SAT) and self-reported stair difficulty. Correlations between staircase use and visual function were analysed, including binocular visual acuity, integrated visual field (IVF), and binocular contrast sensitivity (CS). Linear and logistic regression adjusted by age, sex, and comorbidities inspected the effect of visual parameters on SDT/ SAT and stair difficulty. RESULTS: Visual function best correlated with SDT among staircase use. In mild to moderate glaucoma, area under the log CS function (AULCSF) (ß = -1.648, P = 0.031) was the only visual factor significant for SDT (adjusted R2 = 0.106), whereas AULCSF (ß = -1.641, P = 0.048) and MD of IVFINF0-24 (ß = -0.089, P = 0.013) were associated with SDT in advanced glaucoma (adjusted R2 = 0.589). The AULCSF was the only significant visual parameter related to SAT (ß = -1.125, P = 0.019) and stair difficulty (adjusted odds ratio = 0.003; 95% confidence interval, 0-0.302; P = 0.013). CONCLUSIONS: SDT provides a higher correlation with visual function than self-reported stair difficulty. Patients with impaired CS or inferior IVF defects should be advised on stair safety and referred to low-vision services.

Inhibition of Indoxyl Sulfate-Induced Reactive Oxygen Species-Related Ferroptosis Alleviates Renal Cell Injury In Vitro and Chronic Kidney Disease Progression In Vivo.

The accumulation of the uremic toxin indoxyl sulfate (IS) is a key pathological feature of chronic kidney disease (CKD). The effect of IS on ferroptosis and the role of IS-related ferroptosis in CKD are not well understood. We used a renal tubular cell model and an adenine-induced CKD mouse model to explore whether IS induces ferroptosis and injury and affects iron metabolism in the renal cells and the kidneys. Our results showed that exposure to IS induced several characteristics for ferroptosis, including iron accumulation, an impaired antioxidant system, elevated reactive oxygen species (ROS) levels, and lipid peroxidation. Exposure to IS triggered intracellular iron accumulation by upregulating transferrin and transferrin receptors, which are involved in cellular iron uptake. We also observed increased levels of the iron storage protein ferritin. The effects of IS-induced ROS generation, lipid peroxidation, ferroptosis, senescence, ER stress, and injury/fibrosis were effectively alleviated by treatments with an iron chelator deferoxamine (DFO) in vitro and the adsorbent charcoal AST-120 (scavenging the IS precursor) in vivo. Our findings suggest that IS triggers intracellular iron accumulation and ROS generation, leading to the induction of ferroptosis, senescence, ER stress, and injury/fibrosis in CKD kidneys. AST-120 administration may serve as a potential therapeutic strategy.

Achromatic and chromatic contrast discrimination in patients with type 2 diabetes.

Effects of type 2 diabetes on achromatic and chromatic contrast sensitivity (CS) are still controversial. In this study, we aimed to investigate CS in patients without diabetic retinopathy (no-DR) and in those with non-proliferative DR (NPDR) and proliferative DR (PDR) using psychophysical methods with transient and sustained achromatic stimuli and color patches. Achromatic CS was measured with the pulsed pedestal (PP) paradigm (7, 12, and 19 cd/m2) and pedestal-△-pedestal (P-△-P) paradigm (11.4, 18, and 28.5 cd/m2). A chromatic discrimination paradigm that assesses protan, deutan, and tritan color vision was adopted. Forty-two patients (no-DR n = 24, NPDR n = 12, PDR = 6; male n = 22, mean age = 58.1 y/o) and 38 controls (male n = 18, mean age = 53.4 y/o) participated. In patients, mean thresholds were higher than in controls and linear trends were significant in most conditions. For the PP paradigm, differences were significant in the PDR and NPDR groups in the 7 and 12 cd/m2 condition. For the P-△-P paradigm, differences were only significant in the PDR group in the 11 cd/m2 condition. Chromatic contrast loss was significant in the PDR group along the protan, deutan and tritan axes. The results suggest independent involvements of achromatic and chromatic CS in diabetic patients.

Development and validation of the Visual Function Battery for Children with Special Needs.

AIM: To develop and validate the Visual Function Battery for Children with Special Needs (VFB-CSN). METHOD: This was a scale development and validation study with (1) construct and item generation and (2) evaluations of interrater reliability, acceptability, and content, ecological, and convergent validities. RESULTS: Children with special needs were recruited for the reliability (n = 32) and validity (n = 95) investigations. The construct and items were generated based on literature review and an expert panel. We constructed eight categories, namely visual reflex, ocular muscle balance, visual acuity, oculomotor, visual field, contrast sensitivity, colour/form vision, and visual attention. Both functional assessment and standardized tests were adopted. The reliabilities were high for the whole VFB-CSN (intraclass correlation coefficient [ICC] = 0.90, 95% confidence interval [CI] = 0.80-0.90) and good for the oculomotor, contrast sensitivity, and colour/form vision (ICC = 0.80-0.86, 95% CI = 0.50-0.93). Correlations between the VFB-CSN and the Functional Vision Questionnaire were strong and acceptable for the contrast sensitivity, acuity, and colour/form vision (r = 0.79, r = 0.69, r = 0.69, r = 0.70 respectively). The correlation between the VFB-CSN and standardized visual acuity test was acceptable (r = -0.72). INTERPRETATION: The VFB-CSN is a reliable and valid multifaceted battery for children with special needs. Acceptable psychometric properties were also found for the acuity and contrast sensitivity. WHAT THIS PAPER ADDS: The Visual Function Battery for Children with Special Needs (VFB-CSN) can measure several types of visual function. The VFB-CSN also measures varying degrees of visual impairment in children with special needs. The VFB-CSN provides functional assessment and quantitative measurement for children with disability and difficulty in cooperating on standardized tests.

A non-invasive harmonic analysis to assess risk of retinopathy in type 2 diabetes mellitus.

AIMS: Assessing the hemodynamic changes of diabetic retinopathy (DR) using harmonic analysis of both non-invasively measured radial pulse and photoplethysmography (PPG) signals to propose a DR risk indicator. METHODS: A total of 1879 patients with diabetes were followed on average of 3.5 years. The radial pulse and PPG signals were measured at the beginning of the trial. Kaplan-Meier curves of the DR risk indicator was analyzed. In addition, the correlation between the measurements of the radial pulse and PPG was evaluated. RESULTS: In comparison of the patients' clinical characteristics, years of diabetes, systolic blood pressure, HbA1C, ACR, urinary albumin and fourth harmonic (C4) were higher in the DR group, and eGFR and third harmonic (C3) were lower. Patients in the high-DR risk group had a 1.8-fold higher risk of developing retinopathy than those in the low-risk group (log-rank test, p < 0.001). The correlation coefficient between radial pulse and PPG measurements for C3 and C4 were 0.727 and 0.628, respectively. CONCLUSIONS: The harmonic analysis of radial pulse and PPG signals may be used to reflect the effect of DR in hemodynamics and the derived harmonic components may predict the risk of DR of patients with type 2 diabetes.

Impacts of monocular, binocular, and functional visual acuity on vision-related quality of life in patients with type 2 diabetes.

Although the association between visual acuity (VA) and vision-related quality of life (VRQoL) has been well reported in patients with type 2 diabetes mellitus (T2DM), little is known about how unilateral and bilateral VA affects daily performance in such patients. For this cross-sectional study, patients were recruited from the Diabetes Shared Care Network of the Division of Endocrinology and Metabolism, Zhong-Xiao Branch, Taipei City Hospital in Taiwan. Ninety patients with T2DM (51 men and 39 women) with a mean age of 60.3 ± 10.5 (standard deviation) years, 47% of whom had diabetic retinopathy, were included. The purposes were to compare the impacts of VA in the better eye, both eyes, and three forms of functional acuity scores (FAS) on VRQoL in patients with T2DM. VRQoL and corrected VA were assessed with the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25) and Early Treatment Diabetic Retinopathy Study (ETDRS) chart, respectively. Three FAS algorithms proposed by Colenbrander and the American Medical Association were used to assess FAS. Regression analyses were performed to determine the correlations among the five types of VA, the original composite scores, and the Rasch-calibrated composite scores of the NEI VFQ-25 on all patients with T2DM and on the same patients stratified by diabetic retinopathy (DR) and no-DR. The VA of both eyes had a higher impact on VRQoL and revealed a lower reduction estimated by the two forms of composite scores than did the VA of the better eye and three FAS algorithms (compared with binocular VA ß estimates, - 14.5%, - 15.8%, - 29.3%, and - 11.8% for original composite scores, and - 16.1%, - 14.0%, - 24.6%, and 10.3% for Rasch-calibrated composite scores). When the T2DM group was stratified into DR and no-DR groups, significant associations between VA and VRQoL were observed only in the DR group. The VA of both eyes also had the greatest impact and reduction after stratification. The results indicated that unilateral better-eye VA and VA estimated by the three FAS algorithms seems to underestimate the impact of visual impairment on self-report VRQoL in patients with T2DM. This study provides empirical support for the importance of binocular VA assessment in regular clinical diabetes eye care.

Legibility Assessment of Visual Word Form Symbols for Visual Tests.

For a reliable visual test, it is important to evaluate the legibility of the symbols, which depends on several factors. Previous studies have compared the legibility of Latin optotypes. This study developed a visual function test based on identification visual capacity for a Chinese reading population. The legibility of word symbols was assessed with three methods: (1) Identification of the contrast thresholds of the character sets, (2) patterns of confusion matrices obtained from analysis of the frequency of incorrect stimulus/response pairs, and (3) pixel ratios of bitmap images of Chinese characters. Then characters of similar legibility in each character set were selected. The contrast thresholds of the final five character sets and the Tumbling E and Landolt C optotypes were evaluated. No significant differences in contrast threshold were found among the five selected character sets (p > 0.05), but the contrast thresholds were significantly higher than those of the E and C optotypes. Our results indicate that combining multiple methods to include the influences of the properties of visual stimuli would be useful in investigating the legibility of visual word symbols.

Detecting Visual Function Abnormality with a Contrast-Dependent Visual Test in Patients with Type 2 Diabetes.

In addition to diabetic retinopathy, diabetes also causes early retinal neurodegeneration and other eye problems, which cause various types of visual deficits. This study used a computer-based visual test (Macular Multi-Function Assessment (MMFA)) to assess contrast-dependent macular visual function in patients with type 2 diabetes to collect more visual information than possible with only the visual acuity test. Because the MMFA is a newly developed test, this study first compared the agreement and discriminative ability of the MMFA and the Early Treatment Diabetic Retinopathy Study (ETDRS) contrast acuity charts. Then symbol discrimination performances of diabetic patients and controls were evaluated at 4 contrast levels using the MMFA. Seventy-seven patients and 45 controls participated. The agreement between MMFA and ETDRS scores was examined by fitting three-level linear mixed-effect models to estimate the intraclass correlation coefficients (ICCs). The estimated areas under the receiver operating characteristic (ROC) curve were used to compare the discriminative ability of diseased versus non-diseased participants between the two tests. The MMFA scores of patients and controls were compared with multiple linear regression analysis after adjusting the effects of age, sex, hypertension and cataract. Results showed that the scores of the MMFA and ETDRS tests displayed high levels of agreement and acceptable and similar discriminative ability. The MMFA performance was correlated with the severity of diabetic retinopathy. Most of the MMFA scores differed significantly between the diabetic patients and controls. In the low contrast condition, the MMFA scores were significantly lower for 006Eon-DR patients than for controls. The potential utility of the MMFA as an easy screening tool for contrast-dependent visual function and for detecting early functional visual change in patients with type 2 diabetes is discussed.

A New Visual Stimulation Program for Improving Visual Acuity in Children with Visual Impairment: A Pilot Study.

The purpose of this study was to investigate the effectiveness of visual rehabilitation of a computer-based visual stimulation (VS) program combining checkerboard pattern reversal (passive stimulation) with oddball stimuli (attentional modulation) for improving the visual acuity (VA) of visually impaired (VI) children and children with amblyopia and additional developmental problems. Six children (three females, three males; mean age = 3.9 ± 2.3 years) with impaired VA caused by deficits along the anterior and/or posterior visual pathways were recruited. Participants received eight rounds of VS training (two rounds per week) of at least eight sessions per round. Each session consisted of stimulation with 200 or 300 pattern reversals. Assessments of VA (assessed with the Lea symbol VA test or Teller VA cards), visual evoked potential (VEP), and functional vision (assessed with the Chinese-version Functional Vision Questionnaire, FVQ) were carried out before and after the VS program. Significant gains in VA were found after the VS training [VA = 1.05 logMAR ± 0.80 to 0.61 logMAR ± 0.53, Z = -2.20, asymptotic significance (2-tailed) = 0.028]. No significant changes were observed in the FVQ assessment [92.8 ± 12.6 to 100.8 ±SD = 15.4, Z = -1.46, asymptotic significance (2-tailed) = 0.144]. VEP measurement showed improvement in P100 latency and amplitude or integration of the waveform in two participants. Our results indicate that a computer-based VS program with passive checkerboard stimulation, oddball stimulus design, and interesting auditory feedback could be considered as a potential intervention option to improve the VA of a wide age range of VI children and children with impaired VA combined with other neurological disorders.

Effects of visual rehabilitation on a child with severe visual impairment.

We examined the effects of visual rehabilitation, including a chromatic luminance discrimination program and a fixation training program, on a 6-yr-old boy with severe visual impairment. Single-subject ABA and AB designs were used. The programs were conducted 2×/wk and included 6 to 7 sessions for the baseline phase and 10 to 11 sessions for the intervention phase. Play was integrated into the visual training programs. Goggle visual evoked potential (VEP) testing was used to evaluate neural activity in the primary visual cortex. Correct responses increased and response times were shortened after training in luminance discrimination. The total and maximum fixation time also improved, as did P100 latency and amplitude of VEPs. While walking, the boy was able to detect obstacles he had not noticed before training. The results indicate the value of visual training and the possibility of brain plasticity in a child with severe visual impairment.

Reliability of two visual-perceptual tests for children with cerebral palsy.

OBJECTIVE: We examined the reliability of the Motor-Free Visual Perception Test-Revised (MVPT-R) and the Test of Visual-Perceptual Skills-Revised (TVPS-R) in 52 children with cerebral palsy. METHOD: The MVPT-R and TVPS-R were initially assessed by a single rater and then randomly assigned to the same rater or another rater after 6 to 14 days. RESULTS: For scale-level reliability of both tests, the intraclass correlation coefficients (ICCs) were high. The smallest real differences (SRDs) were largely acceptable. The OICCs of most subscale-level reliability of the TVPS-R were satisfactory. The SRD of each TVPS-R subscale score was notable (>29%). The internal consistency was high for both tests. CONCLUSION: The scale-level reliabilities of both tests were satisfactory in children with cerebral palsy. Although most subscales of the TVPS-R had acceptable test-retest or interrater agreement, all subscales of the TVPS-R had large SRDs, limiting their clinical utility.