Color vision impairments in schizophrenia and the role of antipsychotic medication type

Brain atrophy and cognitive decline in bipolar disorder: Influence of medication use, symptomatology and illness duration

Bipolar disorder (BPD) is a chronic condition characterized by recurrent episodes of mania and depression. To date, the association of biological and psychopathological processes in BPD has not been extensively studied on a cognitive and cortical basis at the same time. We investigated whether brain atrophy (in prefrontal, temporal and occipital cortices) was associated with cognitive, biological and clinical processes in patients with BPD and healthy controls (HCs). A total of 104 participants (56 with BPD) completed tasks that measured attention, memory, information processing speed, inhibitory control, visuospatial working memory and cognitive flexibility. In addition, structural brain scans were obtained using high-resolution MRI. Outcomes of the measurements were examined using robust multiple mediation analyses. BPD patients showed greater cortical atrophy across all regions of interest when compared to HCs, linked to cognitive decline. BPD patients had slower reaction times and markedly increased errors of commission on the tasks. The outcomes were significantly influenced by medication use, symptomatology and illness duration. The findings showcase the complexity of brain structures and networks as well as the physiological mechanisms underlying diverse BPD symptomatology and endophenotypes. These differences were pronounced in patients with BPD, motivating further investigations of pathophysiological mechanisms involved in brain atrophy and cognitive decline.

Working memory and sensory memory in subclinical high schizotypy: An avenue for understanding schizophrenia?

The search for robust, reliable biomarkers of schizophrenia remains a high priority in psychiatry. Biomarkers are valuable because they can reveal the underlying mechanisms of symptoms and monitor treatment progress and may predict future risk of developing schizophrenia. Despite the existence of various promising biomarkers that relate to symptoms across the schizophrenia spectrum, and despite published recommendations encouraging multivariate metrics, they are rarely investigated simultaneously within the same individuals. In those with schizophrenia, the magnitude of purported biomarkers is complicated by comorbid diagnoses, medications and other treatments. Here, we argue three points. First, we reiterate the importance of assessing multiple biomarkers simultaneously. Second, we argue that investigating biomarkers in those with schizophrenia-related traits (schizotypy) in the general population can accelerate progress in understanding the mechanisms of schizophrenia. We focus on biomarkers of sensory and working memory in schizophrenia and their smaller effects in individuals with nonclinical schizotypy. Third, we note irregularities across research domains leading to the current situation in which there is a preponderance of data on auditory sensory memory and visual working memory, but markedly less in visual (iconic) memory and auditory working memory, particularly when focusing on schizotypy where data are either scarce or inconsistent. Together, this review highlights opportunities for researchers without access to clinical populations to address gaps in knowledge. We conclude by highlighting the theory that early sensory memory deficits contribute negatively to working memory and vice versa. This presents a mechanistic perspective where biomarkers may interact with one another and impact schizophrenia-related symptoms.

Elimination of the color discrimination impairment along the blue-yellow axis in patients with hypothyroidism after treatment with levothyroxine as assessed by the Farnsworth-Munsell 100 hue test

Our previous study has shown that individuals with untreated hypothyroidism display significantly higher partial error scores (P E S) along the blue-yellow axis compared to the red-green axis than normal individuals using the Farnsworth-Munsell 100 hue test [J. Opt. Soc. Am. A37, A18 (2020)JOAOD60740-323210.1364/JOSAA.382390]. We wished to determine how color discrimination may change when hypothyroidism has been treated to the point of euthyroidism. Color discrimination was reassessed for 17 female individuals who had undergone treatment for hypothyroidism, and the results were compared with 22 female individuals without thyroid dysfunction. No statistically significant difference was found in the total error score (T E S) for the first and second measurements for both groups (p>0.45). The P E S for the hypothyroid group improved significantly in the previously impaired color regions after the treatment. Color discrimination defects found in untreated hypothyroidism can be negated with treatment of the condition over an appropriate time period.

Myopia and its associated factors among pregnant women at health institutions in Gondar District, Northwest Ethiopia: A multi-center cross-sectional study

Background

Myopia is the most common form of uncorrected refractive error with a growing burden worldwide. It is the principal complaint of most women during pregnancy. Although myopia has led to several consequences across the standard life of pregnant women, there is no previous study in Ethiopia regarding this topic. Thus, this study determined the prevalence of myopia and identifies its associated factors among pregnant women attending antenatal care units at governmental health institutions in Gondar City District, Northwest Ethiopia.

Methods

An institution-based cross-sectional study design was conducted from 08 February to 08 April 2021. From the selected health centres, study participants were recruited by systematic random sampling technique. A pre-tested, structured-interviewer-administered questionnaire consisting of socio-demographic variables, obstetric and clinical-related variables was used to collect the required data. Non-cycloplegic refraction was performed using trial lenses, trial frames, and retinoscopy in a semi-dark examination room. EpiData 3 and STATA 14 were used for data entry and statistical analysis respectively. Both bivariable and multivariable binary logistic regression analyses were executed to identify associated factors of myopia. Variables with a p-value ≤0.05 in the multivariable logistic regression analysis were declared as statistically significant with myopia. Model fitness was checked by Hosmer and Lemeshow goodness of test (at p > 0.05).

Results

A total of four-hundred and twenty-three pregnant women participated with a 100% response rate in this study. The overall prevalence of myopia among pregnant women was 26.48% (95% CI: 22.48-30.91). Eighty-Eight (20.81%) and Eighty-Four (19.85%) of the study participants had myopia in their right and left eyes respectively. The prevalence of myopia was significantly associated with age (AOR = 1.17; 95% CI: 1.09-1.28), the third trimester of gestation (AOR = 2.05, 95% CI: 1.08-3.90), multi & grand multipara (AOR = 3.15; 95% CI: 1.59-6.25), and history of contraceptive use (AOR = 3.30; 95% CI: 1. 50-7.28).

Conclusion

The finding of our study shows that there is a higher prevalence of myopia among pregnant women in our study area. Further prospective analytical studies regarding visual systems among pregnant women, particularly as a result of pregnancy, are strongly recommended.

Altered brain connectivity during visual stimulation in schizophrenia

Schizophrenia (SCZ) can be described as a functional dysconnectivity syndrome that affects brain connectivity and circuitry. However, little is known about how sensory stimulation modulates network parameters in schizophrenia, such as their small-worldness (SW) during visual processing. To address this question, we applied graph theory algorithms to multi-electrode EEG recordings obtained during visual stimulation with a checkerboard pattern-reversal stimulus. Twenty-six volunteers participated in the study, 13 diagnosed with schizophrenia (SCZ; mean age = 38.3 years; SD = 9.61 years) and 13 healthy controls (HC; mean age = 28.92 years; SD = 12.92 years). The visually evoked potential (VEP) showed a global amplitude decrease (p < 0.05) for SCZ patients as opposed to HC but no differences in latency (p > 0.05). As a signature of functional connectivity, graph measures were obtained from the Magnitude-Squared Coherence between signals from pairs of occipital electrodes, separately for the alpha (8-13 Hz) and low-gamma (36-55 Hz) bands. For the alpha band, there was a significant effect of the visual stimulus on all measures (p < 0.05) but no group interaction between SCZ and HZ (p > 0.05). For the low-gamma spectrum, both groups showed a decrease of Characteristic Path Length (L) during visual stimulation (p < 0.05), but, contrary to the HC group, only SCZ significantly lowered their small-world (SW) connectivity index during visual stimulation (SCZ p < 0.05; HC p > 0.05). This indicates dysconnectivity of the functional network in the low-gamma band of SCZ during stimulation, which might indirectly reflect an altered ability to react to new sensory input in patients. These results provide novel evidence about a possible electrophysiological signature of the global deficits revealed by the application of graph theory onto electroencephalography in schizophrenia.

Association between cognition and color discrimination among Lebanese patients with schizophrenia

BACKGROUND

Patients with schizophrenia (SCZ) exhibit poorer color discrimination than normal individuals. Although retinal abnormalities, as well as cortical and subcortical alterations, found in patients with SCZ have been suggested to cause this poor color discrimination, the impact of cognitive impairment remains to be determined. Dopamine (DA) and glutamate (Glu), known to be disrupted in SCZ, are also suggested to play a role in color discrimination. Our objective was to investigate the contribution of cognitive impairment to color discrimination deficits in SCZ and to examine if these deficits are correlated to SCZ symptoms.

METHODS

This study includes 127 patients with SCZ between July and September 2021. The participants completed several questionnaires, specifically the Positive and Negative Syndrome Scale (PANSS), the Montreal Cognitive Assessment (MoCA) test, and the Farnsworth D-15 test, to assess the extent of SCZ symptoms, cognition, and color discrimination respectively.

RESULTS

Higher cognition (Beta = - 0.279) was significantly associated with a lower total error score (TES). Moreover, a higher positive PANSS score (Beta = 0.217) was significantly associated with a higher TES. A multinomial regression analysis taking the type of color blindness as the dependent variable showed that female sex (ORa = 5.46) was significantly associated with a certain type of color blindness.

CONCLUSION

Color discrimination deficits in patients with SCZ may be due to the effect of cognitive impairment and/or SCZ itself.

A case of schizophrenia with congenital color vision deficiency: From the perspective of color universal design to promote medication adherence

Color‐blindness, or more accurately, color vision deficiency (CVD), which is the inability or decreased ability to distinguish different colors, is one of the commonest visual disorders. Patients with schizophrenia usually have multiple types of visual processing impairments, including color vision impairments. Here, we present a case of schizophrenia with congenital CVD. The patient was aware of his color deficiency since elementary school. We assessed his ability to distinguish medicines based on their color, including those that he had been previously prescribed. Although he could distinguish all of the tablets, he could not distinguish the color of the blister packs, specifically that of the bromazepam 2 mg pack (green) from the 1 mg pack (red). This case suggests that CVD patients might misunderstand the color of medications, which might lead to medication errors, or poor drug adherence. The color universal design principle should be considered when designing tablets and their blister packs, in order to improve medication adherence.

Reduced ability to discriminate colours - an under-recognised feature of depressive disorders? A pilot study

Background: Although in clinical practice an impairment of sensory perception is frequently reported by depressed patients no mention of these symptoms is made in DSM-5, ICD-10 or ICD-11. Previous studies on colour perception have largely relied on patient self-reports and few have studied colour discrimination.Methods: The ability to discriminate small colour differences was assessed in 30 patients currently experiencing a moderate to severe depressive episode (ICD-10: F32.1-2, F33.1-2 or F31.3-4) and 32 healthy controls using the colour buttons of the Farnsworth Munsell 100-Hue test. Data were analysed by standard tests for comparing two groups (t-test, Mann-Whitney U-test, Chi-square test) and by ordinal regression and generalised estimating equation models.Results: Depressed patients failed significantly earlier (i.e., at larger differences between adjacent buttons) to discriminate between colours. This finding was retained after adjustment for potential confounders. There was no significant association with age, gender or depression score.Conclusions: We found a reduction in the ability to discriminate colours in depressed patients. This finding underlines the importance of sensory deficits as part of the symptomatology of depression. Sensory impairments should be taken into account in clinical care of patients with depression and should be included in diagnostic manuals. Further studies in larger samples including intra-individual comparisons between the depressed and the remitted state of patients are needed.Key pointsIn clinical practice, an impairment of sensory perception is frequently reported by depressed patients.However, no mention of these symptoms is made in the commonly used diagnostic manuals.In this pilot study, depressed patients and controls differed significantly in terms of the ability to discriminate colours with patients performing worse than their healthy counterparts.Sensory impairments should be taken into account in clinical care of patients with depression and should be included in diagnostic manuals.

Chromatic discrimination measures in mature observers depend on the response window

Our past anecdotal evidence prompted that a longer response window (RW) in the Trivector test (Cambridge Colour Test) improved mature observers’ estimates of chromatic discrimination. Here, we systematically explored whether RW variation affects chromatic discrimination thresholds measured by the length of Protan, Deutan and Tritan vectors. We employed the Trivector test with three RWs: 3 s, 5 s, and 8 s. Data of 30 healthy normal trichromats were stratified as age groups: ‘young’ (20–29 years), ‘middle-aged’ (31–48 years), and ‘mature’ (57–64 years). We found that for the ‘young’ and ‘middle-aged’, the thresholds were comparable at all tested RWs. However, the RW effect was apparent for the ‘mature’ observers: their Protan and Tritan thresholds decreased at 8-s RW compared to 3-s RW; moreover, their Tritan threshold decreased at 5-s RW compared to 3-s RW. Elevated discrimination thresholds at shorter RWs imply that for accurate performance, older observers require longer stimulus exposure and are indicative of ageing effects manifested by an increase in critical processing duration. Acknowledging low numbers in our ‘middle-aged’ and ‘mature’ samples, we consider our study as pilot. Nonetheless, our findings encourage us to advocate a RW extension in the Trivector protocol for testing mature observers, to ensure veridical measures of their chromatic discrimination by disentangling these from other ageing effects—slowing down of both motor responses and visual processing.

Correlates of clinical variables on early-stage visual processing in schizophrenia and bipolar disorder

The use of noninvasive tools can help understand mental states and changes that are caused by medications, symptom severity, and other clinical variables. We investigated low-level visual processing using the contrast sensitivity function (CSF), a reliable, robust, and widely used approach. Our main purpose was (1) to evaluate visual impairments in schizophrenia (SCZ) and bipolar disorder (BPD) patients and (2) to investigate associations between clinical variables and visual function in both diseases. Fifty-six healthy controls (HCs; mean age = 31.04 years), 42 BPD patients (mean age = 32.84 years) who took only lithium, and 39 SCZ patients who took only olanzapine (mean age = 32.80 years) were recruited for this study. CSF differed between groups. Both groups of patients exhibited lower discrimination at low, mid-, and high spatial frequencies compared with HCs. No differences were observed between patients, with the exception of high spatial frequency. These impairments were also related to clinical variables, revealed by a strong effect in the mediation analyses. These findings may aid investigations of other clinical variables and the role of state- and trait-like effects on visual and cognitive processing in these patient populations. This study underscores the need for visual remediation interventions.

Improvement in visual performance after nicotine gum administration in tobacco use disorder: a case report

Chronic tobacco consumption, identified as Tobacco Use Disorder (TUD), is a public health problem. We present a case report of a 37-year-old Brazilian male diagnosed with TUD at age 26, with no comorbidities, that presented visual improvements (i.e., lower thresholds and better discrimination) after nicotine gum administration. Here, we assessed contrast sensitivity and chromatic discrimination using the Metropsis and the Cambridge Colour Test, respectively. Results showed lower thresholds for both visual tasks after the use of nicotine gum. Even considering this is a single case report, our intent is to open new avenues for research involving smoking, addiction and the use of nicotine gum as a replacement tool or adjuvant tool for improvement of visual and/or cognitive processing. It is well known that nicotine gum has protective effects for some diseases, and improves some cognitive functions. However, unclear were its effects on visual processing of people with TUD.

Eye movement impairments in children with malnutrition

Malnutrition is characterised by deficient nutrient ingestion and absorption and is still one of the most important causes of morbidity and mortality in children worldwide. Our main rationale was that protein-energy malnutrition (PEM) may affect eye movement in children with malnutrition. Twenty children without PEM (mean age = 10.8; SD = 1.0 years) and 18 children with PEM (mean age = 10.9; SD = 1.2 years) were included in the present study. We applied three types of tests: one that consisted of a maze and two versions of the Spot the Seven Errors test using boats and elephants. Our results indicated that children with PEM exhibited performance deficits in the maze test (p < .001) and Spot the Seven Errors test for both boats (p < .001) and elephants (p < .001). These data suggest that nutritional impairments during the first year of life (i.e., a critical period) can directly impact eye movement. Eye tracking is a reliable technique to investigate higher-order processes, but our results should be interpreted with caution. Our findings highlight the relevance of cognitive development in malnourished children, which can negatively affect their development. Screening, assessment and rehabilitation strategies are essential in this at-risk population.

Visual impairment and associated factors among pregnant women attending antenatal care units at health institutions in Gondar City Administration, Northwest Ethiopia

Background

Visual impairment is a major public health concern among women of reproductive age groups in Ethiopia, which is getting worse during pregnancy. Though visual impairment has lots of serious consequences across the life course of pregnant women, there is no previous study on this topic in Ethiopia. Thus, this study determined the prevalence of visual impairment and identified associated factors among pregnant women attending antenatal care units at the governmental health institutions in Gondar City Administration, Northwest Ethiopia.

Methods

An institution-based cross-sectional study was conducted. A systematic random sampling technique was used to recruit the study participants. We used an interviewer-administered questionnaire comprising of socio-demographic, clinical and pregnancy-related variables to collect the required data. Snellen’s illiterate “E” chart was used to determine visual impairment. EpiData 3 and Stata 14 were used for data entry and statistical analysis, respectively. Both bivariable and multivariable binary logistic regression analyses were executed to identify associated factors of visual impairment. Variables with a p-value ≤0.05 in the multivariable logistic regression analysis were declared as statistically significant with visual impairment.

Results

A total of 417 (response rate = 98.6%) participants were involved in this study, with a median age of 27 years. The overall prevalence of visual impairment was 22.5% (95% CI: 18.5–26.6). Thirty (7.2%) and thirty-two (7.7%) of the study participants had moderate to severe visual impairments in their right and left eyes, respectively. Participants aged from 31 to 49 years (AOR = 2.1; 95% CI: 1.1–4.0), being 3rd trimester (AOR = 2.4; 95% CI: 1.3–4.5), multi & grand multipara (AOR = 2.3; 95% CI: 1.2–4.6), and history of contraceptive use (AOR = 2.7; 95% CI: 1.2–6.3) had higher chance of visual impairment.

Conclusion

The magnitude of visual impairment among pregnant women was high in the study area. Therefore, routine screening and evaluation of pregnant women for visual condition during antenatal care visits is recommended. Further investigations of visual changes, particularly as a result of pregnancy, are warranted.

Color painting predicts clinical symptoms in chronic schizophrenia patients via deep learning

BACKGROUND

Individuals with psychiatric disorders perceive the world differently. Previous studies indicated impaired color vision and weakened color discrimination ability in psychotic patients. Examining the paintings from psychotic patients can measure the visual-motor function. However, few studies examined the potential changes in the color painting behavior in these individuals. The current study aims to discriminate schizophrenia patients from healthy controls (HCs) and predict PANSS scores of schizophrenia patients according to their paintings.

METHODS

In the present study, we retrospectively analyzed the paintings colored by 281 chronic schizophrenia patients and 35 HCs. The images were scanned and processed using series of computational analyses.

RESULTS

The results showed that schizophrenia patients tend to use less color and exhibit different strokes compared to HCs. Using a deep learning residual neural network (ResNet), we were able to discriminate patients from HCs with over 90% accuracy. Further, we developed a novel convolutional neural network to predict PANSS positive, negative, general psychopathology, and total scores. The Root Mean Square Error (RMSE) of the prediction was low, which indicates higher accuracy of prediction.

CONCLUSION

In conclusion, the deep learning paradigm showed the large potential to discriminate schizophrenia patients from HCs based on color paintings. Besides, this color painting-based paradigm can effectively predict clinical symptom severity for chronic schizophrenia patients. The color paintings by schizophrenia patients show potential as a tool for clinical diagnosis and prognosis. These findings show potential as a tool for clinical diagnosis and prognosis among schizophrenia patients.

Nicotine gum enhances visual processing in healthy nonsmokers

OBJECTIVE

The main purpose of this study was to investigate the isolated effects of nicotine on visual processing, namely contrast processing.

METHODS

Thirteen participants, aged 18-40 years, were enrolled in this double blind, randomized and pilot controlled trial involving nicotine gum administration (placebo, 2-mg and 4-mg doses). The participants' instruction was to detect the location of vertical gratings (0.2; 1.0; 3.3; 5.7; 8.8; 13.2 and 15.9 cycles per degree) when it was presented either left or right on the monitor screen. A repeated multivariate analysis of variance was conducted to analyse the results for the visual processing tasks. Bayesian analyses were also carried out considering maximum robustness to avoid bias.

RESULTS

The findings that nicotine gum administration resulted in better contrast discrimination when compared to placebo gum (p < .001). More specifically, the 4-mg resulted in better visual sensitivity when compared to the 2-mg (p < .01) and the placebo (p < .001) gum. Demographic data were not related to the outcomes.

CONCLUSIONS

These data bring the need for support the findings. If proved, it is possible that nicotine, in small doses, can have a potential therapeutic use for those populations with low vision.

TRIAL REGISTRATION NUMBER

RBR-46tjy3.

Irreversible Primary Visual Cortex Impairment in a Mouse Model of High-Risk Schizophrenia

PURPOSE

Although visual deficits can be observed at any stage of schizophrenia, few studies have focused on visual cortex alterations in individuals at high risk of schizophrenia. This study aimed to investigate the pathological changes of the primary visual cortex in a prenatal mouse model of MK801-induced high-risk schizophrenia.

METHODS

The high-risk schizophrenia model was generated by MK801 injection into pregnant mice. The male offspring without schizophrenia-like behaviors in early adulthood were defined as the high-risk mouse model of schizophrenia (HRMMS) and divided into two groups. One HRMMS group received the antipsychotic agent risperidone beginning at postnatal week 4 and another group did not receive any treatment. After treatment for 4 weeks, in vivo two-photon calcium imaging was performed to characterize the primary visual cortex activity. The novel object recognition test and the prepulse inhibition apparatus test were also implemented to assess the cognitive and behavioral performance, respectively.

RESULTS

Both groups of HRMMS mice, with or without antipsychotic treatment, had decreased neuronal calcium activity, demonstrating primary visual cortex impairment. More notably, antipsychotic treatment did not normalize the impaired neuronal activities in the primary visual cortex. Correspondingly, the treatment did not improve the cognitive or behavioral impairment.

CONCLUSION

Visual cortex impairment might be a prominent feature of individuals at high risk of schizophrenia that cannot be normalized by early treatment with antipsychotic medication, indicating the presence of independent regulatory pathways for visual perception disturbance in schizophrenia. Thus, visual system impairment in schizophrenic patients must be further studied.

THE USE OF ELECTRORETINOGRAPHY AND OPTICAL COHERENCE TOMOGRAPHY IN PATIENTS WITH SCHIZOPHRENIA

The use of electroretinography (ERG) and optical coherence tomography (OCT) has currently expanded beyond ophthalmology alone. The aim of this review is to present the results and knowledge acquired by these two methods in patients suffering from schizophrenia. Reviewing the studies applying ERG and OCT methods in the field of psychiatry, one can conclude that results of the research imply morphological and functional changes of retina in patients with schizophrenia that are not consistent. However, in most studies there was reduction of the amplitude and changes in the implicit time related parameters on ERG and thinning of the retinal nerve fiber layer on OCT. Neurons in the eye use the same neurotransmitters as neurons in the basal brain structures that are most affected in schizophrenia, according to the dopamine hypothesis of schizophrenia. Unlike neurons in the basal brain structures, the neurons in the eye are in vivo available to ERG. Using the aforementioned tests together with clinical diagnostic criteria of schizophrenia, the subgroups with different prognostic and therapeutic specificities within schizophrenia as a group of diseases might be identified more precisely.

Opposite effects of smoking and nicotine intake on cognition

Our main purpose was to investigate how smoking and nicotine interacted with specific aspects of cognitive functioning. The research was conducted in two parts: (i) an investigation of cognition in heavy smokers and healthy nonsmokers, and (ii) an investigation of cognition in healthy nonsmokers enrolled in a clinical trial involving administration of nicotine gum. Results indicated that the relationship between smoking and nicotine was characterized by an inverted U-shaped effect. On the one hand, cognitive test performance of the heavy smokers group was reduced on all of the cognitive tasks used here. On the other hand, healthy nonsmokers who used 2-mg of nicotine gum performed better, whilst the 4-mg group performed worse than the 2-mg and the placebo group. Demographic data were not related to the cognitive tasks. These data suggest that small doses of nicotine can have an activating function that leads to improved cognition, while heavy smoking on a chronic (and possibly acute) basis leads to cognitive impairment.

Color discrimination assessment in patients with hypothyroidism using the Farnsworth-Munsell 100 hue test

There is evidence in the literature that hypofunction of the thyroid gland (hypothyroidism) affects color vision in rodents by influencing the production of the visual pigment opsin. The effect of hypothyroidism on color vision in humans has not been examined in any great detail. In this cross-sectional study we evaluated color discrimination using the Farnsworth-Munsell 100 hue test (FM-100 test) in 25 individuals with pre-treatment hypothyroidism (mean age ${38}\;{\pm }\;{9}.{2}\;\text{yr}$38±9.2yr), and a control euthyroid group, ${ n} ={26}$n=26 (mean age ${39.6}\;{\pm }\;{8}.{4}\;\text{yr}$39.6±8.4yr). There was no statistically significant difference in the total error score ($\surd{\text{TES}}$√TES) between the groups, but the hypothyroid group had a significantly greater partial error score ($\surd{\text{PES}}$√PES) along the blue-yellow (B-Y) axis compared to the red-green (R-G) axis. No statistically significant differences in B-Y and R-G PES were observed in the control group. This study shows that hypothyroidism affects color vision in humans, causing significant impairment in the B-Y color subsystem.

Visual impairments in type 1 bipolar disorder

Objectives: The present study evaluated early visual processing, in terms of the contrast sensitivity function (CSF), in bipolar disorder (BPD) patients.Methods: Data were recorded in 17 healthy participants and 17 outpatients with type 1 BPD, from 20 to 45 years of age. The CSF was measured at spatial frequencies of 0.2, 0.6, 3.1, 8.0, 16.0 and 20.0 cycles per degree (cpd) using Gabor patches and a two-alternative, forced-choice, logarithmic staircase method. The groups were matched for gender, age and level of education.Results: The CSF differed between groups. Patients with BPD had lower discrimination at spatial frequencies of 0.2 cpd (P < 0.001), 0.6 cpd (P < 0.001), 16.0 cpd (P < 0.001) and 20.0 cpd (P < 0.001) compared with healthy subjects. No differences were observed at 3.1 cpd (P > 0.05) and 8.0 cpd (P > 0.05). This visual impairment was related both to longer duration of illness and to greater severity of manic symptoms.Conclusions: The differences in visual processing were pronounced in patients with BPD, which justifies further investigations of the pathophysiological mechanisms that are involved in sensorial alterations.

Spatial contrast sensitivity: effects of reliability, test-retest repeatability and sample size using the Metropsis software

PURPOSE

The goals of the study were to further assess contrast sensitivity to (1) investigate the existence of monocular vs. binocular differences; (2) observe possible differences between sample sizes; (3) investigate the effects of test-retest repeatability.

METHODS

Contrast sensitivity measurements were obtained by presenting eight horizontal sine-wave gratings (ranging from 0.2 to 20 cycles per degree). A three-up-one-down method was used to obtain thresholds with a criterion of 79.4% correct responses for each spatial frequency. The mean of 12 reversals was used for obtaining thresholds, and the two-alternative forced-choice method was used. Data were recorded in 55 naive observers from 20 to 45 years. All participants were free from identifiable ocular disease and had normal visual acuity.

RESULTS

We observed the absence of differences on CSF for both monocular and binocular observers, as well as the absence of differences between large sample sizes. The latter investigation revealed a high degree of repeatability across time (baseline to 6 months later) with the higher test-retest for low and high spatial frequencies.

CONCLUSIONS

Our results indicated that spatial contrast sensitivity measurements were little influenced by variables, such as binocular summation, eye dominance, sample size and time using the Metropsis test. The results obtained here have significance for basic and clinical vision science.

Visual impairments in tobacco use disorder

Prior studies found small effects of chronic smoking on spatial and color vision, but they were inconclusive. This study tries to: (1) replicate and extend these previous findings, and (2) rule in that this relationship is pronounced by tobacco addiction. Data were recorded in 71 healthy controls (M = 33.5 years; SD = 5.4 years) and 63 individuals with tobacco addiction (M = 34.7 years; SD = 4.8 years). Visual processing was assessed in the forms of contrast sensitivity for linear sine-wave gratings (spatial frequencies ranging between 0.2 and 16 cycles per degree) and color discrimination (using the Ellipse and Trivector subtests). The groups were matched for age, gender and level of education. The group with heavy smokers had reduced sensitivity for all spatial frequencies (p < .001), and impairments in color discrimination for both Trivector (all p-values < .001 for Protan, Deutan and Tritan) and Ellipse (all p-values < .001). This study consistently replicates and extended previous findings, and showed that visual processing can be strongly associated with tobacco addiction. These results indicate that excessive use of cigarettes, or chronic exposure to their compounds, affects visual discrimination, supporting the existence of overall deficits in visual processing in tobacco addiction.