Effect of the chromaticity of stimuli on night vision disturbances.

The perception of halos and other night vision disturbances is a common complaint in clinical practice. Such visual disturbances must be assessed in order to fully characterize each patient's visual performance, which is particularly relevant when carrying out a range of daily tasks. Visual problems are usually assessed using achromatic stimuli, yet the stimuli encountered in daily life have very different chromaticities. Hence, it is important to assess the effect of the chromaticity of visual stimuli on night vision disturbances. The aim of this work is to study the influence of the chromaticity of different visual stimuli on night vision disturbances by analyzing straylight and visual discrimination under low-light conditions. For that, we assessed the monocular and binocular visual discrimination of 27 subjects under low illumination using the Halo test. The subjects' visual discrimination was assessed after exposure to different visual stimuli: achromatic, red, green, and blue, both at the monitor's maximum luminance and maintaining the same luminance value for the different visual stimuli. Monocular straylight was also measured for an achromatic, red, green, and blue stimuli. The blue stimulus had the greatest effect on halos in both monocular and binocular conditions. Visual discrimination was similar for the red, green, and achromatic stimuli, but worsened at lower luminance. The greatest influence of straylight was observed for the blue stimulus. In addition, visual discrimination correlated with straylight measurements for achromatic stimuli, wherein greater straylight values correlated with an increased perception of halos and other visual disturbances.

Alcohol effects on drivers' speed management: The influence of visual performance and road complexity.

OBJECTIVE: The aim of this work is to assess how drivers adapt their driving speed as a self-regulation mechanism when driving under the influence of alcohol (DUIA), and the influence of alcohol consumption, visual performance, road complexity, and personal traits. METHOD: Thirty one volunteers took part in the study. All of them underwent three experimental sessions: Baseline (no alcohol), Alcohol 1 (low-moderate dose), and Alcohol 2 (moderate-high dose). Vision was tested by means of contrast sensitivity and retinal straylight. Driving performance was assessed using a driving simulator. The difference between the driving speed and the speed limit was calculated in 10 road scenarios of different complexity. RESULTS: Drivers adapted their driving speed less (i.e., drove faster) in Alcohol 1 condition compared to Alcohol 2 (p = 0.007). This indicate that participants felt more confident under the influence of a low-moderate dose of alcohol. Participants with better contrast sensitivity drove faster (p = 0.021). The complexity of the road and other factors such as driving experience, gender, or DUIA frequency, also influenced speed choice. CONCLUSIONS: Drivers under the influence of a low-moderate dose of alcohol seem to be less aware of the risk. Contrast sensitivity is a good predictor of the speed choice when DUIA. A better understanding of drivers' behavior under the influence of substance use may be useful to adjust and improve the traffic laws and driving regulations.

Effects of alcohol consumption on driving performance in the presence of interocular differences simulated by filters.

The role of interocular differences simulated by filters (fog filter and Bangerter foil) on visual and driving performance in alcohol users was assessed. We found that the binocular visual function deteriorates significantly in terms of contrast sensitivity (from 6 to 18 cpd). Additionally, driving performance is significantly impaired under these conditions as evidenced by increased mean speed, standard deviation of the lateral position, distance traveled outside the lane, reaction time and number of collisions. Furthermore, we found that interocular differences due to intraocular scattering and straylight are directly related to an overall reduction in visual and driving performance. This provided a comprehensive perspective from which to understand the relationship between binocular visual function, interocular differences, and driving performance. In practice, our findings contribute to the understanding of the importance of limiting interocular differences, which can be common among presbyopes corrected using the monovision technique, as well as in cases of cataract or other ocular pathology affecting only one eye, or even in cases of cataract surgery of the first eye. These interocular differences can have an adverse impact on road safety, especially when combined with moderate alcohol consumption.

The Relationship between Anxiety, Visual Function, and Symptomatology in University Students.

Mental health concerns have emerged at the university level, with the psychological well-being of students being increasingly affected. This cross-sectional study investigated the proportion of university students having anxiety, and its effects on their visual function and symptomatology. We included 41 students (26.1 ± 4.8 years), and their visual function was assessed through several tests to produce a general visual performance index (VPI). The visual symptomatology was studied using the Conlon Visual Discomfort Survey and the Quality of Vision (QoV) questionnaire. The students were classified into two groups according to the Generalized Anxiety Disorder Screener (GAD-7) test ("no anxiety" and "anxiety" groups). The visual function evaluation indicated significantly worse VPI in the anxiety group (p = 0.047). These students also showed significantly higher scores in the Conlon survey (p = 0.004) and two subscales of the QoV questionnaire: symptom severity (p = 0.041) and symptom bothersomeness (p = 0.013). Moreover, the multiple linear regression model showed a significant association between visual discomfort according to the Conlon questionnaire and the level of anxiety (r = 0.405; R2 = 0.164; B = 0.405; p = 0.012). It is important to study the influence of psychological factors on vision, not only for refractive error, but also for binocular and accommodative disorders.

Comparison of the influence of alcohol and cannabis on the dynamics of the accommodative response.

PURPOSE: To assess and compare the changes produced by the two most commonly used substances, alcohol and cannabis, on accommodation dynamics. METHODS: A total of 38 young participants (19 females) were enrolled in the study. They were assigned to two groups: a cannabis group (N = 19) and an alcohol group. Participants in the cannabis group underwent two randomized sessions: a baseline session and a session after smoking a cigarette. Participants in the alcohol group underwent three randomized sessions: a baseline session, a session after the intake of 300 ml of red wine (Alcohol 1), and other after the ingestion of 450 ml of wine (Alcohol 2). For the accommodation assessment, the open-field autorefractor WAM-5500 was used. RESULTS: The decrease of the mean velocity of the accommodative response produced by Alcohol 2 condition was significantly greater than that observed for Alcohol 1 and Cannabis (p = 0.046). The direction of the accommodation (near-distance and distance-near) had no effect on the deterioration of the accommodation dynamics following substance use. The target distance had a significant effect on the decrease of the mean velocity following substance use (p = 0.002). The decrease of the amplitude of the accommodative response was associated with a decrease of the peak velocity (p = 0.004) and the increase of the accommodative lag (p < 0.001). CONCLUSIONS: A moderate-high dose of alcohol impairs accommodation dynamics to a greater extent that lower dose of alcohol or smoked cannabis. The deterioration of the accommodation mean speed was higher for a shorter target distance.

Influence of Interocular Differences and Alcohol Consumption on Binocular Visual Performance.

The purpose of this study was to assess the influence of a moderate breath-alcohol content (BrAC of 0.40 mg/L) on binocular visual performance for different visual functions after inducing different levels of interocular differences with the use of filters. A total of 26 healthy young subjects were enrolled. The participants participated in two sessions: one without alcohol consumption and another after alcohol consumption. In each session and for the different filter conditions (subjects were wearing Bangerter foil of 0.8 and BPM2 fog filter on the dominant eye), monocular and binocular visual function was evaluated by measuring visual acuity, contrast sensitivity, visual discrimination capacity (and successively by calculating their corresponding binocular summations) and stereopsis (near and distance stereoacuity). In addition, interocular differences were calculated for different retinal-image quality and straylight parameters. All monocular and binocular visual functions were analyzed and stereopsis was significantly impaired by alcohol and filters (p < 0.05). Interocular differences for different ocular parameters and binocular summations for visual parameters were negatively affected by filters but not alcohol. Significant correlations (averaging all the experimental conditions analyzed) were found, highlighting: the higher the interocular differences, the lower the binocular summation and the poorer the stereopsis and, therefore, the worse the binocular visual performance.

Effect of peripheral refractive errors on driving performance.

The effect of peripheral refractive errors on driving while performing secondary tasks at 40° of eccentricity was studied in thirty-one young drivers. They drove a driving simulator under 7 different induced peripheral refractive errors (baseline (0D), spherical lenses of +/- 2D, +/- 4D and cylindrical lenses of +2D and +4D). Peripheral visual acuity and contrast sensitivity were also evaluated at 40°. Driving performance was significantly impaired by the addition of myopic defocus (4D) and astigmatism (4D). Worse driving significantly correlated with worse contrast sensitivity for the route in general, but also with worse visual acuity when participants interacted with the secondary task. Induced peripheral refractive errors may negatively impact driving when performing secondary tasks.

Assessing the influence of cannabis and alcohol use on different visual functions: A comparative study.

This study aimed to assess and compare the influence of alcohol intake and cannabis smoking on different visual functions. A total of 64 young and healthy volunteers took part in the study. All undertook several randomised experimental sessions in which different visual functions, namely distance stereopsis, retinal straylight, visual discrimination capacity, and contrast sensitivity, were tested. Cannabis smokers (N = 30) took a baseline session and a session after smoking a cannabis cigarette, whereas alcohol users (N = 34) underwent a baseline session, a session after a low alcohol intake (Alcohol 1), and a session after a moderate to high alcohol intake (Alcohol 2). All visual functions were impaired by cannabis and alcohol use, particularly for the Cannabis and Alcohol 2 groups. The deterioration of all visual variables was higher for the Alcohol 2 than for the Alcohol 1 and Cannabis groups, except for retinal straylight, the deterioration of which was equal for the Cannabis group, and distant stereopsis, which was more impaired for the Cannabis group. The Alcohol 2 group experienced the most impairing conditions, although very similar to the cannabis group, and that factors other than the experimental conditions, such as sex and age, also influenced these visual changes. Alcohol and cannabis use clearly impair vision. The deterioration caused by cannabis is similar to, but slightly lower than, that produced by a moderate to high alcohol intake, with the experimental conditions, sex and age all having an impact on the variability of visual deterioration.

Comparison of the effects of alcohol and cannabis on visual function and driving performance. Does the visual impairment affect driving?

BACKGROUND: Alcohol and cannabis are the most widely consumed psychoactive substances worldwide. This study compared the effects of alcohol and cannabis on visual function and driving performance, as well as self-perceived effects. Also, the relationship between visual effects under the influence and driving performance was studied. METHODS: Sixty-four young drivers, with a history of alcohol and/or cannabis use were included. Of these, 33 were allocated to the alcohol group and 31 to the cannabis group. All participants were evaluated in a baseline session. The alcohol group underwent two sessions: after drinking 300 ml and 450 ml of red wine (A1 and A2). The cannabis group attended one session after smoking cannabis (C). Visual function was evaluated at the contrast sensitivity, stereoacuity, and intraocular straylight level. Participants drove a driving simulator. A general score (overall visual score, OVS; overall driving performance score, ODPS) was obtained for both visual functioning and driving performance. RESULTS: The evaluation of visual function demonstrated a significant impairment in OVS for all conditions studied (A1, p = 0.005; A2, p < 0.001; C, p < 0.001) with respect to the baseline session. General driving performance (ODPS) demonstrated a significant worsening for the A2 condition (p = 0.003). Finally, a significant relationship between driving performance and visual function was found (rho=0.163, p = 0.039 and χ2 = 4.801, p = 0.028). CONCLUSIONS: Cannabis and alcohol use negatively impact visual function. However, driving performance was only significantly affected by the higher alcohol dose. This impairment in visual function was significantly associated with worse driving performance.

Effect of interocular differences on binocular visual performance after inducing forward scattering.

PURPOSE: To assess binocular visual performance by means of binocular summation on visual function after inducing monocular forward scattering, and to study the influence of interocular differences on ocular parameters. METHODS: Seven young healthy subjects were recruited. Four Bangerter foils and five fog filters were used to induce monocular forward scattering. To analyse the impact of the scatter, visual acuity, contrast sensitivity, visual discrimination capacity and distance stereoacuity were measured binocularly with the filter placed over the dominant eye. Additionally, interocular differences were calculated for four ocular parameters: the Objective Scatter Index (OSI), Strehl ratio (SR), modulation transfer function cut-off (MTF cut off) and straylight (log[s]). Binocular summation was determined for these visual functions. RESULTS: A statistically significant deterioration in visual acuity, contrast sensitivity and stereoacuity was seen for all of the filter conditions with respect to the natural state (baseline), with the largest change being recorded for the Bangerter foils. Similarly, the interocular difference for the three retinal image quality parameters (OSI, SR and MTF cut-off) and log(s) increased significantly for the Bangerter foil condition, but not for the fog filters (except log(s)). Binocular summation declined gradually with the Bangerter foils, but not for the fog filters. Statistically significant correlations were found, that is, the greater the interocular differences, the lower the binocular summation of the visual functions and the greater the distance stereoacuity. CONCLUSION: Increased forward scattering in the dominant eye resulted in interocular differences, which reduced the overall binocular visual performance, including the binocular summation of several visual functions and distance stereoacuity. The results suggest that marked interocular differences in ocular parameters should be avoided in cases of ocular pathology, amblyopia and emmetropisation procedures (such as refractive surgery) or a monovision correction for presbyopia.

Speed management across road environments of varying complexities and self-regulation behaviors in drivers with cataract.

Evidence suggests that drivers with cataract self-regulate their driving, but there is a lack of objective information. This study compared speed behavior in older drivers with and without cataract and how the parameter is influenced by road traffic complexity and driver characteristics. The study included 15 drivers with cataract and a control group of 20 drivers. Visual status was assessed using visual acuity, contrast sensitivity, and intraocular straylight. Speed management was studied using a driving simulator. Driving difficulty and self-regulation patterns were evaluated by means of the Driver Habits Questionnaire (DHQ). The cataract group showed a significant decrease in visual function in all the parameters evaluated (p < 0.05). These drivers tended to drive at lower speeds than the control group. Road characteristics, gender, and intraocular straylight in the better eye were identified as significant predictors of speed management. Drivers with cataract experience greater driving difficulty, particularly when driving at night (p < 0.05). Drivers with cataract reduce their driving speed more than older drivers without visual impairment. The straylight parameter may be a good indicator of each driver's subjective perception of their own visual ability to drive. This work helps shed light on the mechanisms through which age-related visual impairment influences driving behavior.

Changes in Visual Performance under the Effects of Moderate-High Alcohol Consumption: The Influence of Biological Sex.

The purpose of this study was to analyze the changes in visual functions under the effects of moderate-high breath alcohol concentrations (BrACs), and the influence of biological sex on visual deterioration, considering different factors. A total of 37 healthy habitual alcohol users were enrolled in the experiment. The participants underwent a baseline session and a second session after an intake of 450 mL of red wine, so that all of them reached a BrAC above 0.25 mg/L. Visual performance was assessed by measuring the contrast sensitivity function, the halo perception, the stereopsis, and finally the retinal image quality. A Visual Deterioration Score (VDS) was calculated using the deterioration of these visual variables. All visual functions analyzed were significantly impaired following alcohol consumption (p < 0.05). The VDS was associated with the BrAC (ρ = -0.476). The VDS was also significantly higher in females, with the BrAC having a significant effect on the variability of the VDS in males and females (p < 0.05). However, the body mass index showed no significant effect (p > 0.05). Visual functions were significantly impaired under the influence of alcohol, and this deterioration was greater in females. The deterioration depends on the BrAC reached, being the primary thing responsible for the differences observed between males and females.

Visual performance after the deterioration of retinal image quality: induced forward scattering using Bangerter foils and fog filters.

We induced and evaluated different levels of retinal-image degradation using Bangerter foils and fog filters. We found increased straylight and an important deterioration in visual performance, assessed by means of visual acuity, contrast threshold, and visual discrimination capacity. Bangerter foils induced forward scattering levels comparable to those observed in mature to severe cataracts, with an important impact of halos and starbursts. Fog filters induced lower levels of intraocular scattering, although luminous veils and circular halos were reported. The visual disturbance index positively correlated with intraocular scattering and straylight. Our results show retinal-image quality has an important influence on night-vision performance.

Deterioration of binocular vision after alcohol intake influences driving performance.

In this study, we assessed the influence of moderate alcohol intake on binocular vision, vergence system and simulated driving performance by analyzing the interactions between visual deterioration and driving variables. Thirty young healthy subjects were recruited. For the analysis, we measured: visual function (visual acuity and stereoacuity), phorias and fusional reserves. Also, we checked Sheard's and Percival's criteria at near and far. The accommodative convergence/accommodation (AC/A) ratio was calculated and vergence facility was also obtained at near. A driving simulator was used to assess driving performance under natural conditions and after alcohol consumption with a breath alcohol content of 0.40 mg/l. Alcohol intake significantly reduced binocular visual performance and vergence function, except for vertical phorias, horizontal phoria at near and Sheard's and Percival's criteria at near. Driving performance parameters also presented a statistically significant deterioration after alcohol consumption. A statistically significant correlation was found between the deterioration in overall visual function and overall driving performance, highlighting the influence of the visual deterioration on the driving performance. Moderate alcohol consumption impairs binocular visual and simulated driving performances, implying a greater safety hazard. In addition, deteriorations in binocular visual function and vergence correlated with simulated driving impairment, which indicates that the deterioration of binocular vision due to alcohol consumption affects driving, thus reducing road safety.

Effects of cannabis on visual function and self-perceived visual quality.

Cannabis is one of the most used drugs of abuse in the world. The objective of this study was to analyze the effects of smoking cannabis on vision and to relate these to those perceived by the user. Thirty-one cannabis users participated in this study. Visual function assessment was carried out in a baseline session as well as after smoking cannabis. We evaluated static visual acuity, contrast sensitivity, stereoacuity, accommodative response, straylight, night-vision disturbances (halos) and pupil size. The participants were also divided into two groups depending on whether they perceived their vision to have worsened after smoking cannabis. A logistic regression analysis was employed to identify which visual test could best predict self-perceived visual effects. The study found that smoking cannabis has significant adverse effects on all the visual parameters analyzed (p < 0.05). Self-perceived visual quality results revealed that about two thirds of the sample think that smoking cannabis impairs their vision. Contrast sensitivity, specifically for the spatial frequency 18 cpd, was identified as the only visual parameter significantly associated with self-perceived visual quality (Odds Ratio: 1.135; p = 0.040). Smoking cannabis is associated with negative effects on visual function. Self-perceived visual quality after smoking cannabis could be related to impaired contrast sensitivity.

Changes in accommodation dynamics after alcohol consumption, for two different doses.

PURPOSE: The purpose of this work was to evaluate possible changes in accommodation dynamics caused by the intake of different doses of alcohol. METHODS: A total of 20 emmetropic subjects took part in the study. This involved a baseline session, a session after consuming 300 ml of red wine, and another after consuming 450 ml of the same wine. The accommodation dynamics were characterized for two target vergences (2.5D and 5.0D) using the Grand Seiko WAM-5500 autorefractor, which provided the accommodation and disaccommodation variables. The accommodative facility was measured using flippers of ± 2.00 D. RESULTS: The mean accommodation velocities and velocity peaks were significantly lower after consuming alcohol for the higher intake, particularly for 5.0D (p < 0.05). The response time was significantly higher only for the high-intake condition for 5.0D (p < 0.05). The accommodative microfluctuations were significantly higher for both target vergences for the high-intake condition (p < 0.05). The accommodative facility was significantly impaired in both intake conditions (p < 0.05). The breath alcohol content (BrAC) was correlated with the deterioration of some variables: the accommodative facility (ρ = 0.490), and the velocity peak for 2.5D (ρ = 0.349) and 5.0D (ρ = 0.387). CONCLUSIONS: Alcohol intake affects accommodation dynamics, causing deterioration in the mean velocity, velocity peak, response time, accommodative microfluctuations, and accommodative facility, especially for the target vergence of 5.0D and high alcohol dosages.

Impact of Age-Related Vision Changes on Driving.

Aging leads to impaired visual function, which can affect driving-a very visually demanding task-and has a direct impact on an individual's quality of life if their license is withdrawn. This study examined the associations between age-related vision changes and simulated driving performance. To this end, we attempted to determine the most significant visual parameters in terms of evaluating elderly drivers' eyesight. Twenty-one younger drivers (aged 25-40) were compared to 21 older drivers (aged 56-71). Study participants were assessed for visual acuity, contrast sensitivity, halos, and intraocular straylight, which causes veiling luminance on the retina and degrades vision. Driving performance was evaluated using a driving simulator. The relationships between simulated driving performance and the visual parameters tested were examined with correlation analyses and linear regression models. Older drivers presented impairment in most visual parameters (p < 0.05), with straylight being the most significantly affected (we also measured the associated effect size). Older drivers performed significantly worse (p < 0.05) in the simulator test, with a markedly lower performance in lane stability. The results of the multiple linear regression model evidenced that intraocular straylight is the best visual parameter for predicting simulated driving performance (R2 = 0.513). Older drivers have shown significantly poorer results in several aspects of visual function, as well as difficulties in driving simulator performance. Our results suggest that the non-standardized straylight evaluation could be significant in driver assessments, especially at the onset of age-related vision changes.

Factors determining speed management during distracted driving (WhatsApp messaging).

The objective of this work was to investigate self-regulation behaviours, particularly speed management, under distracted conditions due to WhatsApp use. We also studied the influence of different environments and driver characteristics, introducing visual status as one of them. Seventy-five drivers were evaluated in a simulator study involving two test sessions under baseline and texting conditions. A cluster analysis was used to identify two groups with different visual capacity .Lastly, possible predictors of speed management were studied developing a generalised linear mixed model. Our results show that drivers reduced their speeds in the presence of more demanding driving conditions; while replying to a WhatsApp message, on curved road segments and when parked cars are present. Driving speed also correlated with driver characteristics such as age or dual task experience and human factors such as self-perceived risk. Finally, although there were significant differences in visual capacity between the two groups identified, the model did not identify visual capacity membership as a significant predictor of speed management. This study could provide a better understanding of the mechanisms drivers use when WhatsApp messaging and which environments and driver conditions influence how speed is managed.

Contrast sensitivity and retinal straylight after alcohol consumption: effects on driving performance.

In this study, we aimed to investigate the effects of alcohol intake on visual function and driving performance, as well as on the relationship between these. A total of 40 healthy participants took part in three experimental sessions: one baseline session and two further sessions after consuming two different quantities of alcohol (300 ml and 450 ml of red wine). The breath alcohol content (BrAC) was measured using a breath analyzer. The contrast sensitivity and retinal straylight due to the forward intraocular scattering were measured to characterize visual function, and driving performance was assessed in three different scenarios using a driving simulator. The results showed a deterioration in contrast sensitivity and retinal straylight after drinking alcohol, in addition to an impaired ability to drive, especially for the highest alcohol intake. We also observed that the deteriorated driving performance was a function of the contrast sensitivity and retinal straylight under the effects of alcohol, indicating that these visual variables can partially predict driving performance in these conditions.