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Hazard perception is a vital component to safe driving and hazard perception tests (HPTs) are being used with greater frequency for driver training, assessment and licensure. In this study, we compared a dynamic HPT (Scialfa et al., 2011), which presents short video scenes to observers and a static HPT (Scialfa et al., 2012), which uses still images. Both tests require the observer to indicate the presence of a traffic conflict that would lead to a collision between the "camera" vehicle and another road user or fixed object. Young adult drivers (n=56) completed both forms of the HPT, along with a modified version of the Driver Behavior Questionnaire (Reason et al., 1990) and a measure of simple reaction time. Self-reported collision and moving violation data were also collected. As in previous work, both static and dynamic HPTs had good reliability. The correlation between composite static and dynamic scores was approximately .40, but was reduced to approximately .25 when simple reaction time was controlled. Both HPTs predicted lapses and errors on the Driver Behavior Questionnaire, but neither predicted self-reported collisions or moving violations. Discussion focuses on the differences in visual cues available in dynamic and static scenes and how these differences could influence decisions about potential hazards.

Novice drivers exhibit deficits in hazard perception that are likely to increase their risk of collisions. We developed a static hazard perception test that presents still images to observers and requires them to indicate the presence of a traffic conflict that would lead to a collision. Responses to these scenes were obtained for young adult novice (N=29) and experienced drivers (N=27). Additionally, participants rated the hazard risk and clutter of each scene. Novice drivers rated traffic conflicts as less hazardous and responded more slowly to them. Using a subset of 21 scenes, we were able to discriminate novice and experienced young adult drivers with a classification accuracy of 78% and a scale reliability (Cronbach's alpha) of .91. The potential applications of this research include the development of standardized hazard perception tests that can be used for driver evaluation, training and licensure.

We developed a hazard perception test, modeled on that used currently in several Australian states, that presents short video scenes to observers and requires them to indicate the presence of a traffic conflict that would lead to a collision between the "camera" vehicle and another road user. After eliminating those scenes that were problematic (e.g., many observers did not recognize the hazard), we predicted driver group (novice vs. experienced drivers of similar age) on the basis of individual differences in reaction time, miss rate and false alarm rate. Novices were significantly slower in responding to hazards, even after controlling for age and simple reaction time. After selecting those scenes with the larger group differences, an 18-scene test that would be useful for mass testing exhibited even larger experience effects. There was good reliability in the resulting scale. Results suggest that this brief test of hazard perception can discriminate groups that differ in driving experience. Implications for driver licensing, evaluation and training are discussed.

The authors examined the ability of young novice (M = .19 yrs experience) and experienced drivers (M = 5.1 yrs experience) to identify and localize frequently encountered roadway hazards using static images taken in western Canada. Dependent measures also included subjective ratings of hazard risk and scene clutter. Novice drivers reacted to roadway hazards more slowly while rating them as being less hazardous than young, experienced drivers. Using a small subset of scenes, it was determined that a brief hazard perception test employing static images could classify individuals with high accuracy (78%) and good reliability (Cronbach's alpha = .91).

Quantitative and regional measurement of retinal blood flow in rodents is of prime interest for the investigation of regulatory mechanisms of ocular circulation in physiological and pathological conditions. In this study, a quantitative autoradiographic method using N-isopropyl-p-(14)C-iodoamphetamine ([(14)C]-IMP), a diffusible radioactive tracer, was evaluated for its ability to detect changes in retinal blood perfusion during hypercapnia. Findings were compared to cerebral blood flow values measured simultaneously. Hypercapnia was induced in awaken Wistar rats by inhalation of 5% or 8% CO(2) in medical air for 5 min. [(14)C]-IMP (100 microCi/kg) was injected in the femoral vein over a 30 s period and the rats were sacrificed 2 min later. Blood flow was calculated from whole-mount retinae and 20 microm thick brain sections in discrete regions of interest by quantitative autoradiography or from digested samples of retina and brain by liquid scintillation counting. Retinal blood flow values measured with quantitative and regional autoradiography were higher in the central (108 +/- 20 ml/100 g/min) than in peripheral (84 +/- 15 ml/100 g/min) retina. These values were within the same range as cortical blood flow values (97 +/- 4 ml/100 g/min). The retinal blood flow values obtained on whole-mount retinae were validated by the sampling method. Hypercapnia significantly increased overall blood flow in the retina (24-53%) with a maximal augmentation in the peripheral region and in the brain (22-142%). The changes were stronger in the brain compared to retina (p = 0.016). These results demonstrate that retinal blood flow can be quantified using [(14)C]-IMP and compared with cerebral blood flow. This technique is a powerful tool to study how retinal blood flow is regulated in different regions of the rat retina.

This article reviews the effects of systemic medications and some native vasoactive molecules on ocular blood flow (OBF). Some evidence exists for a positive effect of centrally acting calcium-channel blockers, nitric oxide precursors, adenosine, histamine, estrogens, and ginkgo biloba extract, while evidence for a negative effect on OBF exists for endothelin-1 and indomethacin. Some other molecules appear to have mixed effects, depending on the ocular vascular bed studied or the study protocol. In addition, medically induced changes in systemic blood pressure (BP) have an important impact on OBF, and the direction and magnitude of this effect may depend on the disease status of the patient and of the eye, as well as the absolute level of BP achieved. There are relatively few studies of the effects of systemic medications on OBF in glaucoma patients, and little is known of the long-term impact of such therapies on the preservation of optic nerve structure and function.

Regional anesthesia for ophthalmic surgery has been associated with ischemic complications, such as central retinal vascular occlusion, optic atrophy and ischemic optic neuropathy. Impairment of pulsatile ocular blood flow (POBF) may occur with regional orbital anesthesia. In this study we quantified POBF in patients undergoing regional orbital anesthesia.Eleven patients (12 eyes) with a mean age of 76.5 years having regional orbital anesthesia for cataract or retinal surgery at a private refractive surgical centre in Calgary had POBF monitoring before, during and 15 minutes after induction of anesthesia.There were no significant changes in intraocular pressure or heart rate during the induction phase or 15 minutes after induction of regional orbital anesthesia. However, ocular blood flow indices, including pulse amplitude, pulse volume and POBF, were significantly reduced following attainment of regional orbital blockade (p0.05). With time there was recovery in these variables, but they all remained significantly reduced from baseline 15 minutes later.Ocular blood flow appears to be significantly impaired during regional orbital anesthesia, induced as described. There could be benefit in monitoring POBF to reveal otherwise undetectable deleterious effects on retinal circulation in patients having retrobulbar injections, orbital compression or digital manipulation of the globe.

The focal electroretinogram, which measures the functional integrity of the distal retina of the macula, was recorded with a hand-held stimulator-ophthalmoscope in 26 eyes from patients with non-insulin-dependent diabetes mellitus with normal fundus photography, and in 52 control eyes of similar age range. Implicit time and amplitude of the responses were studied as a function of the age, glycemic control through glycosylated hemoglobin measurement and duration of diabetes. Implicit time and amplitude were significantly delayed (F=5.05, p=0.028) and reduced (F=11.26, p=0.013) in diabetic patients without diabetic retinopathy compared to control subjects. Moreover, there was a significant relationship between the implicit time (r=0.57, p=0.002) and amplitude (r=-0.65, p=0.0004) with the duration of diabetes but not with hemoglobin Alc. These results strongly suggest an early macular dysfunction in non-insulin-dependent diabetes mellitus before the appearance of diabetic retinopathy.

We have developed a hazard perception test (HPT) that presents short video scenes to observers and requires them to identify a traffic conflict that could lead to a collision between the 'camera' vehicle and another road user. In the present study, we compared the performance of young, experienced drivers (M = 21.30 years of age) with that of healthy, older drivers (M = 70.88 years of age). Although an average hazard perception test score based on all scenes did not produce systematic age effects, older adults were systematically slower on a composite hazard perception test score used previously with novice drivers (Scialfa et al., 2011b). Age differences in hazard perception test latencies were mediated by contrast sensitivity, but not simple reaction time. The findings suggest that a brief hazard perception test could potentially be used in the assessment of drivers across the adult lifespan.

PURPOSE. To investigate whether postmenopausal hormone therapy (HT) increases retinal and ONH blood flow (BF) and protects ONH topography and the function of retinal ganglion cells in postmenopausal women (PMW). The effect of estradiol (E2) treatment on retinal tissue perfusion was also investigated in ovariectomized rats, an animal model for menopause. METHODS. Sixty-four healthy PMW were recruited, 29 of whom never used HT (AHT) and 35 of whom had used HT (HT) continuously since the onset of menopause. Blood flow of the inferotemporal retinal artery (ITRA), peripapillary retina, and ONH rim were measured in one eye. The ONH stereometric parameters and the pattern electroretinogram (PERG) were also measured. In ovariectomized rats, the retinal tissue perfusion was assessed using the BF tracer N-isopropyl-p-[ 14 C]-iodoamphetamine ([ 14 C]-IMP) in rats treated with either E2 (n 7) or placebo (n 5). RESULTS. Compared with the AHT group, the HT group presented significantly greater BF of the ITRA (P 0.006), greater rim volume for the entire ONH region (P 0.032), and greater rim volume (P 0.042), height variation contour (P 0.011), mean thickness (P 0.033), and cross-sectional area (P 0.020) of the retinal nerve fiber layer for the inferotemporal region of the ONH when adjusted for age, ocular perfusion pressure, and age at menarche. In ovariectomized rats, E2 treatment significantly increased retinal perfusion in a range of 22% to 45%. CONCLUSIONS. These findings indicate that estrogens and HT increase retinal blood flow and protect the retinal nerve fiber layer. (Invest Ophthalmol Vis Sci. 2010;51:2587‐2600) DOI