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PURPOSE Fell's modification of the Harada-Ito (HI) procedure is often used to tackle subjective torsion usually following superior oblique palsy. There is limited published data on the longer-term outcomes and the effect on horizontal incomitance of the procedure. The purpose of this study is to report on the medium to long-term outcomes of the HI procedure. MATERIALS AND METHODS A retrospective review of 20 patients who had all undergone a single surgeon modified HI procedure to correct subjective torsion was undertaken. Follow-up data were analyzed in relation to stability of torsion measurements, the effect on vertical incomitance of horizontal deviation and the final treatment outcome. RESULTS There was a significant reduction in median maximum torsion from preoperative to immediately post-op (p

Background Falls are the second leading cause of accidental deaths worldwide mainly in older people. Older people have poor vision and published evidence suggests that it is a risk factor for falls. Less than half of falls clinics assess vision as part of the multi-factorial assessment of older adults at risk of falls despite vision being an essential input for postural stability. The aim of our study was to investigate the relationship between all clinically assessed visual functions and falls amongst older adults in a prospective observational individually age-matched case control study. Methods Visual acuity (VA), contrast sensitivity (CS), depth perception, binocular vision and binocular visual field were measured using routinely used clinical methods in falls participants (N = 83) and non-falls participants (N = 83). Data were also collected on socio-demographic factors, general health, number of medications, health quality, fear of falling and physical activity. Logistic regression analysis was carried out to determine key visual and non-visual risk factors for falls whilst adjusting for confounding covariates. Results Older adults have an increased risk of experiencing a fall if they have reduced visual function (odds ratio (OR): 3.49, 1.64-7.45, p = 0.001), specifically impaired stereoacuity worse than 85” of arc (OR: 3.4, 1.20-9.69, p = 0.02) and reduced (by 0.15 log unit) high spatial frequency CS (18 cpd) (OR:1.40, 1.12-1.80, p = 0.003). Older adults with a hearing impairment are also at higher risk of falls (OR: 3.18, 95% CI: 1.36-7.40, p = 0.007). The risk decreases with living in a less deprived area (OR: 0.74, 0.64-0.86, Conclusions The combination of social, behavioural and biological determinants are significant predictors of a fall. The non-visual risk factors include older adults, living in deprived neighbourhoods, socialising less outside of the home and those who have a hearing impairment. Impaired functional visual measures; depth perception and contrast are significant visual risk factors for falls above visual acuity.

BACKGROUND Myasthenia gravis (MG) often presents with ocular signs that mimic other forms of ocular defects, such as isolated cranial nerve palsy. Normal velocity or even hyperfast saccadic eye movements in the presence of deficits of smooth pursuit have been well described in the literature in myasthenic patients. The reason for these paradoxical clinical findings has been reported to be due to increased postsynaptic folding of the fast-twitch fibers responsible for the execution of a saccade which is absent in those fibers responsible for slower, smooth eye movement. Saccadic characteristics therefore offer a point of differential diagnosis between patients suspected of having ocular motility deficits as a result of MG and those caused by other neuropathies. The advent of portable quantitative saccadic assessment means that previously laboratory-based assessments that require specialist equipment and training may now be undertaken clinically, providing a noninvasive test that can aid the differential diagnosis of the condition. The aim of this pilot study was to investigate the feasibility of the saccadometer (Ober Consulting, Poznan, Poland) in detecting the saccadic characteristics associated with myasthenia, specifically normal peak velocity (PV) in a group of patients confirmed with myasthenia. METHODS A group of 5 patients with a confirmed diagnosis of MG were recruited from a single site into the study along with 5 age-matched healthy volunteers. All myasthenic patients had ocular signs such as underaction or limitations of motility confirmed through ocular clinical examination. Healthy volunteers were screened for any underlying ocular motility or neurological defects before inclusion within the study. All participants undertook 100 trials of both 10 and 20° amplitude saccades, and mean PV, amplitude, and latency were recorded using the saccadometer for each individual. Overall, mean PV, amplitude, and latency were collated for both myasthenic and healthy control groups for each saccade size and compared. RESULTS The mean PV was significantly greater (481 ± 103.5 deg/seconds) for myasthenic patients compared with healthy controls (384 ± 42.8 deg/seconds) (P < 0.05) in 10° saccades. PV was also greater in myasthenics for 20° saccades; however, this difference did not reach statistical significance for patients with MG (547 ± 89.8 deg/seconds vs 477 ± 104.5 deg/seconds) (P = 0.14). The latency of participants with MG was not significantly different from those of age-matched healthy participants in 10° saccades but was significantly different for 20° saccades. There was no difference in amplitude measured between the groups. CONCLUSIONS PV for both 10 and 20° saccades was greater in myasthenic patients compared with healthy controls. All myasthenic patients produced normal velocity saccades in the presence of deficits of smooth ocular motility. The results from this small pilot study demonstrate the potential use of the saccadometer in a clinical setting to provide a noninvasive aid in the diagnosis of patients suspected with myasthenia.

To measure the Accommodative Convergence (PD)/Accommodation ratio (D) (AC/A) in a cohort of visually normal participants using common clinical methods.AC/A ratios of 50 visually normal subjects were measured using the distance gradient (DG), near gradient (NG), gradient using synoptophore, (SG) and heterophoria (H) methods in line with current clinical practice.Median AC/A ratios for NG, DG, SG, and H were 2.0 (IQR 2.0), 1.0 (IQR 0.6), 1.0 (IQR 0.6), and 5.0 (IQR 1.7), respectively. There was a statistically significant difference in ratios calculated between all methods in the same subjects (p 0.05). There were differences in DG vs NG, DG vs H, SG vs H, and NG vs H (p 0.05); only DG vs SG did not differ significantly (p 0.05). Lens power toleration was found to affect AC/A ratio in DG (p 0.05) and latent deviation was significantly associated with (p 0.05) AC/A ratio in NG.Calculated AC/A ratios in this cohort were lower than historically cited normal (3-5:1) in all gradient methods. There were differences in AC/A values in the same subjects calculated with different gradient methods, indicating that these methods are not interchangeable and a universal normal range should not be applied for all methods.

AimsThere is a paucity of literature concerning intractable diplopia. The aims of this study were to determine the incidence of intractable diplopia in the UK, identify the causes and any associated risk factors, establish how cases are managed and if the treatment is successful and tolerated.MethodsA 1-year prospective observational study was undertaken via the British Ophthalmological Surveillance Unit (BOSU). This involved implementation of a reporting mechanism, which then triggered distribution of an incident questionnaire to explore clinical details concerning each case and a follow-up questionnaire 6 months later to explore how the case had been managed.ResultsThe incidence of intractable diplopia was 53 cases per year. The most common preceding events were strabismus surgery (32%), no known preceding event, that is,spontaneous (25%), severe head trauma (8%), cataract surgery (6%) and vitrectomy (6%). In the at-risk age group of 7 years and above, the incidence of intractable diplopia following strabismus surgery is 1 in 494 (95% CI; 1 in 296 to 790) cases. A total of nine different treatments were used in the management, with many patients receiving between two and four different methods. The overall success rate was poor, but most effective were opaque intraocular lenses (IOLs) (86%) and opaque contact lenses (50%).ConclusionIntractable diplopia is a relatively rare but important condition. The main risk factor is a pre-existing strabismus, and careful counselling is needed when planning surgical correction in patients with no demonstrable binocular function. Treatment success of intractable diplopia is high when using opaque IOLs, although with additional risk, but is often disappointing via other methods where it can be difficult to eradicate the diplopia successfully.

Occlusion used to treat amblyopia towards the end of the developmental component of the critical period gives a risk of inducing intractable diplopia. In the United Kingdom, the density of suppression is assessed via the Sbisa/Bagolini filter bar, but there is very little research evidence to guide clinical practice or interpretation of the tests used. The aims of this study were to determine current practice and estimate the incidence of intractable diplopia following amblyopia treatment.Current practice and incidence of intractable diplopia following amblyopia were determined via a questionnaire distributed to head orthoptists in every eye department in the United Kingdom. The questionnaire explored testing and test conditions, interpretation of the test results, and cases of intractable diplopia over the last 5 years.There was considerable variation in clinical practice of the measurement of the density of suppression and interpretation of the results to guide the treatment of amblyopia. The minimum age of patients taking the test ranged from 2 to 8 years and the minimum filter considered still safe to continue treatment ranged from 4 to 17. It is estimated there were 24 cases of intractable diplopia over the last 5 years.The issue of intractable diplopia and amblyopia treatment is likely to become increasingly important as there appears to be greater plasticity and scope to treat amblyopia in teenagers and adults than was previously thought. Lack of knowledge of how to evaluate the risk may lead to more cases of intractable diplopia or alternatively treatment being withheld unnecessarily.

Purpose To determine the effect of changing illuminance on visual and stereo acuity. Methods Twenty-eight subjects aged 21 to 60 years were assessed. Monocular visual acuity (ETDRS) of emmetropic subjects was assessed under 15 different illuminance levels (50–8000 lux), provided by a computer controlled halogen lighting rig. Three levels of myopia (−0.50DS, −1.00DS & 1.50DS) were induced in each subject using lenses and visual acuity (VA) was retested under the same illuminance conditions. Stereoacuity (TNO) was assessed under the same levels of illuminance. Results A one log unit change in illuminance level (lx) results in a significant change of 0.060 LogMAR (p

Aim: To evaluate in a pilot study the use of a touchscreen test in very low birth weight (VLBW) children to explore aspects of visuo-motor behaviour, measuring spatial localisation. Results in VLBW subjects will be compared with those in children born at term. It will be investigated whether any deficits found were related to parental reports of visual function difficulties. Methods: A range of visual functions were measured and IQ estimated using subtests from a standardised test. Using a touch-screen monitor to record pointing positions, in task 1 subjects pointed to sequences of visual targets as soon as they appeared and in task 2 they pointed after a memory delay. Results: Thirty-seven VLBW subjects and 32 control subjects were recruited. On task 1 there was no difference in the pointing error magnitude between the groups. Although the errors of the VLBW group were more variable, this was not statistically significant after exclusion of VLBW subjects with IQ

Background/aims Several studies have recently provided insights into how amblyopia may be most effectively managed. Despite the new evidence, a US study reported that a recent randomised controlled trial had made little influence on clinical practice. The aims of this research are to assess current practice of amblyopia management in the UK and to determine the comparability with the evidence-based recommendations. Methods A questionnaire was constructed to assess current amblyopia management practice, particularly in relation to areas investigated by recent research and emailed to every head orthoptist within the UK. Results There was a great deal of variability in the amount of occlusion that was prescribed for moderate and severe amblyopia. Sixty per cent of clinicians indicated that the maximum they would prescribe was in excess of the 6 h recommended by research. Atropine was rarely recommended as a first-line treatment, with occlusion generally being considered to be more effective. Despite recommendations regarding education as a means of reducing non-compliance, only 39% of clinicians always gave written information, although various other methods of enhancing compliance were used. A period of refractive adaptation was allowed by most clinicians but often far less than recommended. Conclusion The uptake of recent research evidence into clinical practice is sporadic and incomplete with one-third of respondents indicating that following the studies, they had made no changes whatsoever to their practice. This is similar to other areas of medicine; the reasons are likely to be varied, and is an area that would benefit from greater attention.

Establish whether the Sbisa bar, Bagolini filter (BF) bar, and neutral density filter (NDF) bar, used to measure density of suppression, are equivalent and possess test-retest reliability. Determine whether density of suppression is altered when measurement equipment/testing conditions are changed.Our pilot study had 10 subjects aged ≥18 years with childhood-onset strabismus, no ocular pathologies, and no binocular vision when manifest. Density of suppression upon repeated testing, with clinic lights on/off, and using a full/reduced intensity light source, was investigated. Results were analysed for test-retest reliability, equivalence, and changes with alteration of testing conditions.Test-retest reliability issues were present for the BF bar (median 6 filter change from first to final test, p = 0.021) and NDF bar (median 5 filter change from first to final test, p = 0.002). Density of suppression was unaffected by environmental illumination or fixation light intensity variations. Density of suppression measurements were higher when measured with the NDF bar (e.g. NDF bar = 1.5, medium suppression, vs BF bar = 6.5, light suppression).Test-retest reliability issues may be present for the two filter bars currently still under manufacture. Changes in testing conditions do not significantly affect test results, provided the same filter bar is used consistently for testing. Further studies in children with strabismus having active amblyopia treatment would be of benefit. Despite extensive use of these tests in the UK, this is to our knowledge the first study evaluating filter bar equivalence/reliability.

Purpose: To compare clinical practice patterns regarding atropine penalization use by UK orthoptists to the current evidence base and identify any existing barriers against use of AP as first-line treatment. Methods: An online survey was designed to assess current practice patterns of UK orthoptists using atropine penalization. They were asked to identify issues limiting their use of atropine penalization and give opinions on its effectiveness compared to occlusion. Descriptive statistics and content analysis were applied to the results. Results: Responses were obtained from 151 orthoptists throughout the United Kingdom. The main perceived barriers to use of atropine penalization were inability to prescribe atropine and supply difficulties. However, respondents also did not consider atropine penalization as effective as occlusion in treating amblyopia, contrary to recent research findings. Patient selection criteria and treatment administration largely follow current evidence. More orthoptists use atropine penalization as first-line treatment than previously reported. Conclusions: Practitioners tend to closely follow the current evidence base when using atropine penalization, but reluctance in offering it as first-line treatment or providing a choice for parents between occlusion and atropine still remains. This may result from concerns regarding atropine’s general efficacy, side effects, and risk of reverse amblyopia. Alternatively, as demonstrated in other areas of medicine, it may reflect the inherent delay of research findings translating to clinical practice changes. [J Pediatr Ophthalmol Strabismus 2014;51(6):363–369.]

PURPOSE. Preterm infants are at increased risk of a variety of cerebral lesions, involving the white matter, cortex, cerebellum, thalamus, and caudate nucleus, many of which could compromise the control of eye movement. Visual problems and disorders of binocularity and alignment have been reported, but little if any quantitative assessment of oculomotor control has been undertaken. The purpose of this study was to extend the initial pilot study and quantitatively examine the control of saccades, smooth pursuit, and antisaccades in children who were born very prematurely. METHODS. A group of preterm (PT) children aged 8 to 11 years (32 weeks’ gestation), who had normal IQ (85) and were free of major disabilities (cerebral palsy, blindness, or deafness), and full-term (FT) control subjects of similar age were recruited from a geographically defined cohort. Antisaccades were examined in 36 preterm and 33 full-term subjects and smooth pursuit and saccades in 21 preterm and 19 full-term subjects, by using infrared oculography. Saccade and antisaccade targets were presented at an amplitude of 5° according to a standard synchronous paradigm, and pursuit was assessed by using a step–ramp paradigm with a target velocity of 14 deg/s. RESULTS. There were no statistically significant differences between the preterm and the full-term subjects in relation to saccade gain, latency, duration, peak velocity, or the proportion of express saccades. Smooth-pursuit latencies tended to be slightly longer in the preterm subjects (leftward: P 0.17, rightward: P 0.02), but there were no significant differences between them and the full-term subjects in pursuit acceleration, open-loop velocity, or peak slow-eye velocity. The main area of deficit in the preterm children occurred in the voluntary control of saccades, with significantly higher antisaccade directional error rates (PT: 73.3% 18.1%, FT: 54.2% 16.9%, mean SD; P 0.001). The latency of the antisaccade error tended to be shorter in preterm subjects (P 0.065), with a greater proportion of errors with latency in the express range (P 0.08). CONCLUSIONS. Despite the increased risk of cerebral lesions, the control of saccades and pursuit was largely normal in the preterm children, suggesting that pathways at the level of the brain stem were principally intact. However, the preterm children had difficulties with the voluntary control of saccades, particularly in the area of inhibition, which may be indicative of a deficit in the region of the dorsolateral prefrontal cortex. This finding is consistent with other reports in preterm children in whom executive function has been found to be compromised, and both these aspects of behavior are likely to share similar areas of cortical control. (Invest Ophthalmol Vis Sci. 2007;48:2595–2601) DOI:10.1167/iovs.06-1425

Aims: To validate the design of updated optotypes to be used in the Kay picture acuity tests to improve the resolution acuity, recognition, repeatability and comparisons with gold standard logMAR acuity assessments. Methods: The study was completed in four phases. Inball phases the pictures were presented on a monitor as a single crowded optotype, with five optotypes at each visual acuity (VA) level. Phase one assessed the resolution acuity for 25 pictures, eight Landolt Csband five ETDRS letters. The recognition phase (phasebtwo) assessed children (18 months to 5 years) to determine which pictures were most commonly identified. During phase three, the resolution acuity of a reduced number of pictures and the Landolt C were reassessed to ensure that fatigue had not influenced the initial results. Phase four compared the new Kay pictures with LEA symbols and the ETDRS (part a), and repeatability of the Kay pictures and the ETDRS chart (part b). Results: 'Phase one (resolution acuity)': 50 adult subjects were tested. The mean (±SD) acuity scores achieved using each of the 25 pictures ranged from -0.123 ±0.124 to -0.308 ±0.105. The mean (±SD)bacuity for the eight Landolt C orientations was -0.059 ±0.120, and -0.128 ±0.101 for the ETDRS letters. Following this analysis, three pictures were removed. Phase two (Recognition): 420 children were assessed (54% male) using the remaining 22 pictures. Analysis resulted in the removal of 10 pictures based on the recognition levels. Phase three (resolution acuity): 43 adult subjects were tested with the remaining 12 pictures. The picture selection was reduced to six based on a combination of similar mean bias levels, recognition levels in all children and recognition levels in the youngest children. Phase four (a) (comparability): 113 adult subjects were tested. The mean bias indicated similar results between the tests. The limits of agreement for ETDRS versus Lea symbols were slightly wider than for ETDRS versus Kay pictures. Phase four (b) (repeatability): 100 adult subjects were tested. Paired 't'-test analysis demonstrated no significant difference between tests in either ETDRS ( p = 0.1) or Kay pictures ( p = 0.1). Mean bias for both tests was 0.01 logMAR with similar limits of agreement. Conclusion: The newly designed Kay picture optotypes have been shown to be reliably recognised by a paediatric population. In a six-picture test format the newly designed optotypes with single picture presentation and crowding bars have been shown to be a reliable and repeatable VA test in an adult population with good agreement with current gold standard VA assessment methods. Normative data in a paediatric population are now required.

Aims: To determine the prevalence of ophthalmic impairments in very preterm compared with term infants, the relation between impairments and cerebral ultrasound appearances and retinopathy, and the correlation with visual perception and motor and cognitive measures. Subjects: 279 children at 7 years of age born before 32 weeks gestation within Liverpool during 1991–92 and attending mainstream schools, and 210 term controls. Methods: Visual acuity was assessed by Snellen chart, and strabismus by the cover test. Stereopsis was determined using the TNO random dot test, and contrast sensitivity using the Cambridge low contrast gratings. Visual and motor abilities were assessed using the Developmental test of motor integration (VMI) and the Movement ABC. Intelligence was measured with the Wechsler intelligence scale for children UK. Perinatal cranial ultrasound and retinopathy data were extracted from clinical records. Results: Children born preterm were significantly more likely to wear glasses, to have poor visual acuity, reduced stereopsis, and strabismus than term controls, but they showed no significant decrease in contrast sensitivity. Ophthalmic impairments were significantly related to poorer scores on the VMI, Movement ABC, and Wechsler IQ tests, but were not significantly related to neonatal cranial ultrasound appearances. Stage 3 retinopathy was related to poorer subsequent acuity. Conclusions: Children born very preterm and without major neurodevelopmental sequelae have an increased prevalence of ophthalmic impairments at primary school age which are associated with visual perceptional, motor, and cognitive defects. The cause may be a generalised abnormality of cortical development rather than perinatally acquired focal lesions of the brain.

VLBW infants are at risk of lesions including intraventricular haemorrhage and periventricular leucomalacia. Those with normal IQ still present with reading difficulties. Oculomotor performance was assessed on 14 VLBWs (IQ85) and 15 full-term age-matched controls. Anti-saccade errors were significantly higher for the VLBWs (78%) compared to full terms (62%) (P = 0.02). Smooth pursuit latency was longer for the VLBWs compared to the full terms. Greater anti-saccade errors may be indicative of a lesion affecting the frontal cortex or developmental delay. Oculomotor deficits in VLBW children may be associated with the higher incidence of reading difficulties that have been reported.

Background/aims: It is well documented that non-concordance with occlusion therapy is both substantial and a major factor leading to treatment failure. Parental understanding in previous work has been found to be poor in key areas such as the critical period and effect of age on prognosis. Research in other areas of medicine has shown that the level of understanding can have a direct effect on the level of concordance. The aims of this study were to assess the ability of educational material in the form of a leaflet, to improve parental understanding of amblyopia and occlusion, and subsequently increase concordance. Methods: Parents of children aged between 1 and 7 years receiving a minimum of 1 hour of occlusion for amblyopia were recruited. A randomised controlled trial was undertaken where, on inclusion, the patients were randomised into a leaflet group, whose parents were issued with written educational material, and a control group whose parents did not receive the written information. Patients were paired and matched for age (

VLBW infants are at risk of lesions including intraventricular haemorrhage and periventricular leucomalacia. Those with normal IQ still present with reading difficulties. Oculomotor performance was assessed on 14 VLBWs (IQ > 85) and 15 full-term age-matched controls. Anti-saccade errors were significantly higher for the VLBWs (78%) compared to full terms (62%) (P = 0.02). Smooth pursuit latency was longer for the VLBWs compared to the full terms. Greater anti-saccade errors may be indicative of a lesion affecting the frontal cortex or developmental delay. Oculomotor deficits in VLBW children may be associated with the higher incidence of reading difficulties that have been reported.

Aims: To determine what practising orthoptists consider to be a normal AC/A ratio and on what evidence this is based. To assess which method of measurement is most commonly used and whether the ratio itself contributes to the diagnosis and management of strabismus in current practice. Methods: A prospective cross-sectional survey was designed and distributed to all orthoptists registered with the British and Irish Orthoptic Society (BIOS). The survey was web-based and consisted of 17 questions relating to the measurement of the accommodative convergence/accommodation (AC/A) ratio and its application to clinical practice. Prior to the survey being distributed nationally, a pilot survey was sent to a small group of practising orthoptists for validation. Results: There was a significant difference ( p < 0.05) in orthoptists’ perception of the normal AC/A ratio (gradient and heterophoria) compared with published research. Ninety-three per cent stated that their definition of ‘normal’ was based on either clinical experience or what they were taught during training, with the gradient method at 33 cm being most commonly used (92.79%). The AC/A ratio is widely used (either ‘always’ or ‘sometimes’) in the diagnosis of convergence excess esotropia (CXS) (97.26%) and intermittent distance exotropia (IDEX) (93.75%) and (either ‘always’ or ‘sometimes’) in the management of CXS (88.89%) and IDEX (79.02%). Conclusion: The majority of orthoptists who participated are primarily measuring the stimulus AC/A ratio clinically. There is a discrepancy between participants’ perception of a normal AC/A ratio and published research, yet the ratio is still used in the diagnosis and management of certain types of strabismus.

Aim: To review the current literature on long-term ophthalmic deficits and behavioural and/or cognitive outcomes occurring in low birth weight (LBW) children and to determine whether there is any link between the ophthalmic deficits and functional out­come. Methods: A literature search was performed focusing mainly on publications from the past 10 years. Results: LBW children are at an increased risk of a large number of ophthalmic deficits, including reduced visual functions (acuity, visual field, colour vision, stereo-acuity and contrast sensitivity), increased prevalence of strabismus and all types of refractive error. These deficits are not restricted to the smallest children; they can occur with increased frequency in nil LBW children. As a group LBNV children have increased risk of cognitive and behavioural deficits, which can affect them through­out their education. There is evidence of an associa­tion between ophthalmic outcome and many aspects of functional ability (e.g. IQ, reading ability). Further research is required to discover whether there is a common aetiology. Conclusion: The evidence discussed supports the need for long-term ophthalmic monitoring, and treatment where necessary, due to the potential impact of LBW on education and development. Currently there is no standardised approach for this. Further discussion is required to optimise the long-term care of all LBW children.

Binding studies have indicated that the density of the cannabinoid CB, receptor is very low in the vestibular nucleus complex compared to other areas of the central nervous system (CNS), suggesting that CB1 receptors may have little functional significance for the vestibular nucleus. However, the dizziness often produced by cannabis suggests that the vestibular system may be implicated. We investigated the effects of the selective CB1 receptor agonist, CP 55940 (the levorotatory enantiomer of desacetyllevonantradol), on medial vestibular nucleus neurons in guinea pig brainstem slices in vitro. Only 3/18 medial vestibular nucleus neurons tested with 1 microM CP 55940 showed changes in firing rate, however these were decreases with an average magnitude of 72.3%; 3/4 neurons tested with 10 microM CP 55940 showed decreases with an average magnitude of 92.7% (P0.05 in both cases). In all cases the effects of CP 55940 were long-lasting. These results suggest that despite the low density of CB1 receptors in the vestibular nucleus complex, they may be of functional significance for the behavioural effects of cannabis use.