Visual risk factors for falls in older adults: a case-control study.

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, <0.001), or socialising more out of the home (OR: 0.75, 0.60-0.93, p = 0.01). 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.

The Use of the Saccadometer to Identify Saccadic Characteristics in Myasthenia Gravis: A Pilot Study.

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.

Outcomes of the Harada-Ito Procedure.

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 < .01) and there remained a significant difference in maximum torsion from preoperative measurement at both the 3-month (p = .02), and 12-twelve month (p = .01) follow-up. HI had a significant effect on associated V-pattern esotropia (p < .05). CONCLUSION: The HI procedure is effective in eliminating subjective torsion initially and reducing incomitant horizontal deviation; however, regression toward preoperative torsion measurement occurs after time.

The Normal Accommodative Convergence/Accommodation (AC/A) Ratio.

BACKGROUND AND PURPOSE: To measure the Accommodative Convergence (PD)/Accommodation ratio (D) (AC/A) in a cohort of visually normal participants using common clinical methods. PATIENTS AND 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. RESULTS: 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. CONCLUSION: 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.

Incidence, risk factors and management of intractable diplopia.

AIMS: There 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. METHODS: A 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. RESULTS: The 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%). CONCLUSION: Intractable 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.

Assessment of the Density of Suppression to Identify Risk of Intractable Diplopia in the United Kingdom.

BACKGROUND/AIMS: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Fiat Lux: the effect of illuminance on acuity testing.

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 < 0.001), an effect that is exacerbated in the presence of induced myopic refractive error (p < 0.001). Stereoacuity scores demonstrate statistically significant overall differences between illuminance levels (p < 0.001). CONCLUSIONS: The findings of this study demonstrate that changes in illuminance have a statistically significant effect on VA that may contribute to test/retest variability. Increases in illuminance from 50 to 500 lx resulted in an improved VA score of 0.12 LogMAR. Differences like these have significant clinical implications, such as false negatives during vision screening and non-detection of VA deterioration, as the full magnitude of any change may be hidden. In research where VA is a primary outcome measure, differences of 0.12 LogMAR or even less could affect the statistical significance and conclusions of a study. It is recommended that VA assessment always be performed between 400 lx and 600 lx, as this limits any effect of illuminance change to 0.012 LogMAR.

A pilot study examining density of suppression measurement in strabismus.

PURPOSE: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.

Use of atropine penalization to treat amblyopia in UK orthoptic practice.

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.

Differences in the stability of zirconium(IV) complexes related to catalytic phosphine dehydrocoupling reactions.

Relating to the catalytic dehydrocoupling of secondary phosphine substrates, zirconium phosphide complexes supported by triamidoamine and pentamethylcyclopentadienyl ligands exhibit different stability that is attributed to ß-hydride elimination.

Oculomotor control in children who were born very prematurely.

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 (>or=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 degrees 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.

Oculomotor control in a group of very low birth weight (VLBW) children.

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.