Robert J. Jacobs

Randomised controlled trial of prevention of falls in people aged 75 with severe visual impairment: the VIP trial

Abstract Objectives To assess the efficacy and cost effectiveness of a home safety programme and a home exercise programme to reduce falls and injuries in older people with low vision. Design Randomised controlled trial. Setting Dunedin and Auckland, New Zealand. Participants 391 women and men aged ≥(1) 75 with visual acuity of 6/24 or worse who were living in the community; 92% (361 of 391) completed one year of follow-up. Interventions Participants received a home safety assessment and modification programme delivered by an occupational therapist (n = 100), an exercise programme prescribed at home by a physiotherapist plus vitamin D supplementation (n = 97), both interventions (n = 98), or social visits (n = 96). Main outcome measures Numbers of falls and injuries resulting from falls, costs of implementing the home safety programme. Results Fewer falls occurred in the group randomised to the home safety programme but not in the exercise programme (incidence rate ratios 0.59 (95% confidence interval 0.42 to 0.83) and 1.15 (0.82 to 1.61), respectively). However, within the exercise programme, stricter adherence was associated with fewer falls (P = 0.001). A conservative analysis showed neither intervention was effective in reducing injuries from falls. Delivering the home safety programme cost

Visual resolution and contour interaction in the fovea and periphery.

NZ650 (£234, 344 euros,

Neonatal Glycemia and Neurodevelopmental Outcomes at 2 Years

US432) (at 2004 prices) per fall prevented. Conclusion The home safety programme reduced falls and was more cost effective than an exercise programme in this group of elderly people with poor vision. The Otago exercise programme with vitamin D supplementation was not effective in reducing falls or injuries in this group, possibly due to low levels of adherence. Trial registration number ISRCTN15342873.

A preliminary report of acuity and contour interactions across the amblyope's visual field

Abstract The experiments provide quantitative data on the nature of contour interaction at the fovea and in the periphery to 10° eccentricity for observers with normal vision. Results with Landolt ring targets similar to those used by Flomet al. (J. opt. Soc. Am.53, 1026–1032) show that contour interaction effects are greater in peripheral vision. In central vision the increase in minimum angle of resolution (MAR) that occurred with the introduction of bars around the Landolt ring is small and much less than the experimental variation, whereas in peripheral vision bars at any of the ring-bar separations tested produced a consistent increase in MAR. Relationships between MAR and eccentricity are presented and compared with those in the literature. Reasons for the variation between previous studies are suggested.

Epidemic influenza myopathy in Cincinnati in 1977.

BACKGROUND Neonatal hypoglycemia is common and can cause neurologic impairment, but evidence supporting thresholds for intervention is limited. METHODS We performed a prospective cohort study involving 528 neonates with a gestational age of at least 35 weeks who were considered to be at risk for hypoglycemia; all were treated to maintain a blood glucose concentration of at least 47 mg per deciliter (2.6 mmol per liter). We intermittently measured blood glucose for up to 7 days. We continuously monitored interstitial glucose concentrations, which were masked to clinical staff. Assessment at 2 years included Bayley Scales of Infant Development III and tests of executive and visual function. RESULTS Of 614 children, 528 were eligible, and 404 (77% of eligible children) were assessed; 216 children (53%) had neonatal hypoglycemia (blood glucose concentration, <47 mg per deciliter). Hypoglycemia, when treated to maintain a blood glucose concentration of at least 47 mg per deciliter, was not associated with an increased risk of the primary outcomes of neurosensory impairment (risk ratio, 0.95; 95% confidence interval [CI], 0.75 to 1.20; P=0.67) and processing difficulty, defined as an executive-function score or motion coherence threshold that was more than 1.5 SD from the mean (risk ratio, 0.92; 95% CI, 0.56 to 1.51; P=0.74). Risks were not increased among children with unrecognized hypoglycemia (a low interstitial glucose concentration only). The lowest blood glucose concentration, number of hypoglycemic episodes and events, and negative interstitial increment (area above the interstitial glucose concentration curve and below 47 mg per deciliter) also did not predict the outcome. CONCLUSIONS In this cohort, neonatal hypoglycemia was not associated with an adverse neurologic outcome when treatment was provided to maintain a blood glucose concentration of at least 47 mg per deciliter. (Funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development and others.).

Effect of defocus on blur thresholds and on thresholds of perceived change in blur: comparison of source and observer methods.

Abstract Acuity and contour interactions were assessed across the visual field of representative strabismic amblyopes. Acuity profiles display large variations between amblyopes who exhibit the same degree of eccentric fixation; however, in no case was foveal acuity significantly better than that found eccentrically. The acuity abnormality for most amblyopes is visual field locus dependent. Contour interactions are abnormal in both form and magnitude for some amblyopes. This abnormality does not depend upon the acuity deficit, is field locus dependent and cannot be easily accounted for by optical, oculomotor or eccentric fixation factors.

An assessment of the iPad as a testing platform for distance visual acuity in adults

A distinctive myopathy was observed in 24 children following influenza B infection. The abrupt onset of severe muscle pain and difficulty in walking began as the respiratory symptoms were waning. The lower extremities, particularly the gastrocnemius and soleus muscles, were involved preferentially. Nasopharyngeal cultures were positive for influenza B Hong Kong in 18 of these patients. Serum creatine phosphokinase levels were significantly elevated (mean 55.2 units) when compared to controls and nine patients with Reye syndrome. The cardiac muscle isoenzyme was detected in the serum of 17 myopathy patients. Serum glutamic oxaloacetic transaminase, but not serum glutamic pyruvic transaminase, was elevated compared to controls (P less than 0.01) but less (P less than 0.001) than the patients with Reye syndrome. Twelve patients underwent muscle biopsy; segmental rhabdomyolysis without inflammation was detected in nine patients. Myopathy is a complication of influenza infection that can be diagnosed by clinical, biochemical, and virologic examination.

Effect of defocus on visual acuity as measured by source and observer methods.

The defocus levels required for normal observers to notice the first perceptible blur of a clear test target (blur threshold) and the least perceptible change in the degree of blurriness of an already blurry target (threshold of perceived change in blur) were measured using both the source and observer methods. In the source method observers viewed defocused stimuli presented on a projection screen, whereas in the observer method focused stimuli were presented to observers who were defocused using lenses placed in the spectacle plane. Blur thresholds were found to be dependent on target size and when the Landolt ring targets were near threshold acuity size blur thresholds were as small as 0.10 D. For larger target sizes (0.6 log min arc or more above threshold acuity size) the blur thresholds remained relatively unchanged and were about 0.18 D. Thresholds of perceived change in blur were found to be independent of the initial defocus level. Measurements of the threshold of perceived change in blur were found to be 0.05 to 0.07 D, which is much smaller than the blur threshold values. Comparison of results from the two methods of producing defocus indicate that the source and observer methods can be used interchangeably. However, for the same angular blur disc diameter, the blur thresholds found with the source method were significantly lower than those found with the observer method.

Influence of age on the multifocal electroretinography

Objectives Visual acuity is a common measurement in general practice, and the advent of new technology such as tablet computers offers a change in the way in which these tests are delivered. The aim of this study was to assess whether measurements of distance visual acuity using LogMAR letter charts displayed on an iPad tablet computer were in agreement with standard clinical tests of visual acuity in adults with normal vision. Design Blinded, diagnostic test study. Setting Single centre (University) in Auckland, New Zealand. Participants University staff and students (n=85). Participants were required to have visual acuity better than 6/60 and wear habitual refractive correction during testing. Participants were excluded if there was any history of ocular pathology. Primary and secondary outcome measures Visual acuity measured under a number of conditions. Results The iPad tablet with its glossy screen was highly susceptible to glare resulting in acuity measurements that were significantly poorer (approximately 2 LogMAR lines) than those made using an ETDRS chart and a standard computerised testing system (n=56). However, fitting the iPad with an antiglare screen and positioning the device away from sources creating reflected (veiling) glare resulted in acuity measurements that were equivalent those made using gold standard charts (n=29). Conclusions Tablet computers are an attractive option for visual acuity measurement due to portability, the ability to randomise letters, automated scoring of acuity and the ability to select from a range of charts. However, these devices are only suitable for use in situations where sources of glare can be eliminated.

Concerns of anophthalmic patients wearing artificial eyes.

The relation between refractive error and visual acuity has been measured by two very different methods. In one called “source methods,” emmetropes or corrected ametropes view defocused stimuli presented on projection screens or photographs. In the type called “observer methods,” focused stimuli are presented to the observers who are either uncorrected ametropes or emmetropes defocused by lenses placed (usually), in the spectacle plane. The study reported in this paper demonstrates for the first time that these two methods of defocusing retinal images and their effects on visual acuity can be correlated. Results show that the source method of producing defocus could be used interchangeably with the observer method in investigating the rates of change of visual acuity with defocus for young normal observers. The angular diameter of the defocused image of a point, the blur disc diameter in object space, allows the two methods to be compared. Although the results show that the two methods are highly correlated, they show that the source method gives a statistically but not clinically significant lower acuity. The results of both methods are used to derive an equation linking refractive error, visual acuity, and pupil diameter.