Are hospital admissions reduced by Acute Medicine consultant telephone triage of medical referrals?

The NHS in England is facing well-documented pressures related to increasing acute hospital admissions at a time when the acute medical bed-base is shrinking, doctors working patterns are increasingly fragmented and many acute hospital trusts are operating a financial deficit. Novel strategies are required to reduce pressure on the acute medical take. We conducted a prospective cohort study to assess the impact of acute medicine consultant triage of referrals to the acute medical take on the number of acute hospital admissions as compared to a historical control cohort. The introduction of an acute medicine consultant telephone triage service was associated with a 21% reduction in acute medical admissions during whole the study period. True admission avoidance was achieved for 28.5% of referrals triaged by an acute medicine consultant. The greatest benefit was seen for consultant-triage of GP referrals; 43% of all GP referrals resulted in a decision not to admit and in 25% the referral was avoided by giving advice alone. Consultant telephone triage of referrals to the acute medical take substantially reduces the number of acute medical admissions as compared to triage by a trained band 6 or higher nurse coordinator. Our service is cost effective and can be job-planned using 6 full-time equivalent acute medicine consultants. The telephone triage service also provides additional benefits to admission numbers beyond its hours of operation and the general management of the acute medical take.

Dystrophin expression in the human retina is required for normal function as defined by electroretinography.

We have studied retinal function by electroretinography in five Becker and six Duchenne muscular dystrophy patients. All had abnormal electroretinograms with a markedly reduced amplitude for the b-wave in the dark-adapted state. Using three antisera raised to different domains of dystrophin, we identified dystrophin in the outer plexiform layer of human retina. The retinal dystrophin is present in multiple isoforms as the result of alternative splicing. The localization of dystrophin to the outer plexiform layer coincident with the abnormal b-wave suggests that dystrophin is required for normal retinal electrophysiology.

Eye-movement responses to disparity vergence stimuli with artificial monocular scotomas.

The effects of artificial monocular scotomas on eye-movement responses to horizontal disparity vergence stimuli were studied in six subjects with normal binocular vision. Subjects viewed stereoscopic 1.5 degrees horizontal step disparity vergence stimuli through liquid crystal shutter glasses. The central portion of the stimulus presented to the right eye was removed to simulate monocular artificial scotomas of variable diameters (2 degrees to 10 degrees ). Eye movements were recorded with a binocular head-mounted eye tracker. Responses included pure vergence, vergence followed by saccades, and pure saccadic eye movements. The rate of responses with saccadic eye movements increased with the diameter of the artificial scotoma (p < 0.0001); there was an increase in the rate of responses starting with saccades (p < 0.0001), as well as an increase in the rate of saccades after initial vergence responses (p < 0.01). The probability of saccades after initial vergence responses was affected by the open-loop gain of the vergence response (p < 0.001). The open-loop gain decreased with increased diameters of the artificial scotomas (p < 0.0001). As the diameter of the artificial scotomas increased, the amplitude of the initial vergence eye-movement responses decreased, and the prevalence of saccadic eye movements and asymmetric vergence increased. The effects of the diameter of artificial monocular scotomas on eye-movement responses in subjects with normal binocular vision are consistent with the effects of diameter of suppression scotomas on eye-movement responses to disparity vergence stimuli in patients with infantile esotropia.

Adaptation of the vestibulo-ocular reflex in amblyopia.

Adaptation of the vestibulo-ocular reflex (VOR) is demonstrated by changes in gain in response to discrepancies between visual and vestibular stimulation. The authors have investigated the effect of monocular asymmetries of OKN in amblyopia upon adapting the gain of the VOR. Adaptation was investigated by modifying the horizontal balance of the VOR. While monocularly fixating a head referenced spot for 2 min, subjects were sinusoidally oscillated on a chair inside an optokinetic drum that rotated in one direction (left or right) at the peak velocity of sinusoidal chair rotation. The VOR was then measured during continued sinusoidal body oscillation in darkness for 1 min. Imbalance of the horizontal VOR gain equalled the ratio of slow phase velocities in the rightward and leftward directions. After rotating the drum in the nasalward direction, an increase was observed in slow phase gain of the VOR in the nasalward direction for either eye of our amblyopes that was significantly greater than similar changes in gain for the normals. Increased VOR gains for the amblyopic group following temporalward stimulation were significantly less than the nasal aftereffect. Gain changes of the VOR in normals had similar magnitudes following nasal or temporal stimulation. These results suggest that disturbances of OKN in amblyopia are common to the pathways that modify the slow phase gain of the VOR.

Visual and vestibular sources of fixation instability in amblyopia.

Extraretinal and visual afferent sources of ocular fixation instability were investigated in a group of strabismic amblyopes. Extraretinal drift-bias was revealed by fixational eye movements in darkness. The resulting dark drift-bias was highly correlated with an imbalance of the vestibulo-ocular reflex (VOR). No significant difference in dark drift-bias or VOR imbalance was found between normal and amblyopic observers. Visual afferent sources of fixation instability were revealed by after-effects of nasalward and temporalward retinal image motion upon ocular drifts in the dark (motion after nystagmus) (MAN). Nasalward biases of MAN were significantly greater in amblyopic than nonamblyopic subjects. Directional biases of optokinetic nystagmus in amblyopia were accounted for by normal unindirectional extraretinal drift sources and by an abnormal visual afferent nasal drift-bias of the fixating eye coupled with reduced sensitivity for detecting errors of retinal slip.

Cortical binocularity and monocular optokinetic asymmetry in early-onset esotropia.

PURPOSE: To investigate the correlation between directional asymmetry in ocular responses to monocularly viewed optokinetic stimuli (monocular optokinetic nystagmus, MOKN) and sensory fusion in infants and toddlers with early-onset esotropia. METHODS: Subjects were 14 infants and toddlers with early-onset esotropia (7-26 months old; median, 10 months), and 16 with no esotropia (6-22 months; median, 11 months) who provided control data. Monocular optokinetic nystagmus in response to a 30 degrees/sec square-wave grating (0.25 cycles/degree) was measured by electro-oculogram. Sensory fusion was assessed with visual evoked potentials (VEPs) to random-dot correlograms after correction of the strabismus angle with Fresnel prisms. RESULTS: All subjects with early-onset esotropia had MOKN with a faster slow-phase component for temporal-to-nasalward (TN) than nasal-to-temporalward (NT) motion. Ninety-three percent of subjects had MOKN asymmetry higher than the 95th percentile of the control group. Of subjects who cooperated with VEP fusion testing, 5 subjects with early-onset esotropia (45%) and 11 control subjects (92%) showed evidence of sensory fusion. CONCLUSIONS: Symmetrical MOKN did not develop in infants and toddlers with early-onset esotropia. This deficit existed in most infants who showed sensory- cortical fusion. These results are consistent with the belief that optokinetic nystagmus asymmetry may not be associated with a deficit in the cortical fusion facility, but rather with deficits in binocular pathways projecting to MOKN control centers. These deficits may be associated with abnormal processing subsequent to sensory fusion or with abnormal processing in motion pathways, which run parallel to sensory fusion pathways.

Electrophysiological evidence of cortical fusion in children with early-onset esotropia.

PURPOSE: To investigate sensory fusion responses in infants and children with early-onset esotropia to gain insights into the sequence of events that leads to strabismus. METHODS: Sensory fusion was tested by measuring visual evoked potential (VEP) responses to dynamic random dot correlograms (DRDCs) in a group of children (n = 23) with early-onset esotropia. Thirteen children were tested before surgical alignment, and 13 children were tested after surgical alignment (three children were tested before and after surgery). If the angle of strabismus was larger than 5 prism diopters, it was corrected with Fresnel prisms (Fresnel Prism and Lens, Scottsdale, AZ). RESULTS: Five (38%) of the 13 children who were tested before surgery showed detectable VEP responses to correlogram stimuli compared with 11 (85%) of the 13 children who were tested after surgical alignment. There were no significant statistical differences between VEP responses to DRDCs from the postsurgery group and VEP responses from an age-matched control group with normal binocular vision. CONCLUSIONS: The presence of cortical sensory fusion in children with early-onset esotropia suggests that a congenital defect of sensory fusion cannot be the root cause of esotropia in most children. The data suggest that sensory fusion, when measured by VEP responses to DRDCs, is more robust than stereopsis to abnormal binocular experience and support the notion that pathways processing correlated/anticorrelated stimuli may not completely overlap with pathways processing disparity information.

OKN asymmetries in orthoptic patients: contributing factors and effect of treatment.

Monocular optokinetic nystagmus (MOKN) was measured (EOG) in response to horizontally moving square wave gratings (0.2 c/deg, 27 and 35 deg/s) in 58 children with amblyopia and/or strabismus (experimental group); the data were compared with that collected from 24 children (aged 3-8 years) with no visual problems (control group). We found OKN asymmetries most often associated with strabismus of early age of onset (less than 2 years). In these children the MOKN asymmetry often occurred in both eyes. In children with later onset strabismus the asymmetry was often confined to the amblyopic eyes. We repeated the measurements on 18 experimental children after 1-3 years of treatment (patching the dominant eye) and compared the results with those recorded in 12 fully binocular control children retested after 1-2 years. Large OKN asymmetries before treatment were still present after the patching treatment. However there was a small, but significant (P = 0.05, t-test), improvement in the nasal-temporal (N-T) slow-phase velocity in the affected eyes of the experimental group, which was not correlated with improvements in visual acuity or linked to the presence of strabismus and/or amblyopia. The main contributing factors to asymmetric OKN affecting both eyes of early onset strabismus seem to be to poor binocularity which would not improve during patching treatment. OKN asymmetries in amblyopic eyes may also result from reduced cortical sensitivity from that eye, which may be minimally improved by patching treatment. Our results suggest a shorter sensitive period of development for OKN pathways than for the development of cortical visual pathways.

Asymmetries of optokinetic nystagmus in amblyopia: the effect of selected retinal stimulation.

Open loop optokinetic eye movements were measured in response to monocular nasalward and temporalward visual field movement presented at four selected retinal sites in 6 strabismic amblyopes and 4 normal observers. Stimulus sites included the central retina (10 X 10 deg), a large field (40 X 32 deg), a large peripheral field with the center (10 X 10 deg) blocked out and a hemiretinal field (15 X 32 deg) excluding the fovea. We found directional preferences of OKN in amblyopia to nasalward stimulus movement for the foveal and concentric peripheral stimuli. The results of peripheral hemiretinal optokinetic stimulation of amblyopic subjects revealed a deficient OKN slow phase response from the temporal hemiretina, particularly for temporalward stimulus movement. There was no marked asymmetry of OKN in the normal group for the concentric stimuli. A normal preference was found for nasalward and temporalward stimulus field movement imaged on the nasal and temporal hemiretinae respectively. These results are interpreted in terms of a model of cortical and subcortical pathways for OKN derived from comparative studies of cat and monkey.

Postnatal development of optokinetic after nystagmus in human infants.

During the first few months of life after birth human infants when tested monocularly move their unoccluded eye nasalward in darkness after viewing a large textured visual field moving either nasalward or temporalward. The eye movements in darkness are optokinetic after nystagmus (OKAN) which is an aftereffect of a reflex horizontal following eye movement, optokinetic nystagmus (OKN). Not until 4-5 months of age did temporalward field motion evoke OKAN with temporalward slow phase. The nasalward slow phase of OKAN that responded earlier to temporalward field motion appears to underlie the delayed development of reflex following eye movements in the temporalward direction.

Emmetropisation in human infancy: rate of change is related to initial refractive error.

Animal studies show that the rate of recovery from experimentally induced refractive errors is related to the level of ametropia induced. The present study examined the rate of emmetropisation occurring in a sample of 22 human infants refracted by near retinoscopy during the first six months of life and then again between 12 and 17 months old. None of the subjects were myopic. Regression analysis revealed that emmetropisation occurred more rapidly in the presence of high refractive errors (P < 0.005 and P = 0.001 for hyperopia and astigmatism respectively). These data confirm the findings of the animal studies and suggest that non-reducing hyperopia and astigmatism in the second year of life may require correction.

A modified protocol for the assessment of visual function in patients with retinitis pigmentosa.

BACKGROUND: The assessment of visual function for retinitis pigmentosa routinely includes: electroretinography, visual acuity and visual field-testing. Patients with retinitis pigmentosa sometimes complain of changes in visual function, which are not paralleled by routine eye tests. AIMS AND OBJECTIVES: To determine which visual function test or group of tests can predict reliably perceived visual function in patients with retinitis pigmentosa METHODS: Subjects with progressive retinitis pigmentosa are recruited from the Ocular genetics program of The Hospital for Sick Children and Mount Sinai Hospital, Toronto. Subjects will be tested four times over the over the period of one year. On each visit they undergo following tests- 1) Central visual acuity (VA) using the crowded logMAR acuity chart, 2) Contrast Sensitivity (CS) using Pelli-Robson contrast sensitivity chart, 3) Visual field test (VF) using Humphrey (10-2), 4) Color vision using Mollon-Reffin 'minimalist' test and 5) Subjective visual function questionnaire testing near and global perceived visual function respectively. RESULTS: Phase I (baseline and visit I measure) results are reported. Total of sixty-eight patients with mean age of 41 years, age range of twelve to sixty seven were tested. Of these thirty-one were males and thirty-seven were females. Repeat testing correlation was high (r>0.8, p<0.05) for all parameters between baseline visit and visit I. The near perceived visual function correlated best with the combination of visual acuity and contrast sensitivity. The global perceived visual function correlated best with combination of visual field and visual acuity. Objective measure of central visual function (HVF 10-2) correlated best with contrast sensitivity. DISCUSSION: The addition of contrast sensitivity and Humphrey visual field to routine visual assessment should improve the quality of the longitudinal data of visual function recorded on these patients. Patients will be re- tested at six months and one-year interval. To date of the sixty-eight subjects twenty-seven have returned for their six-month visit (phase II).

Use of the Mollon-Reffin minimalist color vision test with young children.

PURPOSE: We evaluated the Mollon-Reffin Minimalist (M-R M) color vision test to determine how successfully young children can perform the task and to compare success rates with the American Optical Hardy Rand Rittler (HRR) test and a preferential-looking type test based on the F2 plates (the Pease-Allen color test [PACT]). METHODS: Participants included 146 children (aged 3-10 years) and 32 older subjects (aged 11-39 years). The M-R M test uses 3 series of colored caps coinciding with protan, deutan, and tritan confusion axes, with 6 saturations along each axis. The observer must identify a single colored cap from gray caps of varying lightness. The PACT test consists of 2 cards with targets for detecting red-green and blue-yellow color deficiencies. The tester judges the location of the target on the basis of the child's looking and/or pointing responses. The HRR was performed according to standard instructions, although a more flexible scoring protocol was also used. RESULTS: A significant difference in the children's performance between the "test" item of the 3 tasks emerged (Cochran Q test, P<.001): all children successfully completed the M-R M, 90% successfully completed the PACT, and 88% successfully completed the HRR. Few errors were made on the M-R M red-green series, even among children aged 3 to 4 years, although errors were made with the least saturated blue-yellow cap at all ages. Recommendations are made for the use of the M-R M with children. CONCLUSIONS: The M-R M test can be performed by young children and may prove to be especially useful for detecting and monitoring acquired color vision defects.

Comparison of techniques for detecting visually evoked potential asymmetry in albinism.

PURPOSE: We compared techniques for analyzing visually evoked potential (VEP) asymmetry in children with albinism to find one that could be used effectively and efficiently. METHOD: Subjects included 21 child volunteers, ages 10 months to 6 years (control group) and 21 children with albinism, ages 2 months to 6 years (albinism group). Five-channel flash VEP was performed on all subjects. Electrodes were positioned at Oz, O1, O2, O3, and O4 (10/20 system). Data were analyzed by use of techniques previously described. These included inspection of the VEP waveforms, measurement of hemispheric waveform parameters, calculation of an asymmetry index, and use of a bipolar derivation between left and right hemispheric responses (interhemispheric difference potential). In addition, we quantified the interhemispheric difference potential by use of Pearson's correlation coefficient. Measurements of sensitivity and specificity determined the success of the 5 analysis paradigms. The accuracy of each paradigm represented the ability to classify the data according to volunteer or albinism group and is derived from both sensitivity and specificity measures. RESULTS: Measurement of hemispheric differences in VEP waveform parameters was the least sensitive measure method for detecting multichannel VEP asymmetry in albinism. Comparison of left and right eye interhemispheric difference potential increased accuracy to 67%. Nonquantitative inspection of waveform demonstrated an accuracy of 76%. The asymmetry index and Pearson's correlate measure yielded accuracy rates of 79% and 83%, respectively. CONCLUSION: The efficiency and capability of Pearson's correlate measure in quantifying interhemispheric difference potentials to detect albinotic misrouting makes this a useful and practical technique in a pediatric clinic.

Which ocular and neurologic conditions cause disparate results in visual acuity scores recorded with visually evoked potential and teller acuity cards?

PURPOSE: We investigated whether disparity between visually evoked potential (VEP) acuity scores and Teller Acuity Card (TAC) scores varied according to presence of ocular or neurologic conditions. METHODS: Charts from 175 children (mean age, 34.8 months; range, 3 to 158 months) referred for visual acuity testing were examined. All children had been tested with pattern-alternation VEP and TAC and had undergone a complete eye examination. VEP and TAC acuity scores were relative to age-expected acuity scores for each acuity test. The absence and degree of macular abnormality, retinal abnormality, optic nerve hypoplasia, optic nerve atrophy, cortical visual impairment, developmental delay, cerebral palsy, seizures, and nystagmus were noted. Analysis of variance models were used to determine whether differences between VEP and TAC scores varied according to the presence of specific deficits. Logistic regression analysis determined whether degree of specific deficits was associated with a greater chance of inconsistency between VEP and TAC scores (>0.3 log unit difference). RESULTS: Inconsistent scores were found in 48% of children. Developmental delay was associated with relatively poorer TAC than VEP score, and the chance of inconsistency increased with severity of developmental delay. CONCLUSIONS: Diagnosis-dependent variability exists between TAC and VEP scores. Therefore knowledge of the clinical picture is necessary in interpretation of VEP and TAC scores. It is not clear which test is more useful when a disparity exists, either from this or previous studies. When visual acuity is assessed longitudinally in a given child, then consistency in method for acuity assessment is important.

The modified frisby stereotest.

BACKGROUND: The Frisby stereotest commonly is used in clinical practice to estimate stereoacuity. Assessment of the presence or absence of stereopsis is valuable particularly in toddlers because of the difficulties encountered in this age group with assessment of other aspects of visual function, such as monocular visual acuities. METHODS: The present study describes two modifications to the Frisby stereotest: 1) the introduction of a nonstereo practice plate; and 2) the use of an auditory "reward" for correct identification of the target. These modifications aim to increase the success rate of the test and provide a means to discriminate between testable and untestable children. Subjects were 165 children aged between 0.5 and 47 months. RESULTS: The modifications improved the age range over which results could be obtained with the Frisby test, allowing infants as young as 7 months to complete testing. By 12 months of age, more than 60% of children were able to complete testing. The modifications also allowed the examiner to distinguish untestable children from those without stereopsis. CONCLUSIONS: By simple modification of the Frisby stereotest, the authors have increased the ease with which the Frisby stereotest can be used to assess stereoacuity in infants and children and provided a means by which children unable to cooperate with testing can be distinguished from those without stereopsis.

Primer on visual field testing, electroretinography, and other visual assessments for patients treated with vigabatrin.

Vigabatrin, an irreversible inhibitor of γ-aminobutyric acid transaminase, is an antiepileptic drug indicated in the United States as adjunctive therapy for adult patients with refractory complex partial seizures who have responded inadequately to several alternative treatments and for monotherapy treatment of infantile spasms in patients 1 month to 2 years of age. Approval of vigabatrin in the United States was contingent on the implementation of a Risk Evaluation and Mitigation Strategy (REMS) to manage the threat of a progressive, permanent bilateral concentric peripheral visual field defects (pVFDs) that may occur in patients treated with vigabatrin. The REMS is designed to promote compliance with evidence-based recommendations for baseline (within 4 weeks of the start of treatment) ophthalmologic evaluations and ongoing vision monitoring in all patients treated with vigabatrin. In view of the challenges associated with visual field testing in patients with epilepsy and in infants, clinicians must understand the qualitative (pattern of damage), quantitative (degree of damage), electrophysiologic, and adjunctive techniques recommended for monitoring vigabatrin-treated patients. The objectives of ongoing research are to characterize the onset, progression, and risk of developing vision loss during the first year of vigabatrin treatment and to evaluate the potential of noninvasive imaging as a method for monitoring retinal changes corresponding to the pVFD. This article provides an overview of visual field testing procedures and electroretinography, summarizes the clinical characteristics of vigabatrin-associated pVFDs, and provides recommendations for visual field and visual electrophysiology testing relevant to both adult and infant patients treated with vigabatrin.

Saccades in children with spina bifida and Chiari type II malformation.

BACKGROUND: Saccades are essential for optimal visual function. Chiari type II malformation (CII) is a congenital anomaly of the cerebellum and brainstem, associated with spina bifida. OBJECTIVE: To investigate the effects of CII on saccades and correlate saccadic parameters with brain MRI measurements. METHODS: Saccades were recorded in 21 participants with CII, aged 8 to 19, using an infrared eye tracker. Thirty-nine typically developing children served as controls. Participants made saccades to horizontal and vertical target steps. Nineteen participants with CII had MRI. Regression analyses were used to investigate the effects of spinal lesion level, number of shunt revisions, presence of nystagmus, and midsagittal MRI measurements on saccades. RESULTS: Saccadic amplitude gains, asymptotic peak velocities, and latencies did not differ between the control and CII groups (p > 0.01). No significant differences were found between saccadic gains, asymptotic peak velocities or latencies, and spinal lesion level, number of shunt revisions, presence of nystagmus, or MRI measurements. CONCLUSIONS: Saccades were normal in most participants with Chiari II malformation (CII). Neural coding of saccades is robust and is typically not affected by the anatomic deformity of CII.

Binocular vision: its influence on the development of visual and postural reflex eye movements.

The time course for the development of binocular vision is similar to the time course for the development of mature, symmetrical, monocular optokinetic nystagmus in response to movements of the visual field in the nasalward or temporalward direction. If binocular vision does not develop normally, then the monocular optokinetic response remains immature, or asymmetric. This paper examines the connection between the development of symmetrical OKN and binocular vision, and relates how disturbances in visual development affect the ability of postural reflex eye movements to adapt to changes in the visual environment.