Early Visual Sensory Deficits as Endophenotypes for Schizophrenia

CONTEXT

The imperative to establish so-called endophenotypes-quantifiable measures of risk for neurological dysfunction-is a growing focus of research in schizophrenia. Electrophysiological markers of sensory processing, observable in human event-related potentials, hold great promise in this regard, lying closer to underlying physiology than descriptive clinical diagnostic tests.

OBJECTIVE

Early visual processing deficits, as measured by clear amplitude reductions in the occipital P1 component of the visual event-related potential, have been repeatedly demonstrated in patients with schizophrenia. However, before P1 amplitude may be considered as an endophenotypic marker for schizophrenia, it is necessary to establish its sensitivity to genetic liability.

DESIGN, SETTING, AND PARTICIPANTS

Event-related potential responses to simple visual isolated-check stimuli were examined in 25 clinically unaffected first-degree relatives of patients with schizophrenia and 15 DSM-IV-diagnosed schizophrenia probands and compared with responses from 26 healthy, age-matched control subjects. Using high-density electrical scalp recordings, between-groups analysis assessed the integrity of the visual P1 component across the 3 groups. The study was conducted at St Vincent's Psychiatric Hospital in Fairview, Dublin, Ireland.

RESULTS

Substantially reduced P1 amplitude was demonstrated in both relatives and probands compared with controls with topographical mapping and inverse source analysis localizing this deficit largely to midline regions in early visual sensory cortices and regions of the dorsal visual stream. Additional later differences between these groups, where the relatives actually show larger amplitude responses, may point toward compensatory mechanisms at play in relatives.

CONCLUSIONS

Our findings demonstrate a deficit in early visual processing in clinically unaffected first-degree relatives of patients with schizophrenia, providing evidence that this deficit may serve as a genetic marker for this disorder. The efficacy of using P1 amplitude as an endophenotype is underscored by the observation of a large effect size (d=0.9) over scalp sites where the deficit was maximal.

Attitudes and behaviour of ophthalmologists to smoking cessation

AIMS

Growing evidence suggests a causal association between smoking and eye disease. This study explores the current beliefs and practice among UK consultant ophthalmologists towards delivering smoking cessation advice to eye clinic attenders.

METHODS

A cross-sectional survey using a postal questionnaire of all UK NHS hospital based consultant ophthalmologists was conducted. The questionnaire explored whether: ophthalmologists identify the smoking status of their patients, advise about the increased risk of eye diseases among smokers, and deliver smoking cessation advice. The availability of departmental smoking cessation resources was also ascertained.

RESULTS

The response rate was 55% (485/886). Of the responders 79% were males. Only 35% of responders asked about smoking status every time or most times for new patients and 5% for follow-up patients. In all, 40% claimed to always or usually advise patients to quit smoking and 61% claimed to always or usually mention eye disease as a reason to quit. Only 14% assessed motivation to quit and 22% provided advice and assistance about how to stop smoking to smokers who wished to quit. Female ophthalmologists were more likely to undertake most aspects of smoking assessment and intervention. Only 18% of responders stated that their departments provide information about smoking for patients and 6% stated that support is available for patients wanting to quit smoking.

CONCLUSION

The assessment of smoking status and provision of targeted support for smokers to quit could be substantially improved in UK ophthalmology departments. There is a need to introduce smoking cessation support into routine ophthalmic practice and provide the resources to support this.

Cigarette smoking and thyroid eye disease: a systematic review

PURPOSE

To evaluate the epidemiological evidence for a causal association between tobacco smoking and thyroid eye disease (TED).

METHODS

Systematic review, including quality assessment, of published epidemiological studies and evaluation of the evidence using established causality criteria.

RESULTS

Fourteen papers describing 15 studies were included. There was a positive association between smoking and TED in four case-control studies when compared with control patients with Graves' disease but no ophthalmopathy (odds ratio (OR) 1.94-10.1) and in seven case-control studies in which control subjects did not have thyroid disease (OR 1.22-20.2). Two cohort studies examined the occurrence of new cases of TED; one study found an increased incidence of TED with smoking. Four cohort studies investigated progression or outcome of treatment in patients with established TED, three finding an association between smoking and poorer outcome. The quality of the studies was variable, but the association with smoking was strong in the most methodologically rigorous studies. Other evidence supporting a causal link was a consistent association across studies, a dose-response effect, a reduced risk of TED in ex-smokers, and a temporal relationship.

CONCLUSION

This systematic review provided strong evidence for a causal association between smoking and development of TED. Current-smokers were also more likely to experience disease progression or poorer outcome of treatment. Patients with Graves' disease and the general public should be educated about the risk of smoking and TED. These findings suggest that patients with Graves' disease or TED who are smokers should be given effective support to stop smoking.

Patient safety in cataract surgery

PURPOSE

The recent focus on healthcare errors and safety suggest that practitioners and policy makers might appraise their cataract surgical care from a patient safety perspective. This paper reviews patient safety issues relevant to cataract care. Causation and consequences of incidents in cataract surgery, with implications for policy, are discussed.

METHODS

Models of accident causation from other domains were drawn on and empirically applied to cataract care. Consultation was undertaken with experts in cataract surgery, patient safety, and in risk management. Feedback on patient safety was included from presentations made to staff and patients and from personal insights.

RESULTS

Ophthalmology teams should embrace steps to improve patient safety. The role of incident reporting is advanced, including the provision of a prompt menu of cataract patient safety incidents as suggested by the Royal College of Ophthalmologists.

CONCLUSIONS

Strict attention to detail, risk assessment, and careful consideration of the patient pathway is needed to enhance cataract care. Clinical errors, near misses and complications happen, and may provide an opportunity for learning to reduce the risk of similar events in the future. Investment in staffing and training, appropriate equipment, and development of a safety culture with patient involvement are key elements of safe cataract surgical care. Patients and the public expect that safe cataract care should be commissioned for them. Critical patient safety incidents, including incidents that have led to permanent harm, require careful analysis of underlying systems and/or root causes.

Increases in Alpha Oscillatory Power Reflect an Active Retinotopic Mechanism for Distracter Suppression During Sustained Visuospatial Attention

Human electrophysiological (EEG) studies have demonstrated the involvement of alpha band (8- to 14-Hz) oscillations in the anticipatory biasing of attention. In the context of visual spatial attention within bilateral stimulus arrays, alpha has exhibited greater amplitude over parietooccipital cortex contralateral to the hemifield required to be ignored, relative to that measured when the same hemifield is to be attended. Whether this differential effect arises solely from alpha desynchronization (decreases) over the “attending” hemisphere, from synchronization (increases) over the “ignoring” hemisphere, or both, has not been fully resolved. This is because of the confounding effect of externally evoked desynchronization that occurs involuntarily in response to visual cues. Here, bilateral flickering stimuli were presented simultaneously and continuously over entire trial blocks, such that externally evoked alpha desynchronization is equated in precue baseline and postcue intervals. Equivalent random letter sequences were superimposed on the left and right flicker stimuli. Subjects were required to count the presentations of the target letter “X” at the cued hemifield over an 8-s period and ignore the sequence in the opposite hemifield. The data showed significant increases in alpha power over the ignoring hemisphere relative to the precue baseline, observable for both cue directions. A strong attentional bias necessitated by the subjective difficulty in gating the distracting letter sequence is reflected in a large effect size of 2.1 (η2 = 0.82), measured from the attention × hemisphere interaction. This strongly suggests that alpha synchronization reflects an active attentional suppression mechanism, rather than a passive one reflecting “idling” circuits.

Smoking and cataract: review of causal association

Several risk factors for the development of cataract have been identified. This review evaluates epidemiologic literature that has examined tobacco smoking as a risk factor for cataract formation using established causality criteria. Twenty-seven studies were included in this review. Evidence suggests that smoking has a 3-fold increase on the risk for incident nuclear cataract development. There was also evidence of dose response, temporal relationship, and reversibility of effect. There was limited evidence of an association between smoking and posterior subcapsular cataract, but little or no association with cortical cataract. Thus, the literature review indicated a strong association between smoking and the development of cataract, particularly nuclear cataract. The association fulfills the established criteria for causality. The association between smoking and other types of cataract is less distinct and requires further evaluation.

Smoking and age-related macular degeneration: a review of association

PURPOSE

Age-related macular degeneration (AMD) is the leading cause of severe and irreversible vision loss in the Western world. As there is no effective treatment for all types of AMD, identifying modifiable risk factors is of great importance. This review evaluates the epidemiological evidence associating smoking with AMD.

METHODS

Systematic review of published epidemiological studies evaluated against established criteria for evidence of a causal relationship.

RESULTS

In total, 17 studies (cross-sectional studies, prospective cohort studies, and case-control studies) were included in the review. A total of 13 studies found a statistically significant association between smoking and AMD with increased risk of AMD of two- to three-fold in current-smokers compared with never-smokers. Five studies found no association between smoking and AMD. There was also evidence of dose-response, a temporal relationship and reversibility of effect.

CONCLUSION

The literature review confirmed a strong association between current smoking and AMD, which fulfilled established causality criteria. Cigarette smoking is likely to have toxic effects on the retina. In spite of the strength of this evidence, there appears to be a lack of awareness about the risks of developing eye disease from smoking among both healthcare professionals and the general public.

Cataract care is mobile

Is the direction correct?

Direct costs of glaucoma and severity of the disease: a multinational long term study of resource utilisation in Europe

BACKGROUND

Resource utilisation and direct costs associated with glaucoma progression in Europe are unknown. As population progressively ages, the economic impact of the disease will increase.

METHODS

From a total of 1655 consecutive cases, the records of 194 patients were selected and stratified by disease severity. Record selection was based on diagnoses of primary open angle glaucoma, glaucoma suspect, ocular hypertension, or normal tension glaucoma; 5 years minimum follow up were required. Glaucoma severity was assessed using a six stage glaucoma staging system based on static threshold visual field parameters. Resource utilisation data were abstracted from the charts and unit costs were applied to estimate direct costs to the payer. Resource utilisation and estimated direct cost of treatment, per person year, were calculated.

RESULTS

A statistically significant increasing linear trend (p = 0.018) in direct cost as disease severity worsened was demonstrated. The direct cost of treatment increased by an estimated 86 for each incremental step ranging from 455 euro per person year for stage 0 to 969 euro per person year for stage 4 disease. Medication costs ranged from 42% to 56% of total direct cost for all stages of disease.

CONCLUSIONS

These results demonstrate for the first time in Europe that resource utilisation and direct medical costs of glaucoma management increase with worsening disease severity. Based on these findings, managing glaucoma and effectively delaying disease progression would be expected to significantly reduce the economic burden of this disease. These data are relevant to general practitioners and healthcare administrators who have a direct influence on the distribution of resources.

Visual spatial attention control in an independent brain-computer interface

This paper presents a novel brain computer interface (BCI) design employing visual evoked potential (VEP) modulations in a paradigm involving no dependency on peripheral muscles or nerves. The system utilizes electrophysiological correlates of visual spatial attention mechanisms, the self-regulation of which is naturally developed through continuous application in everyday life. An interface involving real-time biofeedback is described, demonstrating reduced training time in comparison to existing BCIs based on self-regulation paradigms. Subjects were cued to covertly attend to a sequence of letters superimposed on a flicker stimulus in one visual field while ignoring a similar stimulus of a different flicker frequency in the opposite visual field. Classification of left/right spatial attention is achieved by extracting steady-state visual evoked potentials (SSVEPs) elicited by the stimuli. Six out of eleven physically and neurologically healthy subjects demonstrate reliable control in binary decision-making, achieving at least 75% correct selections in at least one of only five sessions, each of approximately 12-min duration. The highest-performing subject achieved over 90% correct selections in each of four sessions. This independent BCI may provide a new method of real-time interaction for those with little or no peripheral control, with the added advantage of requiring only brief training.

Perceptions of blindness related to smoking: a hospital-based cross-sectional study

AIMS

Smoking is associated with several serious eye diseases. Awareness of smoking and blindness, and its potential to act, as a stimulus to assist stopping smoking has not been investigated.

METHODS

A cross-sectional survey using a structured interview of adult patients attending district general hospital ophthalmology, general surgery, and orthopaedic clinics. The interview investigated the awareness and fear of blindness for three established smoking-related diseases, and a distractor condition (deafness), and the likelihood that smokers would quit on developing early signs of each condition.

RESULTS

Response was 89.1% (358/402). In all, 183 (51.1%) of responders were male and 175 (48.9%) female. Only 9.5% of patients believed that smoking was definitely or probably a cause of blindness, compared with 92.2% for lung cancer, 87.6% for heart disease, and 70.6% for stroke. Patients ranked their fear of each of the five conditions, scoring five for the most feared and one for the least feared. Patients were significantly (P<0.01) less fearful of blindness (mean score 2.80) than lung cancer (3.89), heart disease (3.58), and stroke (3.35). About one-half of smokers stated that they would definitely or probably quit smoking if they developed early signs of blindness or the three established smoking-related conditions, with no significant differences in proportions for these four conditions.

CONCLUSION

The findings suggest that awareness of the risk of blindness from smoking is low, but that the fear of blindness is as compelling a motivation to quit as fear of lung cancer, heart disease, and stroke. The link between smoking and eye disease should be publicised to help reduce smoking prevalence.

Neurophysiological markers of alert responding during goal-directed behavior: A high-density electrical mapping study

The ability to dynamically modulate the intensity of sustained attention (i.e., alertness) is an essential component of the human executive control system, allowing us to function purposefully in accordance with our goals. In this study we examine high-density ERP markers of alert responding during the fixed sequence sustained attention to response task (SART(fixed)). This paradigm has proven to be a sensitive clinical metric in patient populations with deficits in their ability to sustain attention (e.g., attention deficit hyperactivity disorder). In this task subjects withhold a button press to an infrequent no-go target ('3') embedded within a predictable sequence of numbers ('1' to '9'). Our data reveal a complex pattern of effects across the trial sequence of the SART, with clear contributions from frontal and parietal cortices to sustained attentional performance. Over occipito-parietal regions, early visual attention processes were increased during trial 2 (i.e., trial in which the digit '2' was presented) and trial 3, giving rise to the so-called selection negativity (SN). Two prominent late components were manifest during trial 2: LP1 (550-800 ms) and LP2 (850-1150 ms) over occipito-parietal and central sites. We interpret the LP1 component on trial 2 as reflecting retrieval of the task goal and the subsequent LP2 as reflecting competition between the currently relevant go response and the subsequent no-go response. On trial 3, an enhanced "no-go N2" (250-450 ms) was seen fronto-centrally in the absence of the "no-go P3" that typically follows. Fronto-polar activity was also seen across all trials and may be indicative of subgoal processes to integrate the association between stimulus and goal. Prior to a lapse of attention (i.e., failure to inhibit a response to "3") the LP1 was significantly attenuated on the preceding trial 2 indicating a failure of anticipatory goal-directed processing. The results are discussed in terms of models of sustained attention involving frontal and parietal cortices.

Reflective consideration of postoperative endophthalmitis as a quality marker

PURPOSE

To study the incidence of acute postoperative presumed infectious endophthalmitis (PIE) in a UK district general hospital over a 10-year period. Consideration of such departmental healthcare-associated infection frequency rates as part of reflective and comparative quality practice in the light of local concerns.

METHODS

Hospital-based retrospective case series: 12 831 cataract extraction operations from 01/01/1995 to 31/12/2004 were studied. All cases of PIE within 6 weeks of cataract surgery were ascertained and investigated in a standardised format. PIE incidence rate per 1000 cataract surgical procedures was contrasted with the existing literature.

RESULTS

Seven isolated PIE cases occurred following phacoemulsification. None followed extra-capsular extractions. The PIE rate was 0.55 [95% CI; 0.22 to 1.12] cases per 1000 cataract extractions, or one PIE case within 6 weeks of surgery in every 1833 [95% CI; 893 to 4545] cataract operations undertaken. Five cases were culture positive. Details of PIE cases are presented.

CONCLUSION

PIE incidence rates in our department are slightly lower than reported case series in similar settings. Whether this is due to a variety of preventive measures deployed locally and/or methods of case ascertainment in published studies is problematic and is discussed. Departmental benchmarking data is important in relation to rare, but critical, patient safety incidents. Collection and monitoring of endophthalmitis outcomes is of merit and may inform patient choice. Surgical site infection surveillance systems of relevance are discussed. Implications for making healthcare safer, including reflective practice are, discussed in relation to cataract care.

Visual spatial attention tracking using high-density SSVEP data for independent brain-computer communication

The steady-state visual evoked potential (SSVEP) has been employed successfully in brain-computer interface (BCI) research, but its use in a design entirely independent of eye movement has until recently not been reported. This paper presents strong evidence suggesting that the SSVEP can be used as an electrophysiological correlate of visual spatial attention that may be harnessed on its own or in conjunction with other correlates to achieve control in an independent BCI. In this study, 64-channel electroencephalography data were recorded from subjects who covertly attended to one of two bilateral flicker stimuli with superimposed letter sequences. Offline classification of left/right spatial attention was attempted by extracting SSVEPs at optimal channels selected for each subject on the basis of the scalp distribution of SSVEP magnitudes. This yielded an average accuracy of approximately 71% across ten subjects (highest 86%) comparable across two separate cases in which flicker frequencies were set within and outside the alpha range respectively. Further, combining SSVEP features with attention-dependent parieto-occipital alpha band modulations resulted in an average accuracy of 79% (highest 87%).

Neuropeptides and the control of food intake in fish

The brain, particularly the hypothalamus, integrates input from factors that stimulate (orexigenic) and inhibit (anorexigenic) food intake. In fish, the identification of appetite regulators has been achieved by the use of both peptide injections followed by measurements of food intake, and by molecular cloning combined with gene expression studies. Neuropeptide Y (NPY) is the most potent orexigenic factor in fish. Other orexigenic peptides, orexin A and B and galanin, have been found to interact with NPY in the control of food intake in an interdependent and coordinated manner. On the other hand cholecystokinin (CCK), cocaine and amphetamine-regulated transcript (CART), and corticotropin-releasing factor (CRF) are potent anorexigenic factors in fish, the latter being involved in stress-related anorexia. CCK and CART have synergistic effects on food intake and modulate the actions of NPY and orexins. Although leptin has not yet been identified in fish, administration of mammalian leptin inhibits food intake in goldfish. Moreover, leptin induces CCK gene expression in the hypothalamus and its actions are mediated at least in part by CCK. Other orexigenic factors have been identified in teleost fish, including the agouti-related protein (AgRP) and ghrelin. Additional anorexigenic factors include bombesin (or gastrin-releasing peptide), alpha-melanocyte-stimulating hormone (alpha-MSH), tachykinins, and urotensin I. In goldfish, nutritional status can modify the expression of mRNAs encoding a number of these peptides, which provides further evidence for their roles as appetite regulators: (1) brain mRNA expression of CCK, CART, tachykinins, galanin, ghrelin, and NPY undergo peri-prandial variations; and (2) fasting increases the brain mRNA expression of NPY, AgRP, and ghrelin as well as serum ghrelin levels, and decreases the brain mRNA expression of tachykinins, CART, and CCK. This review will provide an overview of recent findings in this field.

A parametric feature extraction and classification strategy for brain-computer interfacing

Parametric modeling strategies are explored in conjunction with linear discriminant analysis for use in an electroencephalogram (EEG)-based brain-computer interface (BCI). A left/right self-paced typing exercise is analyzed by extending the usual autoregressive (AR) model for EEG feature extraction with an AR with exogenous input (ARX) model for combined filtering and feature extraction. The ensemble averaged Bereitschafts potential (an event related potential preceding the onset of movement) forms the exogenous signal input to the ARX model. Based on trials with six subjects, the ARX case of modeling both the signal and noise was found to be considerably more effective than modeling the noise alone (common in BCI systems) with the AR method yielding a classification accuracy of 52.8+/-4.8% and the ARX method an accuracy of 79.1+/-3.9 % across subjects. The results suggest a role for ARX-based feature extraction in BCIs based on evoked and event-related potentials.

Ethnic aspects of acute primary angle closure in a UK mulicultural conurbation

AIM

To investigate the incidence and ethnic distribution of patients with symptomatic acute primary angle closure (APAC) who presented to a UK hospital serving a multicultural conurbation by a population-wide case series investigation.

METHODS

Case series chart review of patients aged 30 years and above, who required laser peripheral iridotomy (LPI) for a primary acute angle closure event over a 7-year period. Demographic data for cases were compared to the local resident census data.

RESULTS

A total of 46 local residents aged > or =30 years required LPI for APAC. In all, 96% of patients were Caucasian compared to the local resident population of 89% Caucasian. The overall annual APAC rate for Bolton was 4.14 cases per 100 000 population (95% CI 3.03-5.52). The standardised incidence ratio for the South Asian population was 0.78 (95% CI 0.02-4.34) and 26.6 (95% CI 0.67-148.40) for the Chinese population.

CONCLUSIONS

APAC incidence in South Asians was similar to that among Caucasians. The incidence of APAC patients treated in this UK department is consistent with international experience. Individuals of Chinese ethnicity were at an enhanced risk of APAC. However, these results should be interpreted with caution, as patient numbers are small.

Behavioural and physiological impairments of sustained attention after traumatic brain injury

Sustaining attention under conditions of low external demand taxes our ability to stay on task and to avoid more appealing trains of thought or environmental distractions. By contrast, a stimulating, novel environment engages attention far more freely without the subjective feeling of having to override monotony. Our ability to maintain a goal-directed focus without support from the environment requires the endogenous control of behaviour. This control can be modulated by fronto-parietal circuits and this ability is compromised following traumatic brain injury (TBI) leading to increased lapses of attention. In this paper, we further explore a laboratory paradigm that we argue is particularly sensitive to sustained attention as opposed to other aspects of attentional control involving the selection and management of goals in working memory. The paradigm (fixed sequence Sustained Attention to Response Task--SARTfixed) involves withholding a key press to an infrequent no-go target embedded within a predictable sequence of numbers. We demonstrate that TBI patients in this study make disproportionately more errors than controls on this task. An analysis of response times (RTs) and EEG alpha power across the task demonstrates group differences preceding the critical no-go trial. Controls demonstrate a lengthening of RTs accompanied by desynchronization of power within the alpha band (approximately 10 Hz) preceding the no-go trial. Conversely, the TBI group showed a shortening of RTs during this period with no evidence of alpha desynchronization. These findings suggest that TBI patients may have dysfunctional alpha generators as a consequence of their injury that impairs endogenous control during the task.

Can ophthalmic requests for neuroimaging be improved?

AIM

To review and set guidelines for all neuroradiological referrals from the ophthalmic service in a typical UK district general hospital.

METHOD

Patients referred for diagnostic neuroimaging were identified from the radiology database over a 1-year period. A case note review was undertaken. The clinical indication for and results of neuroimaging performed were ascertained. The justification for neuroimaging was determined.

RESULTS

Of the total 31,411 patients that were seen in the eye department, 103 (0.32%) had diagnostic neuroradiological imaging performed. The indications for imaging were: suspected compressive lesion of the anterior visual pathway in 57 patients (55.3%), acquired ocular motility disturbance in 20 patients (19.4%), suspected orbital pathology in 11 patients (10.6%), cerebrovascular accident in nine patients (8.7%), and six patients (5.8%) were imaged for either headache or sinusitis. Radiological lesion detection rate was highest for cerebrovascular accident (88.8%) and lowest acquired for ocular motility disturbance (4.9%).

CONCLUSION

Ophthalmic requests for diagnostic neuroimaging were found to be unnecessary in only 9% of patients. Guidelines for the referral of ophthalmic patients for neuroimaging are discussed.