Alzheimer's disease: a review for the ophthalmologist

Formulation and characterization of polymeric nanoparticle of Rivastigmine for effective management of Alzheimer's disease

Memory loss or dementia is a progressive disorder, and one of its common forms is Alzheimer's disease (AD), effecting mostly middle aged and older adults. In the present study, we developed Rivastigmine (RIV) nanoparticles using poly(lactic-co-glycolic acid) (RIV-loaded PLGA NPs) and polyvinyl alcohol (PVA). The prepared RIV-PLGA nanoparticles was evaluated for the management of Alzheimer's disease (AD). The nanoparticles were prepared by the slightly modified nano-precipitation technique. The developed formulations were evaluated for particle size, zeta potential (ZP), polydispersibility index (PDI) and surface morphology and drug content. The experimental result revealed that prepared RIV-loaded PLGA NPs (F1) was optimized having particle size (61.2 ± 4.6 nm), PDI (0.292), ZP (-11.2 ± 1.2). SEM study confirms the prepared nanoparticles depicted non-aggregated as well smooth surface particles without any fracture. This formulation (F1) was further assessed for in vivo studies on animal model. A pharmacological screening on an animal model of Alzheimer's disease revealed that RIV-loaded PLGA NPs formulations treat CNS disorders like Alzheimer's effectively. In addition to that, an in-vivo brain cholinesterase estimation study found that, animals treated with optimized formulation significantly (p < 0.01) reduced brain cholinesterase activity when compared to scopolamine-treated animals. According to the above results, it can be concluded that RIV-loaded PLGA NPs are ideal carriers for delivering the drug at a specific target site in the brain, thus may treat Alzheimer's disease efficiently and improve patient compliance.

An Overview of ICA/BSS-Based Application to Alzheimer's Brain Signal Processing

Alzheimer's disease (AD) is by far the most common cause of dementia associated with aging. Early and accurate diagnosis of AD and ability to track progression of the disease is increasingly important as potential disease-modifying therapies move through clinical trials. With the advent of biomedical techniques, such as computerized tomography (CT), electroencephalography (EEG), magnetoencephalography (MEG), positron emission tomography (PET), magnetic resonance imaging (MRI), and functional magnetic resonance imaging (fMRI), large amounts of data from Alzheimer's patients have been acquired and processed from which AD-related information or "signals" can be assessed for AD diagnosis. It remains unknown how best to mine complex information from these brain signals to aid in early diagnosis of AD. An increasingly popular technique for processing brain signals is independent component analysis or blind source separation (ICA/BSS) that separates blindly observed signals into original signals that are as independent as possible. This overview focuses on ICA/BSS-based applications to AD brain signal processing.

The Relationship Between Retinal Nerve Fiber Layer Thickness and Clinical Symptoms of Alzheimer's Disease

Background/Aim: Retinal nerve fiber layer (RNFL) thickness (RT), which can reflect the status of the retinal optic nerve cells, may be affected in patients with Alzheimer's disease (AD). There are few studies on the correlation of RT of patients with AD (AD-RT) with clinical symptoms of various cognitive domains, neuropsychiatric symptoms, and activities of daily living (ADL). This study is to investigate the relationships between RT and the abovementioned clinical symptoms of AD.

Methods: A total of 96 patients with AD were included in this study. RT was measured in these patients using optical coherence tomography (OCT). Demographic variables, RT, and clinical symptoms were compared between the normal and the abnormal AD-RT groups. Clinical symptoms, including cognitive symptoms, neuropsychiatric symptoms, and ADL, were evaluated using a series of rating scales.

Results: The relationships between RT and cognitive symptoms scores were analyzed in patients with AD. Reduced RT was found in 54.4% of patients with AD. The average RT, RT of the superior 1/2 quadrant, and RT of the inferior 1/2 quadrant of both eyes were all significantly decreased in the abnormal AD-RT group (p < 0.001). Overall cognitive function and performance in multiple cognitive domains, including memory, language, attention, and executive function, were also significantly impaired in the abnormal AD-RT group (p < 0.05). For lower RT value, the global cognitive function and the performance in multiple cognitive domains were worse. ADL was significantly compromised in patients with AD having lower RT values (p < 0.05).

Conclusions: Lower RT value appear to be correlated with cognitive impairment, and RT may be an indicator of cognitive decline in patients with AD. Further studies are required to confirm our findings.

Ruta graveolens and rutin, as its major compound: investigating their effect on spatial memory and passive avoidance memory in rats

Context: There are numerous pharmacological activities for Ruta graveolens and its bioactive constituent, rutin, on learning and memory.Objective: This study aimed to examine the effect of R. graveolens and rutin on memory in rats.Materials and methods: In this study animals were treated with the hydroalcholic extract of R. graveolens and rutin by IP injection for 10 days. Behavioural and biochemical tests as well as HPLC analysis and antioxidant activity of extract have been evaluated.Results: R. graveolens extract and rutin significantly increased learning and improved spatial memory, as well as secondary latency; moreover, there were significant increases in the serum and brain antioxidant capacity as well as the level of TBARS in serum and brain tissues. Results also showed that R. graveolens has significant DPPH radical scavenging effect (IC₅₀: 159.17 ± 1.56 μg/mL). The HPLC analysis of extract showed that caffeic acid (19.92 ± 0.01), rutin (40.15 ± 0.01), and apigenin (0.84 ± 0.01) mg/g of dry extract are the main components of the extract.Discussion and conclusion: Regarding the effects of R. graveolens extract and rutin on animal brain cells, memory function, and learning, additional studies, including clinical trials, might be beneficial in producing natural supplementary drugs from this herb.

RE-PERG in early-onset Alzheimer's disease: A double-blind, electrophysiological pilot study

PURPOSE

To evaluate the ability of re-test pattern electroretinogram (RE-PERG), a non-invasive and fast steady-state PERG, to detect inner retinal bioelectric function anomalies in patients with early-onset Alzheimer's disease (AD).

METHODS

The study population consisted of 17 patients with AD-related mild cognitive impairment (MCI), 16 patients with vascular dementia (VD)-related MCI, both assessed using the neuropsychological Mini-Mental State Examination (MMSE) and by structural magnetic resonance imaging, and 19 healthy, age-matched normal controls (NC). All participants were visually asymptomatic, had normal or near-normal general cognitive functioning and no or minimal impairments in daily life activities. Visual field (VF) test, optical coherence tomography (OCT) and RE-PERG, sampled in five consecutive blocks of 130 events, were performed.

RESULTS

There was no statistically significant difference among the three groups with respect to age, VF parameters (mean and pattern standard deviations) and OCT parameters (ganglion cell complex thickness and retinal nerve fiber layer thickness). The mean amplitude in the RE-PERG was significantly lower, but only weakly in the AD group than in NC (p = 0.1) whereas the intrinsic variability of the 2nd harmonic phase was significantly higher in the AD group than in either the VD or NC group (p<0.001).

CONCLUSIONS

RE-PERG is altered in early-stage AD, showing a reduced amplitude with high intrinsic phase variability. It also allows the discrimination of AD from VD. A high intrinsic variability in the PERG signal, determined using RE-PERG, may thus be a new promising test for neurodegenerative diseases.

Evaluation of Retinal Nerve Fiber Layer Thickness, Electroretinogram and Visual Evoked Potential in Patients with Alzheimer's Disease

OBJECTIVE

To study the retinal nerve fibre layer (RNFL) thickness and visual electrophysiology testing in patients with Alzheimer's disease (AD).

METHODS

A cross-sectional, hospital-based study: 25 AD subjects and 25 controls were recruited. Candidates who fulfil the criteria with normal ocular examinations were made to proceed with scanning laser polarimetry, pattern electroretinogram (PERG), and pattern visual evoked potential (PVEP) examinations of the right eye. RNFL thickness, PERG, and PVEP readings were evaluated.

RESULTS

In AD, the mean of average RNFL thickness was 45.28 μm, SD = 3.61, P < 0.001 (P < 0.05), while the superior RNFL thickness was 54.44 μm, SD = 2.85, P < 0.001 (P < 0.05) and inferior RNFL thickness was 47.11 μm, SD = 4.52, P < 0.001 (P < 0.05). For PERG, the mean P50 latency was 63.88 ms, SD = 7.94, P < 0.001 (P < 0.05) and the mean amplitudes of P50 waves were 1.79 μV, SD = 0.64, P < 0.001 (P < 0.05) and N95 waves were 2.43 μV, SD = 0.90, P < 0.001 (P < 0.05). For PVEP, the mean latency of P100 was 119.00 ms, SD = 9.07, P < 0.001 (P < 0.05), while the mean latency of N135 was 145.20 ms, SD = 8.53, P < 0.001 (P < 0.05). The mean amplitude of P100 waves was 3.71 μV, SD = 1.60, P < 0.001 (P < 0.05), whereas the mean amplitude of N135 waves was 3.67 μV, SD = 2.02, P < 0.001 (P < 0.05). RNFL thickness strongly correlates with PERG readings, with P50 latency R = 0.582, R2 = 0.339, P=0.002 (P < 0.05), amplitude of P50 wave at R = 0.749, R2 = 0.561, P ≤ 0.001 (P < 0.05), and amplitude of N95 wave at R = 0.500, R2 = 0.250, P=0.011 (P < 0.05). No significant difference and correlation were observed on PVEP readings.

CONCLUSION

The mean of the average, superior and inferior RNFL thickness were significantly lower in the AD group compared with control. There is also significant difference of PERG and PVEP parameters between AD and controls. Regression analysis showed average RNFL thickness having significantly linear relationship with the PERG parameters.

Integrated Cognitive Assessment: Speed and Accuracy of Visual Processing as a Reliable Proxy to Cognitive Performance

Various mental disorders are accompanied by some degree of cognitive impairment. Particularly in neurodegenerative disorders, cognitive impairment is the phenotypical hallmark of the disease. Effective, accurate and timely cognitive assessment is key to early diagnosis of this family of mental disorders. Current standard-of-care techniques for cognitive assessment are primarily paper-based, and need to be administered by a healthcare professional; they are additionally language and education-dependent and typically suffer from a learning bias. These tests are thus not ideal for large-scale pro-active cognitive screening and disease progression monitoring. We developed the Integrated Cognitive Assessment (referred to as CGN_ICA), a 5-minute computerized cognitive assessment tool based on a rapid visual categorization task, in which a series of carefully selected natural images of varied difficulty are presented to participants. Overall 448 participants, across a wide age-range with different levels of education took the CGN_ICA test. We compared participants' CGN_ICA test results with a variety of standard pen-and-paper tests, such as Symbol Digit Modalities Test (SDMT) and Montreal Cognitive Assessment (MoCA), that are routinely used to assess cognitive performance. CGN_ICA had excellent test-retest reliability, showed convergent validity with the standard-of-care cognitive tests used here, and demonstrated to be suitable for micro-monitoring of cognitive performance.

Visual Features in Alzheimer's Disease: From Basic Mechanisms to Clinical Overview

Alzheimer's disease (AD) is the leading cause of dementia worldwide. It compromises patients' daily activities owing to progressive cognitive deterioration, which has elevated direct and indirect costs. Although AD has several risk factors, aging is considered the most important. Unfortunately, clinical diagnosis is usually performed at an advanced disease stage when dementia is established, making implementation of successful therapeutic interventions difficult. Current biomarkers tend to be expensive, insufficient, or invasive, raising the need for novel, improved tools aimed at early disease detection. AD is characterized by brain atrophy due to neuronal and synaptic loss, extracellular amyloid plaques composed of amyloid-beta peptide (Aβ), and neurofibrillary tangles of hyperphosphorylated tau protein. The visual system and central nervous system share many functional components. Thus, it is plausible that damage induced by Aβ, tau, and neuroinflammation may be observed in visual components such as the retina, even at an early disease stage. This underscores the importance of implementing ophthalmological examinations, less invasive and expensive than other biomarkers, as useful measures to assess disease progression and severity in individuals with or at risk of AD. Here, we review functional and morphological changes of the retina and visual pathway in AD from pathophysiological and clinical perspectives.

The effect of lamotrigine on learning in mice using the passive avoidance model

INTRODUCTION

Lamotrigine (LTG) is an antiepileptic drug that inhibits the release of glutamate by blocking sodium channels. The present study was conducted to evaluate the effect of LTG in different stages of memory using a passive avoidance learning task in mice.

METHODS

Male albino mice in the weight range 20-25g were used. They were divided into four groups (control group and three groups receiving various doses of LTG). LTG was given in three doses of 10, 25, and 50mg/kg as intraperitoneal (IP) injections. The doses of LTG were used in three injection groups: before acquisition, after consolidation, and before retrieval at 24h. The retention latency times in each group were recorded using a step-through passive avoidance task 24h and one week after consolidation.

RESULTS

Retention latency in the group receiving a high dose of LTG (25mg/kg) after one week was significantly increased in comparison to the group receiving a low dose of LTG (10mg/kg) (267±49.96 vs. 198.87±57.22, P=0.015). With injection of LTG after consolidation, the retention latency times were increased in all doses after a one-week retrieval compared to the control (P=0.023). Kaplan-Mayer surveillance analysis also showed significant differences in the latencies of the LTG-receiving group after 24h and one week's retrieval (P=0.041). Administration of LTG before retrieval at 24h showed a significant difference in retention latency time, which was increased for two doses of LTG (10 and 50mg/kg) after one week (203.5±63.67 vs. 270.25±19.78, P=0.024).

CONCLUSION

LTG at higher doses may facilitate the learning process in mice and appears to improve memory function at different stages.

Correlation Between Vision and Cognitive Function in the Elderly: A Cross-Sectional Study

The correlation between vision and cognition is not fully understood. Visual impairment in the elderly has been associated with impaired cognitive function, dementia, and Alzheimer disease. The aim was to study the correlation between near visual acuity (VA), refraction, and cognitive state in an elderly population.Subjects ≥75 years were enrolled in this cross-sectional study. Refraction and near VA was tested. Cognitive function was evaluated with a version of the mini-mental state examination for the visually impaired (MMSE-blind). The eye with better VA and no cataract or refractive surgery was analyzed.One-hundred ninety subjects (81.6 ± 5.1 years, 69.5% female) were included. Good VA (≤J3) was associated with high MMSE-blind (>17) (OR = 3.18, 95% CI = 1.57-6.43, P = 0.001). This remained significant adjusting for sex, age, and years of education. Wearing reading glasses correlated significantly with high MMSE-blind after adjustment for sex and age (OR = 2.14, 95% CI = 1.16-3.97, P = 0.016), but reached borderline significance after adjustment for education. There was a trend toward correlation between myopia and better MMSE-blind (r = -0.123, P = 0.09, Pearson correlation).Good VA and wearing glasses seem to correlate with better cognitive function. Reading glasses can serve as a protective factor against cognitive deterioration associated with sensory (visual) deprivation in old age. The association between myopia and cognition requires further investigation.

Confocal scanning laser tomography of the optic nerve head on the patients with Alzheimer's disease compared to glaucoma and control

The purpose of this study was to evaluate optic nerve head (ONH) differences of the patients with Alzheimer's disease (AD) measured by confocal scanning laser tomography [Heidelberg Retina Tomograph (HRT) III] and compare with glaucoma and control subjects. Eighty-four patients were enrolled into the study: 44 eyes of 24 patients with mild to moderate AD (Group 1), 68 eyes of 35 patients with glaucoma (Group 2), and 49 eyes of 25 heathy volunteers as a control (Group 3). A complete ophthalmologic examination as well as a confocal scanning laser ophthalmoscopic assessment with HRT III were performed on all patients. Mean values of the ONH topographic parameters such as rim area (RA), rim volume (RV), height variation contour, linear cup/disc ratio, cup shape measure, and retinal nerve fiber layer (RNFL) were recorded. Mean values of RNFL thickness was 0.23 ± 0.07 in AD, 0.22 ± 0.09 in glaucoma and 0.24 ± 0.07 in the control group (p = 0.323). RA and RV were significantly lower, and linear C/D ratio was significantly higher in the glaucoma group when compared to AD and control (p < 0.05). There was no statistically significant difference between AD and control for the optic disc parameters tested (p > 0.05). We observed a negative correlation of the age with RNFL in all of the groups (p < 0.005). Age was the most important parameter affecting RNFL. Our results suggest that HRT does not demonstrate ONH differences between AD and control group, while it successfully differentiates glaucoma from AD and control cases of older age.

Visual cortex in aging and Alzheimer's disease: changes in visual field maps and population receptive fields

Although several studies have suggested that cortical alterations underlie such age-related visual deficits as decreased acuity, little is known about what changes actually occur in visual cortex during healthy aging. Two recent studies showed changes in primary visual cortex (V1) during normal aging; however, no studies have characterized the effects of aging on visual cortex beyond V1, important measurements both for understanding the aging process and for comparison to changes in age-related diseases. Similarly, there is almost no information about changes in visual cortex in Alzheimer's disease (AD), the most common form of dementia. Because visual deficits are often reported as one of the first symptoms of AD, measurements of such changes in the visual cortex of AD patients might improve our understanding of how the visual system is affected by neurodegeneration as well as aid early detection, accurate diagnosis and timely treatment of AD. Here we use fMRI to first compare the visual field map (VFM) organization and population receptive fields (pRFs) between young adults and healthy aging subjects for occipital VFMs V1, V2, V3, and hV4. Healthy aging subjects do not show major VFM organizational deficits, but do have reduced surface area and increased pRF sizes in the foveal representations of V1, V2, and hV4 relative to healthy young control subjects. These measurements are consistent with behavioral deficits seen in healthy aging. We then demonstrate the feasibility and first characterization of these measurements in two patients with mild AD, which reveal potential changes in visual cortex as part of the pathophysiology of AD. Our data aid in our understanding of the changes in the visual processing pathways in normal aging and provide the foundation for future research into earlier and more definitive detection of AD.

Screening for Patients with Mild Alzheimer Disease Using Frequency Doubling Technology Perimetry

We compared the visual field performances of patients with mild Alzheimer disease (AD) with normal subjects and detected visual field impairment attributable to the magnocellular pathway using frequency doubling technology-Matrix (FDT-Matrix). We recruited 43 patients with mild AD (mean age: 68.0 ± 7.2 years) and 33 controls who are visually and cognitively normal (mean age: 64.1 ± 6.4 years). All participants had at least two reliable FDT-Matrix 30-2 tests. Reliability indices, global indices (mean deviation and pattern standard deviation), and glaucoma hemifield test results were measured with FDT-Matrix. The mean test duration was significantly longer in patient group compared with controls (p = 0.002). Among the reliability indices, false negatives were higher in patient group than controls (p = 0.003). There were statistically significant differences in mean deviation and pattern standard deviation values (p < 0.0001 and p < 0.0001, respectively) and glaucoma hemifield test results (p < 0.001) between the patient and the control group. Our results imply that the pathogenesis of cognitive deterioration may not only be confined to the cortical area but also to the magnocellular pathway. We underline that FDT testing can be useful for the identification of early impairment and the follow-up of patients with AD.

Vision deficits in adults with Down syndrome

BACKGROUND

In individuals with Down syndrome, virtually all structures of the eye have some abnormality, which likely diminishes vision. We examined basic vision functions in adults with Down syndrome.

MATERIALS AND METHODS

Participants completed a battery of psychophysical tests that probed a comprehensive array of visual functions. The performance of adults with Down syndrome was compared with younger and older adults without intellectual disability.

RESULTS

Adults with Down syndrome had significant vision deficits, reduced sensitivity across spatial frequencies and temporal modulation rates, reduced stereopsis, impaired vernier acuity and anomalies in colour discrimination. The pattern of deficits observed was similar to those seen by researchers examining adults with Alzheimer's disease.

CONCLUSIONS

Our findings suggest that a common mechanism may be responsible for the pattern of deficits observed, possibly the presence of Alzheimer's disease neuropathology in the visual association cortex. We also showed that individuals with mild to moderate intellectual disability are capable of participating in studies employing state-of-the-art psychophysical procedures. This has wider implications in terms of their ability to participate in research that use similar techniques.

Effects of healthy aging on human primary visual cortex

Aging often results in reduced visual acuity from changes in both the eye and neural circuits [1-4]. In normally aging subjects, primary visual cortex has been shown to have reduced responses to visual stimulation [5]. It is not known, however, to what extent aging affects visual field representations and population receptive sizes in human primary visual cortex. Here we use functional MRI (fMRI) and population receptive field (pRF) modeling [6] to measure angular and eccentric retinotopic representations and population receptive fields in primary visual cortex in healthy aging subjects ages 57 - 70 and in healthy young volunteers ages 24 - 36 (n = 9). Retinotopic stimuli consisted of black and white, drifting checkerboards comprising moving bars 11 deg in radius. Primary visual cortex (V1) was clearly identifiable along the calcarine sulcus in all hemispheres. There was a significant decrease in the surface area of V1 from 0 to 3 deg eccentricity in the aging subjects with respect to the young subjects (p = 0.039). The coherence of the fMRI% BOLD modulation was significantly decreased in the aging subjects compared to the young subjects in the more peripheral eccentricity band from 7 to 10 deg (p = 0.029). Finally, pRF sizes were significantly increased within the 0 to 3 deg foveal representation of V1 in the aging subjects compared to the young subjects (p = 0.019). Understanding the extent of changes that occur in primary visual cortex during normal aging is essential both for understanding the normal aging process and for comparisons of healthy, aging subjects with aging patients suffering from age-related visual and cortical disorders.

Abnormalities of the optic disc

The optic disc represents the anterior end of the optic nerve, the most forward extension of the central nervous system (CNS). The optic disc gives a rare glimpse into the CNS. Hence, diseases of the CNS are often manifested on fundus examination. Abnormalities of the optic disc may reflect eye disease (such as glaucoma), problems in development (as in various syndromes), or CNS disease (such as increased intracranial pressure). Each optic nerve is composed of about 1.2 million axons deriving from the retinal ganglion cells of one eye. Optic atrophy is a morphological sequela reflecting the loss of many or all of these axons. Myriad diseases such as hereditary, metabolic, tumor, and increased intracranial pressure can lead to optic atrophy. Some diseases, such as optic disc drusen, intracranial masses, orbital tumors, ischemic optic neuropathies, inflammations, and infiltrations, can produce optic disc edema before leading to optic atrophy. A number of new imaging modalities, such as optical coherence tomography (OCT), quantitate the thickness of the peripapillary retinal nerve fiber layer as an indirect measure of axonal loss or swelling. OCT can therefore be used to quantitate pathology or the response to therapy in various generalized CNS conditions, such as multiple sclerosis.

Pattern electroretinogram (PERG) and pattern visual evoked potential (PVEP) in the early stages of Alzheimer's disease

Alzheimer’s disease (AD) is one of the most common causes of dementia in the world. Patients with AD frequently complain of vision disturbances that do not manifest as changes in routine ophthalmological examination findings. The main causes of these disturbances are neuropathological changes in the visual cortex, although abnormalities in the retina and optic nerve cannot be excluded. Pattern electroretinogram (PERG) and pattern visual evoked potential (PVEP) tests are commonly used in ophthalmology to estimate bioelectrical function of the retina and optic nerve. The aim of this study was to determine whether retinal and optic nerve function, measured by PERG and PVEP tests, is changed in individuals in the early stages of AD with normal routine ophthalmological examination results. Standard PERG and PVEP tests were performed in 30 eyes of 30 patients with the early stages of AD. The results were compared to 30 eyes of 30 normal healthy controls. PERG and PVEP tests were recorded in accordance with the International Society for Clinical Electrophysiology of Vision (ISCEV) standards. Additionally, neural conduction was measured using retinocortical time (RCT)—the difference between P100-wave latency in PVEP and P50-wave implicit time in PERG. In PERG test, PVEP test, and RCT, statistically significant changes were detected. In PERG examination, increased implicit time of P50-wave (P < 0.03) and amplitudes reductions in P50- and N95-waves (P < 0.0001) were observed. In PVEP examination, increased latency of P100-wave (P < 0.0001) was found. A significant increase in RCT (P < 0.0001) was observed. The most prevalent features were amplitude reduction in N95-wave and increased latency of P100-wave which were seen in 56.7% (17/30) of the AD eyes. In patients with the early stages of AD and normal routine ophthalmological examination results, dysfunction of the retinal ganglion cells as well as of the optic nerve is present, as detected by PERG and PVEP tests. These dysfunctions, at least partially, explain the cause of visual disturbances observed in patients with the early stages of AD.

Untreated poor vision: a contributing factor to late-life dementia

Ophthalmologic abnormalities have been described in patients with dementia, but the extent to which poor vision and treatment for visual disorders affect cognitive decline is not well defined. Linked data from the Health and Retirement Study and Medicare files (1992-2005) were used to follow the experiences of 625 elderly US study participants with normal cognition at baseline. The outcome was a diagnosis of dementia, cognitively impaired but no dementia, or normal cognition. Poor vision was associated with development of dementia (P = 0.0048); individuals with very good or excellent vision at baseline had a 63% reduced risk of dementia (95% confidence interval (CI): 20, 82) over a mean follow-up period of 8.5 years. Participants with poorer vision who did not visit an ophthalmologist had a 9.5-fold increased risk of Alzheimer disease (95% CI: 2.3, 39.5) and a 5-fold increased risk of cognitively impaired but no dementia (95% CI: 1.6, 15.9). Poorer vision without a previous eye procedure increased the risk of Alzheimer disease 5-fold (95% CI: 1.5, 18.8). For Americans aged 90 years or older, 77.9% who maintained normal cognition had received at least one previous eye procedure compared with 51.7% of those with Alzheimer disease. Untreated poor vision is associated with cognitive decline, particularly Alzheimer disease.

Influence of mild cognitive impairment on visual word recognition

The present study examined the effects of normal aging and mild cognitive impairment (MCI) on visual word recognition. Madden et al. (1999) reported evidence of general slowing of cognitive processes in Alzheimer's disease (AD) patients relative to younger adults and healthy older adults using a lexical decision task. It was of interest to determine whether similar effects would be observed in MCI patients relative to healthy younger and older adults. We extended the lexical decision task paradigm developed by Allen et al. (2004b) on younger adults to an examination of the effect(s) of MCI on visual word recognition. Results from the present study showed that healthy older adults and MCI patients performed similarly. That is, both groups took longer than younger adults to process words presented in mixed-case than in consistent-case letters. Mild cognitive impairment patients, however, responded significantly more slowly than healthy older adults across all lexical decision task conditions and showed a trend toward larger case-mixing effects than healthy older adults, which suggests that MCI may result in poorer analytic processing ability. Based on the current findings, evidence of a generalized slowing of cognitive processes using a standard lexical decision task can be expanded to include not only AD patients, but also the preclinical stages of the disease as well.

A Sick Eye in a Sick Body? Systemic Findings in Patients with Primary Open-angle Glaucoma

Despite intense research, the pathogenesis of primary open-angle glaucoma (POAG) is still not completely understood. There is ample evidence for a pathophysiological role of elevated intraocular pressure; however, several systemic factors may influence onset and progression of the disease. Systemic peculiarities found in POAG include alterations of the cardiovascular system, autonomic nervous system, immune system, as well as endocrinological, psychological, and sleep disturbances. An association between POAG and other neurodegenerative diseases, such as Alzheimer disease and Parkinson disease, has also been described. Furthermore, the diagnosis of glaucoma can affect the patient's quality of life. By highlighting the systemic alterations found in POAG, this review attempts to bring glaucoma into a broader medical context.

Complex visual hallucinations in the visually impaired: the Charles Bonnet Syndrome

Visually impaired patients may experience complex visual hallucinations, a condition known as the Charles Bonnet Syndrome. Patients usually possess insight into the unreality of their visual experiences, which are commonly pleasant but may sometimes cause distress. The hallucinations consist of well-defined, organized, and clear images over which the subject has little control. It is believed that they represent release phenomena due to de-afferentation of the visual association areas of the cerebral cortex, leading to a form of phantom vision. Cognitive defects, social isolation, and sensory deprivation have also been implicated in the etiology of this condition. This condition, which is most common in the elderly, frequently goes unrecognized in clinical practice, due to both lack of awareness among doctors and patients' reluctance to admit to hallucinatory experiences, for fear of being labeled mentally unstable. Furthermore, patients who comprehend the unreality of their hallucinations may be distressed by the real fear of imminent insanity. Sensitive and sympathetic history taking is essential to ascertain the existence of hallucinations. Reassurance and explanation that the visions are benign and do not signify mental illness have a powerful therapeutic effect. Hallucinatory activity may terminate spontaneously, on improving visual function or on addressing social isolation. There is no universally effective drug treatment but anticonvulsants may play a limited role in aborting the hallucinations. Physician awareness and empathy are the cornerstones of management.