Risk Factors of Sleep Disorder After Stroke:

Risk Factors of Sleep Disorder After StrokeRisk factors of quietness unhinge subsequently calamity A Meta analysis selective information track title Risk factors of residue put let on after lashHighlightsDiabetes mellitus has a 41% increased guess of repose twainer in buffet patients alcoholic drink consumption has a 59% increased try of sleep turn over in stroke patientsHabitual snoring has a 1377% increased risk of sleep disorder in stroke patientsBody-mass forefinger has a 17% decreased risk of sleep disorder in stroke patientsAbstractObjectives To explore the link risk factors of sleep disorder in stroke patients by conducting a meta-analysisMethods PubMed, Medline, Springer, Elsevier Science Direct, Cochrane Library and Google scholar database were fashioned from inception up to May 2014. Studies investigating risk factors for sleep disorder after stroke were included. Characteristics including authors name, year of result, country, sample size, long sequ ence of participants and gender were extracted independently by both reviewers.Results A nub of 8 studies, involving 1381 patients (578 experimental groups and 803 work groups) were eligible for the meta-analysis. The meta-analysis showed that at that place were evidential draw between risk of sleep disorder after stoke between diabetes mellitus (OR = 1.41, 95% CI = 1.09 to 1.84, P OR = 1.59, 95% CI = 1.19 to 2.12, P OR = 14.77, 95% CI = 5.52 to 39.53, P WMD = 0.83, 95% CI = 0.63 to 1.03, P OR = 1.23, 95% CI = 0.72 to 2.1, P 0.05), hypertension (OR = 1.22, 95% CI = 0.83 to 1.80, P 0.05), dyslipidemia (OR = 0.96, 95% CI = 0.70 to 1.33, P 0.05), smoking (OR = 1.27, 95% CI = 0.73 to 2.20, P 0.05), old stroke (OR = 1.05, 95% CI = 0.74 to 1.49, P 0.05), chronic preventive pulmonary disease (OR = 0.79, 95% CI = 0.40 to 1.57, P 0.05) when comp ard with control groups. Further much, the results of Egger test showed no statistical publication bias.Conclusions Diabetes mellitus , alcohol use, ordinary snoring and body-mass index be associated with risk of sleep disorder in patients with stroke.Key words Sleep disorder Risk factors Meta-analysis StrokeIntroductionStroke is a serious global health problem, and exacted as the fourth leading arouse of death and the primary cause of adult disability in all around the world 1-3. Sleep-related breathing disorders (SDB) is a frequent clinical phenomena, and characterized by repetitive apneas and hypopneas during sleep 4, 5.The relationship of SDB with stroke has been investigated in the recent years. M both researches wear delineateed increased incidence of SDB in stroke patients, which could lead to progression of the stroke 6, 7. Further more(prenominal), SDB pursual stroke whitethorn result in high mortality and morbidity 4. Although SDB and stroke confuse universal established risk factors including age, gender, elevated body-mass index (BMI), hypercholesterolemia, hypertension and habitual snoring 8 -10, risk factors leading to SDB in stroke patients remains unclear. Thus, it is important to pick out contri fair(a)ing risk factors or associated conditions that can impact on outcome of SDB following stroke.Previously restless literature and primary analyses on risk factors of sleep disorder after stroke only involved in research of authoritative factor, and statistical power was deficient and insufficient in these studies 4, 11. In this study, to investigate the risk factors for SDB after stroke and obtain a quantitative estimate of the risk, we consistently review the literature that have studied patients with stroke for SDB risk factors, (namely gender, Hypertension, Diabetes mellitus, Dyslipidemia, Smoking, alcohol use, Previous stroke history, Chronic obstructive pulmonary disease, Habitual snoring and Body-mass index)by conducting a meta-analysis.MethodsSearch strategy and study selectionWe retrieved the relevant studies up to May 2014 in several public databases, mai nly including PubMed, Medline, Springer, Elsevier Science Direct, Cochrane Library and Google scholar. The main search words were factor or influence, affect or element or determinant or cause or reason and sleep disorder, apnoea or obstacle or impediment or barrier or obstruction or balk and stroke or cerebral apoplexy or acute cerebral accident and research or survey or study or trial. Meanwhile, elongations from retrieved papers were checked for more relevant studies non identified in database search.Eligibility of relevant studiesFor relevant abstracts, unspoilt publications were retrieved for evaluation on the basis of criteria that were established a priori. All selected research articles were considered except case reports. We want to include studies of any design that reported risk factors in sleep disorders, and relationships between sleep-disordered breathing, sleep apnea or insomnia symptoms and stroke without the limitation of sample size and dictate of age. Studies were excluded from the governing bodyatic reviews and reports that only described sleep disorder after stroke. Studies with no control group were withal excluded. Reviews, reduplicated studies and studies published in language other than side were excluded as well.Data extractionInformation from each study was extracted independently by 2 reviewers using a data extraction form. Study ecumenic characteristics (e.g., author, year of publication, location of participants, design of studies, ethnicity and number of cases), and characteristics of participants (e.g., age, gender and sample size) were recorded (where visible(prenominal)) and doubled-checked. Meanwhile, the centering out size of risk factors of sleep disorder in stroke patients compargond with stroke patients without sleep disorder with corresponding 95% confidence interval (CI) were extracted as reported by authors. The effect size of gender, hypertension, diabetes mellitus, dyslipidemia, smoking, alcohol use, pre vious stroke, chronic obstructive pulmonary disease (COPD) and habitual snoring were measured by, and body-mass index (BMI) by weighted mean difference (WMD). In addition, we contacted authors of incorporated studies to obtain further data for data items that requisite clarification. Discrepancies were resolved by discussing within our research team or contracting with the original investigators via e-mail.Statistical analysisThe meta-analysis was foc utilize on the risk factors of sleep disorder in stroke patients versus stroke patients without sleep disorder. The pooled estimates of effect size of risk factors were attendd by averaging OR or WMD ground on a fixed or random do model depending on the overall heterogeneity. Then, heterogeneity of effect size across studies was evaluated by applying Cochrans Q-statistic and and the I2 statistic 12, 13. P value I2 value 50% was considered to heterogenous across the studies. When substantial heterogeneity was detected, we calculat ed the overall estimate of ORs or WMDs using MantelHaenszel rule in the fixed effect model 14. If non, the pooled estimates were presented base on the random effect model by using DerSimonian and Laid method 15. In addition, the publication bias were evaluated using Eggers linear regression test 16, which measures funnel p parcel out asymmetry by the natural logarithm scale of the effect size.Meta-analysis was performed using the softw are of the STATA package v.11.0 (Stata Corporation, College Station, TX, USA). P value ResultsLiterature research and study characteristicsThe details of the literature search were shown in a flow plot (Figure 1). We obtained 972 citations (131 from Medline, 341 from Pubmed, 164 from Springer, 103 from Elsevier Science Direct, 16 from Cochrane Library and 217 from Google Scholar) with our electronic literature search. We obtain 84 citations after removing duplicates or irrelevant studies. In addition, 47 citations were excluded after screening bas ed on the abstracts. Then 37 remained citations were full-text reviewed for detailed assessment. Finally, 8 citations satisfied the inclusion criteria and were eligible for the meta-analysis.The characteristics and information of the included studies were presented in control panel 1. The 8 selected studies contained 1381 patients with average age (ranging from 43.0 to 75.2 years old), including 578 experimental groups (stroke patients with sleep disorder) and 803 control groups(stroke patients without sleep disorder) 17-24. boilers suit analysis of genderAs shown in Table 2, a total of 7 reprint studies 17-20, 22-24, involving 1321 stroke patients (539 experimental groups and 782 control groups), were eligible for the meta-analysis. Meta-analysis showed no standoff between gender and sleep disorder after stroke was found (OR = 1.23, 95% CI = 0.72 to 2.1, P 0.05), yet withsignificant heterogeneity between studies (Q2 = 22.73, I2 = 73.6%, P the result of Eggers test showed no evi dence of publication bias (P = 0.91) general analysis of hypertensionAs presented in table 2, a total of 8 studies 17-24, including 1381 stroke patients (578 experimental groups and 803 control groups ), were finally eligible for the meta-analysis. Meta-analysis showed no necktie between hypertension and sleep disorder after stroke compared with control groups (OR = 1.22, 95% CI = 0.83 to 1.80, P 0.05), yet with significant between-study heterogeneity was found (Q2 = 14.13, I2 = 50.5%, P In addition, the result of Eggers test showed no evidence of publication bias (P = 0.43).Overall analysis of diabetes mellitusAs shown in Table 2, a total of 7 studies 17, 19-24, involving 1326 stroke patients (549 experimental groups and 777 control groups), were eligible for the meta-analysis. Meta-analysis showed diabetes mellitus had a 41% increased risk of sleep disorder in stroke patients compared with control groups (OR = 1.41, 95% CI = 1.09 to 1.84, P Q2 = 1.59, I2 = 0%, P 0.1). In additi on, the result of Eggers test showed no evidence of publication bias (P = 0.72)Overall analysis of dyslipidemiaAs shown in Table 2, a total of 4 studies 17, 19, 22, 24, involving 832 stroke patients (373 experimental groups and 459 control groups), were eligible for the meta-analysis. Meta-analysis showed no association between dyslipidemia and sleep disorder after stroke compared with control groups (OR = 0.96, 95% CI = 0.70 to 1.33, P 0.05), yet with significant between-study heterogeneity (Q2 = 4.78, I2 = 37.3%, P 0.1). In addition, the result of Eggers test showed no evidence of publication bias (P = 0.68)Overall analysis of smokingAs presented in Table 2, a total of 5 studies 17, 19, 20, 22, 23, containing 1234 stroke patients (495 experimental groups and 739 control groups), were eligible for the meta-analysis. Meta-analysis showed no association between smoking and sleep disorder after stroke compared with control groups (OR = 1.22, 95% CI = 0.83 to 1.80, P 0.05), yet with significant between-study heterogeneity (Q2 = 13.82, I2 = 71.0%, P the result of Eggers test showed no evidence of publication bias (P = 0.43).Overall analysis of alcohol useAs shown in Table 2, a total of 5 studies 17, 19, 20, 22, 23, involving consisting of 1234 stroke patients (495 experimental groups and 739 control groups), were eligible for the meta-analysis. Meta-analysis showed alcohol use had a 41% increased risk of sleep disorder in stroke patients compared with control groups (OR = 1.59, 95% CI = 1.19 to 2.12, P no significant between-study heterogeneity (Q2 = 4.49, I2 = 10.9%, P 0.1). In addition, the result of Eggers test showed no evidence of publication bias (P = 0.65).Overall analysis of previous strokeAs shown in Table 2, a total of 5 studies 17, 19, 21, 22, 24, involving 892 stroke patients (412 experimental groups and 480 control groups), were eligible for the meta-analysis. Meta-analysis showed no association between previous stroke and sleep disorder after str oke compared with control groups (OR = 1.05, 95% CI = 0.74 to 1.49, P 0.05), and with no significant between-study heterogeneity was found (Q2 =2.31, I2 =0%, P 0.1). In addition, the result of Eggers test showed no evidence of publication bias (P = 0.24).Overall effects of chronic obstructive pulmonary disease (COPD)As shown in Table 2, a total of 2 studies19, 22, containing 623 stroke patients (280 experimental groups and 343 control groups), were eligible for the meta-analysis. Meta-analysis showed no association between COPD and sleep disorder after stroke compared with control groups (OR = 0.79, 95% CI = 0.40 to 1.57, P 0.05), yet with no significant between-study heterogeneity was found (Q2 = 0.24, I2 = 0%, P 0.1).Overall effects of habitual snoringAs shown in Table 2, a total of 2 studies 20, 21, involving 422 stroke patients (138 experimental groups and 284 control groups), were eligible for the meta-analysis. Meta-analysis showed habitual snoring had a 1377% increased ri sk of sleep disorder in stroke patients compared with control groups (OR = 0.79, 95% CI = 0.40 to 1.57, P 0.05), yet with no significant between-study heterogeneity was found (Q2 = 1.29, I2 = 22.6%, P 0.1).Overall effects of Body-mass index (BMI) As shown in Table 2, a total of 3 studies 20, 21, 23, involving 494 stroke patients (176 experimental groups and 318 control groups), were eligible for the meta-analysis. Meta-analysis showed BMI had a 17% decreased risk of sleep disorder in stroke patients compared with control groups (WMD = 0.83, 95% CI = 0.63 to 1.03, P Q2 = 0.95, I2 = 0%, P 0.1). In addition, the result of Eggers test showed no evidence of publication bias (P = 0.998).DiscussionIn this study, we conducted a meta-analysis for investigating risk factors of sleep disorder in stroke patients. Based on the data from 8 studies including 1381 patients, the factors (Diabetes mellitus, alcohol use, habitual snoring and BMI) were associated with risk of sleep disorder in strok e patients when compared with control groups, yet with no significant between-study heterogeneity. The magnitude of this association was greatest for habitual snoring with stroke patients experiencing a 1377% increase in risk of sleep disorder compared with stroke patients without sleep disorder. However, thither were no association between risk of sleep disorder after stroke and other factors (gender, Hypertension, Dyslipidemia, Smoking, Previous stroke history and COPD). In addition, there was no indication of publication bias from the result of Eggers test.Researchers have shown increased incidence of SDB in stroke patients, which may lead to a poor outcome and thrumting even 25, 26. SDB progresses from habitual snoring to the increased upper airway resistance syndrome to sleep apnea 27, and it is biologically plausible that habitual snoring could increase the risk of sleep disorder in stroke patients. Habitual snoring is significantly associated with daytime sleepiness, rest little sleep, and hyperactivity, which could lead to sleep disorder 28, 29. In our literature search we did non identify results of any randomized clinical trials evaluating the effect of risk factors on sleep disorder after stroke. However, it is reasonable to infer that habitual snoring may domiciliate to incidence and development of sleep disorder in stroke patients.The previous studies have shown significant gender-related differences in presenting symptoms of patients with SDB 30, and the risk for the development of sleep disorder was significantly lower in women 31. However, in our study, we found no association between gender and risk of sleep disorder after stroke, yet with the intimately significant between-study heterogeneities. This might result from unavoidable difference in study sample sizes and distinct ad merelyments across studies. Thus, we suggest that the present analyses might have underestimated the true effects of gender on risk of sleep disorder after strok e, and further studies are needed to be demonstrated this.The present meta-analysis has a series of limitations, such(prenominal) as lack of uniformity (e.g. sleep disorder diagnostic criteria, the duration of patients with stroke) and exclusion of studies written in languages other than English. Furthermore, another limitation was the narrow reporting of information of the present analysis. After all, the results in this analysis were only obtained data from Asia, Europe, North America and Oceania, and the majority of the included studies did not state if there were any racial differences among participants. The differences in regions and races among studies might have an influence on pooled risk estimates of sleep disorder after stroke.In summary, the present meta-analysis suggest that the factors (Diabetes mellitus, alcohol use, habitual snoring and BMI) is associated with risk of metabolic syndrome. The conclusion has a great significance for public health, especially in countr ies of high incidence of stroke. In addition, further investigations, both epidemiological and mechanistic, are needed to investigate whether regulating these factors can prevent occurrence and development of metabolic syndrome.3D Technology Types and Uses3D Technology Types and UsesCHAPTER 1 INTRODUCTIONThis report exit focus on how different 3D technologies work, it depart include the entire work flow, from recording the action, encoding the footage, playing pole the media via a movie theater offeror or television and finally how the audience views the 3D get hold of or television sop upr, whether it be by means of specially designed glaze or an auto- stereoscopic television.At present the virtually popular way to view 3D media is with the use of specialised glassfules, the most popular being, active shutter glasses, passive polarised glasses and semblance separationbased glasses.Wearing glasses to watch a movie is often mentioned as a negative aspect of 3D. in that respect is a applied science obtainable that allows you to watch 3D on screens without wearing any additional glasses, it is called autostereoscopy, this leave behind also be looked at.The health impacts that result from watching 3D exit also be examined, along with factors that allow prevent a person from being able to correctly view 3D moving pictures.There will be impacts on the entire industry from studios and cinemas to pureer production companies and independent producers if 3D assumes call on the norm and these will be examined.A good place to head start this report is to examine how two of the highest profile media companies around at present are currently viewing 3D technology.Phil McNally stereoscopic supervisor at Disney-3D and Dreamworks was quoted as saying,consider that all technical progress in the cinema industry brought us finisher to the ultimate entertainment experience the dream. We dream in colour, with sound, in an fuzzy world with no time reference . The cinema offers us a chance to dream awake for an hour. And because we dream in 3D, we ultimately want the cinema to be a 3D experience not a flat one.(Mendiburu, 2009)In the BBC Research etiolated Paper The Challenges of Three-Dimensional Television, 3D technology is referred to asa continuing long-term evolution of television standards towards a means of recording, transmitting and displaying images that are indistinguishable from trueity(Armstrong, Salmon, Jolly, 2009)It is clear from both of these high profile sources that the industry is taking the evolution of 3D really seriously, as a result this is a topic that is not only very interesting scarcely will be at the cutting edge of technological advances for the next couple of years.This report will be covering the following thingsWhat does the term 3D mean with reference to film and videoA look at the history of 3D in filmHow does 3D technology workThe implications of 3D on the film business and on cinemasThe methods used to fix the media and also the ways in which the 3D image is re named for the viewerThe reasons I have chosen to do my project on this topic is that I am very kindle in the new media field. 3D video when accompanied with high definition film and video is a field that is growing rapidly. Earlier this year, on 02 April 2009, Sky broadcast the UKs first live event in the 3D TV format, it featured a live music concert by the pop group Keane, it was sent via the companys satellite network using polarisation technology.Traditionally we view films and television in two dimensions, this in essence means we view the media as a flat image. In real life we view everything in three dimensions, this is because we get a slightly different image received in each eye, the brain because combines these and we can work out perspicaciousness of vision and create a 3D image. (this will be explained further in Chapter 3)There is a high level of industrial relevance with this topic, as 3D technol ogy coupled with high definition digital signal is at the cutting edge of mainstream digital media consumption. Further evidence of this is that the sports company ESPN will be entry their new TV channel, ESPN-3D in North America in time for this years Summer Football World Cup.In January 2009 the BBC produced a Research White Paper entitled The Challenges of Three-Dimensional Television on this subject and over the next couple of years they predict that it will start to be introduced in the same way that HD (High Definition) digital television signal is currently being phased in, with pay-per-view movies and sports being the first take advantage of it.Sky have announced that their existing Sky+HD boxes will be able to broadcast the 3D signals so customers will not even need to update their equipment to be able to receive the 3D Channel that they are starting to broadcast later this year.On Sunday January 31st 2010, Sky broadcast a live Premier conference football match between Ars enal and Manchester United for the first time in 3D to selected pubs across the country, Sky equipped the selected pubs with LGs new 47-inch LD920 3D TVs. These televisions use the passive glasses, similar to the ones uses in cinemas as opposed to the more expensive Active glasses which are also an option. (The differences between Active and Passive technologies will be explained in Chapter 8)It is also worth noting that at the 2010 Golden Globe awards, on acceptance of his award for Best Picture for the 3D Box slip Hit Avatar, the Canadian director James Cameron pronounced 3D as the future.At the time of writing this report (27/01/2010) the 3D film Avatar has just taken over from Titanic (also a James Cameron film) to become the highest grossing movie of all time, with worldwide takings of $1.859 billion. This is being accredited to the films outstanding takings in the 3D version of its release, in America 80% of the films box office revenue has been received from the 3D version o f its release.In an industry where money talks, these figures will surely lead to an dramatic increase in production of 3D films and as a result Avatar could potentially be one of the most influential films of all time.After completing this dissertation I hope to be able to have a wide knowledge base on the subject and hopefully this will appeal to companies that I approach about engagementment once I have graduated.In the summer of 2010 when I will be aspect for jobs, I believe that a lot of production companies will have some knowledge of 3D technology and be alert of how in the near future it may be something that they will have to consider adopting in the way that many production companies are already or concisely will be adopting HD into their workflow.In order to ensure that I complete this project to a high standard it is important that I meet a complete understanding of the topic and study a variety of different sources when compiling my research.3D media itself is not a new concept so there are a wide range of books and articles on the theory of 3D and stereoscopy along with anaglyphs.However in recent years there has been a resurgence in 3D with relation to film and TV. This is due mainly to digital video and film production making it easier and cheaper to create and handle the two channels needed for three-dimensional video production.It has proved more difficult to study books and papers on this most recent resurgence of 3D because it is button up superveneing and evolving all the time. I have read various research white papers on the subject, which have been cited in the Bibliography, I have also used websites and blogs along with some recently published books, one of the problems with such a fast moving technological field such as 3D though, is that these books quickly become outdated.CHAPTER 2 HUMAN VISIONIn the real world we see in three dimensions as opposed to the two dimensions that we have become accustomed to when watching TV or at the cinema. Human vision appears in three dimensions because it is normal for people to have two eyes that both focus on the object, in the brain these two images are indeed fused into one, from this we can work out perspicaciousness of vision, this butt against is called stereopsis. All of these calculations happen in the brain without the person ever even noticing, as a result we see the world in three dimensions very naturally.The reason that we see in 3D is because of stereoscopic profoundness perception. There are various complex calculations going on in our brains, this coupled with real experience allows our brain to work out the learning of vision. If it wasnt for this it would be impossible to tell if something was very small or just very far away.As serviceman, we have learnt to judge depth even with only one view point. This is why, if a person has one eye they can still manage to do most things that a person with two eyes can do. This is also why when watching a 2 -D film you can still get a good judge of depth.The term for depth cues based on only one viewpoint is monoscopic depth cues.One of the most important of these is our own experience, it relates to view and relative size of objects. In simple terms, we have become accustomed to object being certain sizes. An example of this is that we expect buildings to be very big, humans are smaller and insects are smaller still. So this means that if we can see all three of these objects next to each other and they appear to be the same size and so the insect must be much closer than the person, and both the insect and the person must be much closer that the building (see figure 1).The perspective depth cue (shown in figure1) was backed up when an experiment was carried out by Ittelson in 1951. He got volunteers to look through a peep hole at some playing cards, the only thing they could see were the cards and so there were no other compositors cases of depth cue available. There were actually three different-sized playing cards (normal size, half-size, and double size), and they were presented one at a time at a distance of 2.3metres away. The half-sized playing card was judged to be 4.6 metres away from the observer, whereas the double-sized card was thought to be 1.3 metres away. Thus, familiar size had a large effect on distance judgement(Eysenck, 2002).Another monoscopic depth cue that is very effective is referred to as occlusion or interposition. This is where an object overlaps another object. If a person is standing behind a tree then you will be able to see all of the tree but only part of the person. This tells us that the tree is nearer to us that the person.One of the most important single view depth cues in called motion parallax, it works on the basis that if a person moves their head, and therefore eyes, then objects nearer to them, whilst not physically moving, will appear to move more than the objects in the distance. This is the method that astronomers use to measure distances of stars and planets. It is in extremely important method of judging depth and is used extensively in 3D filmmaking.In filmmaking, lighting is often talked about as being one of the key elements to giving the picture depth, and this is because it is a monoscopic depth cue. In real life the main light source for millennia has been the sun. Humans have worked out how to judge depth based on the shadows that are portrayed from an object. In 2D films shadows are often used to display depth by casting them across actors faces it allows the viewers to see the recesses and expressions trying to be portrayed.So far all of the methods that have been described for determining depth have been monoscopic, these work independently within each eye. If these were the only methods for determining depth there would be no need for 3D films as it would not add anything because all of these methods could be recreated using a single photographic camera lens. This is not the ca se however, a lot of the more advanced methods used in human vision for judging depth need the use of both eyes, these are called stereoscopic depth cues.A great deal of stereoscopic depth cues are based around the feedback that your brain gets when the muscles in the eye are manipulated to distil your vision on a particular point.One of the main stereoscopic depth cues is called crossroad, this referrers to the way that the eyes rotate in order to focus on an object (see figure 2).If the focus is on a near object, the eyes rotate around the Y axis and converge on a tighter weight , similarly if the focus is on a distant object the rotation means the eyes have a wider angle of convergence.It is a lot less(prenominal) stressful on the muscles in the eye to have a wide angle of convergence and look at objects far away, in comparison looking at very close object for any amount of time causes the muscles in the eye to ache. This is a very important factor that should be considered wh en creating 3D films, as it doesnt matter how good the film is, if it is going to hurt the audience it will not go down well.A second stereoscopic depth cue that we use is called accommodation, this is the way that our eyes changes focus when we look at an object at different distances, it is very closely linked with convergence.Usually when we look at an object very close up, our eyes will change rotation and point towards the object (convergence) allowing us to look at the item, our eyes will at the same time change focus (accommodation). Using the ciliarybody muscles in the eye, the lens will change shape to let more or less light in the same way a camera does, thus changing focus.In everyday life convergence and accommodation normally happen in parallel. The fact that we can, if we wish choose to converge our eyes without changing the focus means that 3D films are possible. When you are sat in the cinema all of the action is projected onto the screen in front of you, so this is where your eyes need to focus. With 2D films the screen is also where your eyes need to converge, but with 3D films this is not the case. When watching a 3D film the focus never changes from the screen, else the whole picture would go out of focus, but objects appear to be in front and behind the screen, so your eyes need to change their convergence to look at these objects without altering their focus from the screen.It has been suggested that this independence of accommodation and convergence is the reason for eye strain when watching a 3D picture as your eyes are doing something that they are not in the habit of doing (see chapter 12 Is 3D bad for you).It is also worth noting that our monoscopic depth cues work at almost any range, this is not the case with stereoscopic depth cues. As objects become further away they no longer appear differently in each eye, so there is no way the brain can calculate a difference and work out depth.The limit occurs in the 100 to 200-yard range, a s our discernment asymptomatically tends to zero. In a theatre, we will hit the same limitation, and this will define the depth resolution and the depth range of the screen.(Mendiburu, 2009)This means that when producing a 3D film you have to be aware that the range of 3D that you have to use is not infinite and is limited to 100-200 yards.CHAPTER 3 Early Stereoscopic History (1838 1920)Three dimensional films are not a new phenomenon, Charles Wheatstone discovered, in 1838, that the mechanism responsible for human depth perception is the distance separating the retinas of our eyes . (Autodesk, 2008)In a 12,000 word research paper that Wheatstone presented to the Royal Society of prominent Britain he described the stereoscope and claimed as a new fact in his theory if vision the observation that two different pictures are projected on the retinas of the eyes when a single object is seen.(Zone, 2007)Included in the paper were a range of line drawings presented as stereoscopic pairs , these were designed to be viewed in 3D using Wheatstones invention, the stereoscope.Wheatstone was not the first person to look at the possibility of receiving separate views in each eye, In the third century B.C, Euclid in his treatise on Optics observed that the left and right eyes see slightly different views of a sphere(Zone, 2007). However, Wheatstone was the first person to create a device to be able to re-create 3D images.Between 1835 and 1839 photography was starting to be developed thanks to work from William Fox Talbot, Nicephore Niepce and Louise Daguerre.Once Wheatstone became aware of the photographic pictures that were available he requested some stereoscopic photographs to be make for him. Wheatstone observed that it has been found advantageous to employ, simultaneously, two cameras fixed at the proper angular positions(Zone, 2007).This was the start of stereoscopic photography.Between 1850 and 1860 work was starting to be done by various people to try and combine s tereoscopic photography with machines that would display a series of images very quickly and therefore using persistence of vision to create a moving 3D image. These were the first glimpses of 3D motion.In 1891 a French scientist, Louis Ducos du Hauron patented the anaglyph, a method for separating an image into two separate colour channels and then by wearing glassing with the same colours but on opposite eyes thereby cancelling out the image, thus reproducing one image, but in 3D.Another method used at this time to create 3D was proposed by John Anderton, also in 1891. Andertons system was to use polarisation techniques to split the image into two separate light paths and then employ a similar polarisation technique to divert a separate image to each eye on viewing.One of the main advantages of polarisation over anaglyphs is that they do not lose any colour information, this is due to the fact that both images retain the original colour spectrums. They do however loose luminance. It is common for a silver screen to be necessary, it serves two purposes, firstly the specially designed screen maintains the separate polarisation required for each image. It also reflects more light than conventional screens, this compensates for the loss of luminance.During 1896 and 1897 2D motion pictures started to take off, and by 1910 after a lot of initial experimenting the creative formats of film that we recognise forthwith such as cuts and framing had started to become evident.In 1920 Jenkins, an inventor that worked hard to try and create a method for recreating stereoscopic motion picture was quoted as saying Stereoscopic motion pictures have been the subject of considerable thought and have been attained in several waysbut never yet have they been terminated in a practical way. By practical, I mean, for example without some device to wear over the eyes of the observer.(Zone, 2007)It is worth noting that this problem of finding a practical method of viewing 3D has sti ll to a large extent not been solved.Chapter 4 Early 3D Feature Films(1922 1950)4.1 The first 3D feature filmThe first 3D feature film, The Power of Love was released in 1922, it was exhibited at the Ambassador Hotel Theatre in Los Angeles. Popular Mechanics powder magazine described how the characters in the film did not appear flat on the screen, but seemed to be moving about in locations which had depth exactly give care the real spots where the pictures were taken(Zone, 2007).The Power of Love was exhibited using red/green glasses using a dual strip anaglyph method of 3D protuberance. (Anaglyphs are explained in chapter 8.3)The film was shot on a custom made camera invented by Harry K.Fairall, he was also the director on the film. The camera incorporated two films in one camera body.(Symmes, 2006)Power of Love was the first film to be viewed using anaglyph glasses, also the first to use dual-strip projection. too in 1922, William Van Doren Kelley designed his own camera rig, based on the Prizma colour system which he had invented in 1913. The Prizma 3D colour method worked by capturing two different colour channels by placing filters over the lenses. This way he made his own version of the red/blue anaglyphic print. Kelleys Movies of the in store(predicate) was shown at Rivoli Theatre in New York City.4.2 The first active-shutter 3D filmA year later in 1923 the first alternate-frame 3D projection system was unveiled. It used a technology called Teleview. Which blocked the left and right eyes periodically in sync with the projector, thereby allowing you to see too separate images.Teleview was not an original idea, but up to this point no one had been able to get the theory to actually work in a practical way that would allow for films to be viewed in a cinema. This is where Laurens Hammond comes in.Hammons designed a system where two standard projectors would be hooked up to their own AC generators, zip at 60Hz this meant that adjusting the AC frequen cy would increase or decrease the speed of the projectors.The left film was in the left projector and right film in the right. The projectors were in frame sync, but the shutters were out of phase sync.(Symmes, 2006) This meant that the left image was shown, then the right image.The viewing device was attached to the seats in the theatre. It was mounted on a flexible neck, similar to some adjustable gooseneck desk lamps. You twisted it around and centred it in front of your face, kind of like a mask floating just in front of your face. (Symmes, 2006)The viewing device consisted of a circular mask with a view piece for each eye plus a small motor that moved a shutter across in front of either the left or right eye piece depending on the daily round of current running through it. All of the viewing devices were powered by the same AC generator as the projectors meaning that they were all exactly in sync.One of the major problems Hammond had to overcome was the fact that at the time f ilm was displayed at 16 frames per second. With this method of viewing you are effectively halving the frame rate. 8 frames per second resulted in a very noticeable flicker.To overcome this Hammond cut each frame up in to three flashes so the new while was 1L-1R-1L-1R-1L-1-R 2L-2R-2L-2R-2L-2R and so on. Three alternate flashes per eye on the screen. (Symmes, 2006)This method of separating and duplicating certain frames effectively resulted in increasing the overall frame rate thereby eradicating the flicker.There was only one film produced using this method, it was called M.A.R.S and displayed at the Selwyn Theatre in New York City in December 1922. The reason the technology didnt catch on was not due to the image, as the actual theory for producing the image has changed very little from the Teleview method to the current active-shutter methods which will be explained later.As with a lot of 3D methods the reason this one did not become mainstream was due the viewing apparatus that was needed. Although existing projectors could be modified by linking them up to separate AC generator, meaning no extra equipment was needed, the headsets that were required did need a lot of investment and time to install. All of the seats in the theatre needed to be fitted with headsets, these were adjusted in front of the audience members. These also had to be linked up to the AC generator so as they were perfectly in sync, this meant that they had to be wired in to the seats.These problems have since been overcome with wireless technologies such as Bluetooth as will be explained later.4.3 The first polarised 3D filmThe next and arguably one of the most important advancements in 3D technology came in 1929 when Edwin H. Land worked out a way of using polarised lenses (Polaroid) together with images to create stereo vision. (Find more on polarisation in chapter 8.6)Lands polarizing material was first used for projection of still stereoscopic images at the behest of Clarence Kenned y, an art history instructor at Smith College who wanted to project photo images of sculptures in stereo to his students. (Zone, 2007)In 1936 Beggars Wedding was released in Italy, it was the first stereoscopic feature to include sound, it was exhibited using Polaroid filters. This was take using polarised technology.The first American film to use polarising filters was shot in 1939 and entitled In Tune With Tomorrow, it was a 15 minute short film which shows through stop motion, a car being built piece-by-piece in 3D with the added enhancement of music and sound effects. (Internet Movie Database, 2005)Between 1939 and 1952 3D films continue to me made but with the Great Depression and the onset of the Second World War, the cinema industry was restricted with its output because of finances and as 3D films were more expensive to make their output started to be reduced.Chapter 5 Golden Age of 3D(1952 1955)With cinema ticket sales plummeting from 90 million in 1948 to 40 million in 1 951 (Sung, 2009) largely being put down to the television becoming coming in peoples front rooms the cinema industry needed to find a way to encourage the viewers back the big screen, 3D was seen as a way to offer something extra to make viewers return.In 1952 the first colour 3D film was released called Bwana Devil,it was the first of many stereoscopic films to follow in the next few years. The process of combining 3D and colour attracted a new audience to 3D films.Between 1950 and 1955 there were far more 3D films produced that at any other time onward or since, apart from possibly in the next couple of years from 2009 onwards, as the cinema industry tries to fight back again against falling figures, this time though because of home entertainment systems, video-on-demand, and legal and illegal movie downloads.Towards the end of the Golden Age, around 1955, the fascination with 3D was starting to be lost. There were a number of reasons for this, one of the main factors was that in order for the film to be seen in 3D it had to be shown on two reels at the same time, which meant that the two reels had to be exactly in time else the effect would be lost and it would cause the audience headaches.Chapter 6 Occasional 3D films(1960 2000)Between 1960 and 2000 there were periodic resurgences in 3D. These were down to new technologies becoming available.In the late 1960s the invention of a single strip 3D format initiated a revivification as it meant that the dual projectors would no longer go out of sync and cause eye-strain. The first version of this single strip 3D format to be used was called Space-Vision 3D, it worked on an over and under basis. This meant that the frame was horizontally split into two, during playback it was then separate in two using a prism and polarised glasses.However, there were major drawbacks with Space-Vision 3D. Due to the design of the cameras required to film in this format, the only major lens that was compatible was the Bernier lens. The focal length of the Bernier optic is fixed at 35mm and the interaxial at 65mm. Neither may be varied, but convergence may be altered(Lipton, 1982).This obviously restricted the creative filmmaking options and as a result was soon superseded by a new format called Stereovision.Stereovision was similar to Space-Vision 3D in that is split the frame in two, unlike Space-Vision though, the frame was split vertically, and they were placed side-by-side. During projection these frames were then put through an anamorphic lens, thereby stretching them back to their original size. These also made use of the polarising method introduced by Land in 1929.A film made using this process was called The Stewardess, released in 1969, it cost only $100,000 to make but at the cinema it grossed $26,000,000 (Lipton, 1982). Understandably the studios were very interested in the profit margin that arose from this film. As a result 3D once again became an interesting prospect for studios.Up until f airly recently films were still shot and edited using old film techniques (i.e. not digitally). This made manipulating 3D films quite difficult, this lack of control over the full process made 3D less appealing to film makers.The digitisation of post-processing and visual effects gave us another surge in the 1990s. But only full digitisation, from glass to glass from the cameras to projector lenses gives 3D the technological biotope it needs to thrive (Mendiburu, 2009).Chapter 7 The Second Golden Ageof 3D (2004 present)In 2003 James Cameron released Ghost of the Abyss, it was the first full length 3D feature film that used the Reality Camera System, which was specially designed to use new high definition digital cameras. These digital cameras meant that the old techniques used with 3D film no longer restricted the work-flow, and the whole process can be done digitally, from start to finish.The next groundbreaking film was Robert Semeckis 2004 animated film Polar Express which was also shown in IMAX theatres. It was released at the same time in 2D and 3D, the 3D cinemas took on average 14 times more money that the 2D cinemas.The cinemas once again took note, and since Polar Express was released in 2004, 3D digital films have become more and more prominent.IMAX are no longer the only cinemas capable of displaying digital 3D films. A large proportion of conventional cinemas have made the append to digital, this switch has enabled 3D films to be exhibited in a large range of cinemas.CHAPTER 8 3D TECHNOLOGIES8.1 3D capture and display methodsEach different type of stereoscopic display projects the combined left and right images together onto a flat surface, usually a television or cinema screen. The viewer then must have a method of decoding this image and separating the combined image into left and right images and relaying these to the correct eye. The method that is used to split this image is, in the majority of cases, a pair of glasses.There are two brack ets of encoding method, passive and active. Passive means that the images are combined into one and then the glasses split this image in to two separate images for left and right eye. In this method the glasses are cheaper to produce and the expense usually comes in the equipment used to project the image. The second method is active display. This method works by sending the alternative images in a very quick succession (L-R-L-R-L-R), the glasses then periodically block the appropriate eye piece, this is done at such a fast rate that it appears to be sustained in both eyes.There are various different types of encoding encapsulated within each of the two methods mentioned above.The encoding can use either colour separation (anaglyph, Dolby 3D), time separation (active glasses) or polarisation (RealD). A separate method, which does not require the use of glasses is done by using a virtual space in front of the screen and is called autosterescopic.In cinemas across the world at the mo ment there are several formats that are used to display 3D films. Three of the main distributors are Real-D, iMAX and Dolby-3D.Once a 3D film has been finished by the studios, it then needs to be vigilant for exhibition in various different formats, this can include amongst other things colour grading and anti ghosting processes.At present there is not a universally agreed format for capturing or playing back 3D films, as a result there are several different versions, these are explained below.A large majority of the latest wave of 3D technology options send the image using one projector, so removing the old problem of out sync left and right images. The methods that do use dual projectors are much more sophisticated that the older versions used in anaglyphic films so have eradicated the old problems of out of sync projectors.8.2 Gho