天津职业大学文本 Abnormal tear dynamics and symptoms of eyestrain in operators of visual display terminals_眼屈光学.pdf_大学文库

Downloaded fmom oom.bmjjoumals.com on 14 August 2005 Oeaup Erirce Med 19:5b- Abnormal tear dynamics and symptoms of eyestrain in operators of visual display terminals H的nshi Naksish线，uidhi Yamad Abstract ditterence in由e【etracthve error ot the too Objectives-To elarify the relation he- eyes),or refractive miscoereetion are also tuven the prevalunce of dry eye kyndrnme important.We have determined the retractive and subjective symptoms of asthenopia in error to be peobably由e的ot common esie of visual display terminal(VDT)operators. symptoms of athinogis amnng VTYT opera- Mfethodf-722 VDT workera (242 subjeet tors and abo have estabbsbed an "expert workers with symptoms of asthenopin and ystem"for analysing the optimal vienal cindi- 48)controls without such symptoms) tions,especially the refractive conditions,for witheut nbvinus nrganic neular dixexex VDT operators reevived an ophthalmological examina- A reduced blinking rae and widenin线od也e tioo consisting ofrefractometry and a tear ocular xurfxce due to the raiene the viewing funetion (pbenol red thread)test. angle could caue symptoms of asthenopia Rexrelta-Mnre than nf symptnmatie ameng these workers.as ooald reduetinn nf the workurs weru found to meet the criteria of stability of the prccorneal tear film.Toda dry eye,and the odds rotio compared with the eoatrols was 4.61 (pe0.001).This odds ympnms of eculxr farig黑，HwT,thg ratin was significantly greater than that reports are based on the cinkal data of obtained forr refractive error (2.31). parients presenting to a certain hospiral,and as Conchvinn-Although thi erass see- focr as we could tell there are no reportx tha tional study cnuld nnt prnve that dry eyus assess the relation berween tear staras and are the cause of asthenopla,the profound symptams af astheropi in my VDT wark- association of dry eyes with symptonis of asthenopia could he verified.It would be Therefore,in the present study,we investi- uefual to carry out tear functinn terts in ed the prupurtice nf ahnormal tear dyncim- workers with symptoms of asthenopla. ics in VDToperators with syptoms od asthe- nopla with the cotton thread test. Krravede:viail diplay tmnit work:dry pe syndrome;osthenopie 5 abjeets and me山hods All the employees belocging to one computer Numerous studies have found a higher the queseionnaire.In thet company at the time prevalence of symptoms of uncomortable eyes of this srudy there were 3274 employer,of smong vsual disply terminal (VDT)opera- whom】756 were m曲mean age33.4)nd ton ermpareal with offioe worken dring m- 1518 were wmen (mean ape 28.3).In Jpan parative xobs not invohing VDTs.Although the there are no large scale computer manudactur- bsolute values reported vars tmong authors, inz plants,so moot ot the employees woek many report that >50%of VD'I wotkers coen- eitlser in research and developmment or sales plnnn od eye discomdort"Therefore,VD'I work departments. Medoal Universiry is tecognied as a high risk factor for eye The questioanske was dieributed at te dispeenfurt ce xthenopis. time of the perindie enal physical hk up ￥a由 There ane many factors which affeo the carried out by the company for our stody.It visal comfoct of VDT opermtors.Extrinsic asked about (a)the status of viual currerstion. Departeent gl Pehlic factors nclude ergonomcs of the VDI itselt (the cuntent of VDT work,(e)toeall working anl the desk and chair with which it is used bours and average hours spent in VDI work sources of gare such as windows or lighting,ill sad Nurding. esch day during the past momth.previous Uniwerity t Twukuba, defined iob related pressures,and others."In and present illnesses er symptoms diamnosed case these factors play the maior part in mthe- by phsicians nnd any current medicarocs,( nopia nf VDT workers,they should he cnmplints ahout werrking condinns (tahle 1). cnmumically impmwed.On the ether hand, and (f)occurrenee and intensity of ocuar amd Comrependecc to factors relted to the visual system of eachs per- De由a出aH, Departncat of y son,xnch ax scpormmndatiun"(acpormmndatiun month ftable 2). Dcourional ad means the dynamic refraction by which the In ()the classification of VDT work was 月instsesid Mnkre rettoctive power of the lens i changed so that based on the recommendation in a repoct from Kamre Mohal t,Dwao-以， cear tmape of vanous obpects 1s formed on the the Natoral Academy of Science in the United Uchu血，1图 retia),discocnfort related to vergion"(ver Sats,"whl中was composed of data eotr男 Preficran 9302.lgan. gions are binceular.conjugate movemets of dara acquisitice,interactive communicato- eegs10a多 1234s1)201t,24 the cyes sllowing the Enet uf sight to mie in a that is.a coenhinatinn of dita entry and data parallel direction),anisometropia (am- acquisition-word processing,and prugram- Aamond I5A回Iw sometrrmia t a cpchitien in whieh there i a ming.The employerx whn answered to (h)that

Abnormal tear dynamics and symptoms of eyestrain in operators of visual display terminals Hitoshi Nakaishi, Yuichi Yamada Abstract Objectives—To clarify the relation between the prevalence of dry eye syndrome and subjective symptoms of asthenopia in visual display terminal (VDT) operators. Method—722 VDT workers (242 subject workers with symptoms of asthenopia and 480 controls without such symptoms) without obvious organic ocular diseases received an ophthalmological examination consisting of refractometry and a tear function (phenol red thread) test. Results—More than 30% of symptomatic workers were found to meet the criteria of dry eye, and the odds ratio compared with the controls was 4.61 (p50% of VDT workers complain of eye discomfort.7 Therefore, VDT work is recognised as a high risk factor for eye discomfort or asthenopia. There are many factors which aVect the visual comfort of VDT operators. Extrinsic factors include ergonomics of the VDT itself and the desk and chair with which it is used, sources of glare such as windows or lighting, ill defined job related pressures, and others.8 In case these factors play the major part in asthenopia of VDT workers, they should be ergonomically improved. On the other hand, factors related to the visual system of each person, such as accommodation9 (accommodation means the dynamic refraction by which the refractive power of the lens is changed so that a clear image of various objects is formed on the retina), discomfort related to vergion10 (vergions are binocular, conjugate movements of the eyes allowing the lines of sight to move in a parallel direction), anisometropia (anisometropia is a condition in which there is a diVerence in the refractive error of the two eyes), or refractive miscorrection are also important. We have determined the refractive error to be probably the most common cause of symptoms of asthenopia among VDT operators and also have established an “expert system” for analysing the optimal visual conditions, especially the refractive conditions, for VDT operators.11 12 A reduced blinking rate and widening of the ocular surface due to the raising the viewing angle could cause symptoms of asthenopia among these workers, as could reduction of the stability of the precorneal tear film.13 14 Toda et al reported that dry eyes comprise most of the symptoms of ocular fatigue.15 However, these reports are based on the clinical data of patients presenting to a certain hospital, and as far as we could tell there are no reports that assess the relation between tear status and symptoms of asthenopia in many VDT workers. Therefore, in the present study, we investigated the proportion of abnormal tear dynamics in VDT operators with symptoms of asthenopia with the cotton thread test. Subjects and methods All the employees belonging to one computer manufacturing company were asked to answer the questionnaire. In that company at the time of this study there were 3274 employees, of whom 1756 were men (mean age 33.4) and 1518 were women (mean age 28.3). In Japan there are no large scale computer manufacturing plants, so most of the employees work either in research and development or sales departments. The questionnaire was distributed at the time of the periodic general physical check up carried out by the company for our study. It asked about (a) the status of visual correction, (b) the content of VDT work, (c) total working hours and average hours spent in VDT work each day during the past month, (d) previous and present illnesses or symptoms diagnosed by physicians and any current medications, (e) complaints about working conditions (table 1), and (f) occurrence and intensity of ocular and other physical discomforts during the past month (table 2). In (b), the classification of VDT work was based on the recommendation in a report from the National Academy of Science in the United States,16 which was composed of data entry, data acquisition, interactive communication— that is, a combination of data entry and data acquisition—word processing, and programming. The employees who answered to (b) that 6 Occup Environ Med 1999;56:6–9 Department of Hygiene, Occupational and Environmental Medicine, Kanazawa Medical University, Japan H Nakaishi Y Yamada Department of Public Health, College of Medical Technology and Nursing, University of Tsukuba, Japan H Nakaishi Correspondence to: Dr Hitoshi Nakaishi, Department of Hygiene, Occupational and Environmental Medicine, Kanazawa Medical University, Daigaku 1-1, Uchinada, Ishikawa Prefecture 920-02, Japan. Telephone 0081 76 286 2211; fax 0081 76 286 9723. Accepted 15 August 1998 Downloaded from oem.bmjjournals.com on 14 August 2005

they use VDTs more than 4 hours daily were considered eligible for this study. The replies to the questions of (e) were divided into yes or no, and the replies to the questions of (f) were scored as follows: no or yes to some extent=1, yes definitely but can be endured=2, and yes definitely and unbearable=3. Those with a total score of 32 or ranking at least one reply of 3 in the replies to the questions of (f) and free from any obvious organic ocular diseases (detected by the answer to (d)) were selected as the target subjects (VDT workers with asthenopia). This selection method is based originally on Suzumura’s asthenopia study17 and was slightly modified by us.12 They received an ophthalmological examination consisting of visual acuity at both near and far distance, refractometry by autorefractometer, and tear function (phenol red thread) test.18 To avoid any type of biases of data due to visual work load just before the examination, all examinations were carried out on a Monday morning before the start of work. Refractive errors were defined according to Nakaishi and Miyao12—that is, presence of uncorrected hyperopia (>+1.0 D for people +0.5 D for people >40 years old), presence of uncorrected astigmatism (>1.25 D for the axis of >30°, 0.75 D for the axis of +0.5 D with correction). Tear function (phenol red thread) test was carried out according to the original method reported by Hamano et al. 18 A cotton thread stained with phenol red is inserted into the lower conjunctival sac through the eyelid instead of a filter paper strip in Schirmer’s test. The cotton thread irritates the eye less than filter paper, and the test period is only 15 s. The test is performed without anesthesia on a closed eye. The cut oV value we adopted was 10 mm/15 s. The definition of dry eye is based on the definition of Yamada et al19 with slight modification—that is, either of the examinee’s eyes exhibiting <10 mm or both eyes exhibiting no more than 10 mm by the phenol red thread test. The controls consisted of colleagues of each subject failing to meet these criteria of subjective symptoms of asthenopia and working in the same workplace matched for age (within 3 years), sex, and status of visual correction (use of glasses, contact lenses, or no correction during VDT work). The controls also received the same ophthalmological examination as the subjects. Several environmental characteristics in all the workplaces were assessed according to the company’s standard8 by industrial hygienists. A flow chart of this study is shown in the figure. Significance was tested by ÷2 test with StatView-J4.5 (Abacuus Concepts). Results and discussion This study was carried out with the assistance of not only representatives of the employers but also of the union, and the members of the company’s occupational environmental health and safety (EHS) section. Hence, the response rate to the questionnaire was very high (99.7%; only 13 people refused to answer the questionnaire), so we can ignore selection bias in response to the questionnaire. There were 242 eligible subjects (100 men, 142 women). Their mean age was 30.3, median 29, and mode 26. Eighty two of these 242 subjects (33.9%) met the criteria of dry eyes, and refractive error was diagnosed in 60 subjects (24.8%). Table 1 Questionnaire for complaints about working conditions 1 The time spent at a VDT is too long 2 Each working period at a VDT is too long 3 Breaks in the working period at a VDT are too seldom 4 Feel overloaded due to deadlines 5 Feel stressful due to monotonous task 6 Room illumination is too bright/dark 7 Screen is glittering or glaring 8 Noise in the workplace (from printer etc is too loud) 9 Air cooling and central heating of the workplace are extreme 10 Humidity of the workplace is too low 11 The height of chair is unadjustable 12 The backrest of chair is inappropriate 13 Space at the desk is inadequate 14 Space between lower leg and seat-pan is inappropriate Table 2 Questionnaire for subjective symptoms 1 Ocular fatigue 2 Ocular pain 3 Double vision 4 Blurred vision 5 Dry sensation 6 Excess blinking 7 Headache 8 Irritation 9 DiYculty in falling asleep 10 Inadequate sleep 11 General fatigue not relieved by rest 12 Pain in hands or arms 13 Shoulder or neck stiVness 14 Shoulder or neck pain 15 Back pain 16 Lumbago 17 Others (if any) Flow chart of the VDT study. Workers Periodic general physical checkup * Near and far visual acuity *Questionnaire Assessment (scoring of subjective symptoms) Controls (asthenopia – group) Target subjects (asthenopia + group) Autorefractometry Tear function (phenol red thread) test Assessment of the working environment Abnormal tear dynamics and symptoms of eyestrain in operators of visual display terminals 7 Downloaded from oem.bmjjournals.com on 14 August 2005

No clear relation between prevalence of dry eyes and age, sex, or corrective status (use of glasses, contact lenses, or no correction) was found. On the other hand, only 48 of 480 controls satisfied the criteria of dry eyes (10.0%) with 60 people satisfying those of refractive errors (12.5%); the odds ratio was 4.61 (p<0.001) for dry eyes and 2.31 (p<0.001) for refractive errors (table 3). The finding of a higher prevalence and thus high odds ratio of dry eyes among the subjects with symptoms of asthenopia compared with controls strongly suggests that we must take dry eye syndrome into consideration when we as occupational health practitioners encounter complaints among VDT workers (because in our study controls were selected to match working condition for every subject, bias due to the diVerences in the working environment can be ignored). Our data suggest that dry eyes might be a more common cause of, or at least more associated with, symptoms of asthenopia than refractive errors among VDT workers. As other researchers have mentioned,15 our results indicate that dry eye syndrome and refractive errors might both be causes of asthenopia in VDT workers, rather than be mutually exclusive, for we found some degree of overlap between these conditions in the subjects (11 people) as well as in the controls (16 people). There have been much experimental data supporting an increase in the prevalence of drying of the eyes,13 20 as well as a report on dry eyes and VDT work in a clinical setting.14 However, there have been no reports assessing the relation between tear status and subjective complaints in a large number of VDT workers. Our results, for the first time, indicate a higher prevalence of dry eye syndrome among VDT workers with asthenopia than among those without asthenopia in an actual working population. One of the diYculties in analysing dry eye syndrome is that the definition of dry eye itself diVers depending on the researcher, at least here in Japan; in 1992, dry eye syndrome was defined as a “quantitative or qualitative abnormality of tear irrespective of keratoconjunctival disorder” at a clinical conference held at Keio University. One author specified that disregard for keratoconjunctival lesions is unique to Japan.19 However, in 1995, the Japan Dry Eye Research Group stated that the term dry eyes must include keratoconjunctival lesions21; the group classified those with only decreased tear secretion without any keratoconjunctival disorder as incomplete dry eyes or intermittent dry eyes and remarked that such a type of dry eyes may be associated with VDT work or use of contact lenses.22 Our data relate to the conventional or incomplete type of dry eyes, because we did not confirm the corneal condition by slit lamp observation but only checked the condition of the tears. Our data also support the general concept that ocular symptoms are associated with small refractive errors.23–25 However, the odds ratio was smaller than that for dry eyes in our study. So we recommend investigation of not only refractive errors but also tear conditions when we encounter VDT workers with symptoms of asthenopia, or for the first stage of prevention, before they start VDT work. At least correction status and tear condition should be checked. For high risk prospective VDT workers (those with corrective errors or dry eyes), specific percautions should be taken—for example, making them wear more suitable glasses during VDT work or apply artificial tear solution as well as the usual action from the aspect of industrial health, to prevent the health problems of VDT work—such as, controlling working time, adjustment of ergonomic variables at the work stations, and controlling workplace humidity, temperature, and lighting. 1 DainoV MJ, Happ A, Crane P. Visual fatigue and occupational stress in VDT operators. Hum Factors 1981;23:421–38. 2 Läubli T, Hunting W, Grandjean E. Postural and visual loads at VDT workplace. Lighting conditions and visual impairment. Ergonomics 1981;24:933–44. 3 Starr SJ, Thompson CR, Shute SJ. EVects of video display terminals on telephone operators. Hum Factors 1982;24: 699–711. 4 Yamamoto S, Visual, musculoskeletal and neuropsychological health complaints of workers using video-display terminal and an occupational health guideline. Jpn J Ophthalmol 1987;31:171–83. 5 Rossignol MA, Pechter ME, Summers VM, et al. Video display terminal use and reported health symptoms among Massachusetts clerical workers. J Occup Med 1987;29:112– 18. 6 Collins MJ, Brown B, Bowman KJ, et al. Task variables and visual discomfort associated with the use of VDT’s. Optom Vis Sci 1991;68:27–33. 7 Bergqvist UOV, Knave B. Eye discomfort and work with visual display terminals. Scand J Work Environ Health 1994; 20:27–33. 8 Hewlett-Packard, EHS Group, VDT/OYce Ergonomics. Environmental, health and safety training. New York: Hewlett-Packard, 1994:5961–7256. 9 Ishikawa S. Examination of the near triad in VDU operators. Ergonomics 1990;33:787–96. 10 Iwasaki T, Kurimoto S. Measurement of vergent eye movement by jumping method before and after VDT work. Acta Ophthalmol 1984;(suppl 164):24. 11 Nakaishi H. Implementation of ophthalmological tests in periodic eye checkups for VDT workers in Japan. Safety Science 1995;20:271–5. 12 Nakaishi H, Miyao M. Establishment of an expert system for visual display terminals (VDT) workers’ periodic eye checkups. In: Anzai Y, Ogawa K, Mori H, ed. Advances in human factors/ergonomics 20B. Amsterdam: Elsevier, 1995: 599–604. 13 Patel S, Henderson R, Bradley L, et al. EVect of visual display unit use on blink rate and tear stability. Optom Vis Sci 1991;68:888–92. 14 Tsubota K, Nakamori K. Dry eyes and video display terminals. N Engl J Med 1993;328:584. 15 Toda I, Fujishima H, Tsubota K. Ocular fatigue is the major symptom of dry eye. Acta Ophthalmologica 1993 71:347– 52. 16 Panel on Impact of Video Viewing on Vision of Workers. Video displays, work and vision. Washington, DC: National Academy Press, 1983. 17 Suzumura A. Diagnosis of asthenopia deduced from chief complaints. In: Mishima S, Tsukahara I, Uemura Y, eds. Asthenopia. Tokyo: Kinbara, 1985:1–9. 18 Hamano H, Hori M, Hamano T, et al. A new method for measuring tears. CLAO J 1983;9:281–9. 19 Yamada M, Yoshino K, Ono M, et al. Dry eye; its concept and definition. Folia Ophthalmol Jpn 1992;43:1289–93. 20 Yaginuma Y, Yamada H, Nagai H. Study of the relationship between lacrimation and blink in VDT work. Ergonomics 1990;33:799–809. Table 3 Prevalence (n (%)) of dry eye and refractive errors among 242 subjects and 480 controls, and their odds ratios (ORs) Asthenopia (+) Asthenopia (−) Dry eye (+) 82 (33.9) 48 (10.0) Dry eye (−) 160 (66.1) 432 (90.0) OR 4.61 p Value <0.01 Refractive error (+) 60 (24.8) 60 (12.5) Refractive error (−) 182 (75.2) 420 (87.5) OR 2.31 p Value <0.01 8 Nakaishi, Yamada Downloaded from oem.bmjjournals.com on 14 August 2005

天津职业大学 文本 Abnormal tear dynamics and symptoms of eyestrain in operators of visual display terminals_眼屈光学

天津职业大学文本 Abnormal tear dynamics and symptoms of eyestrain in operators of visual display terminals_眼屈光学