alvina 78 ABSTRACT To date the use of computers is widely distributed throughout the world and the associated ocular complaints are found in 75-90% of the population of computer users. Symptoms frequently reported by computer users were eyestrain, tired eyes, irritation, redness, blurred vision, diplopia, burning of the eyes, and asthenopia (visual fatigue of the eyes). A cross-sectional study was conducted to determine the etiology of asthenopia in computer-using students. A questionnaire consisting of 15 items was used to assess symptoms experienced by the computer users. The ophthalmological examination comprised visual acuity, the Hirschberg test, near point accommodation, amplitude accommodation, near point convergence, the cover test, and the alternate cover test. A total of 99 computer science students, of whom 69.7% had asthenopia, participated in the study. The symptoms that were significantly associated with asthenopia were visual fatigue (p=0.031), heaviness in the eye (p=0.002), blurred vision (p=0.001), and headache at the temples or the back of the head (p=0.000). Refractive asthenopia was found in 95.7% of all asthenopia patients with accommodative insufficiency (AI), constituting the most frequent cause at 50.7%. The duration of computer use per day was not significantly associated with the prevalence of asthenopia (p=0.700). There was a high prevalence of asthenopia among computer science students, mostly caused by refractive asthenopia. Accommodation measurements should be performed more routinely and regularly, maybe as screening, especially in computer users. Keywords : Asthenopia, acomodative insuffieciency, computer users, students *Department of Ophthalmology, Medical Faculty, Trisakti University **Department of Ophthalmology, Faculty of Medicine, University of Indonesia Correspondence dr. Husnun Amalia, SpM Department of Ophthalmology, Medical Faculty, Trisakti University Jl. Kyai Tapa No.260 Grogol Jakarta 11440 Phone: 021-5672731 ext.2614 Univ Med 2010;29:78-83 Accommodative insufficiency as cause of asthenopia in computer-using students Husnun Amalia*, Gusti G. Suardana**, and Widya Artini** May-August, 2010May-August, 2010May-August, 2010May-August, 2010May-August, 2010 Vol.29 - No.2 Vol.29 - No.2 Vol.29 - No.2 Vol.29 - No.2 Vol.29 - No.2 UNIVERSA MEDICINA INTRODUCTION The number of computer users has rapidly increased throughout the world and is expected to reach 1 billion by the year 2010 as a result of an increasing number of new computer users in developing countries such as China, India and Russia.(1) There is a growing body of evidence that the use of computers can adversely affect visual health. Working at a computer terminal is invariably associated with ocular disorders that may affect visual acuity. Initially research was focused on the ocular effects of radiation hazards, but subsequently came to include symptoms due to exposure of the eyes to video d i s p l a y t e r m i n a l s ( V D T ) , k n o w n a s t h e 79 Univ Med Vol.29 No.2 computer vision syndrome.(2) Several studies showed that around 75% of computer users had visual problems. (3,4) Symptoms frequently reported by computer users were eyestrain, tired eyes, irritation, redness, blurred vision, diplopia, burning of the eyes, and asthenopia.(5-7) The main cause of asthenopia is thought to be fatigue of the ciliary and extraocular muscles due to the prolonged accommodation and vergence required by near vision work. A n o t h e r c a u s a t i v e f a c t o r t h a t h a s b e e n implicated in asthenopia is dryness of the eyes resulting from an increased exposed surface area of the cornea when focusing straight ahead (rather than down at written text) and a d e c r e a s e d b l i n k r a t e d u e t o m e n t a l concentration.(8,9) Etiologically, asthenopia may be classified a s m u s c u l a r a s t h e n o p i a a n d r e f r a c t i v e asthenopia. Muscular asthenopia may be caused by heterophoria, intermittent heterotropia, and convergence insufficiency (CI), whereas refractive asthenopia is due to ammetropia, presbyopia, accommodative insufficiency (AI), and a combination of accommodative and convergence insufficiency. Anomalies of convergence may be detected by means of the near point convergence (NPC) test, while accommodative abnormalities are detected by the near point accommodation (NPA) test.(10) Symptoms occurring in asthenopia are redness, heaviness of the eye, dry eye, frontal headache with periocular pain and occipital headache, blurred vision, intermittent diplopia at near fixation, and difficulty of focus, especially when reading and writing. (11) Computer-related headache and eyestrain are reported during as m a n y a s 1 0 % t o 1 5 % o f r o u t i n e e y e examinations, and several investigators state that nearly 50% of VDT workers experience some eye discomfort . The World Health Organization has initiated a program to eradicate blindness in the year 2020, known as Vision 2020.(12) Asthenopia is a reversible condition and does not result in a reduction of performance o r e f f i c i e n c y o f t h e p a t i e n t . R e f r a c t i v e asthenopia can be corrected by glasses, whilst muscular asthenopia may be corrected by accommodative and convergence training. Current technological advances can prevent asthenopia symptoms through appropriate ergonomic design of the VDT.(13) Available data show that there are large numbers of computer and internet users. Consequently, the risk of asthenopia in computer users may reach epidemic proportions in the foreseeable future. The purpose of the present study was to determine the prevalence of asthenopia and its etiology in computer users. METHODS Design of the study This study was an analytical study with cross-sectional approach, with the objective of determining the prevalence of asthenopia, in order to ascertain the extent of ocular health hazards resulting from computer use. The study was conducted in February 2007 at the Faculty of Medicine, University of Indonesia, Jakarta. Subjects of study The subjects of this study comprised 99 s t u d e n t s f r o m t h e F a c u l t y o f C o m p u t e r Science, University of Indonesia. The inclusion criteria in this study were strata 1 and strata 2 students with visual acuity of 6/6 with or without correction who were willing to fill in t h e q u e s t i o n n a i r e a n d t o r e c e i v e a n ophthalmological examination. The exclusion criteria were presence of manifest heterotropia, amblyopia, and ocular disorders capable of obstructing the visual axis. Data collection Data collection was carried out by means of a questionnaire and several ophthalmological tests. The data collected by questionnaire comprised demographic status, total hours of near-vision work and 15 items on subjective complaints due to asthenopia. Responses to the 80 Table 1. Distribution of etiologies of asthenopia 15 items in the questionnaire were scored as follows: 0, never; 1, infrequent; 2, occasionally; 3, relatively frequent; 4, frequent; and 5, always. The total score for the 15 questions given to each subject ranged from 0 to 75. Subjects were considered to be at risk of suffering from convergence insufficiency if their total score was ≥9. Subjects having a total score of <9 were assigned to the group with negative symptoms, while those with a total score of ≥9 were placed in the group with positive symptoms.(14) Subsequently the subjects received an ophthalmological examination, comprising determination of visual acuity, the Hirschberg test, tests for NPA, amplitude accommodation (AA), and NPC, the cover test (CT), and the alternate cover test (ACT). Subjects were diagnosed as suffering from AI if the obtained AA score was less than the normal score for age according to Donder’s table.(11) The AA score for the age range of 17-19 years is ≥11 D, 20- 24 years 8 D, 25-29 years ≥6 D, 30-34 years ≥5 D, and 35-39 years ≥4 D (D=dioptries). NPC is the convergence ability of the patient’s eye in maintaining fusion, and the test result is expressed in cm. A score of <10 cm is said to be normal and a score of >10 cm means that the subject has CI.(8) Data analysis The study data were divided into two groups, i.e. data on the group of subjects with asthenopia and data on the group of normal subjects. The relationships between variables of the asthenopia group and the normal group were analyzed using the chi square tests. A p- value of <0.05 was considered significant. The data analysis used the SPSS program version 15.0. RESULTS The total number of subjects who were willing to participate in this study was 133, of whom 34 did not meet the inclusion criteria, for t h e f o l l o w i n g r e a s o n s : o n e s u b j e c t h a d congenital cataract, four subjects suffered from manifest heterotropia, and 29 subjects did not complete the questionnaire. The total number of subjects who participated until completion of the study was 99, consisting of 61 (61.4%) males and 38 (38.4%) females. Mean age of the subjects (± SD) was 20.2 ± 1.8 years, with a range of 18 up to 26 years. The majority of the subjects (68 persons or 68.3%) used a computer from 3-6 hours per day, and only 7 (7.1%) used a computer for <2 hours per day. The prevalence of asthenopia in the present study was 69 (69.7%), while that of normal subjects was 30 (30.3%). Ta b l e 1 s h o w s t h e d i s t r i b u t i o n o f etiologies of the asthenopic subjects. Among the two principal causes of asthenopia, i.e. refractive anomalies and muscular anomalies, refractive anomalies accounted for the majority of asthenopia causes (95.7%), where AI ranked highest at 50.7%. The results of the analysis (Table 2) indicated that there was a significant difference between the two groups for the symptoms of visual fatigue (p= 0.031), heaviness (p=0.002), difficulty of recall of recent reading (p=0.001), parietal or occipital headaches (p=0.000), blurred vision (p=0.001), confusion during reading (p=0.014), and failing focus or loss of concentration during reading (p=0.003). Most of the subjects in the asthenopia group were active at the computer for 2-4 hours per day. Amalia, Suardana, Artini Accommodative insufficiency and asthenopia 81 Univ Med Vol.29 No.2 Complaints p Visual fatigue 0.03 1* Redness 0.10 6 Heaviness in eye 0.00 2* Dry eye 0.08 8 Drowsiness 0.18 4 Difficulty of recall of recent reading 0.00 1* Per iocular pain 0.22 9 Parietal/occipital headaches 0.00 0* Blurred vision 0.00 1* Occasional diplopia 0.10 3 Line skipping during readin g 0.20 7 Confusion during readin g 0.01 4* Difficulty of focus/loss of concentration 0.00 3* Need for momentary rest for the eyes 0.05 2 Floating tex t 0.69 5 Table 2. Analysis of subjective complaints between asthenopia and normal groups * Significance Table 3. Distribution of asthenopia in relation to duration of computer use (hours/day) Duration of computer use (hours/day)* Asthenopia p Present (%) Absent (% ) < 2 3-4 5-6 > 7 4 (57.1) 27 (73.0) 20 (64.5) 18 (75.0) 3 (42.9) 10 (27.0) 11 (35.5) 6 (25.0) 0.700 * Chi-square test From Table 3 it is apparent that duration of daily computer use was not significantly associated with occurrence of asthenopia (p=0.700). DISCUSSION To date the use of computers has spread e x t e n s i v e l y t h r o u g h o u t t h e w o r l d a n d accompanying ocular complaints occur in 75- 90% of the population of computer users.(2) The present study showed a high prevalence of asthenopia of 69.7% in computer users. Essentially similar results were obtained in an Indian study on computer users aged 18-55 years, of whom 46.3% suff er ed from asthenopia.(1) A study in Italy on bank employees f o u n d t h a t 3 9 . 1 % o f t h e s u b j e c t s h a d asthenopia.(5) A total of 92.9% of computer science students in our study had ocular complaints, of w h o m 6 9 . 7 % s u ff e r e d f r o m r e f r a c t i v e anomalies. Blehm et al. obtained similar results, where 75–90% of computer users had ocular complaints.(2) In all probability their subjects h a d o c u l a r s u r f a c e a b n o r m a l i t i e s a n d photophobia, which were not investigated in their study. Ocular surface abnormalities are caused by dry eye and problems with contact lenses. Dry eye may be due to reduced blinking r e f l e x e s a n d e n v i r o n m e n t a l f a c t o r s . ( 1 , 2 ) Photophobia is sensitivity of the eye to light, and computer users are commonly exposed to intense illumination and monitor flicker.(16) The usual cause of intense illumination is a window facing the operator and a less than adequate ambient lighting. AI is the major cause of asthenopia, because computer-related activities overburden t h e a c c o m m o d a t i o n m e c h a n i s m . T h e concurrence of refractive errors leads to an increased probability of subjective complaints. The occasional occurrence of blurred vision is due to failure of the accommodative mechanism to maintain focus on near objects. Blurred vision may be remedied by fitting a positive spherical lens or by accommodative training, in which case the subject with AI is fitted with a spherical lens of +0.75D up to +1.25D for near vision.(17) Accommodative training may be accomplished by means of the flip lens technique,(3,4) which uses 2 negative spherical lenses and 2 positive spherical lenses, each differing 0.5D in power. 82 The patient is asked to focus on an object located at a distance of 40 cm in front of her, then the lenses are placed in turn, with the patient attempting to maintain focus on the object. The procedure is repeated 5 times daily, each time for a period of 3 minutes. CI is a condition where a person lacks the ability for maintaining binocular convergence. This condition is the most frequent cause of muscular asthenopia, being found in 3-5% of the general population.(5) and in 4.3% of the asthenopia group of the present study. CI may be managed by convergence training, also known as pencil push up,(19) where the patient focuses on her thumb or on a pencil held in her hand. The object is held vertically at arm’s length in front of the eye, then the object is slowly moved towards the eye, while the p a t i e n t a t t e m p t s t o m a i n t a i n b i n o c u l a r convergence. This procedure is performed 3-4 times daily for 5 minutes and in general the patient will recover within 5-15 weeks. R e f r a c t i v e e r r o r s m o s t f r e q u e n t l y encountered are myopia (21.7%), astigmatism (2.9%), and compound myopic astigmatism ( 4 . 3 % ) , w h i c h m a y b e c o r r e c t e d w i t h glasses.(18) On the other hand, the combination of AI and CI is managed by accommodative and convergence training.(6) In the asthenopia group of the present s t u d y, c o m p u t e r - r e l a t e d a c t i v i t i e s w e r e apparently more frequent than other types of near work. There are still conflicting opinions on the relationship of duration of computer use to occurrence of asthenopia. A total of 73.0% o f s u b j e c t s w i t h a s t h e n o p i a p e r f o r m e d computer-related activities for periods of 3–4 hours per day, but no significant association was found between duration of computer use and the occurrence of asthenopia. In contrast, a study in India found that mean computer use of 78 minutes duration was associated with occurrence of asthenopia.(5) Seven subjective complaints were proven to be significant in the asthenopia group, i.e. visual fatigue (p=0.031), heaviness (p=0.002), difficulty of recall (p=0.001), blurred vision (p=0.001), parietal or occipital headaches (p=0.000), confusion during reading (p=0.014), and failing focus or loss of concentration during reading (p=0.003). Visual fatigue and heaviness in the eye may be caused by inability to maintain binocular fixation, occurring in subjects with CI.(3) Blurred vision and failing focus are due to inability of the accommodation mechanism to maintain focus on near objects, as found in s u b j e c t s w i t h A I . I n s u b j e c t s w i t h p o o r accommodation there also occur headaches when reading.(19) The above symptoms may diminish and disappear with management of the asthenopia. Improving the ergonomic design of workstations and modifying the work habits of computer users (with supplementary breaks) have been shown to have positive effects on visual fatigue in these workers.(20,21) Asthenopia has been extensively studied in the computer literature, and the most commonly used assessment method is self- r e p o r t i n g , b e c a u s e t h i s i s a r a p i d a n d inexpensive method that can be applied to general populations. However, the method carries the risk of self-reporting bias, whereby the personal experiences of the respondent may affect the recall, interpretation, and reporting of symptoms. CONCLUSIONS This study suggests that asthenopia is a common problem among students who are computer users and is mostly caused by accommodative insufficiency. ACKNOWLEDGEMENTS We hereby wish to express our graditude to the Dean of the Faculty of Computer Science, University of Indonesia, for the support and facilities accorded to us in conducting this study. We also thank the students of above faculty as the participants of the study for their willingness and cooperation. Amalia, Suardana, Artini Accommodative insufficiency and asthenopia 83 Univ Med Vol.29 No.2 REFERENCES 1. Bhanderi DJ, Choudhary S, Vikas G, Doshi VG. A community-based study of asthenopia in computer operators. Indian J Ophthalmol 2008; 56:51-5. 2. Blehm C, Vishnu S, Khattak A, Mitra S, Yee RW. Computer vision syndrome: a review. Surv Ophthalmol 2005;50:253-62. 3. Anshel J. Visual ergonomics in the workplace. AAOHN J 2007;55:414-20. 4. Rajeev A, Gupta A, Sharma M. Visual fatigue and computer use among college students. Indian J Comm Med 2006;31:192-3. 5. Mocci F, Sera S, Corrias GA. Psychological factors and visual fatigue in working with video display terminals. Occup Environ Med 2001;58: 267-71. 6. Cole BL. Do video display units cause visual problems?-a bedside story about the processes of public health decision-making. Clin Exp Optom 2003;86:205-20. 7. Sheedy JE, Hayes JN, Engle J. Is all asthenopia the same? Optom Vis Sci 2003;80:732–9. 8. Verma SB. Computers and vision. J Postgrad Med 2001;47:119–20. 9. Vertinsky T, Forster B. Prevalence of eye strain among radiologists: influence of viewing variables on symptoms. AJR 2005;184:681–6. 10. Carlson NB, Kurtz D. Ocular Examination. 3rd ed. New York: McGraw-Hill; 2004. 11. Abdi S, Rydberg A. Asthenopia in schoolchildren, orthoptic and ophthalmological findings and treatment. Doc Ophthalmol 2005;111:65-72. 12. Gilbert C, Foster A. Childhood blindness in the context of vision 2020 - the right to sight. Bull World Health Organ 2001;79:227–32. 13. Tracy BD. Computer vision care: clear path to productivity. Compensation Benefits Management 2001;17:49-51. 14. Borsting EJ, Rouse MW, Mitchell GL, Scheiman M, Cotter SA, Cooper J, et al. Validity and reability of the resived convergence insufficiency symptom survey in children aged 9 to 18 years. Optom Vis Sci 2003;80:832-8. 15. Clark C. End user computing ergonomics facts or fads? J Organiz End User Comput 2006;18:66- 76. 16. Zhang M, Bi LF, Ai YD, Yang LP, Wang HB, Liu ZY, et al. Effect of taurine supplementation on VDT work induced visual stress. Amino Acids 2004;26:59-63. 17. Sterner B, Abrahamsson M, Sjostrom A. Accommodative facility training with long term follow up in a sample of school aged children showing accommodative dysfunction. Doc Ophthalmol 1999;99:93-101. 18. Jenkins RH. Characteristics and diagnosis of convergence insufficiency. Am Orthopt J 1999; 49:7-11. 19. Adler P. Efficacy of treatment for convergence insufficiency using vision therapy. Ophthal Physiol Opt 2002;22:565-71. 20. Van den Heuvel SG, de Looze MP, Hildebrandt VH, The KH. Effects of software programs stimulating regular breaks and exercises on work- related neck and upper-limb disorders. Scand J Work Environ Health 2003;29:106–16. 21. Ketola R, Toivonen R, Hakkanen M, Luukonen R, Takala E, Viikari-Juntura E. Effects of ergonomic intervention in work with video display units. Scand J Work Environ Health 2002;28:18–24.