Vision-related problems among the workers engaged in jewellery manufacturing.

BACKGROUND: American Optometric Association defines Computer Vision Syndrome (CVS) as "complex of eye and vision problems related to near work which are experienced during or related to computer use." This happens when visual demand of the tasks exceeds the visual ability of the users. Even though problems were initially attributed to computer-related activities subsequently similar problems are also reported while carrying any near point task. Jewellery manufacturing activities involves precision designs, setting the tiny metals and stones which requires high visual attention and mental concentration and are often near point task. It is therefore expected that the workers engaged in jewellery manufacturing may also experience symptoms like CVS. AIM: Keeping the above in mind, this study was taken up (1) To identify the prevalence of symptoms like CVS among the workers of the jewellery manufacturing and compare the same with the workers working at computer workstation and (2) To ascertain whether such symptoms have any permanent vision-related problems. SETTING AND
DESIGN: Case control study.
MATERIALS AND METHODS: The study was carried out in Zaveri Bazaar region and at an IT-enabled organization in Mumbai. The study involved the identification of symptoms of CVS using a questionnaire of Eye Strain Journal, opthalmological check-ups and measurement of Spontaneous Eye Blink rate. The data obtained from the jewellery manufacturing was compared with the data of the subjects engaged in computer work and with the data available in the literature. STATISTICAL ANALYSIS: A comparative inferential statistics was used. RESULTS AND
CONCLUSION: Results showed that visual demands of the task carried out in jewellery manufacturing were much higher than that of carried out in computer-related work.

INTRODUCTION

Our eyes are in constant use during every waking minute. The way we use our eyes can determine how well we work throughout our lifetime. Over 80% of our learning is mediated through our eyes indicating that how much important is our vision. The light rays striking the retina generate potentials in the light receptors; impulses initiated in the retina are conducted to the cerebral cortex, where they produce the sensation of vision.

Vision disturbance is a silent adversary that only appears after a long period of continued exposure. In modern life, one of the visually demanding jobs is working with a computer or visual display terminal (VDT). The users of the computer experience visual problems, cumulatively known as Computer Vision Syndrome (CVS).[1] American Optometric Association defines CVS as “complex of eye and vision problems related to near work which are experienced during or related to computer use.” CVS occurs when the viewing demand of the tasks exceed the visual abilities of the user. The causes of computer vision syndrome are a combination of individual visual problems, poor workplace conditions, and improper work habits (prolonged work exposure, sitting in non-optimal posture), high concentration, continuous looking at a fixed object, and lesser blinking of eyelids. When one looks at any close object, the eyes perform three simultaneous actions: Contraction of pupil (miosis), accommodation, and convergence. The last two are the most important from the view point of CVS. Convergence occurs when the eyes turn “inward and downward” toward the nose when one views close objects. These inward and downward movements require contractions of extra ocular (Medial Rectus and Superior Oblique) muscles of the eyes and may contribute to eyestrain.[23] Sheedy (1991) categorized the various symptoms into one of the following groups.[4] The groups are (a) visual symptoms, (b) ocular symptoms, (c) asthenopia (eye strain), (d) photophobia (sensitivity to lights), and (e) musculoskeletal symptoms. Visual symptoms include blurred vision or squinting (constant, intermittent, or when changing viewing distant), frequently losing place and diplopia. Uncorrected refractive error (incorrect far or near vision), accommodation problems, binocular alignment problems, dry eyes are the causes of visual symptoms. On the contrary, ocular symptoms include irritated eyes (itching, burning, dry, aching, or red eyes), excessive tearing, excessive blinking, and contact lens intolerance. Asthenopia includes eyestrain, headaches, and fatigue. Refractive, accommodation, binocular, or illumination problems may lead to asthenopia. In asthenopia, it is often difficult to differentiate the problems due to visual and ocular symptoms. Photophobia includes glare or annoying brightness and flickering sensation. Musculoskeletal symptoms include neck, shoulder, back, wrist, and arm discomforts.

The CVS is no different from the problems that job holders experience with other near point tasks. There are no special hazards or risks inherent in computer work that is different from reading a printed text or doing near point tasks. Study carried out by Woods in UK had shown that the data processing workers had experienced eye problems such as tired eyes, headache, impaired visual performance, red or sore eyes.[5] Studies have shown that the workers of the electronics industries also suffered from different eye problems.[6] In another study carried out in India, the workers of salt industry reported the visual problems related to eye redness, glare sensitivity, watery eyes, burning eyes, dimness of vision, and photophobia.[7] Studies have shown that the workers of a semiconductor manufacturing industry working in 12-hour shifts using microscope, experienced eye fatigue.[8] Soderberg et al., found that the operators engaged in microscope work had also experienced different visual strain symptoms.[9] Jewellery manufacturing activity involves various precision designs, setting the metal as well as the stones, polishing, and filing. At every stage of manufacturing, checking the quality of the product is very important in jewellery manufacturing. As any rework increases the labor cost and material cost, the workers need to pay a high attention towards the quality of the product. In such a case, the workers may require to pay a higher visual attention. Therefore, it is expected that the workers of the jewellery manufacturing may also experience the symptoms like CVS at their workplace. Keeping this in mind, this study was taken up with following objectives:

Objective

To identify the prevalence of symptoms like Computer Vision Syndrome (CVS) among the workers of the jewellery manufacturing and compare the same with the workers working at computer workstation.

To ascertain whether such symptoms have any permanent vision-related problems.

MATERIALS AND METHODS

Subjects

Two hundred and thirty young male subjects from the jewellery manufacturing and 100 from an IT-enabled organization were voluntarily participated in this study. The objectives and modalities of the study were discussed at the time of introduction. The participants were informed that they could withdraw themselves at any point of time if they were not comfortable with the experiment. Signed informed consents were obtained from all the participants. Prior permission from the respective manufacturing units and the organizations for conducting the study were also obtained.

Location of the study

The study was carried out in Zaveri Bazaar region of Mumbai, one of the jewellery hubs in India and at an IT-enabled organization at Mumbai.

Inclusion criteria

Minimum 1 year of work experience on the same job was the inclusion criteria for this study.

Symptoms like CVS identification

The subjects were explained the objectives of the study. General information like age, working hours per day, years of experience were collected through structured questionnaire. To identify the symptoms like CVS, questionnaire of the Computer Eyestrain Journal[10] was administered. The questionnaire has a total 15 adjectives (problems) related to the feeling of visual symptoms. The subjects were asked to tick (√) the adjectives (problems) while working at their workplace. Presence of any two of these adjectives (problems) was considered as the presence of symptoms of CVS. The total 15 adjectives (problems) were divided in five groups according to the classification of Sheedy (1991)–visualsymptoms, ocular symptoms, asthenopia, photophobia (sensitivity to lights) and musculoskeletal symptoms.[4]

Eye check-up

Head posture, ocular movement, convergence, visual accommodation, fundus, ocular positions were examined by a qualified ophthalmologist for the workers engaged in jewellery manufacturing. Tension of the sclera (intraocular pressure) was measured by tonometer. The check-ups were carried out twice in a day; in the morning before the beginning of the work and in the evening after the completion of the day's work.

Measurement of eye blinking rate

Since the activity of the jewellery manufacturing involves higher level of visual attention, it was felt that the blinking rate may be lower than that of the normative values available in the literature. In view of the above, blinking rate was measured using a Handycam (Model No. DCR–PC108E–Sony Corporation, Japan). The recording was carried out for 15 minutes. The camera was focused on the workers' eyes to record the blinking of eyes while working. The recorded videos were replayed and using an event marker, numbers of blinking were recorded for the entire period of 15 minutes. Using a stop watch with a recording facility of 1/100 th of a second, eye focus times were also recorded.

RESULTS

The study population was the workers engaged in jewellery manufacturing and the workers of an IT-enabled organization. The mean age, height, and weight of the subjects of the jewellery manufacturing were 22.98 (±4.40), 170.88 (±6.32), and 63.58 (±10.03), respectively. The mean age, height, and weight of the participants of the IT-enabled organization were 29.5 (±8.35), 170.31 (±7.23), and 68.47 (±10.98), respectively. The demographic data of the subjects are presented in the Table 1 and the other results (CVS symptoms, their comparative analysis) are presented in Tables 2–7 [Figure 1].

Table 1

Demographic data of the subjects

Table 2

The results of presence of computer vision syndrome among the workers engaged in jewellery manufacturing and the computer workers

Table 7

Comparison of spontaneous eye blink rate of the workers engaged in jewellery manufacturing with normative data available in literature

Figure 1

Jewellery manufacturing–metal setting (very small object)

The results show that the symptoms of the CVS are more prevalent among the jewellery manufacturing workers in comparison to the workers working at IT-enabled organization. Odds ratios (ORs) showed that the symptoms like CVS are higher among the workers of the jewellery manufacturing. Results also showed that the symptoms related to visual, ocular surface, photophobia, and musculoskeletal were significantly higher for these workers. However, the symptoms related to asthenopia did not show any significant difference between the two groups of the workers.

The result of ophthalmological tests carried out on jewellery manufacturing workers showed that the fundus condition was normal, the intraocular pressures were found to be within the normal range, and there was no change in the opthalmological condition in the morning and in the evening (92.16% right eye and 95.45% left eye) of the workers engaged in jewellery manufacturing. The result of opthalmogical tests showed that there is no difference between the result of morning and evening for the head posture (OR: 0.585; 95% confidence interval, CI: 01.872–1.8304), ocular position (OR: 0.8106; 95% CI: 0.4138–1.588), ocular movement (OR: 2.0309; 95% CI: 0.2804–14.7086), convergence (OR: 0.885; 95% CI: 0.457–1.714), and visual accommodation (OR: 0.585; 95% CI: 0.288–1.188) among the workers engaged in jewellery manufacturing activity [Figure 2].

Figure 2

Jewellery manufacturing–source of glare

Table 7 showed that the average blinking rate of the workers engaged in jewellery manufacturing while performing their tasks was significantly lower than the normative value of spontaneous eye blink rate (SEBR) available in the literature (Michael et al., 2006.)

DISCUSSION

When one looks at any close object, the eyes perform three simultaneous actions: Contraction of pupil (miosis), accommodation, and convergence. The last two are most important from the view point of development of CVS. Accommodation to a near point occurs when the lens capsule in one's eyes change shape to focus on a close object. This encompasses contraction of ciliary muscles of the eyeball. Convergence occurs when the eyes turn “inward and downward” towards the nose when one views close objects. These require contractions of extra-ocular (Medial rectus and Superior oblique) muscles of the eye. Both of these can contribute to eyestrain.[23] The work of the jewelry manufacturing is precise. The gold and metal/stone pieces used are very small in size, often difficult to see through naked eyes. These result in higher visual and mental attention. Over and above, while making such jewellery piece, the workers need to place their eyeball in adducted and downward position. As jewellery activities require long duration of exposure and continuous quality checking, the extra-ocular muscles may get tired. The above conditions may be the reason for higher visual discomfort.

Many individuals who work at a video display terminal (VDT) reported a high level of job-related complaints and symptoms, including ocular discomfort and muscular strain. The elements of working at a computer which make it visually demanding include frequent saccadic eye movements (ocular motility) and continuous eye focusing (accommodation) and alignment (vergence) demands. Problems occur when the visual demands of the task exceed the visual abilities of the individual to comfortably perform the task. The results of the study showed that the 65.22% workers of the jewellery manufacturing were suffering from the “symptoms like CVS” which was significantly higher than that of the workers engaged in computer work.

Eyestrain can be defined and perceived by different people by different ways. The visual science dictionary defines asthenopia or eye strain as the subjective complaints of uncomfortable, painful, and irritable vision. It consists of 24 different types of symptoms based on various causes. Asthenopia can be caused from the problems such as focusing spasm, different vision in each eye, astigmatism, hyperopia (far-sighted), myopia (near-sighted), excess light, voluntary focusing, eye coordination difficulties, and other difficulties. In the jewellery manufacturing, symptoms of eyestrain (42.42%) can be due to longer duration of eye focus time, coordination and lower blinking rate. However, no difference was obtained between the two groups of the workers probably due to similar nature of visual activity (eye focus and coordination). A study carried out by Schlote et al., in 2004 on computer workers had reported the average SEBR after an exposure of 30 minutes was 5.9 ± 4.6.[11] The values are similar to the SEBR values obtained in the present study.

Headache is another “discomfort” symptom and is the primary reason most people seek an eye examination. They are also one of the most difficult maladies to diagnose and treat effectively. Visual headaches most often occur toward the front of the head (there are a few exceptions to this), occur most often toward the middle or end of the day, do not appear upon awakening, often occur in a different pattern on weekends than during the work days, can occur on one side of the head more than the other, and other more general symptoms. VDT workers most likely get tension-type headaches. These can be precipitated by many forms of stress, including anxiety and depression; numerous eye conditions, including astigmatism and hyperopia; improper workplace conditions, including glare, poor lighting, and improper workstation set-up.[5121314] The result of headache showed that the workers engaged in jewellery manufacturing and computer are not significantly different (OR: 0.8622, 95% CI: 0.4600–1.6162). In the case of workers engaged in jewellery manufacturing, the cause of such headache may be the improper workplace condition, poor lighting, and improper workstation. Anxiety and depression also may be the cause of such headache, but it needs further investigation.

The front surface of the eye is covered with a tissue that consists of glands which secrete the tears. These tears cover the eye surface and maintain moisture for normal eye function. The tears also help to maintain the proper oxygen balance of the external eye structures and maintain the optical properties of the visual system. The normal tear layer is cleaned off and refreshed by the blinking action of the eyelids. Blink rates vary with different activities-faster when one is very active, slower during sedate or requires concentration. The size of the eye opening is related to the direction of gaze as one gaze higher, the eyes open wider. The amount of evaporation roughly relates to eye opening, the higher gaze angle. It has been shown that most of VDT users have a reduced average blinking time, and an increased rate of tear evaporation, each of which is a major risk of developing short-term dry eyes. Tests have shown that individuals blink less than half their normal rate when carrying computer work.[15] The result showed that the symptoms of dry eye are 21.21% in jewellery manufacturing is significantly higher (OR: 4.217, 95% CI: 1.623–10.9538) than that of computer workers. This might be because of longer eye focus time.

As the result of opthalmological tests showed that the fundus condition is normal and the intraocular pressure for both the eyes comes under the normal range (10–20 mm hg), it can be conclude that there is no permanent effect on the workers' eye condition. Although, it is important to notice that the workers are very young and the mean work experience were 6.73 years (±4.51). It may be assumed that if these conditions continue for the whole working life it may cause permanent disorders. A follow-up study may be required to understand these long-term effects.

CONCLUSION

Nature has designed our visual system to be so dominant that we will alter our body posture to accommodate any deficiency in the way we see. In many office situations, the vision of an employee is compromised and they must adapt their postures to ease the strain on the visual system. These situations will cause obvious physical problems which can be easily remedied with the proper workstation and work environment designs.

The present study shows that the workers engaged in jewellery manufacturing are having prevalence of “symptoms like CVS.” Although the activities are not technically same as in the case of computer-related jobs but natures of some of the activities are similar. As this study shows that there is vision-related problems (that are similar to the CVS) in jewellery manufacturing, it is recommended that the workplace needs to be modified to enhance the eye health and proper training for eye rest and eye exercise.

Table 3

The results of 15 individual symptoms like computer vision syndrome among the workers engaged in jewellery manufacturing and computer workers

Table 4

Percentage responses of the five divisions of computer vision syndrome according to the classification of sheedy

Table 5

Results of evaluation of fundus condition and intraocular pressure

Table 6

Percentage of eye-related problems based on opthalmological evaluation