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Year : 2019  |  Volume : 27  |  Issue : 1  |  Page : 12-16

Comparison of Ocular Complaints and Visual Acuity Among Dry-Yam Grinders and Nongrinders in Two Selected Markets in Ibadan

1 Department of Nursing Science, Bowen University, Iwo, Osun State, Nigeria
2 Department of Nursing Science, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria
3 Department of Physiological Sciences, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria

Date of Web Publication4-Jul-2019

Correspondence Address:
Matthew I Olatubi
Department of Nursing Science, Bowen University, Iwo, Osun State
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/njo.njo_32_18

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Background: Dry-yam grinding like any other grinding process is usually associated with a lot of dust released into the atmosphere. Aims: This study examined and compared the eye complaints of dry-yam grinders and nongrinders, and evaluates the differences in their visual acuity (VA) test scores. This was with a view of determining influence of yam powder on the eye health of the grinders. Settings and Design: The study was conducted among grinders and nongrinders in two major markets in Ibadan. The study design was ex post facto. Materials and Methods: Participants were recruited using purposive sampling technique. Data were collected using interviewer-administered questionnaire and Snellen chart. Statistical Analysis Used: Frequency, mean, independent sample t-test, and Pearson’s moment correlation were use for statistical analyses. Results: Among 252 grinders and nongrinders who participated in the study, eye complaints such as foreign body in the eye (59.5% vs 29.0%) and headache (57.9% vs 37.3%) were more prevalent among grinders compared to nongrinders. More grinders had severe eye complaints (12.7% vs 3.2%). Mean eye complaints among the grinders were 6.92 ± 4.83 compared to 3.76 ± 4.37 among nongrinders. Dry-yam grinders exposed to yam powder had significantly more eye complaints and longer duration of complaints (P = 0.01). There was a weak positive linear correlation (0.167) between the duration of exposure to yam powder and severity of eye complaints. Grinders were observed to have a significantly lower VA on both the eyes (P = 0.01). Conclusion: Dry-yam grinders have more eye complaints than nongrinders. Grinders are encouraged to conform to safety dictates, such as using appropriate personal protective equipment and go for prompt eye assessment so that possible eye morbidity can be diagnosed and treated.

Keywords: Air pollution, complaints, dry yam, grinders, ocular, visual acuity

How to cite this article:
Olatubi MI, Ogunfowokan AA, Akomolafe RO, Faremi FA. Comparison of Ocular Complaints and Visual Acuity Among Dry-Yam Grinders and Nongrinders in Two Selected Markets in Ibadan. Niger J Ophthalmol 2019;27:12-6

How to cite this URL:
Olatubi MI, Ogunfowokan AA, Akomolafe RO, Faremi FA. Comparison of Ocular Complaints and Visual Acuity Among Dry-Yam Grinders and Nongrinders in Two Selected Markets in Ibadan. Niger J Ophthalmol [serial online] 2019 [cited 2020 Jun 1];27:12-6. Available from:

  Introduction Top

Globally, the protection of workers against work-related illnesses and injuries over time has been an issue of enormous concern to employees, workers, occupational health nurses, governments, and the public. This is because a safe working environment does not only promote the physical, mental, and social well-being of workers, but also saves cost associated with medical bills, compensation, work interruption, loss of experienced personnel, and others resulting from accidents at the workplace.[1]

One of the hazards in the workplace that had been found to have numerous health implication especially of the eye, the organ of sight, is dust.[2] Eye had been described as the light of the body. Several work processes generate dust into the atmosphere in a proportion that is usually injurious to human health. One of such work endeavors is dry-yam grinding like other grinding processes.[2]

Grinders have immensely contributed to the growth of informal sector in many resource-poor nations of the world such as Nigeria.[3] The informal sector is the readymade recourse for the majority of active population of Nigeria. Activities in this sector are nonstructured and unregulated by the government. Unique features of most workers in these industries are that they are predominantly self-employed, work for long hours than those in regular employment, and are hardly aware of or protected under occupational health and safety standards, which predispose the affected individuals to higher risks of health hazards.

Occupational exposure to dust is a widely known phenomenon, especially in developing countries,[4] and the adverse effects of ambient air pollution and particulate matter have been well established.[5] Coarse airborne particles have shown to have an adverse effect on health.[6],[7] Apart from the effects of dust on respiratory system, another part of the human body that dust affects most is the eye, causing burning eye, red eye, itching eye, conjunctivitis, and, at times, resultant nasal sinus carcinoma.[8],[9]

Visual impairment such as refractive error, presbyopia, pterygium/pingueculae, conjunctivitis, suspected glaucoma, and cataract has been found to be prevalent among industrial mine workers.[10] Wood dust has also been associated with increased incidence of superficial conjunctiva or corneal foreign body among sawmill workers.[11] Osman and Pala[12] in a study conducted among wood workers reported that 43.0% of their participants had experienced red eyes and 41.2% had itching eyes. The complaints of itching eyes and redness of the eyes were more frequent among workers working for 10 years or more than those working for less than 10 years.

Using the International Classification of Diseases (ICD) criteria,[13] in an effort to evaluate the visual status of mine workers who were directly involved in mining and/or are exposed to the mining environment, Ovenseri-Ogbomo et al. found that severe visual impairment [visual acuity (VA) # 6/18] was observed in 12 (3%) individuals and moderate impairment (VA # 6/9–6/12) was found in 102 (25.1%), whereas others 292 (71.9%) had normal VA of 6/6 or better. In addition, they found out that 11 (2.7%) workers came under category one (VA # 6/18–6/60) of the ICD grades of visual impairment if their vision was left uncorrected.[10]

The health implications of dust inhalations from various industrial processes on workers and people exposed to such dust had been documented. From all indications, the amount of dust people are exposed to and the duration of such exposure had been found to determine the severity of the eye morbidity. This morbidity had also been found to reduce workers’ productivity. This morbidity is worse in informal sector of the economy such as dry-yam grinding where there is minimal or no regulation and poor adherence to safety policies and guideline. Dry-yam grinding in Gbagi and Bodija market, as found in many markets in south-west Nigeria, is largely performed in closed and poorly ventilated shops with no personal protective equipment used by majority of the grinders, and large amount of yam powder in the form of dust is released into the atmosphere. In addition, there is no specific healthcare program to assess and cater for the health of the grinders. Although previous studies had reviewed eye complaints and assessed VA among people engaged in a number of work process,[2] little or none had been documented about dry-yam grinders, hence this study. This study identified and compared the eye complaints of dry-yam grinders and nongrinders, established the differences in VA test scores of dry-yam grinders and nongrinders, and determined the influence of duration of exposure to yam powder on the severity of eye complaints of dry-yam grinders.

  Materials and Methods Top

This study employed ex post facto design. This is a variance of experimental design that is assumed that the dry-yam grinders have been exposed to yam powder and the researcher only assessed the effects of the yam powder. This study was conducted in Gbagi and Bodija markets in Ibadan. The two markets were specifically chosen because they have large number of dry-yam grinders and their economic importance to the people of Ibadan and Oyo State, in general. Gbagi is the largest market in Oyo State and second largest after Kano market in Nigeria. The market has many dry-yam grinders. On the other hand, Bodija market is the biggest agrarian market in Ibadan; it houses the highest number of dry-yam grinders in the city. In all, 252 participants consisting of 126 grinders and 126 nongrinders were determined using Cohen[14] sample size calculation formula for comparative groups participated in the study.

Among the dry-yam grinders, purposive sampling technique was used to select grinders who met the inclusion criteria until the sample size was complete. Purposive sampling technique was also adopted to select every other trader that fulfills the inclusion criteria in the two markets for the nongrinders (control group). The inclusion criteria among dry-yam grinders are that grinder must have been on the job for at least 1 year with no history of smoking, whereas for nongrinder, it was that traders are not into any dusty occupation or living close to any dust-producing factory with no history of smoking. Traders who do not have shops, kiosks, warehouses, or stalls, or those situated less than 100 to grinder’s shop of dust-producing places were excluded; those who had been previously diagnosed for any eye impairment, and grinders with a history of smoking or any eye condition were excluded from the study.

To collect data, this study used interviewer-administered questionnaire developed from literature review, tape rule, Snellen chart, and VA report sheets. The questionnaire consists of three sections. Section A elicits the sociodemographic characteristics of the participants, whereas section B contains six Likert-scale questions (of everyday − 4, every week − 3, every month − 2, every year − 1, and none − 0), which elicit the eye complaints of the participants. The highest mark obtainable was 24, whereas the least was 0. Eye complaints were categorized into severe (14–24), representing 60% and above; moderate (9–13), representing 40% to 59%; and low (0–8) complaints, representing less than 40% of the total obtainable score.

Section C assessed the duration of the complaints using six Likert-scale questions of less than 1 year, 1 to 5 years, 6 to 10 years, and more than 10 years. The duration of complaints was categorized as short duration (less than 5 years) and long duration (6 years and above). The questionnaire was translated to Yoruba for easy understanding to participants who do not understand English.

The validity of the questionnaire was established through face and content validity criteria, whereas reliability was established using test–retest method. The instrument yielded correlation coefficient of 0.972 using Spearman’s rho correlation coefficient. Ethical clearance was received from Health Research Ethic Committee (HREC) of the Institute of Public Health, Obafemi Awolowo University, Ile-Ife, with HREC no. IPHOAU/12/388.

Questionnaire administration and VA tests were conducted on the grinders in their meeting hall after their weekly association meeting, whereas that of the nongrinders were performed at selected conducive well-lighted area in each zone of the markets. VA test was performed for all the participants using the Snellen’s chart. A chair was placed at a distance of 6 m from where the Snellen’s chart was hanged. Each participant was made to sit comfortably on the chair and keep both eyes open. They were asked to cover their left eye with their palm and read out loud what they could see on the chart with their right eye from the beginning to the smallest line of letters they could see. Pictures direction chart was used for participants who were illiterate (illiterate Snellen’s chart). This test was repeated for the left eye. Results were recorded in the VA report sheet.

VA scores were grouped according to the ICD criteria for classifying VA, that is, VA ≤ 6/18 as severe visual impairment, 6/9–6/12 as moderate visual impairment, and ≥6/6 as normal vision.[13] Data generated for the study were analyzed using Statistical Package for the Social Sciences (SPSS) version 16 (SPSS Inc. Released 2007, SPSS for Windows, Version 16.0, Chicago, SPSS Inc.). In the statistical analysis, both descriptive and inferential statistics were used. Hypotheses generated were analyzed using independent sample t-test, Pearson Chi-square, and Pearson’s moment correlation coefficient to compare duration of exposure to yam powder and severity of eyes and respiratory complaints among grinders.

  Results Top

The results showed that 60.3% of the grinders and 53.2% of the nongrinders in the study were male. The mean age of the grinders was 44.75 ± 12.28 years, whereas that of nongrinders was found to be 40.58 ± 14.30 years. The average number of years that the grinders had spent on the job was 16.21 ± 10.39 years. Prevalence of eye complaints from [Table 1] showed that foreign body in the eye (59.5%) and headache (57.9%) were the most prevalent eye complaints among grinders compared to 29.0% foreign body in the eye and 37.3% headache among nongrinders. Inflamed eyeball was the least among the two categories (10.3% for grinders and 4.8% for nongrinders). The mean complaints in all the variables examined were more among grinders compared to nongrinders on a scale of 0 to 4. Foreign body in the eye was observed to be highest with mean of 2.08 ± 1.84, followed by headache 1.36 ± 1.37 and itching eye 1.26 ± 1.59. The least was observed to be inflamed eyeball 0.25 ± 0.84.
Table 1 Prevalence of eyes complaints among participants

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Findings of this study showed that 12.7% of the grinders have severe eye complaints compared to 3.2% among nongrinders. Mean eye complaints among the grinders were observed to be 6.92 ± 4.83 compared to 3.76 ± 4.37 among nongrinders [[Table 2]]. Results from [Table 3] showed that grinders have longer duration of eye complaints compared to nongrinders as 30.2% of grinders have long duration of foreign body in the eye compared to 7.1% nongrinders; 20.6% grinders have long duration of red eye compared to 9.5% nongrinders. The VA of the participants showed that for both eyes, grinders have more severe visual impairment compared to nongrinders. For the right eye, 16.7% of the grinders had severe visual impairment, whereas 34.9% had moderate visual impairment compared to 7.1% severe and 16.7% moderate for the nongrinders, whereas for the left eye, 14.3% had severe and 32.5% had moderate visual impairment among the grinders compared to 7.1% severe and 14.3% moderate visual impairment among the nongrinders [[Table 4]].
Table 2 Eyes complaints among participants

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Table 3 Comparison duration of eye complaints between grinders and nongrinders

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Table 4 Visual acuity test score of the participants

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There was a weak positive linear correlation (0.167) between the duration of exposure to yam powder and severity of eye complaints. Therefore, as duration of exposure to yam powder increases, there was increased severity of eye complaints. However, the correlation is not significant (P = 0.06). Dry-yam grinders exposed to yam powder had significantly more eyes complaints compared to the unexposed group (P = 0.01). In addition, dry-yam grinders exposed to yam powder were observed to have significantly lower VA on both eyes compared to the unexposed group (P = 0.01).

  Discussion Top

Among the various eye complaints examined in this study, complaints of foreign body in the eye, headache, itching eye, and red eye were found to be the most prevalent among the grinders. This supports burning eye, red eye, and itching eye that were mentioned among wood workers by Milanowski et al.[8] Although Milanowski et al.’s[8] study pointed out that conjunctivitis is one of the prevalent complaints among their sample population, prevalence of conjunctivitis was very low among dry-yam grinders in this study. In another related study among wood workers, Osman and Pala[12] reported red eye and itching to be the most common eye complaints among wood worker.

In our study, grinders were observed to have longer duration of eye complaints compared to nongrinders. Among the grinders, foreign body in the eye was observed to have the longest duration followed by red eye, whereas itching eye and headache have the same duration. These findings support the submission of Uhumwangho et al.[11] that workers exposed to wood dust often complain of foreign body in the eye with resultant corneal-related morbidities. This study established that dry-yam grinders exposed to yam powder have more eyes complaints compared to the unexposed group (P = 0.01). Similar results were also obtained when eye complaints were compared separately between grinders and nongrinders. Uhumwangho et al.[11] in their study among people exposed to wood dust had similar submission.

Ovenseri-Ogbomo et al.[10] reported that 3% of mine workers have severe visual impairment, whereas 25.1% have moderate visual impairment. This study found out that more grinders have severe and moderate visual impairment compared to that reported among miners in Ovenseri-Ogbomo et al.’s[10] study. In addition, when compared to nongrinders, grinders were observed to have more severe and moderate visual impairment in our study. This implies that visual complaints of the grinder’s especially foreign body in the eye will most likely be responsible for the reduced vision noticed among the grinders. It can be inferred that exposure to yam powder is capable of causing reduced vision. This assertion is further confirmed in this study by the significant lower VA among dry-yam grinders exposed to yam powder compared to people unexposed to yam powder in our study (P = 0.01).Osman and Pala[12] also reported that furniture workers exposed to wood dust for more than 10 years seem to have more frequent eyes complaints than those working for less than 10 years. In this study, weak but positive linear correlation (0.167) was observed between duration of exposure to yam powder and severity of eye complaints; therefore, as the duration of exposure to yam powder increases, there will be minimal increase in the severity of eye and respiratory complaints. In previous studies, classical morbidities of people exposed to cotton dust had been found to be associated with durations of exposure.[15],[16]


Although effort was made to use a control group that has minimal exposure to dust, but in the real sense, it is difficult to rule out exposure to some form of dust from cooking fumes and other sources whose gravity cannot be ascertained. The headache assessed among the yam grinders cannot be totally attributed to dust; this is because the grinding process produces a lot of noise that is capable of causing headache.

  Conclusion Top

Dry-yam grinding was found to be associated with higher frequency of eyes complaints. People unexposed to yam dust have significantly better vision compared to dry-yam grinders, and the severity of such complaints is associated with duration of exposure. Therefore, dry-yam grinders are susceptible to eyes diseases. Hence, dry-yam grinders and others exposed to dust should be encouraged to always use personal protective equipment and to go for eyes assessment from time to time, so that eye impairments can be diagnosed on time before they become severe and/or permanent morbidity.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Hughes P, Phil E. Introduction to health and safety in construction. 2nd ed. Oxford, UK: Elsevier Ltd; 2007. p. 61.  Back to cited text no. 1
Johncy SS, Ajay KT, Dhanyakumar G, Raj NP, Samuel TV. Dust exposure and lung function impairment in construction workers. J Physiol Biomed Sci 2011;24:9-13.  Back to cited text no. 2
Olusanya BO, Bamigboye BA, Somefun AO. Permanent hearing loss among professional spice grinders in an urban community in Southwest Nigeria. J Urban Health 2012;89:185-95.  Back to cited text no. 3
Aigbedion I, Iyayi SE. Environmental effect of mineral exploitation in Nigeria. Int J Phys Sci 2007;2:33-8.  Back to cited text no. 4
Bakke PS, Hanva R, Gulsvik A. Relation of occupational exposure to respiratory symptoms and asthma in a general population samples: Self reported versus interview-based exposure data. Am J Epidemiol 2001;154:477-83.  Back to cited text no. 5
Brunekreef B, Forsberg B. Epidemiological evidence of effects of coarse airborne particles on health. Eur Respir J 2005;26:309-18.  Back to cited text no. 6
Sandstrom T, Nowak D, Van Bree L. Health effects of coarse particles in ambient air: Messages for research and decision making. Eur Respir J 2005;26:187-8.  Back to cited text no. 7
Milanowski J, Gora A, Skorska C, Krysińska-Traczyk E, Mackiewicz B, Sitkowska J et al. Work-related symptoms among furniture factory workers in Lublin region (Eastern Poland). Ann Agric Environ Med 2002;9:99-103.  Back to cited text no. 8
Bussi M, Gervasio CF, Riontino E, Valente G, Ferrari L, Pira E et al. Study of ethmoidal mucosa in a population at occupational high risk of sinonasal adenocarcinoma. Acta Otolaryngol 2002;122:197-201.  Back to cited text no. 9
Ovenseri-Ogbomo GO, Ocansey S, Abu EK, Kyei S, Boadi-Kusi SB. Oculo-visual findings among industrial mine workers at Goldfields Ghana Limited, Tarkwa. Ophthalmol Eye Dis 2012;4:35-42.  Back to cited text no. 10
Uhumwangho OM, Njinaka I, Edema OT, Dawodu OA, Omoti AE. Occupational eye injury among sawmill workers in Nigeria. Asian J Med Sci 2010;2:233-6.  Back to cited text no. 11
Osman E, Pala K. Occupational exposure to wood dust and health effects on the respiratory system in a minor industrial estate in Bursa/Turkey. Int J Occup Med Environ Health 2009;22:43-50.  Back to cited text no. 12
World Health Organization. International statistical classification of diseases and related health problems. 10th revision, 2nd ed. Geneva: World Health Organization; 2005.  Back to cited text no. 13
Cohen J. Quantitative methods in psychology: A power primer. Psychol Bull 1992;112:155-9.  Back to cited text no. 14
Wang XR, Eisen EA, Zhang HX, Sun BX, Dai HL, Pan LD et al. Respiratory symptoms and cotton dust exposure; results of a 15 year follow up observation. Occup Environ Med 2003;60:935-41.  Back to cited text no. 15
LeVan TD, Koh WP, Lee HP, Koh D, Yu MC, London SJ. Vapor, dust, and smoke exposure in relation to adult-onset asthma and chronic respiratory symptoms: The Singapore Chinese Health Study. Am J Epidemiol 2006;163:18-28.  Back to cited text no. 16


  [Table 1], [Table 2], [Table 3], [Table 4]


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