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Nigerian Journal of Physiological Sciences
Physiological Society of Nigeria
ISSN: 0794-859X
Vol. 22, Num. 1-2, 2007, pp. 55-58
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Nigerian
Journal of Physiological Sciences, Vol. 22, No. 1-2, 2007, pp. 55-58
Ocular Effects of Chronic Exposure to Welding Light on Calabar Welders
K.
G. Davies1; U. Asana2; C. O. Nku3 and E. E.
Osim3
1Department of physiology, Faculty of Basic Medical
Sciences, University of Uyo, Uyo, Nigeria
Departments of Ophthalmology2
and Physiology3, college of Medical Sciences, University of Calabar, Calabar , Nigeria E-mail: emeosim@yahoo.com
Received: 27/2/2007
Accepted:23/5/2007
Code Number: np07009
Summary
It was generally
observed that welders in Calabar, Nigeria did not always wear their protective
goggles during welding. Since chronic exposure to welding light can impair
vision this study was done to assess the effect of exposure to welding light on
ocular function of welders in Calabar, Nigeria. There were 195 subjects
comprising 110 welders (test) and 85 control subjects. Both groups were all
male and had similar age range. The tests employed were clinical examination
for ocular disorders, assessment of visual acuity, and opthalmoscopy. Test
questionnaire was also used to record information on length of service,
precautionary measures at work place, age and past ocular illnesses. The study
also compared incidence of ocular disorders between the two groups of welders
(arc and carbide welders). The mean ages of the welders and their control were
not significantly different (27.53 ±
10.0 vs 27.78 ± 8.5 yrs respectively).
There was a significantly (P<0.01) higher incidence of pingueculum,
cataract, allergic conjunctivitis, corneal opacity, and keratoconjunctivitis
(arc eye) in welders than in their control subjects. However, visual acuity,
incidence of pterygium and glaucoma were similar. Between the two groups of
welders, the incidence of pterygium, corneal opacity and keratoconjunctivitis
was significantly (P< 0.01) higher in arc welders than carbide welders. The
incidence of pingueculum and glaucoma were however, similar. In conclusion,
chronic exposure to welding light without adequate precaution may cause ocular
disorders. Arc welding is more dangerous to ocular function than carbide
welding. Length of service and age are predisposing factors to ocular disorders
in the welding business.
Key Words: Keratoconjunctivitis, incidence, cataract, pterygium.
Introduction
Welding emits
a wide spectrum of radiations ranging between 200nm 1400nm. These radiations
include ultraviolet (UV) rays (200-400nm). Visible light (400-700nm) and
infrared rays (700-1400nm). Ultraviolet radiation and far infra-red (IR) are
absorbed by the cornea and lens whereas visible light and near infra-red
penetrate to the retina (Fich et al, 1993; Voke, 1999).
Unprotected
exposure of the eyes to these rays is known to cause both acute and chronic
ocular disorders. Acute exposure to UV radiation for instance, causes
photokeratitis (commonly called, welders flash eye or arc eye). This
condition, known for more than a century now, is associated with arc welders
who strike the arc before lowering their protective helmet. (Voke, 1999). It is
characterized by foreign body sensation (grittiness), photophobia, tearing,
blepharospasm and pain. Phtotokeratitis is usually seen a few hours following
exposure and typically resolved within 72 hours. It does not have long-term
squelae (Voke, 1999; Magnavita, 2002). Chronic UV radiation exposure on the
other hand is associated with a high prevalence and incidence of long term
changes in the outer part of the eye in welders (Narda et al, 1990; Norm
et al, 1991).
Radiation in the visible and near IR spectrum
(400-1400nm) penetrates the eye to be absorbed by the retina and may cause
thermal or photochemical damage. Retinal damage induced by arc welding is
referred to as phototoxic maculopathy. In most cases, retinal injuries heal
spontaneously without loss of vision (Magnavita, 2002). However, severe burns
of the macula may lead to permanent, complete or partial loss of central
vision.
The prevalence
and seriousness of eye disorders depend on both the intensity and
characteristics of emitted radiation and the availability of protective
measure. Studies performed on Europeans showed that degenerative changes in the
macula were very frequent among East European welders, who did not often adhere
to protective measures. On the other hand, retinal lesions were infrequent among
Western Europeans who, usually adopted protective measure (Gos et al,
1984).
However, such
studies have not been done in Nigeria which is generally characterized with
poor compliance to eye safety rules (Okoye 2002). Therefore, this study aimed
at determining the visual acuity and prevalence of ocular disorders among
welders and compared with a control population. The incidence of ocular
diseases between two groups of welders (arc and carbide welders) was also
compared.
Materials and Methods
Subjects were
randomly selected from Calabar municipality, Cross River State, Nigeria. Test subjects were welders operating along the major streets of Calabar municipality who
gave their consent. The control group comprised apparently healthy males of
similar age as the test group who were not welders. Tests conducted were
clinical examination for ocular disorders namely: pterygium, pingueculum,
conjunctivitis, photokeratitis, corneal scars and cataract. Other procedures
were visual acuity assessment (using Snellens chart), direct ophthalmoscopy
and slit lamp ophthalmoscopy. Test questionnaires were used to record
information on length of service, precautionary measures at work place, age and
past ocular illnesses.
A total of 195
subjects, comprising 110 welders and 85 control subjects were employed in this
study. The welders were of 2 categories namely; arc welders (n=90) and carbide
welders (n=20).
Statistical Analysis
The student
t-test was used to determine the significant difference between mean values in
the test and control groups. P-values less than 0.05 were taken as significant.
The chi square test was used to test for significance between two percentages.
P values less than 0.05 was considered as statistical significant.
Results
The mean ages of the welder and their control were
not significantly different (27.53 ± 10.0 vs 27.78 ± 8.5 yrs respectively). The
mean duration of exposures of the welders to welding light was 8yrs ± 8.5,
Visual acuity was not significantly different between the welders and their control
(0.988 ± 0.04 vs 1.01 ± 0.04).
Ocular disorders amongst all the welders and their
control
The following disorders were significantly higher
in welders than in control: keratoconjuncttivitis, pingueculum, cataract,
allergic conjunctivitis and corneal opacity. However, the incidence of
peterygium and glaucoma subjects was similar in both groups. (Table 1)
Ocular disorders amongst Arc welders only and their
control
The incidence
of all the ocular disorders studied except glaucoma was higher in arc welders
than their control (Table 2).
Ocular disorders amongst carbide welders only and their control
The incidence
of pingueculum and allergic conjunctivitis was significantly higher in carbide
welders than in their control. However, the incidence of pterygium, cataract,
corneal opacity and glaucoma subject was similar in both groups (Table 3).
Table I: Comparison of Ocular Disorders between Control and Test Groups
Ocular Disorders |
Welders
(%) |
Controls
(%) |
Significance |
Pterygium |
18 |
14 |
N.S |
keratoconjuctivitis |
80 |
0 |
*** |
Pingueculum |
19 |
7 |
* |
Cataract |
2.5 |
0 |
** |
Allergic Conjunctivitis |
20 |
7.7 |
** |
Corneal Opacity |
5.8 |
0 |
** |
Glaucoma |
13.89 |
11.5 |
N.S |
*
= p<0.05; ** = P<0.01; *** =P<0.001; NS = Not statistically
significant
Table 2: Comparison of Incidence of Ocular Disorder between Arc Welders and
Control subjects.
Ocular Disorders |
Welders (%) |
Controls (%) |
Significance |
Pterygium |
21 |
14 |
* |
Pingueculum |
18 |
7 |
** |
Cataract |
2.2 |
0 |
** |
Allergic Conjunctivitis |
20 |
7.7 |
** |
Corneal Opacity |
7 |
0 |
** |
Glaucoma Suspect |
10 |
10 |
N.S |
* = P<0.05; ** = P<0.01; NS = Not statistically significant.
Table 3: Comparison of
Incidence of Ocular Disorders between Carbide Welders and Control Subjects
Ocular Disorders |
Welders
(%) |
Controls
(%) |
Significance |
Pterygium |
11.8 |
14 |
N.S |
Pingueculum |
20 |
7 |
* |
Cataract |
0 |
0 |
N.S |
Allergic Conjunctivitis |
20 |
7.7 |
** |
Corneal Opacity |
0 |
0 |
N.S |
Glaucoma |
12 |
11.5 |
N.S |
Keratoconjunctivitis |
0 |
0 |
N.S |
Table 4: Comparison of Incidence of Ocular Disorders between Arc and
Carbide Welders
Disorders |
Arc Welders
(%) |
Carbide Welders
(%) |
Significance |
Pterygium |
21 |
11.0 |
* |
Pingueculum |
18 |
20 |
N.S |
Cataract |
2.2 |
0 |
** |
Allergic Conjunctivitis |
20 |
20 |
N.S |
Corneal Opacity |
7.7 |
0 |
** |
Glaucoma |
12 |
10 |
N.S |
Keratoconjunctivitis |
100 |
0 |
*** |
NS = not significant vs control; * = P<0.05 vs
control; ** = P<0.01 vs control, *** = P<0.001 vs control
Ocular disorders amongst arc
welders and Carbide welders
The incidence of
keratoconjunctivitis, cataract, pterygium and corneal opacity was higher in arc
welders than in Carbide welders. Incidence of pingueculum, allergic
conjunctivitis and glaucoma was similar between the two sub-groups of welders.
(Table 4).
Discussion
This study has
shown that chronic exposure to welding light without adequate precautionary
measures caused ocular orders. There was a higher incidence of pingueculum,
cataract, keratoconjunctivitis, corneal scars and allergic conjunctivitis
(P<0.01) among welders than in control subjects. The incidence of pterygium
and glaucoma was however similar between test and control subjects. Except for
pterygium whose incidence was not different between welders and their control,
the findings in this study are in agreement with the results of other
investigators who showed that the incidence of pterygium, cataract, pingueculum,
corneal scars and keratoconjunctivitis (arc eye) was higher in welders than in
control subjects (Voke, 1999). The contrast in the incidence of pterygium
between this study and that reported by other workers may be due to the fact
that in this study, welders comprised carbide and arc welders unlike in other
studies mentioned above that used only arc welders. It is well established
that carbide welding generally presents little hazard to the eyes since
ultraviolet emission is quite small and the brightness of the flame is not much
more than candle flame (Sliney et al, 1980). This fact has also been
demonstrated by this study. Comparison of the incidence of ocular disorders
between carbide welders and control were similar for all ocular disorders
examined for except for pingueculum and allergic conjunctivitis which were
higher in the carbide welders. It may also be due to ethnic differences since
this is the first study of this kind using blacks.
On the other
hand, comparison of incidences of the disorders between arc welders and control
showed that all the disorders examined for except glaucoma subjects were higher
in arc welders. As already stated, this study also found higher incidence of
allergic conjunctivitis among welders. This finding has not been reported in
literature. It is possible therefore, that the investigators did not look for
it. There may also be a racial difference, since this is the only study that
used blacks in the tropics as subjects.
It is likely
that the causative factor for the increased ocular disorders is chronic
exposure to welding light. However, it is conceivable that other confounding
causative factors maybe responsible. Various gases are emitted during welding
and can cause ocular disorders. This may likely be the reason carbide welders
who (unlike arc welders) were not exposed to any hazardous light source also
had higher incidence of pingueculum when compared with the control. It is also
very likely that the higher incidence of allergic conjunctivitis was due to metal
smoke emitted during welding. Unfortunately it was not possible to measure the
gases emitted or quantify the amount of light that entered the eyes of the test
subjects owing to technical reasons. The above speculations are in agreement
with report by AFSCME, (2004) which state that welding smoke can affect any
part of the body.
The higher incidence of corneal
scar amongst the welders, though not related to welding light may be another
cause of ocular disorders. Corneal scar is usually caused by iron filling or
other foreign body penetration. Unfortunately these workers were not informed
of these hazards during their training or apprentice.
In conclusion,
chronic exposure to welding light without adequate precautionary measures may
cause ocular disorders including allergic conjunctivitis not previously
reported. Arc welding is more dangerous to ocular function than carbide
welding.
Acknowledgement
We acknowledge the staff members
of the Department of Ophthalmology, UCTH, Calabar. Of particular note are Drs.
Ibanga, Inyang, Eduvie, Chukwu and Etim who carried ocular examination in the
hospital and fundoscopy.
References
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©Physiological Society of Nigeria, 2007
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