Occupational eye disorders
Transcript of Occupational eye disorders
Occupational
eye disorders
History
vision before and after the injury
visual loss was sudden or gradual
presence of a foreign body is suspected, the worker should be asked about the
type of material that might be involved (a magnetic metal such as iron or steel, a
nonmagnetic metal such as aluminum or copper, or an organic material such as
wood) because this information is helpful for determining the method of
treatment and for prognosis
Soluble metallic salts from iron-or copper-containing foreign bodies can cause
irreversible toxic damage to the retina, best prevented by their prompt removal.
Less-soluble materials, such as aluminum, plastic, or glass, are associated with a
better prognosis
Organic foreign bodies, such as pieces of wood or splinters of plant
material, may introduce an intraocular infection that frequently is
difficult to treat and has a very poor prognosis
ocular pain, irritation, itching, or periocular swelling. Severe pain
and photophobia (light-induced pain) in a red eye suggest
intraocular involvement and warrant immediate ophthalmologic
evaluation. Discharge from the eye is caused by conjunctival
irritation or conjunctivitis. Itching is typical of allergic reactions.
Blurred vision, difficulties in seeing, ergonomic and spectacle
problems are other common complaints
Evaluation
evaluation prior to employment is important to
determine the worker’s capacity to perform in that
work
In the evaluation not only are measurements made
but also the worker’s vision is assessed in terms of
the requirements of each particular occupation.
Examination
A. External Eye Examination:
1. Eyelids
symmetry of the lids of both eyes
lacerations that cross the lid margins
Except in the case of a suspected ruptured or lacerated globe, the lid can be everted to
search for foreign bodies on the upper tarsus.
2. Orbits
Palpate the orbital rims, and note discontinuities and
crepitus caused by subcutaneous air from fractures of the paranasal sinuses
3. Conjunctiva
o examine the conjunctiva, evert the lids by applying gentle pressure over the
superior orbital rim of the upper lid or over the malar eminence of the lower lid,
Inflammation caused by trauma usually produces a watery discharge (tears), in
contrast to the purulent mucoid discharge of bacterial conjunctivitis. Viral or
chlamydial conjunctivitis is characterized by lymph follicles in the inferior fornix
of the conjunctival sac along with a watery discharge
4. Corneas
light reflection on the normally smooth corneal surface
A fluorescein paper strip moistened with sterile saline or a topical anesthetic can be
used to stain the tears on the surface . The stain diffuses into any area of disrupted
epithelium and stains it bright green
5. Anterior chambers
Hyphema (hemorrhage into the anterior chamber) is almost
always a sign of significant injury
Hypopyon (purulent material in the anterior chamber) is
characterized by a white or gray layer of inflammatory
cells at the chamber bottom
6. Pupils
round, black, and equal in size
Pupillary reactions to light
B. Test of Ocular Motility
Limitation of upward or downward gaze occurs frequently
in orbital floor fractures and may be the result of
accompanying edema or mechanical restriction
C. Ophthalmoscopic Examination
1. Red reflex
darkened room with the instrument set at 0 or +1, and the eyes should be observed
at arm’s length, approximately 60 cm (2 ft), so that the reflex in both of them can
be seen at the same time and compared
2. Optic discs
presence of papilledema. Optic discs usually are well vascularized and have a
good pink color
3. Optic cups
The width of each optic cup is usually one-third or less the diameter of the whole
optic disc. If it is as large as half the diameter, or if the optic cups are not similar
in both eyes, there is an increased risk for glaucoma
4. Retinal vessels
The vessels should be examined along the upper and lower arcades
proceeding from the optic disc, and the presence of
hemorrhages, exudates
5. Maculae and foveae
Each macula should be checked for alterations in its usual
relatively featureless appearance. Its center, the fovea, always can be
located 2.5 disc diameters temporal to the optic disc. Its concave
center usually shows a small, bright foveal light reflex
D. Measurement of Intraocular Pressure
measured with a Schiotz tonometer or with an applanation tonometer
Angle-closure glaucoma accounts for only approximately 5% of all
glaucoma; it usually presents with acute aching pain in the involved eye
with moderate redness of the globe and blurred vision, sometimes
described as colored halos around bright lights
Angle-closure glaucoma can occur only in eyes with anatomically
shallow anterior chambers and narrow chamber angles .pilocarpine 1–4%
every 15 minutes for 1–2 hours The production of aqueous humor is
reduced with a topical ophthalmic β-adrenergic blocker and a carbonic
anhydrase inhibitor
Intravenous urea or mannitol infusions are effective, but oral ingestion of glycerin is as effective, safer, and more easily available
Open-angle glaucoma accounts for most cases of glaucomatous visual loss (90%). Its onset is insidious, there is no pain, and visual symptoms are noticed only after severe irreversible loss of visual field has occurred
Open-angle glaucoma accounts for most cases of glaucomatous visual loss (90%). Its onset is insidious, there is no pain, and visual symptoms are noticed only after severe irreversible loss of visual field has occurred
E. Test of Visual Acuity
measured with a Snellen chart, if possible, or with a near-acuity card
and recorded appropriately. Each eye should be tested separately,
first without correction (glasses or contact lenses) and then
with correction;
The Landolt C optotype and number charts are universally accepted,
but the EDTRS and the old Snellen chart are also acceptable in the
United States. Luminance at the chart needs to be 80 candelas per
square meter or higher.
If visual acuity is poor and a refractive error is suspected, the chart or card can be read through a pinhole as a substitute for corrective lenses
If acuity is less than 20/200, the greatest distance at which fingers can be counted
the greatest distance at which hand movements
If vision is poorer than this, light perception can be tested
Metric visual acuity charts use 6 m as the standard test distance; therefore, 6/6 = 20/20
The peak of the light-sensitivity curve of the eye is at a wavelength of about 555 nm. This means that our best vision is in yellow-green light.
Snellen chart
EDTRS
Landolt c
Color vision Color vision appears to be particularly sensitive to toxic exposures, including a
number of different solvents, mercury, and certain pharmaceuticals
There are two types of color vision tests: screening tests and quantitative tests:
Screening tests such as Ishihara pseudoisochromatic plates and Waggoner H-R-R
plates are designed to detect even minor inherited deviations of color perception
The Ishihara plates detect only red–green confusion while the Waggoner H-R-R
plates detect blue–yellow defects also.
The severity of color vision deficiency of a healthy worker is assessed using the
Farnsworth Panel D-15 test, the Good-Lite 16 Hue test or the Lanthony
desaturated test that utilize arranging color pigments so they are adjacent to colors
of similar hue
Waggoner HRR
Farnworth D-15 Panel
Good-Lite 16 Hue test
Farnsworth-Munsell 100 Hue test is used in diagnostic
work when lesions in the retina or in the pathways are
suspected. Each eye is tested separately. This test is
more cumbersome and time consuming to administer
and more costly to run, but is helpful in assessing
changes due to neurotoxic substances
All color vision tests must be used under daylight type
During the last 10 years color vision changes have
continued to be reported due to exposure to styrene,
toluene, perchlorethylene, carbon disulfide, metallic
mercury, and mercury vapor.
F. Test of Visual Fields
Visual fields should be tested, especially in patients with
suspected head injury or a significant decrease in visual acuity.
Each eye is tested separately by confrontation. The patient is asked
to look at the examiner’s eye while the examiner’s hand moves
toward the center of the visual field.
Automated visual fields and Goldmann visual fields provide
quantitative techniques to evaluate visual fields; islands of loss of
vision (scotomas) within the visual field can be documented. Field
defects in the lower part of the visual field increase risk of accident,
Contrast Sensitivity Testing
Hamilton-Veale Contrast Sensitivity Test
Disorders of the cornea and conjunctiva
Allergic conjunctivitis Allergic conjunctivitis occurs in nearly all occupations and is caused
by a long list of workplace and other environmental allergens
If there are no known workplace antigens or irritants but symptoms
worsen at work, dry eyes from low humidity in the workplace or
decreased blinking during near work activities may be contributing
to the symptoms.
mucous discharge, dryness, itching, burning, foreign body
sensation, and tearing.
Thin threads of mucus in the lower fornix are almost pathognomonic
of an allergic reaction.
Chronic blepharitis is common and must be treated before diagnostic testing for allergic
conjunctivitis is possible. Treatment includes warm compresses and ointments, which
contain hydrocortisone, gently rubbed on the lid margin in the evening. If thick cheesy
discharge can be expressed from the meibomian glands the use of systemic tetracycline is
considered.
The case history is key in determining the likely etiology of allergic conjunctivitis. The type
and duration of symptoms during working days and weekends should be recorded
Environmental factors should be noted, including ventilation, sources of irritating and
allergic exposures, such as carpeting, cleaning agents, smoking, various chemicals used in
the workplace (including those used by adjacent workers)
artificial tears
n any treatment, avoidance of any preservatives in the medications used, especially
benzalconium chloride, is important. Topical mast-cell stabilizers and antihistamines are
effective
because of the possibility of increased intraocular pressure, potentiation of herpetic or
fungal keratitis, and of cataract formation, topical steroids should be prescribed only by an
ophthalmologist
Dry eye syndrome
the symptoms are often worsened by low humidity at the workplace
Symptoms are similar to those of allergic conjunctivitis and generally
worsen as the day goes on and with near vision tasks
Exposure to tertiary amines may cause corneal opacities. Trimethylamine
is used in the synthesis of choline, tetramethylammonium hydroxide, plant
growth regulators or herbicides, strongly basic anion exchange resins, dye
leveling agents and a number of basic dye
Triphenylamine is an organic compound with formula (C6H5)3N. In
contrast to most amines, triphenylamine is nonbasic. Its derivatives have
useful properties in electrical conductivity and electroluminescence, and
they are used in OLEDs as hole-transporters
Ultraviolet (UV) light-induced
keratoconjunctivitis
The symptoms first appear within hours after UV exposure and vary from a slight
irritation to severe sloughing of the epithelium with intense pain and tearing
UV light is absorbed in the cornea and the lens, with only minimal amounts
reaching the retina in normal eyes. Regular plastic lens materials absorb UV light.
UV burns of the cornea should be treated with sterile ointment, tight bandaging
and pain medication
subacute damage may also occur from lower levels of exposure to UV light.
Symptoms include dryness or foreign-body sensation in the late night and early
morning hours. Chronic exposure may lead to thickening of the conjunctiva and
changes in the corneal surface.
Disorders of the lens
correlation between a high level of exposure to UV-B light and
cortical and posterior subcapsular cataracts
most eyeglass materials effectively absorb UV light, workers who
wear regular glasses are less exposed to environmental UV radiation
outside their working hours than are those who do not use spectacles
or sunglasses
Exposure to organic nitrate explosives has been reported to be
associated with cataract formation
prevalence of cataracts was noted in glass and metal workers, felt to
be related to short-wave infrared radiation
Disorders of the retina and optic pathways
Light-induced retinal damage can occur from
phototoxicity or thermal injury .The former is typically
caused by short-wavelength light, the latter by visible and
infrared light.
Blue light seems to have particularly unfavorable effects
on the elderly retina
Exposure to lasers can cause serious, permanent loss of
central vision
Laser burns
Grade 1, retinal edema;
Grade 2, retinal coagulation necrosis;
Grade 3, necrosis with hemorrhage;
and Grade 4, hemorrhage bursts into the vitreous
Extended exposure to very low-level laser energy may
cause subtle damage to the retina; this has been reported in
ophthalmologic surgeons who perform laser coagulations
regularly over a period of several years.
A number of solvents have been reported to cause altered color
vision, most commonly in the blue–yellow axis
chronic exposure to styrene, toluene, perchloroethylene, n-hexane,
carbon disulfide and solvent mixtures.
Carbon disulfide has also been reported to cause changes in the
retinal capillary bed resembling diabetic retinopathy
Eye strain and visual ergonomics
Symptoms of eyestrain include sore eyes, headaches, and fatigue, often associated
with intensive close work, including reading and use of video display terminals
Poor contrast or small text may force workers to function too close to their visual
threshold
If the direction of gaze is too high, blinking decreases, and dry spots appear now
and then on the cornea, causing discomfort
Poor placement of a video display terminal may cause glare from a window or
artificial lighting
When visual targets are placed lower, not only is the head posture better, but also
eye irritation becomes less common as the lid aperture becomes smaller, blinking
more frequent, and thus the tear layer on the cornea more stable
Accidents
The CDC indicates that eye injuries are a leading cause of
work-related diseases and injuries in the United States
Between 5% and 19% of all industrial accidents involve
eye injuries 84% of which were considered minor
only 1.5% were wearing safety glasses
Superficial foreign bodies
Superficial foreign bodies are the most commonly
occurring work-related eye injuries.
After it is removed, antibiotic ointment is applied. Corneal
abrasions usually heal within 48 hours but it is wise to use
ointment nightly for a week
Complications of corneal abrasions include infection and
recurrent erosions
Penetrating ocular foreign bodies
If a penetrating injury is suspected, the eye should
be covered with a sterile patch when the patient is
sent to the emergency clinic
21% occurred at the workplace,
fewer than 10% of the injured were wearing
eyeglasses or goggles,
and only 1.5% were wearing safety glasses
Chemical injuries
strong acids and bases
Immediate irrigation is essential to minimize permanent vision loss
Irrigation is continued while transporting the patient to an emergency room for further treatment
protective eyewear should always be worn when handling corrosive or caustic fluids and gases, preferably behind a protecting window or screen
Electromagnetic radiation
Visible and ultraviolet wavelengths have been associated
with pterygium and macular degeneration
Infrared exposure in glass and metal workers has been
associated with cataract formation
Microwaves may be associated with cataract formation
Workers should have an eye examination and
photographic documentation of any eye pathology prior to
working in places where there is risk of exposure to laser
Prevention 60% of workers who suffer eye injuries did not wear eye protection at the
time of the injury; 40% of those who wore protection wore the wrong kind
of protection.
(1) making an assessment of operations and exposures that pose a risk;
(2) checking for visual problems in routine health exams;
(3) reducing exposures by requiring the use of appropriate protective
eyewear, and worksite and engineering modifications;
(4) planning for eye emergencies;
(5) reviewing written procedures and strategies for preventing and dealing
with eye injuries
neurotoxic chemicals in the environment should be known and carefully
avoided in the workplace