Although it has been claimed that the majority of eye injuries do not result in a serious visual loss it must not be assumed that the average eye injury is unimportant. Given the right set of circumstances and in the absence of correct treatment, by far the majority of eye injuries have the potential to cause very serious and permanent damage.
Concussion injuries may result from a direct or indirect blow and mostly involve reversible damage to the eye. There may be some associated damage and rupture of small blood vessels and then the term contusion (bruise) is best applied.
Initially there may be only minor injury to the cornea and some swelling and bleeding in the conjunctiva. However the corneal injury may be such that its functional capacity and its transparency are permanently impaired resulting in loss of vision.
Hemorrhages may occur in the structures within the eye and these sometimes have serious consequences. The lens of the eye may be torn from its attachments and this will cause permanent distortion of images transmitted to the brain and an upset to the focusing power of the eye.
In the lens there may develop a loss of transparency in the form of a concussion cataract which is mostly of the rosette type. The degree of regression of concussion cataracts is variable but in general in younger people the opacity may remain stationary or even regress while in older people a progression is more likely.
Perhaps the most important effect of a blow on the eye is the production of fluid and swelling in the retina at the back of the eye. This occurs quite frequently and may be accompanied by a loss of vision. If this patient is treated adequately, which usually requires hospitalization and immobilization, almost perfect vision may return. However until the excess fluid is completely absorbed there is always the possibility of the retinal tissue becoming separated from the rest of the eye. This may result in a serious loss of vision or a blind eye.
One important factor can be derived from a study of concussion injuries. Even though there may be little or no injury visible on even close external examination of the eye and the visual loss may be minimal the final consequences may be very severe even to blindness.
Injuries which result in laceration to the lids or the eye itself are important because they permit entry of ever-present bacteria, viruses or other organisms into either the eye or the blood stream. Even with immediate surgery and massive doses of antibiotics, serious visual loss may result.
3. External Abrasions and Foreign Bodies
The most important frequent eye injuries are those which involve the external aspects of the cornea and conjunctiva and the majority of these involve a foreign body in the eye.
Fortunately the majority of foreign bodies are easily removed and cause little damage. However, following any corneal abrasion or following any foreign body embedded in the cornea either before or after removal there is a constant risk of corneal ulceration. Such a corneal ulcer may heal, leaving a minute and insignificant corneal scar, or it may penetrate through the cornea and cause an intraocular infection which may result in the eye being permanently blind.
The extent of the corneal damage is often dependent upon the nature of the corneal foreign body. Some materials may carry potentially dangerous bacteria or viruses whereas red-hot metallic particles are mostly sterile. Some particles are corrosive or consist of substances including some metals which dissolve in the corneal fluids and these may cause increased damage, corneal scarring and interference with vision.
Some of the most extensive corneal scars result from chemicals such as lime, acids, alkalis, solvents and detergents, and there may be serious visual loss and considerable disfigurement.
4. Intraocular Foreign Body
Probably the most important group of eye injuries is that associated with particles of some foreign material which gain entry to the inside of the eye. These are of particular interest for three main reasons:
- most are preventable by application of correct safety principles;
- the effect on vision is often serious. Up to 40 percent lead to blindness or removal of the eye or the figure may be as high as 60 percent;
- correct and early diagnosis is often difficult.
This third factor warrants elaboration as it indicates the reasons for the poor prognosis in some cases.
When a worker is hit in the eye by a very small but fast-moving particle the immediate pain and reaction may be such that he is not able to indicate with any degree of certainty whether the particle has penetrated the eye or not. If the particle is small, the hole through which it enters the eye may close immediately and so may not be readily observable even under close examination. This is particularly true if the body has penetrated the sclera or white of the eye.
Once in the eye the object may not be visible by ordinary examination techniques as it may be hidden within or behind one of the internal structures of the eye. Even use of X-rays may not locate a foreign body either because it is too small or because it is not opaque to X-radiation.
If the foreign body is not removed from the eye the consequences may be particularly bad if it contains either iron (or steel, etc) or copper (including brass). In the majority of industrial cases the particles are magnetic and the majority of these contain iron. Once located the ferromagnetic particles can mostly be removed by means of careful surgery in conjunction with a strong electromagnet.
Siderosis may result from a particle of iron within the eye that is as small as 0.00015 gm or five millionths of an ounce. As a result of the electrical charges within the eye the iron becomes ionized into small charged particles that are found deposited in all of the structures of the eye.
This process may begin within 24 hours and is particularly destructive to the receptor cells of the retina. It also causes cataract and glaucoma and unless the foreign body is removed in time most of these eyes go blind.
If the retained particle contains copper then it becomes electrolytically dissociated and is deposited in the cornea to give the golden brown Kayser-Fleischer ring, in the lens to give sunflower cataract and in the retina. Prognosis remains uncertain — some deteriorate slowly, many remain stationary for an indefinite period.
Of course these conditions may be complicated by an infective condition of the eye as a result of the introduction of bacteria or viruses with the foreign body. Irrespective or the nature of the retained particle such an eye may be totally destroyed as a result of infection.
7. Chemical Injuries
The destructive capacity of such substances as lime, acids, strong alkalis and some solvents are in general well-known. The skin of the face and eyelids may be extensively scarred and disfigured. The eye is sensitive to such corrosive materials and extensive corneal scarring and blindness are frequently the result. Further emphasis on this type of injury does not seem necessary in the limited space available here.
8. Radiation Injuries
The cornea transmits radiation of wavelengths between 270 nm and 3000 nm and this includes visible light and some ultraviolet and infrared radiation. The commonest effect of ultraviolet radiation on the eye in industry is that known as “welder’s flash”.
The maximum effect is on the cornea and is due to radiation around 280 nm, part of which is absorbed and part transmitted. The effect occurs some 5 to 12 hours after exposure and causes swelling, reddening the watering of the eyes and severe pain. Fortunately these symptoms are seldom followed by permanent sequelae, but in its injured state the cornea is always prone to secondary infection.
Infrared radiation in the wavelength range from 760 nm to 5000 nm mostly passes through the cornea and hence affects either the lens or the retina.
Following exposure to intense heat over many years, the lens of the eye may develop a cataract which is often known as “glass blower’s cataract” and was also found in foundrymen and chainmakers. The lens develops extensive white opaque areas and there is loss of vision.
In the short-term, if the eye is directed towards a source of radiation the lens transmits both visible light and infrared radiation and in fact focuses these on to a small area of the retina. The resultant intense concentration of energy gives rise to a burn of the retina which may result in a hole in this nervous receptor layer. Some loss of vision almost always occurs but is dependent upon the actual intensity of the radiation.
The most common examples are due to viewing a solar eclipse. The exposure time to produce an eclipse burn is one minute or less. Similar damage may result from exposure to the flash of the short circuiting of a strong current.
Finally, exposure to other forms of radiation may give rise to various ocular changes. These changes may involve the conjunctiva as a conjunctivitis, the cornea as edema or opacification, the lens as cataract formation and occasionally there are other intraocular effects such as glaucoma or retinal injury.
Cataract formation can occur from exposure to X-rays, gamma rays and neutrons, while corneal injury and even perforation can follow exposure to beta rays. Obviously persons using such equipment or radioactive substances should take special precautions.