Trauma, or injury, to the eyeball and associated structures may involve any of the parts. In modern industry many preventive measures are taken to avoid damage to this important system. The commonest injury is that of a foreign body under a lid. Even a minute particle is very irritating and soon conjunctivitis ensues. If the foreign particle remains and irritation continues, ulceration may develop. Whenever a foreign body is embedded in the eyeball, as is frequently seen in the unprotected welder’s eye where hot particles strike the globe, treatment is by manual or surgical removal as soon as practical, with medications to combat inflammation. Great care must be taken to prevent chronic inflammation and ulceration, especially over the cornea.
Peri-ocular hematoma (around-eye blood- swelling), or “black eye,” commonly occurs when blunt objects strike the orbit. In this area there is little tissue resistance to combat a broken vessel under the skin, so that blood collects rapidly and quite extensively. Treatment is medical, or none, as the blood is slowly absorbed.
Penetrating wounds of the eye are those in which an object pierces the eyeball, while perforating wounds are those where the object passes completely through the eyeball. Such may be seen with bullet wounds, knife stabs, and falls onto or blows with a piercing object. These injuries are most serious to the sight of the eye and frequently demand emergency surgery, the specific procedure resting with the extent and the location of injury.
Sympathetic ophthalmitis is an inflammation of an eyeball stemming from effects of a chronic inflammation of the other eye. Such condition demands serious consideration of enucleation (removal) of the initially involved eye, in order to save the vision of the second eye. Inflammation of the first eye is almost always the result of injury, and by the time this chronic inflammation starts to involve the second eye, the vision in the first eye has been partially or totally lost; therefore sacrifice of the primarily involved eye to spare the sight of the second is not a great loss.
Retinal detachment is a separation of the retina from its attachment to the choroid layer. This occurs as a result of injury or from degeneration. Fluid collects behind the retina, displacing it from its bed. Specific and weird visual symptoms occur which proceed to loss of vision. Treatment rests with operation wherein the fluid is allowed to drain from the under-retinal surface by holes placed through the back of the eyeball, by use of diathermy needles. As the fluid slowly drains the retina falls back into place and becomes adherent. Diligent after-care is imperative.
Hemorrhage within the eyeball, usually the result of blunt injuries, regardless of how extensive and regardless of whether in the anterior or the back chamber, necessitates prompt extensive care. Usually such hemorrhage will absorb, but if it does not, permanent opacity may result, and if in the line of vision it may cause visual impairment.
New growths of this system may involve any part, but fortunately none is common. Both benign and malignant tumors demand early surgical removal. The benign growths must be eliminated before visual impairment occurs; malignant growths must be removed as early as possible to prevent spread to other parts. Often with malignancy, sacrifice of an entire eye becomes necessary. Spread of malignant neoplasm from other parts of the body to the eye does not frequently occur but may be seen, especially with multiple pigmented lesions which sometimes pass to the choroid layer.
Exophthalmos is a protrusion of the eyeball from its socket. This may involve one eye, as in the case of diseases of the orbit, or both eyes, as commonly seen in thyroid disease. Inflammations and tumors behind the eye may give rise to such a protrusion. When the causative factor is corrected, the eyeball usually recedes to its normal position; however, in the presence of the overactive thyroid gland exophthalmos occasionally remains after the gland has been corrected to normal function.
The eyeballs are held in place and movement accomplished by a set of six muscles about the eye. Normally they are held in absolute alignment and movement is simultaneous. Any deviation from the normal equal alignment is called strabismus. This may be due to any of several causes but most commonly is a result of congenital disparity in the muscle lengths of the two eyes. When the eyes turn inward, the condition is medial strabismus; and outward deviation is lateral strabismus. Many cases of strabismus are correctable by special glasses and by eye exercises. Correction of the condition by surgery is often indicated. Operation may entail the lengthening of an eye muscle (tenotomy or muscle recession), or the shortening of a muscle (muscle advancement or resection). The specific procedure depends on the specific defect.
A disturbance of the fluid circulation in the eyeball may result in increased internal pressure, the condition known as glaucoma. This is called primary glaucoma when it occurs spontaneously, and secondary glaucoma when associated with or following some other eye disturbance, such as injury or infection. The disease may be acute or chronic, may involve one eye or both. Initial symptoms include severe pain and progressive vision loss. The underlying cause is blockage of the outflow canal, and treatment must be directed toward establishing a drainage tract. In the early stages medical measures may be effective, but often operative procedures are the only means of relief. These include partial iridectomy (iris-out), various false filtering tracts in the front parts of the eyeball, or producing an opening through the sclera for drainage (sclerotomy). In far-advanced glaucoma enucleation (eyeball removal) may be necessary. The results are usually favorable, however, when accomplished early in the course of the disease. But the vision lost before treatment is undertaken seldom improves. When glaucoma occurs as a result of malignant tumor, enucleation is always indicated.
ERRORS OF REFRACTION
Normally the lens of the eye has a focal length just sufficient to cast the image of distant objects exactly onto the retina, when the eye is in a relaxed state. Whenever such does not occur, an error of refraction is said to exist. Various terms designate such errors:
- Hyperopia (image brought to focus behind retina) —Farsightedness.
- Myopia (image brought to focus in front of retina) —Nearsightedness.
- Astigmatism (parts of image brought to focus irregularly on retina).
- Presbyopia (loss of elasticity of lens so loss of power of accommodation).
Errors of refraction are correctable by the wearing of artificial lenses (glasses or spectacles) and have no operative surgical aspects; therefore, they are not within the scope of this book for detailed discussion.