Secondly, such rays (peripheral vision) may be scattered by such scarring and cause unusual sensitivity to bright light. The cuts may also damage the very sensitive deeper layers of the cornea creating problems in later life, although the operation is too new to know whether and to what extent this is the case. The effects of cuts cannot easily be measured, while the ability of the tissue to heal totally may prejudice even the short-term benefits. The presence of a small degree of short sight may seem a great inconvenience to a young person, and he or she is often willing to take a long-term risk for the sake of an immediate improvement. Read the rest of this entry »
In order to maintain its transparency the lens, a living structure, requires nourishment and metabolic activity. Any agency which disturbs the normal metabolism of the lens will cause a greater or lesser opacification, which is by definition a cataract. Nourishment is provided by the aqueous humour in which the lens lies, the necessary substances passing through the outer capsular membrane to reach the cells within. There are no blood vessels in the lens. Most of it consists of a form of protein, rather like egg-white, which does not occur elsewhere in the human body. Lens protein in different animals is exactly the same. This curiosity, which is called organ specificity rather than species specificity, means that if someone becomes allergic to any animal’s lens, he will also become allergic to his own. Read the rest of this entry »
At the beginning of this century the most prominent cause of blindness was infections of the eye. The eye is exposed externally to infections because of the very delicate skin-lining of the lids and sensitive outer membrane of the eye itself. Other tissue areas of equal susceptibility to infection are the nose, mouth and genitalia. It is even possible for all these orifices to be infected by the same organism.
Since the the availability of antibiotics has drastically reduced the incidence of chronic consequences following an infection. Many serious infections, provided they are treated quickly, no longer inflict severe damage. Read the rest of this entry »
Contusions
Severe blows to the face and eyes are relatively rare in life; but casual blows and knocks are common, occurring mostly in the home or on the sports field. For those involved in warfare they are common enough injuries. Explosions exert great changes of air pressure upon the body, followed by a rebound as the pressure suddenly drops again. This is the invisible fist of the battlefield, and of some industrial accidents. The eye can be convulsed from its muscle connections and the orbit severely damaged. Most explosions are also associated with flying debris (it could be shrapnel, it could be glass), so that injury is often compounded by different types of damage. Other instances where contusive damage occurs are motor accidents, especially where safety belts are not worn, champagne bottle corks, squash balls and fireworks. Read the rest of this entry »
More familiar to us are X-rays, harmful to our tissues in large doses. They can cause cataract and retinal damage. In practice X-rays used for diagnostic purposes are of low dosage, and their effects, both as regards the patient and the practitioner, are controlled. In high intensity they can be used in narrow beams to burn away tissue. (Laser is an example of concentrated light rays.) If such beams are directed on the eye, immediate and irreparable damage would be done. The eye is designed to cope with normal light, i.e. that part of the light (electro-magnetic radiation) between the infra-red and ultra-violet parts of the spectrum. The spectrum extends considerably further in each direction, and the eye can only absorb small low-dosage radiations from these outer areas. In outer space such radiations abound, but the earth’s atmosphere acts as a screen protecting us from harmful rays. Read the rest of this entry »
