1. Characteristics of the Crystalline Body
Cataracts is a condition in which the "crystalline body" in the eye becomes clouded, resulting in deterioration in its transparency but, before proceeding any further, let's talk a little more about the crystalline body (lens) itself.
The crystalline body in the eyeball functions like a convex lens and, when the muscle called the “ciliary body" contracts, the "zonule of Zinn," a ring of fibrous strands that creates a link between the ciliary body and the crystalline body, slackens, causing the crystalline body to expand, resulting in focal adjustment. This process is called "regulation." When the ciliary body relaxes, the crystalline body is pulled by the zonule of Zinn, to become flat. In this status, in other words, the status in which regulation is relaxed, the crystalline body is in a state of rest, and refraction when this is the case is the actual refraction of the eye (nearsightedness, farsightedness, astigmatism)
Furthermore, the regulatory ability degrades with increasing age, and there are various theories on the reasons for this, including deterioration in the elasticity of the crystalline body and changes in the relationship between the positions of the zonule of Zinn and the crystalline body. In addition, advancing age increases the amount of insoluble proteins in the crystalline body, and it is the resulting increase in cloudiness that causes cataracts.
2. What problems do cataracts produce?
As described above, we all suffer from degraded transparency of the crystalline body to a greater or lesser degree as we grow older.
To a certain extent, this is true, and, examination using a slit-lamp microscope, an instrument used by eye care professionals, reveals that cloudiness of the crystalline body develops in most people once they reach the age of 75 or more, although the extent of the condition differs from person to person. That having been said, this phenomenon falls within the scope of physiological changes that occur naturally with advancing age and does not need to be characterized as cataracts, and the term "cataracts" is only applied as the name of a medical condition when the result leads to the manifestation of some kind of symptoms.
As well as general subjective symptoms that are not necessarily cause for concern, a symptom common at the onset of cataracts is a sensation of dazzling brightness outside on fine days. This is not, however, a sustained symptom, but rather manifests itself only in bright environments. It is believed that this is caused by diffuse reflection of incoming light due to the cloudiness of the crystalline body, and is often characterized by the word "glare."
Moreover, once the nucleus at the center of the crystalline body becomes cloudy, myopia, or nearsightedness, develops (nuclear cataract), and people suffering from this condition may find that, as a result, the spectacles they have been using no longer match their eyesight. Although very rare, there are cases of people who find that they are able to see objects at close range with the naked eye that they previously needed their spectacles to see clearly. Although such people sometimes mistakenly believe that their eyes have improved, in many cases, this phenomenon may be caused by cataracts.
3. Predisposition to cataracts and prevention
The mechanism that gives rise to the manifestation of cataracts is not yet fully understood.
Nevertheless, as well as cataracts brought on by increasing age, there are a number of other types of cataracts including congenital cataracts and uveitis, which are complicated cataracts that occur along with with diseases of the eyeball, diabetic cataracts, dermatogenic cataracts, (occurring concomitantly with dermatosis such as atopic dermatitis) and steroidal cataracts. In other words, diseases such as these represent risk factors that may exacerbate cataracts. Other risk factors include ultraviolet rays, bruising and smoking.
Avoiding such risk factors is one important way to prevent the onset of cataracts.