Concerns of people in middle to senior age groups, cataracts
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.
As described above, we all suffer from degraded transparency of the crystalline body to a greater or lesser degree as we grow older.
Some people say that, when this happens, all elderly people will develop cataracts.
To a certain extent, this is true, and, examination using a slit-lamp microscope, an instrument used by ophthalmologists, 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, in fact, be caused by cataracts.
In actual fact, 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 concomitantly 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. Although opinions exist to the effect that there is little scientific basis for the effectiveness of preventative medications, logically speaking, it is probably reasonable to expect that such medications would be effective to a certain extent.
Since the most common kind of cataracts is due to advancing age, let's focus our attention on this type.
Outpatients often ask me questions such as "How are surgical procedures for cataracts performed?" or "What level of vision should I have before I undergo surgery?" The last 20 years have seen great advances in surgical procedures for cataracts and nowadays, such procedures can be performed safely in a relatively short time. However, I do have my doubts about eye specialists who inform a patient that he/she has cataracts and recommend surgery, even if that patient is suffering no inconvenience whatsoever.
The way in which a person feels inconvenience relates to that person's lifestyle. The perception of inconvenience of people who want to continue engaging in activities such as tennis or golf, reading books or working just as they did in their younger days, for example, is different to that of people who almost never leave their homes and are just quietly living out the remainder of their lives.
It is, therefore, impossible to make decisions that apply uniformly to everyone based solely on eyesight. "Glare" is also often used as a yardstick. Surgery is appropriate for patients who have been diagnosed by an ophthalmologist with cataracts that are moderate or worse and are experiencing a certain consequent degree of inconvenience in their daily lives, even if they have eyesight of 1.0 or better.
Almost all surgical procedures for cataracts nowadays involve the implantation of intraocular lenses.
Normally, a fixed-focus lens, and in many cases, a lens for intermediate to long distance focus is implanted. However, people with a special need for close range vision due, for example, to their occupations, may have a lens for close range focus implanted. Since this procedure will cause almost complete loss of the eye's regulatory ability, people with implants for long distance focus require senior spectacles to see objects at close range.
An acquaintance of mine who is an ophthalmologist enjoys nothing better than reading paperbacks in bed, and therefore underwent surgery to have a lens implanted for this purpose, but people with such implants then require spectacles for long-distance focus.
Recently, bifocal intraocular lens implants represent cutting-edge medical treatment (not covered by health insurance). Since this type of lens is designed to enable both long-distance and short-distance focus, they are becoming the mainstream in the west, but they are very costly and one needs to carefully consider the pros and cons before deciding whether or not to go ahead with the necessary surgical procedure.
Although surgery on patients with cataracts with other optical abnormalities presents no problems, surgery on people with some kind of abnormality may present difficulties, although such cases are extremely rare. For example, if a person with a disease of the retina was to undergo surgery for cataracts, their vision would become brighter, but difficulty in seeing caused by the disease of the retina may not change at all, or, in some cases, may become even more pronounced.
In addition, a patient suffering from strabismus (lazy eye) in one eye for some reason undergoing cataract surgery designed for patients who have been living with vision in only one eye may, after surgery, experience polyopia (double vision), visual confusion or increased glare, phenomena that are difficult to rectify and are highly problematic. People, for example, with diseases in parts of the fundus of the eye such as the macula, or with extreme myopia should only make a decision regarding surgery after extensive consultation with their physician.
Editorial supervision: Masato Wakakura, Director, Inouye Eye Hospital