The eye lens is the part of the eye that is behind the iris and in front of the vitreous body, and occupies most of the so-called posterior chamber. It is a formation that consists of properly arranged lens threads (fibrils) and is transparent under normal conditions. Clouding of the eye lens initially affects only part of the lens, but over time it can progress and affect the entire lens. It most often occurs in old age, but also under the influence of a large number of other factors. Proces zamućivanja očne leće naziva se mrena ili katarakta.
Formation and division of barbells:
- Congenital cataract (lat. Cataracta congenitalis)
This type of cataract is already visible when the child is born or appears immediately after birth. It can be inherited or caused by other factors during pregnancy. Inherited cataracts can occur independently or combined with other changes in the eye or other organs, and their cause lies in the genetic structure. Of the many factors that can affect the formation of cataracts during pregnancy, we can list only a few, such as drug or medication abuse during pregnancy, radiation, maternal illness in the first trimester of pregnancy (roeteln, mumps, hepatitis), etc. Consequences that cataracts leave on the vision of a newborn are very difficult, but fortunately the number of such children is small.
- Complicated cataract (lat. Cataracta complicata)
Complicated cataracts can occur at any age. The disease occurs as a result of numerous factors that slow down and change the normal development and nutrition of the lens (lens metabolism). Depending on the factor that caused such a change, we divide complicated cataracts into several groups. For the sake of simplicity, we will also include those cataracts that are strictly medically defined differently.
Diabetes
Long-term diabetes (10-20g), especially if the blood sugar values are high, can cause a specific type of cataract, but this does not mean that every cataract that occurs in diabetics is caused by this particular disease. Given that diabetes also causes other eye disorders, it is not possible to say precisely if and when lens opacification will occur, but its development is usually faster than with ordinary cataracts. Cataracts are treated and operated on in the same way as all other types of cataracts. The best possible prevention is sugar control and strict adherence to diabetic therapy.
Blood dialysis
During dialysis, the blood is changed and purified from substances that the body is not able to expel on its own. These substances have a harmful effect on the body, and among other things, they can disturb the normal nutrition (metabolism) of the lens and thus cause or accelerate its clouding. Therefore, dialysis itself is not the cause of cataracts, but the disease that led to the need for it. The speed of development of such a cataract can vary, which largely depends on the state of the underlying disease.
Inflammation
Inflammatory conditions that also affect the inner parts of the eye lead to significant changes in the structure of the affected tissues, which are sometimes of a permanent nature. Cataracts formed in this way develop very quickly, and the parallel existence of other eye complications, such as eye pressure, is typical. Cataract surgery is only possible for a long time after the inflammation has completely healed, so that the inflammation does not flare up again due to the surgical intervention. The success of the operation depends primarily on the consequences of the inflammation on other structures of the eye.
Eye trauma
Blunt injury to the eye, although it does not create an open eye wound, nevertheless, due to its pressure and bruising, causes the effect of force and counterforce on the eye structures and thus causes a cataract. An injury with a sharp object where a foreign object pierces the eye (a piece of metal, glass, etc.) can directly damage the lens and cause it to become cloudy almost instantly or within a few hours. Both mechanisms of eye injury can cause another consequence, which is the displacement of the eye lens to the front or back (subluxation or luxation, lat. subluxatio sive luxatio). A lens that is not in its normal place no longer has its true optical role, due to its movement it can damage the structures it comes into contact with, and it often becomes cloudy.
Cataract caused by electric shock or lightning strike should definitely be mentioned as a subtype of traumatic cataract, which fortunately are still rare.
Radiation
Irradiation of the eye with short wavelengths (infrared, X rays) damages all structures of the eye, especially the lens due to its high sensitivity. Infrared-induced cataracts were common in glassblowers exposed to high temperatures and radiation. The appearance of such a cataract is typical, and the treatment is the same as for other types of cataracts. Irradiation with X-rays and radioactive radiation (X-ray devices, tumor irradiation, atomic bomb) depending on the amount of radiation causes the formation of cataracts, but it should be emphasized that in the medical application of the mentioned devices, care should be taken that the dose of radiation and its direction are such that they do not harm the eye lens, so the danger of barbel is extremely low under the mentioned conditions.
Use of medicines
The use of certain drugs in large quantities, which, although necessary for the treatment of the underlying disease, can cause cataracts. This group primarily includes corticosteroid preparations and much less frequently some other medicines and gold preparations. Their potential toxicity does not in any way mean that the mentioned drugs should be avoided, but only that their use must be strictly according to the doctor’s instructions and controlled
- Senile cataract (lat. cataracta senilis)
Senile cataract is the name for that type of cataract that appears in old age without the influence of the above-mentioned factors. It is the result of weakened and disturbed nutrition of the lens, during which there are changes in the structure of its threads. The appearance of this type of cataract cannot be predicted by anything, and there is no evidence that it will occur in people whose parents had it. It develops gradually, most often after the age of 60. As the cataract becomes thicker, it slowly leads to a weakening of vision.
Symptoms of cataracts:
The only symptom of cataracts is weakening or loss of vision. It is usually gradual and lasts from several months to several years. Depending on the cause, this period can be significantly shorter, for example in the case of an eye injury, if the lens of the eye is also affected, cataracts can occur within a few hours. Since cataracts are not always the only cause of vision loss, if it is suspected, it is necessary to have an ophthalmologist’s examination.
Establishing a diagnosis:
Cataracts are diagnosed on the basis of a slit lamp (biomicroscopic) examination and visual acuity determination by an ophthalmologist. It is important to assess how much the decrease in visual acuity is affected by the cataract itself, and how much by any other eye disease. In case of stronger cataracts, where due to their density it is not possible to see the fundus directly, it is necessary to do additional tests such as ultrasound. It can prove or exclude the existence of other diseases and thus better predict the outcome of the operation.
Cataract treatment:
Treating cataracts is difficult regardless of the cause. In the case of initial cataracts where only minor opacities have occurred, it is possible to apply therapy in the form of drops. There are several manufacturers of drugs for the treatment of cataracts, but the effectiveness of all these drugs is limited. With them, it is possible to slow down or even stop the further development of cataracts, but it is not possible to clarify the opacities that have already appeared in the lens. Quinax drops are examples of more successful drops. By slowing down the development of cataracts in some of its forms, it is possible to postpone the operation for a long time. However, with all severe cataracts, operative treatment is the only successful treatment.
Cataract surgery is performed when the patient is no longer able to perform daily tasks due to impaired vision. In the past, operations were performed only when the vision was very weak, that is, when the cataract “ripened”, but today, with the development of more modern operation techniques with the use of very sophisticated devices, operations can be performed in the earlier stages of the disease. In this way, it is possible to provide the patient with good vision earlier, which is especially important for people in workplaces where very precise vision is required.
We distinguish between two basic types of operative techniques :
- classic extracapsular
- ultrasound or phacoemulsification
Extracapsular cataract surgery:
This is the method of operation that until recently was used in almost all cases.
After the examination, in which the need for surgery is determined, the patient is instructed to do the necessary tests. These consist of blood and urine tests, sugar control, lung and heart imaging, and electrocardiographic results (ECG), and additional tests are performed if necessary. Based on these findings, the internist or anesthesiologist makes a decision about the patient’s condition and whether surgery can be performed. In addition to the above, the patient should undergo an ultrasound examination of the eye in order to determine the existence of some changes in the vitreous or on the fundus of the eye which, due to the density of the cataract, are not visible with other methods. As part of this examination, the dioptre strength of the artificial lens that will be implanted in the eye during surgery is calculated.
Cataract surgery is performed under local anesthesia (drops and injection), and only in exceptional cases under general anesthesia. The operation itself is completely painless, but the patient feels that something is being done. The operative procedure lasts 10-20 minutes, including preparations (washing the operative field, anesthesia) a little longer. After the surgery, the patient stays in the hospital for 2-3 days, after which the treatment continues at home. If there are no complications, i.e. if everything goes well, the first control is performed 7 days after leaving the hospital, and the second control two months after the operation. At the second control, threads (stitches) are removed from the eye. During the treatment, vision gradually improves, and the highest and definitive visual acuity is achieved one month after the sutures are removed, when glasses are prescribed and when, under normal circumstances, the treatment is considered complete.
Certain complications are possible during the operation and all the time after it. These are bleeding in the eye, eye pressure and inflammation, which, depending on the intensity, can reduce visual acuity to a greater or lesser extent. Bleeding usually subsides quickly and leaves no consequences, and patients with certain blood clotting disorders and diabetics are more prone to them. Elevated eye pressure after surgery returns to normal within one to two days with therapy and does not cause any long-term consequences. If the pressure lasts for a long time, appropriate permanent therapy is also necessary, and this is most often the case with patients who have had glaucoma before. Eye inflammations can be caused by a large number of factors, so it is often difficult to find their true cause. Most often, these are bacteria, fungi or viruses that enter the eye during or after surgery via air or instruments, and especially in the case of touching or scratching the eye with unclean hands. Certain types of inflammation are caused by the body’s response to the implanted eye (intraocular) lens, but the need to remove the lens rarely arises. Heavy physical efforts or blows to the eye can cause stitches to burst, which greatly complicates further treatment and its outcome. Itching of the eye after surgery is caused by the sutures and is the result of the normal wound healing process.
A clouded eye lens (cataract) that is removed from the eye during extracapsular surgery. The tip of the ballpoint pen is also shown in the picture for size comparison.
An artificial lens that is implanted in the eye during surgery with the aim of replacing the loss of refractive power of the eye due to the lack of the natural eye lens. Next to the lens is shown a needle with a thread used to sew the surgical opening on the eye. In the upper part, a centimeter scale is shown.
Phacoemulsification:
Phacoemulsification is actually about breaking up the cataract with ultrasound, although people like to call this operation laser. It is important to correct this error because laser is not used in this case, nor is there currently another type of cataract surgery that could be called laser surgery. This type of surgery is more recent and offers certain advantages compared to classic surgery, which is why more and more surgeries are performed with this technique today. The operation is performed under local or general anesthesia. The operative incision is smaller, and the postoperative recovery is faster, which is important for people who need to be ready for work as soon as possible. Complications that can occur are the same as with classic surgery, but they occur somewhat less often. Visual acuity several months after surgery does not differ from that achieved with extracapsular surgery. There are a large number of variants of this operation, so I will not describe it in detail here.
It is important to emphasize that after cataract surgery it is necessary to wear glasses. Sometimes they are needed for distance and proximity, and sometimes they are not needed for distance. This depends on the dioptric power of the built-in lens and on some of its other characteristics.
The goal of both surgeries is to remove the clouded eye lens affected by the cataract and implant an artificial one in its place. In exceptional circumstances, it is possible to install the lens in the front eye chamber. The lenses are made of artificial materials that are very stable and do not cause any eye problems. The lens is not felt, nor does the patient have to or can remove it from the eye. A well-fitted lens remains in the eye forever, and its position can only be changed by trauma to the eye.
Literature:
M.Sc. sc. Pavan Dr. Joško, “Eye Diseases”, Zagreb 2003.
