Cataract is an ocular disease where the lens becomes opaque, it may occur:
- A small local opacity,
- A widespread loss of transparency.
To be clinically significant, cataracts should cause a significant reduction in visual acuity.
Cataracts can occur in one or both eyes.
It can not be spread from one eye to the other.
What is the lens?
The lens is the transparent lens of the eye that helps focus the light or an image on the retina.
- The retina is the light sensitive tissue at the back of the eye.
- In a normal eye, the light reaches the retina passing through the clear lens.
- Once it reaches the retina, the light is translated into nerve signals that are sent to the brain.
- The lens should be clear for a sharp image that will be transmitted to the retina.
- If the lens is covered by cataracts, the image you see will be blurred.
Cataract is the most common cause of vision loss in people over 40 and is the leading cause of blindness in the world.
According to statistics, there are more cases of cataracts in the world in relation to:
Types of cataract
Acquired cataracts are associated with numerous genetic and environmental factors, some types of cataracts are:
1. Cataract related to age . As the name suggests, this type of cataract develops as a result of aging.
2. Secondary cataract . Cataract may form again after cataract surgery (relapse).
It is a complication in which the lens capsule becomes opaque.
3. Traumatic cataract . Cataracts can develop after an injury to the eye, sometimes after a few years.
4, Drug induced cataract . It can be caused by the use of cortisone and antipsychotics.
5. Cataract associated with diseases . Cataracts occur most often in people who suffer from:
- Diabetes mellitus (is one of the most frequent causes of juvenile cataract)
- Eye diseases
- Wilson’s disease
- Myotonic dystrophy
- Down Syndrome
- Atopic dermatitis
6. Radiation cataract. After exposure to certain types of radiation, cataracts may develop.
Some children are born with cataracts or develop it in childhood, often in both eyes. These cataracts may be so small that they do not affect vision, otherwise it may be necessary to remove the lens.
cataract This type of congenital cataract can be classified into two types:
1. Anterior polar cataract The anterior polar
cataract is bilateral and symmetrical in most cases. Generally, this type of cataract is small and not progressive, but is associated with other ocular anomalies. The previous polar cataract does not affect the vision and the person does not need treatment.
2. Polar posterior
cataract Normally, the posterior polar cataract is unilateral and large, and is near the center of the lens. This type of cataract generally affects the view because of its size and central position.
cataract This type of cataract has different forms:
1. Sutural Cataract
This type is also known as starry cataract.
These cataracts appear as longitudinal opacity of branching.
Typically, this type of cataract is bilateral and symmetrical. Generally, sutural cataract is hereditary.
This type of cataract does not affect vision and does not require treatment.
2. Zonular or lamellar cataract
This is the most common type of congenital cataract, is often bilateral, symmetrical and is characterized by the presence of opaque inner layers of the lens, alternating with transparent layers.
The lamellar cataract is progressive.
Sometimes this type of cataract is caused by exposure of the mother to a toxic material during pregnancy when the baby is developing.
Lamellar cataracts appear as a disk-shaped opacity with equal contours in both eyes in size and density.
3. Complete Cataract
In this type of cataract, all the fibers of the lens have opacity and therefore are not transparent. This cataract may be unilateral or bilateral.
Some cataracts may be partial or incomplete at birth, but usually become totals quickly or in a short period of time.
This cataract has a worse effect on sight among all types of congenital cataract.
Sort by location
The posterior subcapsular cataract occurs at the back of the lens.
People with diabetes or who take high doses of cortisone have a higher risk of developing subcapsular cataracts.
A nuclear cataract is usually associated with aging.
Nuclear cataract forms deep in the central (nucleus) area of the lens.
In more advanced forms, the lens may have different shades of color and the disease is a distinction between:
- White waterfall
- Brunescens Cataract
- Cataract nigra
The cortical cataract is characterized by white opacity similar to a wedge, which begins on the periphery of the lens and extends towards the center.
This type of cataract occurs in the cortical region of the lens, that is, the part of the lens around the nucleus.
Classification according to opacity of the crystalline nucleus
- Immature cataract : partially opaque crystalline, blurred vision.
- Mature or total cataract : completely opaque crystalline, total loss of sight .
- Hypermadura cataract (advanced stage): liquefied cortical matter.
- Morganian waterfall : the nucleus falls and is immersed in a milky liquid.
Risk factors for cataracts
The following factors may increase the chances of developing cataracts:
- Age ;
- Close relatives who have / had cataracts ( hereditarydisease );
- Depending on the diet of the blood group , milk and dairy products are the cause of cataracts.
- Exposure to ionizing radiation – Airplane pilots have a higher risk of nuclear cataract than others, this risk is associated with exposure to cosmic radiation;
- Statins – researchers at the University of Waterloo, Canada, reported in the journal “Optometry and Vision Science” that people taking statins have a greater risk of developing senile cataract;
- Prolonged exposure to sunlight ;
- Prolonged use of cortisone – many people with asthma often inhale steroids, such as people with chronic obstructive pulmonary disease;
A study conducted at the Center for Vision Research at the University of Sydney, Australia, showed that the risk of cataracts is higher for patients taking these medications.
- Eye diseases : Anterior inflammation of the eyes, lsion of the eye, high myopia, glaucoma, retinal detachment .
- Exposure to lead may increase the risk of developing cataracts, according to scientists at the National Institute of Environmental Health Sciences in the United States.
- Loss of α-crystallin function : a specific type of protein (alpha crystallin) begins to lose its function when the eye ages.
The loss of function of the alpha crystallin protein causes formation and acceleration of cataract formation in the eye.
Signs and symptoms of cataracts include:
- Blurred vision or blurred vision;
- Growing difficulty in night vision;
- Sensitivity to light ( photophobia ) and reflections;
- See “halos” around the lights;
- Loss of vision (advanced stage);
- Fading or yellowing of colors;
- Double vision in one eye.
First, blurred vision caused by cataracts can affect only a small part of the lens of the eye.
At this stage, there may be no loss of vision.
When the cataract increases, the view creates many clouds and the light that passes through the lens is distorted.
Complications of cataract
Blindness – if the cataract is not treated can lead to total loss of vision. Higher mortality rates – people over 50 years of age with cataracts and those aged 49 to 74 years with age-related macular degeneration, appear to have higher mortality rates by 11 years than those without visual impairment, according to with a study conducted by a team of researchers at the University of Sydney in Australia.
Diagnosis of senile cataract
Usually, the doctor or ophthalmologist will easily see a cataract when examining the eyes.
Sometimes a cataract is detected during a routine eye check, before the patient notices the vision disturbance.
The cataract is identified through a complete eye examination, which includes:
1. Measurement of visual acuity. This graphic test measures vision at different distances.
2. Examination of refraction . Test of refractive problems (myopia, astigmatism and farsightedness ).
3. Examination of the ocular fundus . The ophthalmologist puts a few drops in the eyes to enlarge or dilate the pupils.
The ophthalmologist uses a special magnifying glass to examine the retina and optic nerve, looking for signs of damage or other eye problems. After the examination, the near vision may be blurred for several hours.
4. Examination on the slit lamp . The slit lamp is an instrument made up of a microscope that emits a light. This examination allows the ophthalmologist to see the structures at the front of the eye.