Current Course Topic:
Cataracts. According to the World Health Organization, they affect an estimated 20 million people worldwide!
A cataract is a cloudy or opaque region of the normally transparent lens in the eye.
The lens is located behind the colored part of the eye, which is called the iris. It consists of three parts: the capsule, the cortex and the nucleus. The capsule is the outer membrane that surrounds the cortex, which then surrounds the center of the lens-its nucleus. It is similar to a peanut M&M, where the colorful shell is the capsule, the chocolate is the cortex and the peanut is the nucleus.
Just like there are three regions of the lens, there are three types of cataracts.
The most common clouding of the lens occurs in the nucleus. Typically this nuclear cataract is found in older people. The lens gradually grows cloudy as the person ages. When the opaque area increases, it prevents light rays from passing through the lens to focus on the retina, the light sensitive tissue at the back of the eye. Typically the person experiences blurred vision, glare, increased nearsightedness, and distortion of images that they see in either eye. The longer we live, the more likely we are to develop cataracts. Over 60% of people whose visual acuity is less than 20/400 (WHO definition of blindness) have age-related cataracts.
| Healthy Eye | Eye with a Cataract |
|---|---|
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Since we look at objects that are located at different distances, we need to adjust in order to see all of them clearly. The lens is able to stretch and thicken in order to make this adjustment and allow us to see. Sometimes even when the lens doesn't have a cataract, the person's vision is blurry when looking at things that are either close or very far away. In such a case, an eye doctor (ophthalmologist) prescribes eyeglasses to help correct the problem. The eyeglasses have a lens similar to the one in our eyes, except that it's plastic and isn't able to change
I need to tell you about the other two types of cataracts. There is also a cortical cataract that affects the lens cortex (remember, the chocolate part of an M&M). These opacities originate on the outside edges of the lens and seem like wedge-shaped spokes of a bicycle. When they gradually extend toward the center of the lens, they interfere with the path of light and significantly effect both near and distance vision. People who have diabetes tend to develop these types of cataracts.
Finally, subcapsular cataracts start to develop as small opacities at the back of the lens. They are also associated with diabetes. They start to affect vision when they have grown quite significantly. Sometimes when people have to use drops like corticosteroids in their eyes to treat inflammation, the active ingredient in these drops can cause the proteins to become cloudy.
You're right, there are some other known causes of cataracts. Although age is a significant factor, they are also caused by injuries like inadvertently hitting the eye. Someone can be born with cataracts or acquire them when they are exposed to damaging sunrays or certain chemicals.
Traumatic cataracts are caused by being hit in the eye. Getting something stuck in the eye is a very terrible thing. In those cases, the cataract forms in the back of the cortex and leads to progressive loss of vision. When a sharp object punctures the eye and comes in contact with the lens capsule, the lens totally opacifies either immediately or at some later time.
Babies born with cataracts have what is called congenital cataracts. They occur most often when the mom has some sort of infection, like rubella, or sometimes other family members also have cataracts and the baby gets them because of a genetic link.
The environment plays a key role in cataract formation. The lens is made up of protein, a substance that is configured in a way to be completely clear. It's necessary for this protein to be clear in order for us to see through it. Sun emits high-energy light rays, called ultraviolet rays, that cause the lens protein to stop being clear. Some chemicals in the environment may be able to reach through the outer layers of the eye and can affect those lens proteins, also causing them to become opaque. These types of cataracts are called "induced" cataracts.
Diet might also have something to do with cataracts. There is not much information as to how diet and cataracts relate, but vitamin deficiencies, for example, could contribute to cataracts.
We CAN treat cataract blindness. The sight is restored to the eye by a surgery that removes the cloudy lens. What's more important is that cataracts that are due to environmental factors are preventable!
Part of the answer lies in the fact that modern cataract techniques are used very frequently in developed countries. The patients can afford the surgery there. For instance the United States government alone spends 3.4 billion dollars on approximately 1.35 million surgeries every year.
I know, but the story is worse in developing countries. There usually isn't direct access to an ophthalmologist and the cataracts typically progress to the "absolute cataract" stage where the pupil glows a "pearly white," instead of being black. At this point the individual's vision is reduced to seeing only hand motions or just being able to tell light from dark. These patients will not be able to go for screening unaided, and typically would have been blind for quite a time prior to being seen. These people are truly blind and need our help.
I am very hopeful, however. Let me tell you a story that makes me think that we could help all of the people out there with treatable blindness!
There is this woman, Nilima. She is very old and has lived with her son and his wife in a one-room hut on a remote Tibetan plateau. For the past 5 years she has been unable to work to help her family. She is blind in both eyes. Ten years ago, she had to move in with her son because she couldn't provide for herself. Going to market for provisions, she would come back weary and bruised. The mountain passes became treacherous and the once hour-long walk to the next valley took a day of near crawling to avoid the obstacles that seemed to crop up out of nowhere. She had burned her fingers misjudging the distance to the fire and had to stop helping with the cooking. Her deteriorating vision made her dizzy and confused. Finally she became reduced to staying in the corner of the room in hopes of staying out of way of bustle of daily living. She had to be fed and be led outside, fully relying on her son and daughter-in-law and their two children. In the mountainous regions every person is vital for survival of the family, therefore Nilima's family can do little to help her during the day. No one in their village has ever heard of a name or cure for this blindness, but there are at least one hundred more people that suffer, both children and adults, out of a village of 300 people.
Yes, you're right, but Nilima doesn't know that yet. Besides, what could be done with them in such a remote region? About a month ago, a traveling physician's assistant came to the village and asked everyone to bring out their ill relatives, those that have been blind. Nilima's eldest grandson came back from work and helped her meet the newcomer just outside their door. There, the assistant shined light in her eye and determined that she can be cured from the depths of her closed world by a new surgery. He saw the dense ivory-white of her lens and said that a surgeon can remove the hard as stone lens that is blocking her vision. He told her that an old school house that is shared with their neighboring village has been set up as the place for the surgeons to do their work. The family immediately decided to see if this procedure could help Nilima. Nilima's son carried her on his back to the place of the surgery.
…After a day of travel, the patients were all assembled at the school and prepared for the night. They had to bring their own sheets since there is nowhere for them to stay. While Nilima and the other people from her village anxiously awaited the arrival of the doctors who would perform their miracles, the physician's assistant asked them and their relatives about the histories of their blindness. Most everyone in the region reported to have been blind for over three years. Several explained that they were literally struck blind in an unfortunate accident while working to repair a bridge across a rushing river; they had fallen on the shaky rocks and hit their eyes in the process. No one owned sunglasses, and they wear brimmed hats only on special occasions. I must note that the life expectancy of a blind person is less than half that of a sighted person. And in the mountainous regions it is less than three years if the person has to survive on their own.
The next day the doctors finally arrived, having trekked from a regional ophthalmology center. Nilima was prepared for surgery by having iodine swabbed around her left eye, her eyelashes were also cut to prevent post-operative infection. She will undergo another cataract surgery to help her see from her right eye a day later. Her eye was numbed and she is given drops to dilate the pupil and stabilize the pressure in the eye to help the surgery go smoothly. The doctor used a microscope to help the delicate surgery. The doctor makes a cut at the junction of the cornea and sclera….
The cornea is the clear part in the front of the eye and the sclera is the white tough outer coat of the eye.
After the initial cut at the junction of the cornea and sclera, the surgeon made a circular cut in the anterior (front) part of the capsule. He then removed the cataractous lens like a peanut from the M & M-like lens capsule. Placing a clear plastic intraocular lens into the capsule completed the surgery. This lens will from now on function to focus light properly at the back of the eye. The whole surgery takes about 7 minutes. Within 7-8 hours, the surgeons operate on the cataracts of all of Nilima's neighbors as well. At the conclusion of each surgery, a patch was placed over the eye and the patient taken to wait in the post-operative section of this schoolhouse.
Ah, they can see immediately, but the patches are important to let the eye start to heal. There was an incision after all… In Nilima's case the next morning started a day of joy. As physicians were taking off the patches, the patients and their relatives witnessed the power of surgical miracle. Nilima was able to see her family for the first time in five years; another patient saw his first sky since developing cataracts as an infant!
Yes, the basis of the surgery is the same. The conditions of the surgery are a little different. Instead of an operating room and bulky equipment, the doctors can use portable microscopes in carefully disinfected locations, such as our schoolroom. Doctors Geoffrey Tabin and Sanduk Ruit developed the actual technique that cured Nilima. They call it the high volume extracapsular cataract extraction with intraocular lens implantation and teach it to local doctors in their camps in the Himalayas. Their goal is to eliminate the backlog of treatable blindness in the region. The project is part of Vision 2020 initiative.
Yes, this procedure has proven to be extremely effective for treating cataracts in remote settings, time and time again. After the patients receive surgery on their second eyes, they are carefully instructed about caring for their eyes while the incisions are healing. Within a week they should be able to fully function in their communities.
For instance, from the schoolhouse, Nilima walked proudly and on her own. She brought home sunglasses for her family to protect their eyes from harmful penetrating sunrays.