Ophthalmology
Keratoplasty is the procedure whereby abnormal corneal tissue is replaced by a healthy donor cornea.
The eyes A close up of a young person's eyes. The eyes are responsible for four-fifths of all the information our brain receives. Here you can find out a bit more about how they work, common problems that affect vision and the work Sightsavers does to treat and prevent avoidable blindness. You can also find out more about the people whose lives have been changed thanks to donations from people like you. How do eyes work? (click image to see enlarged version or click here for text alternative) Graphic of an eye with information about its different parts The images we see are made up of light reflected from the objects we look at. This light enters the eye through the cornea. Because this part of the eye is curved, it bends the light, creating an upside down image on the retina (this is eventually put the right way up by the brain). The retina is a complex part of the eye, but only the very back of it is light sensitive. This part of the retina has roughly the area of a 10p coin, and is packed with photosensitive cells called rods and cones. Cones are the cells responsible for daylight vision. There are three kinds – each responding to a different wavelength of light: red, green and blue. The cones allow us to see images in colour and detail. Rods are responsible for night vision. They are sensitive to light but not to colour. In darkness, the cones do not function at all. How do we see an image? The lens focuses the image. It can do this because it is adjustable – using muscles to change shape and help us focus on objects at different distances. The automatic focusing of the lens is a reflex response and is not controlled by the brain. Once the image is clearly focused on the sensitive part of the retina, energy in the light that makes up that image creates an electrical signal. Nerve impulses can then carry information about that image to the brain through the optic nerve.
In cataract surgery, the lens inside your eye that has become cloudy is removed and replaced with an artificial lens (called an intraocular lens, or IOL) to restore clear vision. The procedure typically is performed on an outpatient basis and does not require an overnight stay in a hospital or other care facility.
When foreign organisms such as bacteria enter the body, the immune system sends white blood cells to fight the infection. This causes swelling (inflammation) at the site of infection and the death of nearby tissue, creating a hole called a cavity, which fills with pus to form an abscess.
Cosmetic iris implants have not been evaluated by any U.S. regulatory agency or tested for safety in clinical trials. While the implants are not approved by the U.S. Food and Drug Administration, it has been reported in the media this month that the surgery is being performed overseas. During iris implant surgery, an artificial iris made of silicone is folded and inserted into a slit that has been cut into the cornea. Then the iris is unfolded and adjusted to cover the natural iris. Local anesthesia is used.
The cornea occupies the front center part of the outer wall of the eye. It is made of collagen fibers in a very special arrangement so that the cornea is clear. One looks through the cornea to see the iris and pupil. The cornea bends light coming into the eye so that it is focused on the retina.
Diabetic retinopathy (die-uh-BET-ik ret-ih-NOP-uh-thee) is a diabetes complication that affects eyes. It's caused by damage to the blood vessels of the light-sensitive tissue at the back of the eye (retina). At first, diabetic retinopathy may cause no symptoms or only mild vision problems. Eventually, it can cause blindness. The condition can develop in anyone who has type 1 or type 2 diabetes. The longer you have diabetes and the less controlled your blood sugar is, the more likely you are to develop this eye complication.
A chalazion is a lump of the lid that is caused by obstruction of the drainage duct of an oil gland within the upper or lower eyelid. This lump may increase in size over days to weeks and may occasionally become red, warm, or painful.
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Red eyes usually are caused by allergy, eye fatigue, over-wearing contact lenses or common eye infections such as pink eye (conjunctivitis). However, redness of the eye sometimes can signal a more serious eye condition or disease, such as uveitis or glaucoma.
Keratitis is an inflammation of the cornea — the clear, dome-shaped tissue on the front of your eye that covers the pupil and iris. Keratitis is sometimes caused by an infection involving bacteria, viruses, fungi or parasites. Noninfectious keratitis can be caused by a minor injury, wearing your contact lenses too long or other noninfectious diseases. If you have eye redness or other symptoms of keratitis, make an appointment to see your doctor. With prompt attention, mild to moderate cases of keratitis can usually be effectively treated without loss of vision. If left untreated, or if an infection is severe, keratitis can lead to serious complications that may permanently damage your vision.
Pink eye (conjunctivitis) is an inflammation or infection of the transparent membrane (conjunctiva) that lines your eyelid and covers the white part of your eyeball. When small blood vessels in the conjunctiva become inflamed, they're more visible. This is what causes the whites of your eyes to appear reddish or pink. Pink eye is commonly caused by a bacterial or viral infection or an allergic reaction. It may affect one or both eyes. Pink eye can be irritating, but it rarely affects your vision. Treatments can help ease the discomfort of pink eye. Because pink eye can be contagious, early diagnosis and treatment can help limit its spread.
Less than a decade ago, corneal transplantation took a big leap forward with the introduction of Descemet’s stripping endothelial keratoplasty (DSEK), which removes only Descemet’s membrane and the diseased endothelium and replaces them with a thin, tripartite donor graft of posterior corneal stroma, Descemet’s membrane, and healthy endothelium. Then came DSAEK, in which the donor graft is prepared with an automated microkeratome, allowing for easier donor preparation and reproducible results by surgeons and eye bank technicians.1 DSAEK has proved to have many advantages over penetrating keratoplasty (PK) and its endothelial predecessors (see “A Brief History of Endothelial Keratoplasty”). Now DSAEK is being compared with a newer technique, Descemet’s membrane endothelial keratoplasty (DMEK), which has emerged as a promising alternative—grafting only Descemet’s membrane and endothelium, allowing for a pure anatomical replacement of only what was removed and the possibility of even better vision with quicker healing.1 Although indications for these procedures are similar, each has unique benefits and drawbacks. Five cornea surgeons offer their perspectives on the procedures and their thoughts on whether it may be time to move to the newer surgery.
A cornea transplant, also called keratoplasty, is a surgical procedure to replace part of your cornea with corneal tissue from a donor. Your cornea is the transparent, dome-shaped surface of your eye that accounts for a large part of your eye's focusing power. A cornea transplant can restore vision, reduce pain and improve the appearance of a damaged or diseased cornea. Most cornea transplant procedures are successful. But cornea transplant carries a small risk of complications, such as rejection of the donor cornea.
LASIK, which stands for laser in-situ keratomileusis, is a popular surgery used to correct vision in people who are nearsighted, farsighted, or have astigmatism. All laser vision correction surgeries work by reshaping the cornea, the clear front part of the eye, so that light traveling through it is properly focused onto the retina located in the back of the eye. LASIK is one of a number of different surgical techniques used to reshape the cornea.
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