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Retinal Implant: Give Light for Blind

Blindness is inability to see, or lacking visual perception due to physiological or neurological factors. In the context of eye disease, total blindness is same as death, since it means the eye doesn't have any function as sense organ.

Blindness is frequently used to describe severe visual impairment with residual vision. Those described as having only light perception have no more sight than the ability to tell light from dark and the general direction of a light source.

There are lot of causes for blindness, some are reversible, while others are irreversible. Most of irreversible cases are related to retinal problems, such Age-related Macular Degeneration, Retinitis Pigmentosa, Diabetic Retinopathy, etc.

Scientists have already seen this retinal blindness as a problem to solve. To help people to have light or vision. With recent technologies and knowledges, we are entering the era of tissue replacement either with sophisticated tools or new engineered tissues.

Retinal Implant
This is a new technology, that have been researched for quite long period. In sense organ, cochlear implant or other hearing aids for patient have been introduced already. But, retinal implant still in development.

German doctors announced a breakthrough in retinal implants, the fledgling technology that aims to restore sight in people cursed by a form of inherited blindness.

Over the past seven years, Ocular surgeons have pioneered electronic implants that are attached to the retina and are linked by wire to a small external camera that is mounted to a pair of spectacles. The camera picks up light and sends the image in the form of an electrical signal, via a processor unit, to the implant. The implant then feeds the data to the optic nerve which leads from the eyeball to the brain.

Latest innovation is subretinal device, a kind of implant that takes a step forward by capturing light that travels naturally through the eye's lens. Correctly known as a sub-retinal implant, it entails a microchip comprising some 1,500 light sensors that are attached underneath the retina, thus replacing some of the lost receptors.

What the brain receives through the optic nerve is a tiny image comprising 38 pixels by 40 pixels -- points of light that are each brighter or dimmer according to the light that falls on the chip. Three patients fitted with the new device were able to see shapes and objects, and one was able to walk around a room by himself, approach people, read a clock face and distinguish between seven shades of gray.

It could eventually revolutionize the lives of up to 200,000 people worldwide who suffer from blindness as a result of retinitis pigmentosa. Retinitis pigmentosa is a degenerative disease in which light receptors in the retina, on the back of the eyeball, gradually cease to function.

A subretinal implant -- sits underneath the retina, directly replacing light receptors lost in retinal degeneration. It uses the eyes' natural image processing capabilities beyond the light detection stage to produce a visual perception in the patient that is stable and follows their eye movements. Other types of retinal implants -- known as epiretinal implants -- sit outside the retina and because they bypass the intact light-sensitive structures in the eyes they require the user to wear an external camera and processor unit.

Current situation
Clinical reports to date have demonstrated mixed success, with all patients report at least some sensation of light from the electrodes, and a smaller proportion gaining more detailed visual function, such as identifying patterns of light and dark areas.

The clinical reports indicate that retinal implants are potentially useful in providing crude vision to individuals who otherwise would not have any visual sensation. It remains unclear whether the low level vision provided by current retinal implants is sufficient to balance the risks associated with the surgical procedure, especially for subjects with intact peripheral vision.

Other aspects of retinal implants need to be addressed in future research, including the long term stability of the implants and the possibility of retinal neuron plasticity in response to prolonged stimulation.

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May 4th 2012 @ 10:15

Posted By: yulius hermanto - Category: Novel Technology, Eyes Problems

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Surgery for Cataract

Cataract or clouding of lens, causes blurred vision, and if severe enough could lead to blindness. Cataract has become world leading cause of blindness especially in underdeveloped nations. Thus cataract has significant on human health issues, especially related to the eyes.

Most of the cataract related to aging process, with the development of our science and technology in medicine, thus will increase the amount of elderly population. Thus will increase the burden of cataract patients. Besides that, sedentary lifestyle that occurs nowadays also brings health complication such as diabetes mellitus. Diabetes also become a risk factor the development of early cataract.

Well, in conclusion that amount of cataract patients are gonna raise, because the increase amount of elderly population and lifestyle associated disease such as diabetes.

Eventhough cataract has the greatest burden in number of patients but cataract is curable cause of blindness compare to the others causes such as glaucoma, macular degeneration, diabetic retinopathy, etc.

Treatment of Cataract
I already described about the pathophysiology of cataract in my previous article that the process of cataract development is lens protein clumping that being caused by lot mechanisms.

Scientists have found a lot of mechanisms that lead to cataracts, but until now the only effective method of cataract is by surgery.

Cataract surgery is very successful in restoring vision. In fact, it is the most frequently performed surgery in the United States, with more than 3 million Americans undergoing cataract surgery each year. Nine out of 10 people who have cataract surgery regain very good vision, somewhere between 20/20 and 20/40.

Although surgery is the only remedy for cataracts, it is almost never an emergency. Most cataracts cause no problem other than reducing a person's ability to see, so there is no harm in delaying surgery.

Early cataracts may be managed with the following measures:
- Stronger eyeglasses or contact lenses
- Use of a magnifying glass during reading
- Strong lighting
- Medication that dilates the pupil. (This may help some people with capsular cataracts, although glare can be a problem with this treatment.)

Some cataracts develop to a certain point and then stop. Even if a cataract does progress, it may be years before it interferes with vision. Very rarely do people need immediate cataract surgery.

Indications for Cataract Eye Surgery
In general, surgery is indicated for people with cataracts under the following circumstances:
The Snellen eye test reports 20/40 or worse, with a cataract being responsible for vision loss that cannot be corrected by glasses.
Performing everyday activities has become difficult to perform to the point that independence is threatened, or the patient is at risk for accident or injury.

Cataract Eye Surgery

However, whether surgical treatment is appropriate or not further depends on the patient's specific condition and needs. Some examples include:
Even if the criteria for surgery are met, a very sick, elderly person in a nursing home may have less need for sharp vision than an active younger adult. Among very elderly patients (85 years and older), especially those with serious health problems, there are also higher risks for complications during surgery and poor outcomes afterward. Nevertheless, these cautions should not prevent the elderly from having this procedure; vision improvement rates are still over 85%.

Even if the criteria for surgery are not met, some people with eye tests of 20/40 or better might want surgery because of problems with glare, double vision, or the need to have an unrestricted driver's license.
Even if the criteria for surgery are not met, if retinal disease is also suspected, the doctor may perform cataract surgery in order to have a clear view of the eye. Because of the risks, albeit small ones, of poorer vision or blindness, no one should be forced to have cataract surgery if they don't want it or are not strong enough to have the procedure.

Treatment Decisions for Cataracts in the Second Eye. If a person has a cataract in a second eye, the issues for decision making are the same as for the first eye. The timing of the procedure in the case of two cataracts is unclear. Doctors have long recommended postponing surgery on the second eye until the first eye has healed and the results are known. However, many patients have trouble reading and performing ordinary tasks while waiting for a second surgery. Patients with double cataracts should discuss all options with their surgeon.

Cataract Surgical Procedures
All cataract procedures involve removal of the cataract-affected lens and could be continue to replace it with an artificial lens or not, it's depends on the patient's eye conditions.

Phacoemulsification
Phacoemulsification (phaco means lens; emulsification means to liquefy) is the most common cataract procedure performed in the United States.

The procedure generally involves:
- The surgeon makes a small incision usually 3 mm.
- A thin probe that transmits ultrasound is then used to break up the clouded lens into small fragments.
- The tiny pieces are sucked out with a vacuum-like device.
- A replacement lens is then inserted into the capsular bag where the natural lens used to be.
In most cases, this is an intraocular lens (IOL), which is foldable and slips in through the tiny incision.

Because the incision is so small, it is often watertight and does not require a suture afterward, particularly if a foldable lens has been used. A suture may be needed if a tear or break occurs during the procedure or the surgeon inserts a rigid lens that requires a wider incision.

Phacoemulsification requires only local anesthesia. Newer methods for administering local anesthesia produce few complications. Most phacoemulsification procedures now take about 15 minutes, and the patient is usually out of the operating room in about an hour. There is little discomfort afterward, and visual rehabilitation takes about 1 - 3 weeks.

Phacoemulsification is sometimes combined with glaucoma surgical procedures, for patients who have both glaucoma and cataracts.

Extracapsular or Intracapsular Cataract Extraction
Extracapsular cataract extraction, the original standard procedure, is now generally used only in patients who have an extremely hard lens. It typically involves the following steps:
- The ophthalmologist works under an operating microscope to make a small incision in the cornea of the eye.
- The surgeon then extracts the clouded lens through this incision.
- The capsule is left in place, which adds structural strength to the eye and enhances the healing process. (Less commonly in intracapsular cataract extraction, the surgeon removes the lens and the entire capsule. This procedure has greater risks for swelling and retinal detachment.)
- A replacement lens is then usually inserted.
- A small suture is needed to stitch the incision together.
It takes about 2 - 4 weeks to completely restore vision.

Intraocular Lens Replacement
Before the invention of IOLs, cataract patients were treated by lens extraction and using glasses, but the power of glasses in very high known as aphakic glasses. Most of the patients having discomfort using those glasses, because there are side effects of using glasses with high dioptri.

Intraocular Lens

Nowadays, in about 90% of cataract operations, an artificial lens, known as an intraocular lens (IOLs), is inserted. Most IOLs are made out of acrylic, although other materials, such as silicon, are also used.

IOLs are designed to improve specific aspects of vision. The choices include:
1. Lenses that address a single fixed focal point. Such lenses are suitable either for reading or distance vision, but not both. If a distance lens is implanted, the surgeon prescribes glasses or contact lenses for reading. If a reading lens is implanted, lenses for seeing distances will be prescribed.

2. Lenses that address multifocal points. Multifocal lenses can focus at different points for both reading and distance vision. However, contrast may be reduced, and some patients experience glare and halos, particularly at night.

3. Lenses are available that will correct astigmatism after cataract surgery.

Complications of Cataract Surgery
Modern cataract surgery is one of the safest of all surgical procedures. Most complications, even if they occur, are not serious. They can include:

Swelling and inflammation. Risk is about 1%. This complication is particularly harmful for patients with existing uveitis (chronic inflammation in the eye, which can be due to various medical conditions).

Glare. Patients may experience glare after surgery from light scattering at the edges of the new lens, particularly with square-edged IOLs, which are typically used with posterior capsular cataracts. In most cases, this is a temporary problem that resolves after a few weeks.

Materials used in some lenses trigger an immune response in some patients. This causes inflammation and tiny deposits of tissue in the eye that lead to secondary cataracts -- called posterior capsule opacification.

Retinal detachment. In rare cases, the retina at the rear of the eye can become detached. Risk is very low (0.1%), and phacoemulsification poses less of a risk for this than older standard surgery.

Glaucoma. This is an eye condition in which the pressure of fluids inside the eye rises dangerously. Risk is very low, but patients should be sure to avoid activities after surgery that increase pressure.

Infection. This is very rare (0.2%) but may be significant if it does develop.
Blisters on the cornea.

Bleeding can develop inside the eye. Risk is about 1% for minor bleeding and 1 in 10,000 for severe bleeding.

An implanted IOL can become damaged or dislocated. Risk is very low.

The surgery itself can produce vision loss or impairment. The risk for this is 1 in 1,000. (Phacoemulsification poses less of a risk than standard surgery.)

Conclusion
Cataracts is curable cause of blindness, the only effective method for treatment of cataracts is surgery. There are several procedures in cataract surgery, it should choose depends on patient's conditions.

The timing of cataract surgery is the greatest concern, because most of the cataract isn't emergency cases. The important consideration is the visual improvement related to daily activities.

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August 8th 2011 @ 12:53

Posted By: yulius hermanto - Category: Novel Technology, Eyes Problems

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Refractive Eye Surgery

Introduction
Blurred vision is common complaint that seen in eye clinics. There are a lot of cause of blurred vision, one of them is refraction abnormality.
Refractive disease of the eye is the most common cause of blurred vision in mankind. In United States about 120 millions have refraction abnormality.

The good news is that refraction abnormality can be corrected with the usage eyeglasses or contact lens. Refractive surgery is used to correct common eye disorders such as nearsightedness, farsightedness, and astigmatism. Refractive surgery is designed to alter the shape of the cornea in order to improve the patient's vision. Since the development of refractive eye surgery, the technique has been widely used and modified with the invention of technology.

Laser Eye Surgery

History of Refractive Eye Surgery
The first refractive eye surgeries probably were done in ancient Greece. These ancient eye surgeries involved removal of cataract (clouding of the lens in the eye). In the 1850s, the first refractive lensectomy (removal of the lens of the eye for purposes of correcting high myopia) were performed. In the late 19th century, the first corneal surgery for correction of astigmatism was performed. Astigmatism was reduced with a horizontal incision in the corneal stroma.

Modern day ophthalmic surgeons have been performing refractive surgery for the treatment of myopia (nearsightedness), hyperopia (farsightedness), and astigmatism (irregular shaped cornea) for many years, but the past decades have produced rapid change and growth by means of refined techniques and the emergence of laser vision surgery.

In 1978 a refractive procedure called radial keratotomy (RK) was introduced in the United States. RK involves making a number of cuts in the cornea to change its shape and correct refractive errors. Following the introduction of RK, doctors routinely corrected nearsightedness, farsightedness, and astigmatism, using various applications of incisions on the cornea.

In the 1980s a new type of laser, called the excimer laser, was developed. Though originally used to etch computer chips, ophthalmologists began using the excimer laser successfully in refractive surgery techniques to remove very precise amounts of tissue from the eye's surface. Excimer lasers revolutionized refractive surgery by providing a degree of safety and precision that was previously unattainable with other techniques. Nearly all lasers used today are excimer lasers.

The first generation lasers were called "broad beam lasers." The results were satisfactory and still today a small number are used. Later, scanning lasers were developed where a small spot or strip of laser beam rapidly scans the cornea.

Photorefractive Keratectomy
Like other types of refractive surgery, the goal of Photorefractive Keratectomy (PRK) is to reshape the cornea so that light traveling through it is properly focused onto the retina located in the back of the eye.

A numbing drop will be placed in your eye, the area around your eye will be cleaned, and an instrument called a lid speculum will be used to hold your eyelids open. Using one of several techniques, the central epithelium is removed. An excimer laser, which delivers a pulsing beam of ultraviolet light, is then used to reshape the stroma. The procedure takes about 10 minutes for both eyes. In a relatively short time after the procedure, usually three to four days, the epithelium will heal over the exposed area.

The outcome of PRK is quite good, since it is highly accurate in correcting many cases of refractive error. It has been estimated that approximately 80% of patients have 20/20 vision without glasses or contact lenses one year after the surgery; 95 - 98% have 20/40 vision or better without glasses or contacts.

People with myopia, or nearsightedness, with or without astigmatism, and those with moderate amounts of hyperopia, or farsightedness, with or without astigmatism, are potential candidates for PRK.

Many patients experience some discomfort in the first 24 to 48 hours after PRK surgery, and almost all experience sensitivity to light. Other side effects may include: Dry eyes, Infection, Glare, Seeing halos around images. These are most noticeable when you're viewing lights at night, such as while you're driving.
While longer term side effects that may occur such as: loss of best vision achieved with glasses, seeing a minor glare which can be permanent, mild halos around images, dry eyes.

LASIK
The acronym LASIK stands for Laser-Assisted In Situ Keratomileusis, and is a procedure that permanently changes the shape of the cornea using an excimer laser. The goal of LASIK is to reshape the cornea, or the clear front part of the eye, so that light traveling through it is properly focused onto the retina.

People with myopia, or nearsightedness, with or without astigmatism, and those with moderate amounts of hyperopia, or farsightedness, with or without astigmatism, are potential candidates for LASIK.

Some patients experience discomfort in the first 24-48 hours after LASIK surgery. Other side effects may include: dry eyes, glare, seeing halos around images. These are most noticeable when you're viewing lights at night, such as while you're driving.

LASIK Procedures

The FDA has found that LASIK is generally safe and effective, although there are some risks to the procedure. These risks may include: Corrections can only be made by additional LASIK surgeries. LASIK is technically complex. Problems may occur when the doctor cuts the flap, for example the flap can become unhinged or the microkeratome can potentially cut too deep. These problems can adversely, and permanently, affect the patient's vision.
The eye may hemorrhage due to the pressure from the suction ring.
The flap can dislodge following trauma, even years after the procedure.
LASIK is more likely to cause a loss of "best" vision with or without glasses at one year after surgery. Your best vision is the highest degree of vision that you have achieved wearing your contact lenses or eyeglasses.

Differences Between PRK and LASIK
The primary difference between PRK and LASIK refractive surgery is that in LASIK, the vision correction occurs under an epithelial flap, while in PRK, the vision correction is performed on the surface of the cornea after the epithelium has been removed. The epithelial cells then heal during the following three to four days, in order to cover the cornea.

Many providers believe that LASIK offers numerous advantages over refractive vision correction performed on the cornea's surface (PRK). There is often a more rapid improvement in vision and decreased discomfort with LASIK, since the surface epithelial cells have been preserved and do not need to heal or regrow. However, there are additional risks associated with the LASIK procedure.

In some patients, PRK is a safer alternative that may promise better outcomes. Patients who might benefit from PRK include those in whom the cornea might be too thin for LASIK, or in some patients with corneal irregularities or scars. Occupational demands may also make PRK a better option because flaps created during LASIK can easily be lifted, even years after surgery.

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July 24th 2011 @ 03:29

Posted By: yulius hermanto - Category: Novel Technology, Eyes Problems

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