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E-Articles - Facts About Photorefractive Keratectomy (PRK)
Here are five facts about PRK. To understand them, we first need some background information.
Not everybody is a good candidate for traditional LASIK surgery. Over the past decade or so several good LASIK variations have been developed so that more people can benefit from refractive surgery.
All the LASI
Not everybody is a good candidate for traditional LASIK surgery. Over the past decade or so several good LASIK variations have been developed so that more people can benefit from refractive surgery.
All the LASI
According to USFDA, a combination product is one composed of any combination of a drug and device; biological product and device; drug and biological product
K variations are known as refractive surgery. Refraction is the bending of light rays by a lens of some type. In our eyes we have a lens that bends light rays as they enter our eye. We also have the cornea, which acts as a lens and bends those light rays even more than the lens does. In fact, it does 75% o
; or drug, device, and biological product and fixed dose combination would include two or more combinations of drug.
Examples of combination products may in
Examples of combination products may in
the bending.
What is the cornea?
It’s the clear part in the front of the eye, through which we can see a person’s eye color and pupil. It has a curved shape, so that when light rays enter it, they are bent at an angle, which varies according to two factors:
· The exact curvature of the cornea
What is the cornea?
It’s the clear part in the front of the eye, through which we can see a person’s eye color and pupil. It has a curved shape, so that when light rays enter it, they are bent at an angle, which varies according to two factors:
· The exact curvature of the cornea
lude drug-coated devices, drugs packaged with delivery devices in medical kits, and drugs and devices packaged separately but intended to be used together.
· The distance from which the light rays have traveled to the eye. Light from far objects is bent less than light from near objects.
All types of LASIK surgery increase visual clarity by correcting the curvature of the cornea. When a cornea is too steep, it bends light rays too much, so that instead of fo
All types of LASIK surgery increase visual clarity by correcting the curvature of the cornea. When a cornea is too steep, it bends light rays too much, so that instead of fo
here is enormous increase in the number of combination products entering the market in the recent years. Combination products have proven advantages but fixe
using on the retina, they focus in front of it (nearsightedness). When a cornea is too flat, it bends light too little, causing those rays to focus behind the retina (farsightedness).
What is the retina?
It’s the inside back surface of the eye, with light-sensitive cells, and special cells that pick
What is the retina?
It’s the inside back surface of the eye, with light-sensitive cells, and special cells that pick
d dose combinations are still in the process of convincing regulatory authority on their advantages over the single ingredient formulations.
Combination pro
Combination pro
up color. The eye’s main nerve, the optic nerve, connects to the retina, receiving neural information from it about images brought by the light rays. The optic nerve carries this information to the brain, which interprets it, finds a name for it, and presto! We know we’re looking at a woolly sheep and not
ucts have become life saving products for the pharmaceutical companies who doesn’t have many innovative molecules in their product pipeline and have been inc
dog or baby deer. In a normal eye, that woolly sheep is very clear and can’t be mistaken for a dog or deer. In a nearsighted or astigmatic eye it might look so blurry that it could be a dog or deer. In a farsighted eye, it might be perfectly clear if it’s the right distance away for your individual degree
easingly used in the product life cycle management. Even the companies having product patents are trying to extend their product life cycle through the combi
of farsightedness. But if it approaches you, it will become increasingly blurry.
Correcting the cornea
In a LASIK treatment, the laser is focused with extraordinary precision on particular tiny spots on the cornea. The exact spots, their number, and the depth to which they’ll be treated, are determi
Correcting the cornea
In a LASIK treatment, the laser is focused with extraordinary precision on particular tiny spots on the cornea. The exact spots, their number, and the depth to which they’ll be treated, are determi
nation products and maximize the revenues. But the companies involved in this practice are overlooking that they are burdening the patients both economically
ed by your LASIK surgeon beforehand, in a well-thought-out treatment plan for your particular eyes. The laser vaporizes these tiny spots, changing the curvature of the cornea.
The cornea has layers and the surface layer, the epithelium, is soft and fast-growing. Beneath it is the stroma, which does not re
The cornea has layers and the surface layer, the epithelium, is soft and fast-growing. Beneath it is the stroma, which does not re
and physically. They need to rightly judge the benefits of the combination products and they have to even look at the risks involved when combining the produ
grow, and this is where the LASIK treatment is done. That means that somehow, some epithelial cells need to be removed to give the laser access to the stroma. In traditional LASIK, this is done by first cutting a thin flap of surface tissue and bending it back while treatment is done, then replacing it. Th
ts. Some of the combination products were well accepted by physicians while others suffered. Companies involved in development of combination products are fi
s flap is about as thin as the width of a human hair.
PRK Fact #1: No flap is created.
Instead, a laser (or sometimes a surgical tool and certain chemicals) is used to vaporize a thin layer of epithelial cells. Now the surgeon can treat the stroma underneath, reshaping the cornea according to your treatm
PRK Fact #1: No flap is created.
Instead, a laser (or sometimes a surgical tool and certain chemicals) is used to vaporize a thin layer of epithelial cells. Now the surgeon can treat the stroma underneath, reshaping the cornea according to your treatm
ding difficulty in defining their combination products and facing various challenges from selecting a combination to marketing it.
Following aspects would a
Following aspects would a
ent plan. Afterwards, he places a bandage contact lens over the treated area, instead of replacing any flap. Both methods give protection to the stromal layer as the cornea heals its surface layer.
PRK Fact #2: PRK is a good method for people with extra thin or steep corneas.
Cutting a flap on the surfac
PRK Fact #2: PRK is a good method for people with extra thin or steep corneas.
Cutting a flap on the surfac
dd to the challenges in developing combination products:
Which markets to tap where the combination products can do fairly well?
Which combination prod
Which markets to tap where the combination products can do fairly well?
Which combination prod
of an eye that has an average corneal thickness is not problematical, although of course it must be done very carefully and precisely. If your cornea is extra thin, that will disqualify you for traditional LASIK, but not for PRK, since no flap will be cut at all. If your cornea is extra steep, that increa
cts are meaningful and rational?
Which therapeutic categories to select?
Which Combinations can address unmet needs of the patients?
Do combin
Which therapeutic categories to select?
Which Combinations can address unmet needs of the patients?
Do combin
sed curvature increases the risk of cutting a flap incorrectly, perhaps with a hole in the middle, or cut too deeply. This also disqualifies you for traditional LASIK, but not for PRK.
PRK Fact #3: The corneal epithelium will regrow in a matter of days.
The surgeon has removed those surface cells permane
PRK Fact #3: The corneal epithelium will regrow in a matter of days.
The surgeon has removed those surface cells permane
tions increase the patient compliance?
What would be the developing cost?
How to tackle the risks encountered during combination product developmen
What would be the developing cost?
How to tackle the risks encountered during combination product developmen
tly, but the cornea will replace them. This takes five or six days, during which time you need to wear that bandage contact lens for protection.
PRK Fact #4: Recovery time is longer than for traditional LASIK.
When a flap is created, folded back, and then replaced, it’s the eye’s own tissue, and heals up
PRK Fact #4: Recovery time is longer than for traditional LASIK.
When a flap is created, folded back, and then replaced, it’s the eye’s own tissue, and heals up
t?
As combination products don't fit into the traditional categories of drugs, medical devices, or biological products, the USFDA is in the process of devel
As combination products don't fit into the traditional categories of drugs, medical devices, or biological products, the USFDA is in the process of devel
very quickly indeed. When the cornea must create new epithelial cells to replace lost ones, it takes longer. A traditional LASIK patient does not need to wear any bandage contact lens, because the flap acts as a bandage. A PRK patient needs to use good self-care after the procedure for perhaps two weeks,
ping new procedures for reviewing their safety, efficacy and quality.
Professional from academic institutions, pharmaceutical industries, health care indust
Professional from academic institutions, pharmaceutical industries, health care indust
nd sometimes a month or so, as the eyes completely heal.
The eyes may be a bit watery, sensitive to light, and sore, as if there’s an eyelash or something in there. A prescription painkiller takes care of any discomfort, and as long as you refrain from rubbing your eyes, doing too much reading or computer
The eyes may be a bit watery, sensitive to light, and sore, as if there’s an eyelash or something in there. A prescription painkiller takes care of any discomfort, and as long as you refrain from rubbing your eyes, doing too much reading or computer
y and representatives from various regulatory agencies are working out to design the regulatory requirements for manufacture and sale of combination products
work, or getting too little sleep, recovery will be over in a matter of weeks and you’ll have a lifetime of clear vision ahead of you.
PRK Fact #5: The results are typically astounding.
If you have been near- or far-sighted all your life, or astigmatic, and have used glasses or contact lenses for years,
PRK Fact #5: The results are typically astounding.
If you have been near- or far-sighted all your life, or astigmatic, and have used glasses or contact lenses for years,
.
As there is an increasing trend of the combination products companies manufacturing such products should be able to tackle the problems involved in the de
As there is an increasing trend of the combination products companies manufacturing such products should be able to tackle the problems involved in the de
you’ll be ecstatic at your new clear vision! You’ll see a lot of improvement as soon as the bandage contact lenses are removed, and even more as the next few weeks go by.
At Griffin and Reed Eye Care in the Sacramento area, California, the work of improving people’s vision remains perpetually exciting. Th
At Griffin and Reed Eye Care in the Sacramento area, California, the work of improving people’s vision remains perpetually exciting. Th
elopment. They need to be wiser in analyzing the market trends and the regulatory requirements.
Companies that provide selfless information through particip
Companies that provide selfless information through particip
eir patients are more than pleased: they’re amazed and grateful, and many of them give testimonials, such as this one:
A miracle! One of the best decisions of my life. Griffin & Reed Eye Care's staff was extremely considerate and kind and made it the best medical experience I have ever had.
- Cheri K
A miracle! One of the best decisions of my life. Griffin & Reed Eye Care's staff was extremely considerate and kind and made it the best medical experience I have ever had.
- Cheri K
tion in industry events and feedback to regulatory authorities would be able to face the challenges and will be successful in developing combination products
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