What are phakic lenses?
- What do they treat?
- Can they be removed?
- What is the difference between phakic intraocular lenses and intraocular lenses following cataract surgery?
- Anatomy of the Eye
- How Phakic Lenses Work
Phakic intraocular lenses, or phakic lenses, are lenses made of plastic or silicone that are implanted into the eye permanently to reduce a person's need for glasses or contact lenses. Phakic refers to the fact that the lens is implanted into the eye without removing the eye's natural lens. During phakic lens implantation surgery, a small incision is made in the front of the eye. The phakic lens is inserted through the incision and placed just in front of or just behind the iris.
For more details on phakic lens implantation surgery, go to Before, During and After Surgery.
What do they treat?
Phakic lenses are used to correct refractive errors, errors in the eye's focusing power. All phakic lenses approved by the FDA are for the correction of nearsightedness (myopia).
The cornea and natural lens of the eye focus light to create an image on the retina, much like the way the lens of a camera focuses light to create an image on film. The bending and focusing of light is also known as refraction. Imperfections in the focusing power of the eye, called refractive errors, cause images on the retina to be out of focus or blurred.
People who are nearsighted have more difficulty seeing distant objects than near objects. For these people, the images of distant objects come to focus in front of the retina instead of on the retina.
Ideally, phakic lenses cause light entering the eye to be focused on the retina providing clear distance vision without the aid of glasses or contact lenses.
Surgery is not required to correct nearsightedness. You can wear glasses or contact lenses instead to correct your vision. Depending on how nearsighted you are, and other conditions of your eye, other refractive surgery (surgery to correct refractive errors) options may be available to you, including PRK (Photorefractive Keratectomy) and LASIK (Laser Assisted In-Situ Keratomileusis).
Can they be removed?
Phakic lenses are intended to be permanent. While the lenses can be surgically removed, return to your previous level of vision or condition of your eye cannot be guaranteed.
What is the difference between phakic intraocular lenses and intraocular lenses following cataract surgery?
Phakic intraocular lenses are implanted in the eye without removing the natural lens. This is in contrast to intraocular lenses that are implanted into eyes after the eye's cloudy natural lens (cataract) has been removed during cataract surgery.
Anatomy of the Eye
The first part of the anatomy of the eye animated illustration shows an external side view of the eyeball with the parts labeled. The sclera, cornea, iris, pupil, and optic nerve are identified. The second part of the illustration shows an internal side view with the eye cut in half from front to back. It identifies the sclera, cornea, anterior chamber, iris, pupil, posterior chamber, natural lens, retina, and optic nerve.
How Phakic Lenses Work
The illustration of how phakic lenses work shows the side view of eye as if you cut it in half from front to back and you were looking at the inside. It shows light rays from a stop sign being focused by the cornea and lens onto the retina of an eye that needs no vision correction. It depicts the clear retinal image of the stop sign being sent to the brain by the optic nerve. When light rays come into focus on the retina, we see the object clearly.
The image of the same stop sign is focused in front of the retina in a nearsighted (myopic) eye. The light rays from the stop sign that fall onto the retina are out of focus creating a blurred image. The blurred retinal image is sent to the brain by the optic nerve. When light rays do not come into focus on the retina, we see the object as blurred.
The inset image shows the clear retinal image of the stop sign being sent to the brain by the optic nerve. This is the idealized results of the phakic lens bending light from the stop sign to redirect the focused image onto the retina. When light rays are redirected by the phakic lens onto the retina, the nearsighted eye sees distant objects more clearly.