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How the eye works • Light rays enter the eye through the clear cornea, pupil and lens. • These light rays are focused directly onto the retina, the light-sensitive tissue lining the back of the eye. • The retina converts light rays into impulses, sent through the optic nerve to your brain, where they are recognized as images. • 70% of the eye's focusing power comes from the cornea and 30% from the lens.
Refractive errors • Inability to see clearly is often caused by refractive error. • Four types of refractive error: • Myopia (nearsightedness) • Hyperopia (farsightedness) • Astigmatism • Presbyopia
Refractive errors: myopia • In myopia (nearsightedness), there is too much optical power in the eye • The distance between the cornea and the retina may be too long or the power of the cornea and the lens may be too strong. • Light rays focus in front of the retina instead of on it. • Close objects will look clear, but distant objects will appear blurred. Myopia, or nearsightedness
Refractive errors: hyperopia • In hyperopia (farsightedness), there is too little optical power. • The distance between the cornea and the retina may be too short. • Light rays are focused behind the retina instead of on it. • In adults (but not children), distant objects will look clear, but close objects will appear blurred. Hyperopia, or farsightedness
Refractive errors: astigmatism • In astigmatism, the cornea is curved unevenly—shaped more like a football than a basketball. • Light passing through the uneven cornea is focused in two or more locations. • Distant and close objects may appear blurry. Astigmatism occurs when light passes through football-shaped cornea and/or lens
Refractive errors: presbyopia • Presbyopia is an age-related condition in which your eyes gradually lose the ability to see things up close, because the lens of the aging eye can no longer change shape. • When we are young, the lens in our eyes is flexible and is able to change focus easily between near and far objects, like an autofocus on a camera. • At around age 40, this flexibility begins to gradually decrease, making it more difficult to see objects up close, unless the eye has nearsightedness.
What is accommodation? • The eye’s lens, which provides your focusing power, has four primary functions: • Transparency: To provide a clear medium through which light rays from an object can reach your retina. • Optical: To focus a sharp image of an object on the retina. • Anatomic: To create a functional barrier between the anterior and posterior segments of the eye. • Accommodation: To vary the eye’s refractive power, thus providing clear images of objects over a wide range of distances.
What is refractive surgery? • A group of outpatient surgical procedures used to alter how your eye focuses light rays on the retina, thereby improving vision and reducing dependence on glasses and contact lenses. • In most cases, refractive surgery affects the shape of your cornea to redirect how light is focused onto the retina. Popular procedures include LASIK, LASEK, PRK and CK. Refractive surgery procedure on the cornea
What is refractive surgery? • Most refractive surgery is performed on the cornea and affects only the front of your eye, while the rest of your eye will change naturally as you age. • In some cases, refractive surgery procedures don’t reshape the cornea; instead, the eye’s natural lens is either replaced or enhanced by an implantable lens that helps correct vision.
What are accommodative intraocular lenses (IOLs) and multifocal intraocular lenses (IOLs)? • An artificial lens that is surgically implanted in the eye, replacing the eye’s natural lens. • Enables your eye to regain its focusing and refractive ability. • The cornea is not reshaped. • Used to treat nearsightedness (myopia), farsightedness (hyperopia) and the inability to focus at near with age (presbyopia).
What is an accommodative intraocular lens (IOL)? • The accommodative IOL is hinged to work in coordination with the eye muscles. • The design allows the accommodative lens to move forward as the eye focuses on near objects, and move backward as it focuses on distant objects. A type of accommodative intraocular lens (IOL)
What is a multifocal IOL? • A multifocal lens has several rings of different powers built into the lens. • The part of the lens (ring) you look through will determine if you see clearly at a far, near or intermediate distance (this is sometimes called pseudo-accommodation). A type of multifocal intraocular lens (IOL)
How is the IOL procedure performed? • The IOL is implanted in a surgical procedure, performed on an outpatient basis under local anesthesia and taking approximately 20-30 minutes.
How is the IOL procedure performed? • In addition to a pre-operative eye exam, measurements of the eye are taken to give the surgeon the necessary information to perform the procedure. These measurements include: • Refractive error measurement. • Pupil evaluation and size measurement. • Keratometry: measurement of the form and curvature of the cornea. • A-scan: Measurement of the axial length of the eye from the cornea to the retina. • Calculations to determine the correct power of lens (IOL) to use. A phoropter is used to measure refractive errors
How is the IOL procedure performed? • After the eye is numbed with topical or local anesthesia, one to three small incisions are made close to the edge of the cornea. • After the procedure, these incisions are usually “self-sealing,” requiring no stitches. Small incisions are made close to the edge of the cornea for inserting the IOL
How is the IOL procedure performed? • A tiny, high-frequency ultrasound instrument is inserted into the eye to break up the center of the eye’s natural, crystalline lens. • The natural lens is then gently vacuumed out through one of the incisions. The eye’s natural lens is suctioned out through an incision
How is the IOL procedure performed? • An IOL is folded and inserted through the same incision that was used to extract the natural lens. • The IOL is then unfolded and placed into the "capsular bag" that originally surrounded the natural lens. IOL in the eye
How is the IOL procedure performed? • Once the accommodative or multifocal IOL is implanted, your eye can focus on near, intermediate and far distances. The IOL firmly in place
Considerations for the accommodative/multifocal IOL procedure • May be an option for people with cataracts or people without cataracts who are presbyopic and want to reduce or eliminate their need for glasses.
Considerations against the accommodative/multifocal IOL procedure • The focusing ability of the lens may not be fully realized for six to eight weeks after the procedure. • Your eye must re-learn how to focus on objects at various distances in order to see clearly.
Risks and possible side effects of accommodative/multifocal IOL surgery • Over-correction or under-correction (with a possible need for a re-treatment). • Infection. • Increased floaters or retinal detachment. • Dislocation of implant. • Loss of vision.
Is refractive surgery right for you? • Advanced surgical procedures, including accommodative and multifocal IOLs, are creating more opportunities for people who want to be less dependent on glasses or contacts. • Surgery may not entirely eliminate your need for corrective lenses. Glasses/contacts may still be needed for activities such as fine or detailed work, reading and perhaps night driving. • If an accommodating or multifocal IOL is used, then reading as well as distance vision may be improved.
Is refractive surgery right for you? • A large part of the success of any refractive surgery depends on your understanding of the procedure and your expectations. • Since refractive surgery is an elective procedure, you have the opportunity and responsibility to become fully informed about its risks and benefits. • Your ophthalmologist will explain the specific technique, its benefits, as well as possible risks and side effects associated with your case.
Discuss options and questions with your ophthalmologist • With the help of your ophthalmologist, it’s ultimately your responsibility to weigh the risks and side effects of a procedure with the benefits it has to offer. • If you decide refractive surgery is right for you, you may join millions of people who have reduced their dependence on glasses or contacts.