PHAKIC INTRAOCULAR LENS (“Implantable Contact Lens”)
This technology uses an implant placed inside the eye to correct levels of nearsightedness or farsightedness outside the range of LASIK. Although phakic IOL technology gives outstanding visual quality, the risk of this surgery is higher than that of LASIK since this procedure actually involves entering inside the eye, unlike LASIK. The Staar Visian Implantable Collamer Lens and the the Verisyse lens (formerly called the Artisan lens) are examples of phakic IOLs, or “implantable contact lenses. Phakic intraocular lenses at this point are not capable of incorporating wavefront technology.
Bioptics is the technique of combining LASIK or PRK with the phakic IOL (implantable contact lens) for additive correction. Because LASIK or PRK work at the surface of the cornea and the phakic IOL works inside the eye, bioptics allows treatment beyond the range of either approach individually.
CK (Conductive Keratoplasty)
Used to treat farsightedness, CK works by inserting fine needles into the peripheral cornea which emit radio waves to shrink the corneal collagen. In this way, a “purse-string” effect is used to constrict the peripheral cornea, which, in turn, steepens the central cornea to correct farsightedness. Although CK has an excellent safety profile, it does not treat astigmatism and can, in fact, create astigmatism. Also, the results of CK tend to be temporary. Dr. Shapiro generally prefers LASIK over CK for correcting farsightedness.
LTK (Laser Thermal Keratoplasty)
LTK treats farsightedness by the same peripheral constriction strategy that CK uses, but creates this constriction with holmium laser pulses rather than radio waves.
The corneal inlay is placed under a LASIK-type flap or inside a corneal “pocket” made with a femtosecond laser, without the use of excimer laser sculpting of the corneal shape. Although past research has explored the use of corneal inlays to treat high ranges of farsightedness and nearsightedness, corneal inlays today are seen as best being used to treat presbyopia, the age-related inability to see up close. The only presbyopia correcting corneal inlay currently approved by the FDA is the Kamra by Accufocus. It involves placing a very thin synthetic membrane under a LASIK flap or in a corneal pocket created with a femtosecond laser. It has a very small aperature in its center which dramatically expands the “depth of field” (the range of focus). In this way, it uses “small aperature” optics to give both good near and far vision. It is placed in the non-dominant eye. It is expected that two other presbyopia correcting corneal inlays will also soon be approved by the FDA: the Raindrop by ReVision Optics and the Presbia Flexivue Microlens.
RK/AK (Radial Keratotomy/Astigmatic Keratotomy)
These procedures use microscopic incisions to reshape the corneal tissue to correct nearsightedness and astigmatism.
ALK (Automated Lamellar Keratoplasy)
Essentially a mechanical form of LASIK, this is the procedure upon which LASIK is based. With ALK, a similar flap is created and the underlying tissue is sculpted mechanically rather than with a laser. ALK, in one form or another of its evolution, has been around since the 1940s.
Two C-shaped rings (Intacs) are placed in the peripheral cornea to change its shape. Originally, Intacs were developed as a reversible way to correct nearsightedness, but the accuracy of the results were not as good as LASIK or PRK. Intacs eventually found a good role in treating a genetic corneal disease called “keratoconus,” which is its primary use today. Because corneas with keratoconus are mechanically weaker than normal, insertion of Intacs can buttress the tissue and give it new strength while also improving its optical shape.
CLEAR LENS EXTRACTION/REFRACTIVE LENS EXCHANGE
A cataract is a clouding of the lens in the eye (which sits deep inside the eye, behind the pupil). Cataract surgery involves removing the cloudy lens and replacing it with a plastic lens called the “implant.” The patient’s correction can be placed in the implant, allowing the patient to achieve vision without glasses after cataract surgery. Some types of lenses even correct for presbyopia as well.
Cataract surgery can be performed on patients without cataracts. This is called “clear lens extraction” since the lens that is removed is clear and healthy – not cloudy. Since the goal of clear lens extraction is to put an implant in the eye which corrects the vision in an alternative procedure to LASIK or PRK, clear lens extraction is also called “refractive lens exchange.” In Dr. Shapiro’s opinion, clear lens extraction or refractive lens exchange should be reserved for patients who are not candidates for laser vision correction. Because this is intraocular surgery, the risks involved are higher than those associated with LASIK or PRK.
Multifocal lenses are implants used in cataract surgery or clear lens extraction to replace the natural lens (see above). They allow patients to see near and far simultaneously, decreasing or eliminating the need for reading glasses. Multifocal lenses, however, achieve this by making an “optical compromise.” With these lenses, some light rays focus for near and some light rays focus for far, meaning that there is no pure focus anywhere. Some patients notice a decrease in night vision and contrast resolution, but many say this is a worthwhile trade off to gain the ability to see both near and far without glasses at an age that reading glasses would otherwise be required. ReStor, ReZoom, and the Technis Multifocal are all examples of multifocal lenses.
Intracor is a procedure which uses the femtosecond laser to make circular disruptions in the cornea which start below the corneal surface and end above the bottom layer of the cornea. The goal is to weaken the cornea within the treated zone to allow it to bow forward to correct reading vision in patients with presbyopia (the age related loss of reading ability).
Supracor involves using an excimer laser to create an aspheric shape in the center of the cornea to expand the range of focus and aid in correction of presbyopia.
PresbyLASIK involves using an excimer laser to create a complex shape in which part of the cornea focuses for distance and part of the cornea focuses for close. This allows correction of presbyopia. Although there have been some very successful outcomes with PresbyLASIK, the results have not been uniformly as good as hoped for. PresbyLASIK is not currently approved by the FDA.
SCLERAL EXPANSION SURGERY
Scleral expansion surgery is based on the theory that expanding the outer wall of the eye by placing bands in it, we can create more room for the lens to move inside the eye and correct or delay presbyopia. Results have been mixed to date, but there is great promise to this procedure.