Presbyopia is an age-related condition that results in the gradual loss of the ability to change the eye’s focus from distance to near. Most patients experience presbyopia around the age of 40-45, when near vision becomes more challenging. Most of us are familiar with the reading glasses that are available at supermarkets and pharmacies — these glasses are useful and provide focusing power that replaces the gradual loss of the eye’s natural focusing power.
Presbyopia is believed to be due to a progressive loss of elasticity of the lens inside the eye. Focusing, otherwise known as accommodation, is accomplished by the use of small muscles inside the eye called ciliary muscles. These muscles, when contracting, are believed to reduce the tension on tiny fibers inside the eye. Because these fibers suspend the lens, with reduced tension, the lens can change its shape when the ciliary muscles contract. As the eye’s natural lens loses its elasticity throughout one’s lifetime, the ability to focus at near distances decreases. Eventually, the natural lens hardens and yellows to the point where by age 75-85, most patients have developed a cataract.
Patients who are naturally nearsighted (eyeglass prescription begins with a minus sign) typically see more clearly at near than at distance. For this reason, some nearsighted patients adapt to presbyopia by simply removing their distance glasses. This does not work for all prescriptions, as without glasses, patients with large nearsighted corrections require that the reading material be held very closely to the eye, while smaller nearsighted corrections may not provide enough effect to overcome presbyopia and reading material may still remain blurry. Astigmatic patients often experience blurry vision at both distance and near, and farsighted patients (eyeglass prescription begins with a plus sign) typically will have worse near vision than distance vision.
So, what are the options to correct presbyopia?
The first and obvious option is the use of reading glasses or bifocals. However, most people find this option to be less desirable due to the intrusive nature of these appliances on one’s lifestyle and convenience. Many patients do not like the cosmetic appearance of bifocals, or the inconvenience of needing to locate a pair of reading glasses when reading a menu or cell phone screen.
Bifocal contacts lenses are an option, but these lenses can be difficult to fit, and adapting to these lenses is difficult for many patients due to decreased contrast in vision and difficulties in fitting the lenses. Many, if not most, patients experience a gradual reduction in tear production throughout life. This effect is particularly apparent for women around the age of menopause when the tear production begins to decrease more rapidly. Dryness of the eyes can be a reason why many patients become intolerant of contact lenses, leading many patients to seek alternatives such as laser vision correction.
Laser Vision Correction
Laser vision correction procedures are probably the most commonly selected surgical method to address blurry vision. These procedures are extremely effective in correcting refractive errors such as nearsightedness, farsightedness and astigmatism. They do not restore the natural elasticity of the lens in the eye, however, and cannot reverse the effects of aging. As a result, some patients who are older than age 40 will require reading glasses to see up close after LASIK or PRK (just as they would require reading glasses worn over their distance contact lenses prior to laser vision correction).
Options to address presbyopia with LASIK or PRK include a presbyopic correction, or monovision. Typically, one of two techniques is used: a multifocal corneal ablation to create a variable power in the cornea, similar to a multifocal contact lens; or, the treatment is adjusted to the non-dominant eye to leave the eye slightly nearsighted, thus providing additional help for seeing at focal points close up. These methods have been used successfully for many patients. However, as with any procedure, results may vary from person to person. Adaptation can be slow or difficult for some people. Patients who require excellent stereovision or depth perception may not be the best candidates for this procedure. A consultation with the staff at King LASIK can help you to assess if these options are suitable for you.
Corneal inlays are a newer option for the correction of presbyopia. In the United States, there are at least two corneal inlays that are undergoing investigations with the U.S. Food and Drug Administration. The idea is that implantation of a small disc in the cornea, under a laser-made corneal flap, can create a pinhole effect to increase the range of vision or depth of field. A pinhole can be used to partially (and approximately) correct nearsightedness because many of the peripherally scattered rays that are outside the pinhole are blocked. Many people who are nearsighted have noticed that squinting can improve the vision temporarily — this is an example of a pinhole effect. Like squinting, however, the use of corneal inlays will limit the number of rays that reach the fovea, and this may limit the patient’s perception of visual clarity, similar to how most patients would prefer their clear vision with glasses or contacts versus the clearer vision that is experienced when looking through a pinhole or with squinting.
The Kamra inlay (from AcuFocus) and the PresbyLens (from Revision optics) are two examples of corneal inlays that are undergoing investigation at this time. Previous versions of corneal inlays have not had great success due to biocompatibility issues, perhaps related to the thickness of the inlays and the depth of implantation. Corneal clouding, thinning and melting have been reported with the implantation of previous inlays, and this is probably due to the blockage by the inlay of the flow and diffusion of oxygen and nutrients through the cornea.
The Kamra inlay is made of opaque polyvinylidene fluoride and it has a 3.8 mm outer diameter and a 1.6 mm central hole or aperture. These inlays are 5 microns thick and they have thousands of small holes or perforations, which are designed to allow diffusion of nutrients through the cornea. These inlays are typically implanted in the patient’s non-dominant eye and the pinhole effect can be used to improve a patient’s depth of field. The small hole in the center of the inlay allows for a pinhole effect to partially correct the distance vision. Typically, these inlays are placed at a depth of 200 microns beneath the corneal surface. A femtosecond laser such as the Intralase IFS laser is used to create a pocket or flap for the placement of the corneal inlay. The inlay implant can be removed if patients do not like the visual outcome; however, this does require an additional procedure. Patients who wear glasses for distance will usually have LASIK performed for distance with implantation of the inlay implant following distance correction. Typically, LASIK is performed first, and the non-dominant eye correction is adjusted to provide a nearsighted correction to aid with near vision. The inlay is thought to provide a pinhole effect to aid the distance vision. However, in comparison, the use of the excimer laser alone, without the use (or expense) of the inlay is generally a very satisfactory outcome for many patients. Planning to leave the patient’s non-dominant eye at -0.75 D can provide some help with reading, even without the use of a corneal inlay. Prior to undergoing laser vision correction, the doctors at King LASIK can demonstrate monovision as a treatment for presbyopia, and we will help you evaluate which options are best for you.
The PresbyLens (also known as Vue+) is made by Revision Optics and this is also undergoing investigational trials at this time. This hydrogel lens has a 2mm diameter and it adds plus power to the central cornea, designed to help with one’s near vision. Like the Kamra inlay, it is placed in the non-dominant eye under a laser-made corneal flap which then covers the inlay.
Clear Lens Extraction
Another possible option for the correction of presbyopia is the complete removal of the eye’s natural lens, otherwise known as a clear lens extraction, followed by implantation of an intraocular lens. For patients in the pre-presbyopic age range (under age 45), this option is usually not preferred because removal of the eye’s natural lens means complete loss of accommodation. When the lens in the eye is removed, an intraocular lens is almost always placed.
For presbyopic patients who undergo cataract surgery, there are multiple options for intraocular lens implantation, ranging from a monofocal lens where clear distance vision is usually planned, to various multifocal lenses such as the Tecnis Multifocal, Restor lens or Crystalens. Each of these lenses has pros and cons; further information about them can be found elsewhere on our website and on the Internet. If you have cataracts, cataract surgery followed by implantation of either a monofocal or multifocal/accommodating lens can be a good option to reduce your dependence on reading glasses. However, some patients would prefer to have the clearest distance vision, and for that reason, they may select a monofocal lens with the use of reading glasses for near. A discussion with your cataract surgeon will help you to select the best lens for your needs. Removal of the eye’s natural lens is not the first choice for correcting vision and it is generally reserved for patients who are developing cataracts. Intraocular surgery has risks including intraocular infection and retinal detachment, and for this reason, we generally do not advise that patients undergo cataract or lens based surgery until they are developing cataracts.
Schedule a Consultation at King LASIK
There are multiple options for correcting presbyopia and there are other ideas in development. While these techniques may not restore the focusing power of the eye to that of a teenager, they may be of great help in reducing the need for reading glasses. When you come for your consultation at King LASIK, we will help you determine which vision correction options are best for you. Our goal is to help you to achieve your visual goals so that you may enjoy your lifestyle and everyday activities with the clearest vision possible.
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