Presbyopia, the loss of ability to see objects clearly at near distance, is a medical condition that everyone will experience at some point in their lives. It is a fairly predictable phenomenon of aging and is due to the gradual and progressive hardening of the lens, which is accompanied by a decrease in length and strength of the ciliary muscle. This muscle plays a central role in the process of accommodation, which is responsible for the normal changes in the optical power of the eye that enables us to see objects clearly as distance varies.
Persons with presbyopia may first notice that they hold objects further away from their eyes than their usual reading distance. This tendency may be associated with signs and symptoms, such as headaches and blurred vision, which are worse in dim light and when tired. The diagnosis may be ascertained with a comprehensive eye examination that consists of a series of tests to evaluate the functioning of the retina, visual field, acuity, refraction and muscle integrity.
Nonsurgical treatment for those without other eye problems is simply adopting the wearing of suitable reading glasses. More complicated cases (i.e. patients with existing problems of vision) may require specialized eyeglasses, such as bi- or tri-focal glasses or progressive lenses. For aesthetic, convenience or other reasons, some persons may prefer to use contact lenses, which are either mono- or multi-focal, depending on desire and necessity. Surgery is an option for those persons who cannot or would rather not use contact lenses or wear glasses. There are a number of options to choose from, including refractive surgery, corneal inlays and lens implants.
Refractive surgery is performed to change the shape of the cornea in such a way that near vision is improved after the procedure. The result of this surgery is mono-vision and it is done with the help of a laser, which reshapes the cornea slightly differently in each eye. In one eye, it is reshaped to allow for near vision and in the other eye it is reshaped for far vision.
This surgery is basically the same as wearing a mono-vision contact lens, with the exception being the patient no longer has to manually place contact lenses into the eyes. Thus, it is generally suggested that patients try mono-vision lenses, before undergoing the more permanent procedure of refractive surgery. This allows the patient to determine whether or not they would be comfortable with mono-vision. With mono-vision it takes some time for the brain to adapt to the new artificial way of seeing objects clearly.
Corneal inlay treatment is the insertion of minute plastic rings at the corneal edge to alter its curvature or the index of refraction or the depth of the focus. This procedure, unlike refractive surgery, is reversible in that the plastic rings may be removed at any time. Moreover, it is associated with fewer side effects and risks in comparison to the other surgical options for the treatment of presbyopia. There are three main types of inlay. These are refractive optic inlays, corneal reshaping inlays and small aperture inlays, which function as suggested in their appellations.
In this surgery, the natural lens is removed and it is replaced with a synthetic lens. There are many different types of implants that may be used to correct presbyopia. However, they are not capable of fully restoring near-vision quality. In fact, they may even decrease the quality of vision, and therefore there may still be a need for eyeglasses when performing near vision tasks. Additionally, the surgery is associated with risks, such as increased intraocular pressure, infection and inflammation.