Refractive surgery for
Refractive surgery is performed to correct refractive errors such as nearsightedness (myopia), farsightedness (hyperopia) and astigmatism. This kind of treatment serves as an alternative to glasses and contact lenses. The intention of refractive surgery is to produce emmetropia (normal eyesight). In cases where patients still require corrective lenses, the correction is minimal. There is usually no need to resort to glasses or contact lenses.
Within certain limits, all three so-called refractive errors can be treated with cornea laser surgery or lens implantations. However, the prognosis for visual acuity is also dependent on other factors such as retinal damage or congenital amblyopia. Higher correction levels can be achieved with lenses than with corrective laser surgery on the cornea. Moreover, the lens method is a reversible process; it can be undone at any time. In contrast, the laser method is irreversible because the removal of tissue is permanent.
Implantation of phakic lenses
This method involves the implantation of an artificial lens, which compensates for the refractive error in the same way that a contact lens would. These lenses are called pseudo phak lenses because the natural lens (Greek: phakos) remains in place within the eye. The artificial lens is placed either in front of the iris (artisan lens) or between the iris and the natural lens (ICL – Intraocular Collamer Lens). The main consideration for or against the implantation of such a lens is how much space is naturally available in the anterior eye segment. These conditions should be evaluated precisely, using modern instruments, before surgery.
Necessary conditions for the implantation of an additional lens into the eye
The decisive factor for the implantation is whether or not there is enough depth in the anterior chamber. This is usually the case with short-sighted (myopic) eyes because they are generally longer than “normal” eyes, automatically providing greater anterior chamber depth. Hence, the anatomical requirements are fulfilled in over 90% of all myopia cases. In the case of far-sighted (hyperopic) eyes, the opposite is true. Far-sighted eyes are tighter and shorter than “normal” eyes. Fulfillment of the necessary anatomical conditions for lens implantation is much less common with hyperopic eyes (only about 50% of all cases).
Correction of presbyopia
The natural lens is removed and replaced with an artificial lens, as is the case with cataracts. Bifocal lenses are available for these cases. These lenses boast alternating near and distance zones, which are arranged in concentric circles. Furthermore, these lenses generate “stray light” and reduce contrast sensitivity, especially in dim light. However, some patients may perceive small rings of light or halos around some sources of light (e.g. headlights) at night. These minor disadvantages are usually inconsequential, measured against the ability to see clearly without glasses. A high percentage of subjective satisfaction can be achieved (in over 90% of all cases) as a result of a precise preliminary examination and meticulous determination of the conditions. At less than 2%, the risk of having to replace such a lens due to intolerance is well within a tolerable threshold.