The term “permanent contact lenses” refers to surgical solutions designed for long-term vision correction. These devices are a significant advancement over traditional external lenses that require daily maintenance and frequent replacement. Understanding the intended lifespan of these corrective implants is a primary concern for anyone considering the procedure. The durability of these internal lenses is dictated by their materials and interaction with the eye’s natural biology. This article explores their intended lifespan and the conditions that might necessitate a change.
Clarifying the Terminology
The phrase “permanent contact lenses” refers to two distinct categories of vision correction, one of which is not truly permanent. The first is the Extended Wear (EW) contact lens, a traditional soft lens placed on the eye’s surface. These lenses are approved for continuous use for seven to 30 days, including sleeping. However, they must be removed, cleaned, and replaced on a strict schedule to prevent infection, making them a temporary convenience.
The truly permanent solution is the Implantable Collamer Lens (ICL), which is a type of Phakic Intraocular Lens (PIOL). These are microscopically thin, corrective lenses that a surgeon places inside the eye, typically between the iris and the eye’s natural lens. Unlike EW lenses, ICLs are not worn on the surface and do not require daily handling or cleaning by the patient. The ICL is designed to remain in the eye indefinitely.
Expected Durability of Implantable Lenses
Modern Implantable Collamer Lenses are engineered to provide vision correction for the patient’s entire life. The lens material is not expected to degrade or break down over time within the eye’s aqueous environment. This long-term stability is primarily due to the proprietary material, Collamer, which is a unique blend of collagen and polymer.
Collamer is highly biocompatible, meaning the body does not recognize it as a foreign object, which prevents rejection or chronic inflammation. The lens remains clear and stable, resisting the clouding or deterioration that can affect other materials over decades. Clinical studies tracking patients for 20 years or more have consistently shown that the ICL maintains its clarity and corrective power.
The ICL does not “expire” like a traditional contact lens because it is protected inside the eye, away from environmental factors and repeated handling. Its durability is a result of its flexible, non-reactive composition. The lens is intended to function as a permanent fixture, with its longevity limited only by the natural aging processes of the eye itself.
Conditions Requiring Early Removal or Replacement
While the ICL is designed to be permanent, there are specific, practical scenarios in which it may need to be removed or exchanged. The most common medical reason for a secondary procedure relates to the initial fit, specifically the vault measurement. Vault refers to the distance between the implanted lens and the eye’s natural lens, a space that must be precisely maintained by the surgeon.
If the vault is too high, the ICL sits too close to the iris and can potentially increase intraocular pressure, raising the risk of angle-closure glaucoma. Conversely, a low vault means the ICL rests too close to the natural lens, which can interfere with nutrient flow and lead to the development of an anterior subcapsular cataract. In either case, incorrect vault sizing is the most frequent cause for a lens exchange, where the original ICL is replaced with one of a different size.
Another scenario for removal is the natural aging process of the eye, particularly the development of a cataract. Since ICLs are placed in front of the natural lens, they must be explanted before cataract surgery can be performed. The surgeon removes the ICL, then removes the eye’s now-cloudy natural lens, and finally replaces it with a new, permanent intraocular lens designed to correct both the cataract and the refractive error.
Less common indications for a lens exchange include a significant, unexpected change in the patient’s refractive error after the procedure or complications from ocular trauma. Since ICL implantation is performed after a patient’s prescription has stabilized, a major shift is rare but would necessitate replacement. The ability to safely remove the ICL without permanently altering the eye’s structure is a key feature that provides a safety net against these potential long-term changes.