The desire to complete a Halloween costume often leads people to purchase colored or special-effect contact lenses. These decorative lenses, also called costume or fashion contacts, change the eye’s appearance without correcting vision. They are safe only when treated with the same care and medical oversight as traditional vision-correcting lenses. Purchasing lenses without a prescription can lead to severe, sight-threatening complications.
Why Decorative Contacts Require a Prescription
The U.S. Food and Drug Administration (FDA) classifies all contact lenses, including purely decorative ones, as Class II medical devices. This regulatory status means that federal law requires all contact lenses to be dispensed only with a valid prescription from a licensed eye care professional. Any retailer selling these products over the counter or online without requiring prescription verification is doing so illegally.
A prescription is necessary not because of a need for vision correction, but to ensure the lens is physically compatible with the wearer’s eye. Every eye has a unique shape, and contact lenses are not a one-size-fits-all product. An eye doctor must measure the specific curvature of the cornea and the diameter of the eye to determine the correct lens parameters.
The prescription includes two measurements: the base curve (BC) and the diameter (DIA). The base curve defines the curvature of the back surface of the lens and must match the curvature of the cornea. The diameter determines the total width of the lens and how much of the eye’s surface it covers. A lens that is too flat, too steep, too large, or too small will rub against the cornea, causing discomfort and potentially damaging the surface tissue.
Common Eye Injuries from Improper Use
The most immediate risk from improperly fitted or unsanitary lenses is microbial keratitis, a serious and rapid infection of the cornea. These infections are primarily caused by bacteria, such as Pseudomonas or Staphylococci, but can also involve fungi like Fusarium or the parasitic amoeba Acanthamoeba. The contact lens itself traps microorganisms and debris against the cornea, compromising the eye’s natural defense mechanisms.
When a decorative lens is ill-fitting or poorly manufactured, it can cause a corneal abrasion, a scratch on the eye’s surface. This trauma acts as an entry point for pathogens, allowing them to penetrate the corneal tissue and multiply. Untreated infections can lead to a corneal ulcer, a painful, open sore that causes permanent scarring and irreversible vision loss within hours.
Another significant danger, particularly with cheap lenses, is corneal hypoxia, or oxygen deprivation. The cornea relies primarily on direct absorption from the air for its oxygen supply. A thick, low-quality lens material acts as a physical barrier, restricting the necessary flow of oxygen to the corneal cells. This lack of oxygen causes the cornea to swell (edema), which can lead to blurred vision. Prolonged hypoxia can trigger a non-reversible complication where new blood vessels grow into the clear cornea (neovascularization), permanently impairing vision.
Essential Safety Steps for Wearers
The first step for anyone considering decorative contacts is to schedule a comprehensive eye exam and fitting with an eye care professional. This visit ensures the lens is sized correctly for your unique corneal measurements, preventing mechanical damage from a poor fit. The eye doctor will also issue a valid prescription that specifies the exact brand, base curve, and diameter of the approved lens.
Once a prescription is secured, lenses should only be purchased from licensed retailers who require prescription verification before sale. This avoids the risk of obtaining counterfeit or non-sterile products often sold at novelty shops, street vendors, or unauthorized online sellers. Always ensure the lenses are FDA-cleared, as this confirms they meet manufacturing and material safety standards.
Strict hygiene protocols are mandatory every time the lenses are handled to prevent introducing pathogens to the eye. This includes washing hands thoroughly with soap and water and drying them with a lint-free towel before touching the lenses. Only fresh, sterile contact lens solution formulated for disinfection should be used for cleaning and storage; never use tap water, saliva, or expired solution.
Users must adhere to the prescribed wear and replacement schedule. Lenses should never be shared, as this transmits bacteria and introduces a non-fitted lens to a different eye shape. It is also imperative to remove lenses before sleeping, showering, or swimming. Sleeping in lenses dramatically increases the risk of hypoxia and infection, and water is a primary source of the Acanthamoeba parasite.