Wearing cosmetic or colored contact lenses is a popular way to change one’s appearance, but the process is complicated for individuals with astigmatism. The desire for a cosmetic effect must be balanced against the medical necessity of correcting their vision condition. Safety and proper fit are the primary considerations for anyone placing a medical device onto the sensitive surface of the eye. This requires understanding the eye’s shape, the regulatory framework, and the potential health consequences involved.
Understanding Astigmatism and Vision Correction
Astigmatism is a common condition resulting from an irregular shape in the eye’s cornea or lens. Instead of being perfectly spherical, like a baseball, the astigmatic eye is curved more like the side of a football, having two different curves or meridians. This irregular curvature causes light to focus at multiple points instead of a single one on the retina, making vision blurry or distorted at any distance.
Correcting this condition requires a specialized lens design known as a toric lens. A standard, spherical contact lens, including non-prescription colored lenses, has the same power across its entire surface. This design cannot accommodate the two different power requirements of an astigmatic eye. Toric lenses are engineered with different powers along two primary axes to properly focus light.
Toric lenses include a stabilization mechanism, often a thicker zone or ballast, designed to prevent rotation on the eye. If a non-toric lens is placed on an astigmatic eye, it spins freely with every blink, making any visual correction inconsistent. Therefore, a simple non-prescription contact lens, even a zero-power (plano) lens, will not provide clear vision for an individual with astigmatism.
The Legal Requirement for All Contact Lenses
By federal law, all contact lenses are classified as medical devices, regardless of whether they correct vision or are purely cosmetic. This classification applies even to colored or costume lenses that have zero refractive power (plano lenses). They must be dispensed only with a valid prescription from an eye care professional because the physical fit of the lens is as important as the optical power.
A contact lens prescription includes the spherical and cylindrical power, along with two physical measurements: the base curve and the diameter. The base curve determines how steeply the lens curves to match the cornea’s shape. The diameter specifies the overall size of the lens, and these measurements are determined during a professional contact lens fitting after a comprehensive eye exam.
If a lens is too flat, too steep, or the diameter is incorrect, it can cause severe complications by restricting the flow of tears or oxygen to the cornea. Purchasing a lens without a fitting means selecting a generic fit that may not match unique corneal dimensions. Even a plano lens requires a professional fitting to ensure the physical dimensions are compatible with the eye’s surface.
Visual Distortion and Physical Health Risks
Wearing a standard non-prescription lens over an astigmatic eye results in poor visual quality due to the design mismatch. The spherical lens shape will not align with the irregular curvature of the cornea. This leads to continued blurry vision, visual distortion, and an effect called ghosting. The lens will also feel unstable, spinning or moving excessively, which is distracting and degrades vision.
The physical health risks of wearing an improperly fitted contact lens are significant. A lens that is too tight can lead to corneal oxygen deprivation (hypoxia), causing swelling and compromising tissue. Conversely, a lens that is too loose can move excessively and cause a painful corneal abrasion, which is a scratch on the delicate surface of the eye.
The most serious risk is the potential for severe eye infections, such as microbial keratitis, caused by bacteria, fungi, or amoebas. Lenses purchased from unverified sources and worn without professional instruction on hygiene significantly increase the chance of infection. These infections can rapidly lead to corneal ulceration, intense pain, and permanent vision loss if not treated immediately.
Safe Paths to Cosmetic Contact Lenses
People with astigmatism can safely wear colored or cosmetic contact lenses, but they must use a product specifically designed for their condition. The solution is obtaining a prescription for colored toric lenses. These lenses combine the necessary power correction and rotational stability with the desired cosmetic tint, and are custom-made to address the unique cylindrical power and axis of the astigmatism.
The process must begin with a comprehensive eye examination and a contact lens fitting conducted by an eye care professional. This evaluation ensures the eye is healthy and provides the exact measurements for the base curve, diameter, and specific toric power required. Securing a prescription for a colored toric lens ensures both the cosmetic outcome and the medical integrity of the fit, minimizing serious health risks.