Contact lens wearers often panic when they mix up their left and right lenses. Since most people require a different prescription or fit for each eye, knowing which lens belongs where is necessary for clear vision and comfort. Understanding proper identification methods is important for maintaining eye health and ensuring you get the full benefit of your corrective lenses.
Primary Identification Methods
The easiest way to identify a lens is by checking the packaging or storage system before the lens is removed. Blister packs for disposable lenses are clearly marked with the correct eye designation, often using ‘OD’ for the right eye and ‘OS’ for the left eye. The packaging also indicates the specific power, measured in diopters, allowing you to match the lens to your prescription.
Reusable contact lens cases are typically molded with an ‘L’ and an ‘R’ on the respective sides. Some manufacturers also use color-coding to simplify the process. Consistently using these labeled compartments is the most reliable way to prevent a mix-up.
Physical Distinctions When Lenses Are Loose
If a lens is loose and its identity is uncertain, you must rely on physical properties to confirm its orientation. The most common check is the “Taco Test,” which determines if a soft lens is inverted or correctly oriented. To perform this, place the lens on your fingertip to form a cup shape, then gently fold it between your thumb and forefinger.
If the lens is correctly oriented, its edges will curl inward, resembling a taco shell. An inverted lens will resist the fold, and its edges will flare outward, looking like a saucer. Additionally, some manufacturers embed nearly invisible laser etchings, such as the numbers “123,” on the lens edge; these numbers read correctly when the lens is right-side out.
Consequences of Wearing the Wrong Lens
Inserting a lens intended for the other eye can lead to immediate visual disturbances. If the prescription power differs between your eyes, wearing the wrong lens results in blurred or distorted vision. This incorrect input forces the eyes and brain to compensate, often leading to eye strain, headaches, or fatigue.
Each lens is also fitted to the specific curvature of the eye, known as the base curve. If a lens designed for one eye’s curve is worn on the other, the slightly off fit causes discomfort. A poorly fitting lens may move excessively or, if too tight, impede the flow of tears beneath the lens. This can cause irritation, redness, and the feeling of having something in the eye.
Prevention Strategies for Future Use
Establishing a consistent routine is the best way to ensure lenses are always placed in the correct eye. A simple strategy is the “Right First” rule, where you consistently handle, clean, and insert the right lens before addressing the left. This habit minimizes the chance of accidental swapping.
Utilize clearly labeled or color-coded storage cases, and make it a practice to clean the right side of the case before the left during your routine. Replacing your contact lens case at least once every three months helps maintain hygiene and keeps the identification markings clear. If you hold a lens whose identity is genuinely unknown, and you cannot test the prescription by sight, it is safest to dispose of it and use a fresh lens.