Contact lenses provide a convenient and effective way to correct vision, but wearers often face the difficulty of distinguishing between the right and left lens. Placing the correct lens on the correct eye is necessary for achieving clear vision and maintaining ocular comfort throughout the day. Understanding the specific methods for identification is therefore an important part of daily lens wear.
Initial Identification Through Packaging and Prescription Details
The most reliable method for ensuring correct lens placement begins before the blister pack is even opened. All contact lens packaging is clearly marked to indicate the intended eye. The letter ‘R’ denotes the right eye, and ‘L’ specifies the left eye, making the initial segregation straightforward.
Ophthalmologists and optometrists also use standardized Latin abbreviations on prescriptions and packaging to designate the eyes. The abbreviation “OD” stands for oculus dexter, which refers to the right eye, while “OS” represents oculus sinister, indicating the left eye. These markings ensure that the correct optical correction is consistently applied according to the professional’s direction.
Wearers should cross-reference the power, or diopter (D), listed on the packaging with the specific prescription provided by their eye care professional. This power is the numerical value that defines the lens’s strength and is the primary difference between the two lenses for many users. Before inserting a new lens, confirming that the diopter on the blister pack matches the prescribed strength for that specific eye is the most direct way to avoid a mix-up.
Physical Identification Methods for Unlabeled Lenses
Once lenses are removed from their original packaging and placed into a storage case, identification can become more challenging. Fortunately, many manufacturers incorporate subtle physical markings to help wearers orient and identify the lens correctly. A common technique involves a tiny laser-etched marker, often the sequence “123,” embedded into the lens material near the edge.
To locate this marker, the lens should be placed on the tip of a finger and held up to a bright light source. When the lens is correctly oriented and not inside-out, the numbers “123” should be clearly readable from the outside, similar to reading a clock face. If the numbers appear backward, the lens is likely inside-out and needs to be flipped before insertion to ensure proper fit and comfort on the eye.
For individuals with a significant difference in prescription between their eyes, known as anisometropia, the lenses might also exhibit a slight visual difference. Lenses with a much higher minus power that corrects for nearsightedness are often slightly thicker at the edges compared to those with a lower power. However, this method of visually distinguishing thickness or curvature is unreliable for small power differences and should not be depended upon as a primary identifier.
Consequences of Wearing the Wrong Lens
Accurate lens placement is not simply a matter of convenience; it directly affects visual health and comfort. The immediate effect of wearing the wrong prescription is typically blurred vision, as the eye is not receiving the precise optical correction it requires to focus light onto the retina. This incorrect focus forces the eye muscles to work harder in an attempt to compensate for the disparity.
This overcompensation commonly leads to symptoms such as eye strain, fatigue, and persistent headaches throughout the day. Over time, consistently wearing the wrong prescription can contribute to worsening visual acuity and general eye discomfort that compromises the quality of vision. While rare, extended periods of incorrect correction in children or teenagers whose visual systems are still developing could potentially interfere with normal visual development.
Developing Consistent Habits for Storage and Insertion
The most effective way to prevent future mix-ups is to establish a strict, repeatable routine for handling lenses during insertion and removal. This routine should involve always starting with the same eye, such as always inserting the right lens first in the morning. Similarly, the removal process at the end of the day should also consistently begin with the right lens to maintain the segregation protocol.
It is important to use a properly designated contact lens case that features clear ‘R’ and ‘L’ markings on the respective wells. When cleaning and storing lenses, the wearer should fully complete the cleaning, rinsing, and storage of the first lens before moving to the second. This prevents the possibility of setting down one lens or accidentally placing it into the wrong side of the case while distracted.