Leaving contact lenses or their solution inside a hot vehicle is a common mistake that can seriously compromise eye health. The interior of a car exposed to direct sunlight can quickly reach temperatures far exceeding manufacturer recommendations for lens storage. Understanding the physical and chemical changes that heat causes to contact lenses and their care products is important for preventing discomfort, injury, and potential infection. This issue involves the integrity of a medical device placed directly onto the eye.
High Temperatures and Contact Lens Safety
The answer to whether contact lenses can be left in a hot car is clear: they should never be stored in such a high-heat environment. Manufacturers and health regulatory bodies require lenses to be stored within specific temperature parameters, typically at stable room temperature, which is generally below 77°F (25°C). Temperatures inside a car on a sunny day can soar well above 120°F (49°C), causing a rapid deviation from these safety standards. This extreme heat exposure can permanently alter the delicate balance of the product.
How Heat Damages Lenses and Solution
Heat primarily affects the polymer material of the lens and the multipurpose solution it rests in. Contact lenses are made from hydrogel or silicone hydrogel polymers that rely on a precise water content and shape for proper fit and vision correction. When exposed to excessive heat, these polymers can undergo physical changes, such as a decrease in water content, which alters the lens’s base curve and diameter. This heat-induced distortion means the lens will no longer conform correctly to the eye’s surface.
The contact lens solution itself is also vulnerable to heat damage. Extreme temperatures can cause the water in the solution to evaporate rapidly, leading to a concentration of preservatives and salts. This change in concentration can make the solution irritating to the eye upon insertion. More concerning is the potential for heat to destabilize the disinfecting agents within the solution, which reduces their ability to kill harmful microbes.
Using Compromised Contact Lenses
Placing a heat-damaged lens into the eye carries significant risks to ocular health. A lens that has warped or become dehydrated will not fit properly, which can lead to severe discomfort and physical injury to the cornea. The altered fit causes the lens to rub against the eye’s surface, potentially resulting in microscopic corneal abrasions that are painful and create an entry point for pathogens.
A compromised lens also severely affects the eye’s oxygen supply, a condition known as hypoxia. An ill-fitting or dehydrated lens can impede the flow of oxygen to the cornea, leading to irritation, redness, and corneal swelling. Furthermore, if the disinfecting agents in the solution were destabilized by heat, the lens is no longer adequately sterile. This loss of microbe-fighting power promotes the growth of bacteria and other microorganisms, greatly increasing the risk of serious eye infections like keratitis.
Guidelines for Safe Contact Lens Storage
To protect your vision, always store contact lenses and solution in a cool, dry place, keeping them away from direct sunlight and any heat source. Never leave them in environments where the temperature is uncontrolled, such as a glove compartment, a gym bag left in the sun, or a window sill. If you need to transport your lenses, it is best to use an insulated bag or container to maintain a stable, cool temperature.
The safest practice is to always adhere to the storage instructions printed on the product packaging, which typically specify room temperature. If there is any doubt about whether your lenses or solution have been exposed to high heat, the contents should be discarded immediately. The momentary inconvenience of replacing a lens or bottle of solution is a small price compared to the risk of damage to your eyes.