The high temperatures and humidity of a traditional sauna, which can range from \(70^\circ\text{C}\) to \(90^\circ\text{C}\) (\(158^\circ\text{F}\) to \(194^\circ\text{F}\)), create an environment that is generally incompatible with modern eyewear. Even infrared saunas, with lower temperatures, pose a risk to both the glasses and the wearer. The common dilemma of needing vision correction should be resolved by prioritizing both personal safety and the integrity of the optical equipment. The simple answer is that you should not wear standard eyeglasses in a sauna.
Immediate Safety Concerns
The most immediate danger of wearing glasses in a sauna relates to frames made with metal components, which act as heat conductors. Metals like stainless steel or titanium absorb heat quickly, potentially reaching temperatures high enough to cause first-degree burns on the nose bridge or behind the ears. They retain heat longer than the surrounding air.
Beyond the burn hazard, the rapid change in temperature and high humidity cause lenses to fog almost instantly. This heavy condensation renders the glasses functionally useless for vision correction, creating a significant safety hazard. Poor visibility makes it difficult to navigate the space, increasing the chance of a trip or fall.
The Impact of Heat on Eyewear Materials
The high heat of a sauna can cause permanent damage to almost every part of a pair of glasses, starting with the frame material. Many modern frames are made from thermoplastics like acetate, nylon, or standard plastic, which have low softening points. Prolonged exposure to high heat causes these materials to warp and permanently deform, ruining the custom fit of the glasses.
The lenses and their specialized coatings are particularly susceptible to thermal damage, which can lead to a condition known as “crazing”. Most lenses today are made from plastic polymers like polycarbonate or high-index materials, and they are typically covered with multiple layers of anti-reflective or anti-scratch coatings. Crazing occurs when the lens material and the thin surface coatings expand and contract at different rates due to the heat, creating a web of fine, hairline cracks across the lens surface. Once crazing appears, the visual quality of the lens is permanently compromised. The thermal expansion mismatch separates the coatings, which cannot be repaired and necessitates a complete lens replacement.
Vision Correction Options for Sauna Use
For individuals who require vision correction to navigate safely, the best practice is to simply remove the glasses before entering the sauna and rely on ambient light and memory to move around. If your prescription is mild, navigating with caution without glasses may be the simplest solution to avoid all risks of damage and injury.
Contact Lenses
Contact lenses are generally considered a better alternative than glasses for use in a sauna, though they also carry a risk of discomfort. The dry, hot air can cause the lenses and eyes to dry out, leading to irritation. If contact lenses are worn, it is advisable to keep the session relatively short and use rewetting drops immediately afterward to maintain comfort and eye health.