Why do my scleral lenses fog up when it's humid?

Humidity usually helps, not hurts

Wearers talk far more about dry air than humid air. Many say they can wear their lenses longer and more comfortably in humid places, and that dry climates, air conditioning, airplane cabins, and heated homes are what make their eyes and lenses struggle. Some run humidifiers for exactly that reason. See scleral lenses in wind and air conditioning.

So when your vision turns foggy on a hot, muggy day, humidity itself is rarely the whole story. We didn’t find research that looks at weather and scleral lens fogging specifically. What wearers describe points to a handful of other causes that show up more in summer.

Step 1: find where the fog is

Before changing anything, work out where the haze actually is:

1. Take off your glasses or sunglasses. If the fog disappears, it was on them, not on your lens.
2. Blink a few times, or use a fitter-approved preservative-free drop. If vision clears, even briefly, the haze is on the front of the lens.
3. If nothing you do from outside helps, the haze is probably in the fluid behind the lens.

Common summer causes

Glasses steaming up. Walking from an air-conditioned building or car into warm, humid air makes glasses and sunglasses fog over within seconds. If you wear glasses over your lenses, or moisture-chamber or wraparound glasses, this is easy to mistake for lens fog. Some wearers find foam-sealed or silicone-sealed glasses steam up more in humid weather, and swap to a more vented style for summer. See moisture chamber glasses with scleral lenses.

Sweat in the eyes. Sweat running off the forehead into the eye can sting and smear the front of the lens. Wearers who run, cycle, or work outside often use a sweat-wicking headband or cap.

Sunscreen and skin products. Sunscreen on the forehead and lids can travel into the eye with sweat or water and coat the lens. Many wearers keep sunscreen away from the area right around the eyes and rely on a hat and sunglasses there instead. See makeup and skin care.

Pollen and dust. Outdoor time in summer often means more airborne debris on the eye surface and lens. See scleral lenses and allergies.

Ordinary midday fogging. Many wearers get some haze behind the lens a few hours into the day, whatever the weather. A review of the research describes midday fogging as particles building up in the fluid between the lens and the eye during wear, and suggests it may ultimately be related to inflammation, which has different sources in different people.^[1] A long, hot day outdoors may simply be a long wear day. See midday fogging.

What helps

• For fog on glasses: wipe them, let them adjust to the air for a minute, or try a more vented style in summer.
• For fog on the front of the lens: blink, use a fitter-approved preservative-free drop, and keep sweat and sunscreen out of the eye.
• For fog behind the lens: take the lens out, rinse it, refill with fresh sterile saline, and reinsert. Topping up in place doesn’t work: see can you add saline after inserting a scleral lens?
• On long outdoor days: carry a small kit so you can refill, and keep supplies out of direct sun and hot cars. See can heat or freezing damage scleral lenses or solutions?

What wearers say

Experiences are mixed. Some wearers say hot, humid weather makes fogging worse, especially when exercising or sweating. Others say their eyes feel better than ever in humid weather, and that their fog comes from heat, sweat, or dust rather than the air itself. Several found that what they thought was lens fog was their sunglasses steaming up. People who fog regularly often find a fit adjustment, a different fill solution, lid treatment, or a lens surface coating helped, each worked out with their fitter.

What to ask your fitter

• Is my fog on the front of the lens or behind it?
• Could a fit change, a different saline, or a surface coating help?
• Do I have lid or allergy problems that could be adding to the fog?
• Is a midday remove and refill reasonable on hot days outdoors?