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    Wearing guide

    Vision that changes during the day

    If your vision shifts over the day in a way that cleaning and refilling don't fix, it's worth working out why. Here's how to sort it out and what your fitter will look at.

    By the Scleral Lens Team · Updated October 2, 2026 · 6 published sources cited

    The short answer

    Start by telling fluctuation from fogging. Fogging looks hazy or milky and usually improves when you remove, rinse, and refill the lens. Fluctuation is a change in focus that a fresh fill doesn't fix. It can come from the lens settling onto the eye over the first hours, or from the cornea swelling slightly under the lens. Both are things your fitter checks for and can adjust, so note when it happens and tell them.

    Before you start

    Time: A few days of notes, then a follow-up visit.

    • A notebook or phone to log what you notice and when
    • Fresh saline and your tools, to test whether a refill helps
    • Your glasses, to compare vision after the lens comes out

    Step by step

    1. Check each eye on its own

      Cover one eye at a time. Note which eye changes and how.

    2. Ask: hazy or out of focus?

      Milky, smoky, or smeary vision points to fogging. Clear but slightly out of focus points to fluctuation.

    3. Try a fresh fill

      Remove the lens, rinse it, refill with fresh preservative-free saline, and reinsert. If vision snaps back, it was likely fogging.

    4. Log the timing

      Write down how long after insertion it starts, how long you wore the lens that day, and anything that makes it better or worse.

    5. Check your vision after removal

      Notice whether your vision with glasses is hazier than usual for a while after the lenses come out. Mention this to your fitter.

    6. Book your fitter, and keep the appointment timing in mind

      Ask whether to arrive having worn your lenses for several hours, so they can see how the lens behaves once it's settled.

    These are general steps. If your fitter taught you differently, follow your fitter: your lens and eyes are theirs to know. Print the mirror cards to keep by your sink.

    Fogging or fluctuation?

    These two get mixed up, but they’re different problems with different fixes.

    Fogging Fluctuation
    What it looks like Hazy, milky, smoky, or smeary Clear but slightly out of focus, or a shift in sharpness
    Fresh fill helps? Usually, at least for a while Not really
    Common causes Debris in the saline, poor wetting on the lens front Lens settling, corneal swelling, a prescription that needs adjusting
    Read more Midday fogging This page

    If you’re not sure, the refill test is the quickest way to tell: remove, rinse, refill with fresh saline, reinsert, and see whether your vision comes back.

    Settling: why the first hours matter

    A scleral lens rests on the white of your eye. Over the first hours of wear, it gradually sits a little closer to the eye, and the layer of saline between lens and cornea gets thinner. In a study of 20 people with keratoconus wearing two different mini-scleral lenses, more than half of the settling happened in the first 2 hours.[1]

    That’s one reason your fitter may check your vision and fit after you’ve worn your lenses for a while, not just right after insertion. If the prescription that looked right on day one is a little off once the lens has settled, they can recheck your prescription through the lens and adjust the power.

    Corneal swelling

    Some corneas swell slightly while a scleral lens is on. Researchers who study it note that persistent swelling can reduce vision, especially in eyes where the cornea’s inner cell layer, which keeps it clear, works less well.[4] That’s why fitters look for it, often right after you take your lenses out.

    What the research shows. A 2026 meta-analysis pooled 22 studies covering 830 eyes. While the lens was on, central corneal thickness increased by about 8 micrometers on average, a small but statistically significant change. After the lens came off, there was no significant difference. The authors concluded that changes were minimal and largely reversible, and that daytime wear of modern high-oxygen lenses appears physiologically safe, with selective monitoring advisable in high-risk patients.[2]

    Some eyes swell more. In a study of 12 eyes with corneal transplants that wore scleral lenses for 8 hours, the cornea swelled by 7.2% on average, more in full-thickness transplants than partial ones, and more in older grafts.[3] A review of scleral lenses for irregular corneas lists corneal swelling, along with midday fogging, among the limitations of lens wear.[5]

    What fitters can change. Your fitter can look for swelling at your visits, often just after you remove the lenses. If it’s a concern, options can include changes to the lens design, changes to your wearing schedule, or a lens with small holes near the edge. In a short study of 20 healthy adults, adding three small holes (fenestrations) near the edge of the lens reduced central corneal swelling by 39% on average compared with the same lens without holes. The authors note that longer studies in people with eye disease are still needed.[4]

    What to bring to your follow-up

    • Which eye, and whether it’s hazy or out of focus.
    • When it starts: how many hours after insertion.
    • Whether a refill helps.
    • How your glasses work right after the lenses come out.
    • Your wear time on the days it happens.

    Ask whether your fitter wants you to arrive having worn your lenses for several hours, so they can see the problem when it’s happening.

    Common mistakes

    • Wearing lenses longer than the schedule your fitter gave you.
    • Assuming any change is fogging and refilling over and over without telling your fitter.
    • Arriving at a follow-up with lenses you put in minutes earlier, when the problem only shows up hours later.
    • Sleeping or napping in your lenses.

    Common questions

    What does it mean that a lens 'settles'?

    After you put a scleral lens in, it gradually sits a little closer to the eye, so the layer of saline between the lens and your cornea gets thinner. Fitters account for this when they design and check your lens.

    Is corneal swelling dangerous?

    In most eyes, the swelling measured during daytime scleral lens wear is small and goes away once the lens is out. Some eyes, such as those with a corneal transplant, are more prone to it, which is why fitters check. Follow your wearing schedule and keep your follow-up visits.

    My vision is blurry with my glasses after I take my lenses out. Is that a problem?

    Mention it to your fitter. They can check for corneal swelling and other causes. If it doesn't clear, or comes with pain, redness, or light sensitivity, call your eye doctor today.

    Could my prescription just be wrong?

    Possibly. Fitters often recheck your prescription through the lens once it has settled, and adjust the power if needed.

    Keep going

    Guide

    Blurry right after insertion

    Check for a bubble first: shine a light and look in the mirror. Then make sure the right lens is in the right eye, and look for film, smudges, or specks on the lens. Most of the time, removing the lens, cleaning or rinsing it, refilling to the brim, and reinserting fixes it.

    Guide

    Your first two weeks with scleral lenses

    Expect it to be slow and awkward at first. That's normal. Practice every day at a calm time, follow your fitter's wearing schedule exactly, do the three checks after every insertion, and keep notes for your follow-up. Decide after two to three weeks, not after two to three days.

    Guide

    Midday fogging

    First work out where the fog is. If blinking or a rewetting drop clears it for a moment, it's probably on the front of the lens. If it doesn't, it's probably in the saline behind the lens: take the lens out, rinse, refill with fresh saline, and reinsert. Either way, tell your fitter: changes to the fit, a lens coating, or treating dry eye can all help.

    Sources

    1. Bagatur Vurgun E, Akkaya Turhan S, Toker AE. Size matters: a comparative study on midday fogging and lens settling in patients with keratoconus wearing mini-scleral lenses with two different diameters. Eye Contact Lens. 2025;51(2):53-57. doi:10.1097/ICL.0000000000001135 pubmed.ncbi.nlm.nih.gov
    2. Martinez-Perez C, Sánchez-González MC, Sánchez-González JM. Corneal and intraocular pressure responses to scleral lens wear: a meta-analysis. Ophthalmic Physiol Opt. 2026;46(4):765-778. doi:10.1007/s44402-026-00110-7 pubmed.ncbi.nlm.nih.gov
    3. Raj A, Kumari A, Dumpati S, Willcox M, Vincent SJ, Kumar M. Corneal and endothelial parameters following scleral lens wear in post-keratoplasty eyes. Ophthalmic Physiol Opt. 2026;46(4):779-785. doi:10.1007/s44402-026-00111-6 pubmed.ncbi.nlm.nih.gov
    4. Fisher D, Alonso-Caneiro D, Vincent SJ. The effect of limbal fenestrations on scleral lens-induced central corneal oedema. Ophthalmic Physiol Opt. 2026;46(2):404-408. doi:10.1007/s44402-026-00052-0 pubmed.ncbi.nlm.nih.gov
    5. Gindina S, Kang JJ, Jacobs DS. Scleral lenses for correction of irregular astigmatism: advances and limitations. Curr Opin Ophthalmol. 2025;36(4):282-287. doi:10.1097/ICU.0000000000001149 pubmed.ncbi.nlm.nih.gov
    6. U.S. Food and Drug Administration. Contact Lens Risks. Content current as of September 4, 2018. fda.gov

    Last updated October 2, 2026. Found an error or a newer study? Let us know and we'll correct the page.