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    Question

    What are fenestrated scleral lenses?

    A fenestration is a tiny hole drilled through the lens. Fenestrations have been used for decades, but only recently have studies measured what they do.

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

    The short answer

    A fenestrated scleral lens has one or more tiny holes, usually near the edge over the limbus, where the cornea meets the white of the eye. The idea is to let more tears, oxygen, or carbon dioxide move in and out of the fluid behind the lens. Recent small studies in healthy eyes found fenestrations reduced corneal swelling and debris in the fluid over a few hours. The catch is that air can enter through the holes and form bubbles, and long-term evidence in people with eye disease is still missing.

    Key points

    • Fenestrations are small holes, typically 0.1 to 2 mm across, placed near the edge of the lens.
    • In 20 healthy adults, three 1 mm fenestrations reduced central corneal swelling by 39% on average over 3 hours.
    • The same lenses showed less debris build-up in the fluid reservoir.
    • Bigger or more holes may let in larger air bubbles; studies so far are short and in healthy eyes.

    What a fenestration is

    A scleral lens holds a pool of saline against your cornea and seals gently on the white of your eye. That seal is part of what makes the lens stable, but it also limits how much fresh tear fluid flows in behind it. Tear exchange matters because fresh tears carry oxygen to the cornea and wash out waste and debris.[1]

    Fitters have several ways to increase tear exchange: fitting the landing zone slightly flatter, adding channels on the back surface, or adding fenestrations.[1] A fenestration is a tiny hole through the lens, usually placed over the limbus. Fenestrations have been used since the glass scleral lenses of the 1940s, but few studies had measured their effect until recently.[1]

    A common layout is three holes spaced evenly around the lens, so at least one stays within the eye opening if the lens rotates. Reported sizes range from 0.1 to 2 mm.[1] Holes or grooves can also reduce the suction that makes some small lenses hard to remove.[6]

    What the recent studies found

    A research group in Australia has published a series of short studies on fenestrated scleral lenses, all in healthy adults with normal corneas.

    • Corneal swelling. Twenty healthy adults wore the same lens with and without three 1 mm fenestrations for 3 hours each. Central corneal swelling was 39% lower on average with the fenestrated lens. The benefit appeared whether or not an air bubble was present behind the lens.[1] An earlier study using a single much smaller hole (0.3 mm) in nine people found less swelling at the edge of the cornea near the hole, but no clear difference in the center.[4]
    • Debris in the fluid. In the same 20 adults, debris in the fluid reservoir built up over 3 hours with both lenses, but more with the non-fenestrated lens, roughly 2 to 5 times more depending on the measure used (only one of the two measures reached statistical significance).[2]
    • Tear flow. A pilot study of nine people wearing a lens with one 0.3 mm hole found two patterns: some eyes had low tear flow and some had high flow. The low-flow group had more corneal swelling, though the difference wasn’t statistically significant.[3]

    These are useful early results, but they come from short wear in young, healthy eyes. The authors say longer studies in people with eye disease are needed.[2]

    The trade-off: bubbles

    Holes let air in as well as tears out. In the swelling study, half the participants wore the fenestrated lens with a small, moving bubble at the edge that didn’t affect their vision.[1] The authors note from clinical experience that larger or more numerous fenestrations make it more likely that a large bubble gets in and drifts toward the center of vision.[1] A bubble over the center blurs vision and leaves that part of the cornea without fluid.

    Who might be offered one

    Reducing corneal swelling matters most when the cornea can’t pump fluid out well, for example after a corneal transplant. Fenestrations are one of several tools for lowering oxygen stress, along with more oxygen-permeable materials, thinner lenses, less fluid between lens and cornea, and limiting wear time.[5] Your fitter may suggest a fenestrated design if your cornea swells, if debris clouds your lens during the day, or if a lens is hard to remove. Ask what they’re aiming to fix and how you’ll know if it’s working. For more on swelling, see do scleral lenses change the shape of your cornea?

    Common questions

    Will a fenestrated lens stop my midday fogging?

    It might help some people, but that hasn't been shown yet. A small study in healthy eyes found less debris build-up behind fenestrated lenses over three hours. Whether that translates into less fogging over a full day, in people with dry eye or other conditions, still needs to be studied.

    Do I fill a fenestrated lens differently?

    Follow your fitter's instructions for your specific lens. Because fluid can escape through the holes and air can get in, your fitter may give you specific tips for filling and inserting it.

    Is a bubble under a fenestrated lens a problem?

    A small bubble at the edge that doesn't affect your vision or comfort may be acceptable, and in research studies such bubbles were tolerated. A bubble that drifts over the center of your vision, or that causes discomfort, is something to report to your fitter.

    Keep reading

    What is scleral lens vault, or clearance?

    Vault, also called clearance, is the gap between the back of a scleral lens and the front of your cornea, filled with saline. Too little and the lens can touch the cornea as it settles; too much and less oxygen reaches the cornea and vision can be affected. Published reviews cite targets of roughly 100 to 200 or 100 to 300 microns after the lens settles, but they also stress that the right vault is whatever keeps your vision clear, your eye comfortable, and your cornea healthy.

    What are scleral lenses made of?

    Modern scleral lenses are made of rigid gas permeable plastics, such as fluorosilicone acrylates, that let oxygen pass through to the cornea. A material's oxygen permeability is rated as its Dk; scleral lens materials are generally high-Dk. But a scleral lens is thicker than a regular contact lens and sits over a layer of saline, and both reduce the oxygen that reaches your cornea. So lens thickness and fluid depth matter as much as the material itself.

    Do scleral lenses change the shape of your cornea?

    Scleral lenses are designed to vault over the cornea rather than press on it, so they aren't meant to reshape it. Studies find small, temporary changes: slight corneal swelling while the lens is on, and minor curvature changes that mostly return to baseline after the lens comes out. Eyes with a weakened inner corneal layer, such as after a transplant, can swell much more, so they need closer monitoring. Scleral lenses are not a treatment to stop keratoconus from progressing.

    What is a toric landing zone?

    The landing zone is the outer ring of a scleral lens that rests on the white of the eye. Many eyes are steeper in some directions than others, so a lens with an evenly curved landing zone can press harder in some spots and lift in others. A toric landing zone is curved differently in two directions to match that shape, and quadrant-specific or fully custom landing zones go further. In small studies, toric landing zones reduced lens flexing and rotation and improved tear exchange.

    Sources

    1. 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
    2. Fisher D, Colorado LH, Alonso-Caneiro D, Vincent SJ. Scleral lens fenestrations and fluid reservoir debris. Ophthalmic Physiol Opt. 2026;46(5):1211-1217. doi:10.1007/s44402-026-00150-z pubmed.ncbi.nlm.nih.gov
    3. Fisher D, Iqbal A, Alonso-Caneiro D, Collins MJ, Vincent SJ. Tear dynamics during fenestrated scleral lens wear: a pilot study. Ophthalmic Physiol Opt. 2026;46(4):786-793. doi:10.1007/s44402-026-00102-7 pubmed.ncbi.nlm.nih.gov
    4. Iqbal A, Fisher D, Alonso-Caneiro D, Collins MJ, Vincent SJ. Regional variations in corneal oedema during open-eye fenestrated scleral lens wear. Ophthalmic Physiol Opt. 2025;45(3):618-626. doi:10.1111/opo.13489 pubmed.ncbi.nlm.nih.gov
    5. Macedo-de-Araújo RJ, Fadel D, Barnett M. How can we best measure the performance of scleral lenses? Current insights. Clin Optom (Auckl). 2022;14:47-65. doi:10.2147/OPTO.S284632 pubmed.ncbi.nlm.nih.gov
    6. Şengör T, Aydın Kurna S. Update on contact lens treatment of keratoconus. Turk J Ophthalmol. 2020;50(4):234-244. doi:10.4274/tjo.galenos.2020.70481 pubmed.ncbi.nlm.nih.gov

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