ICL vault: normal, high and low
What vault is, what the numbers mean, why there is no single correct value, and when it actually matters.
Vault is the small gap between the back of the ICL and the front of your natural lens, measured in microns. Most surgeons are comfortable across a broad range, often described as roughly 250–750 microns, but there is no single correct vault number. It differs between eyes and shifts within the same eye as your pupil changes with light. What matters is a lens that fits your eye across conditions, not a target figure.
Vault is the number patients fixate on after surgery, usually because they were given one at a follow-up visit and then went looking for what it meant. It is a genuinely useful measurement, and it is also the most commonly misread number in ICL care, because it is treated as a fixed score when it is really a dynamic property of how a particular lens fits a particular eye.
What is ICL vault?
The ICL is designed to arch over your natural crystalline lens rather than rest on it. Vault is the height of that arch: the distance, in microns, between the back surface of the ICL and the front surface of your own lens. Adequate vault keeps the implant clear of your natural lens and preserves the normal flow of fluid inside the eye; excessive vault crowds the iris forward.
What is a normal ICL vault?
Ranges around 250–750 microns are commonly cited as comfortable, and many eyes sit in the middle of that band. Treat these as orientation rather than a pass/fail line: surgeons interpret a vault number alongside your anterior chamber depth, your angle anatomy, your pupil size and your eye pressure. The same 300-micron vault can be entirely unremarkable in one eye and worth watching in another.
| Vault band | Typical interpretation | What usually happens |
|---|---|---|
| Low (roughly under 150–250 µm) | Tolerated well by the EVO central-port design | Usually observed; periodic checks of the natural lens |
| Normal (roughly 250–750 µm) | The comfortable working range for most eyes | Routine follow-up |
| High (roughly above 750–1000 µm) | Iris pushed forward; angle may narrow | Pressure and angle monitored; exchange for a smaller lens if persistent and problematic |
These bands are approximate and vary between surgeons and published series. Your own surgeon’s interpretation of your eye is what counts.
Why there is no single “ideal” vault
Peer-reviewed research by Matt Hirabayashi, MD, Gurpal Virdi, MD and colleagues measured ICL vault and the anterior chamber angle under varying lighting conditions and found that both shift measurably as the pupil dilates and constricts (Clinical Ophthalmology, 2026). A vault recorded in a brightly lit exam room is not the vault your eye has in a dark room. That is reassuring rather than alarming, it means a single number was never going to capture the fit, but it does mean chasing one specific figure is the wrong goal.
What causes a high vault?
- A lens that is longer than the space it sits in, the dominant cause.
- A deep anterior chamber with a prominent natural lens, which raises the arch.
- Dim lighting and pupil dilation, which transiently increase measured vault.
- Youth, vault tends to be higher earlier and drift down over the years.
What causes a low vault?
- A lens that is shorter than the space it sits in.
- A shallow anterior chamber, where there is simply less room to arch. Outcomes in eyes with ACD under 3.0 mm have been specifically studied and can be good when sizing is done carefully (Clinical Ophthalmology, 2025).
- Natural thickening of the crystalline lens with age, which gradually reduces vault over time.
Does low vault cause cataracts?
This was a legitimate worry with the older, non-ported ICL, where a low vault could restrict fluid flow between the implant and the natural lens. The EVO ICL’s central port keeps that fluid moving regardless of vault, and the ICL-related cataract risk with modern lenses is at or near zero. In current practice a low vault is usually monitored rather than treated.
How is vault measured?
Most commonly with anterior-segment OCT, which captures a cross-section of the front of the eye and allows the gap to be measured directly in microns. Ultrasound biomicroscopy (UBM) can also measure it. At the slit lamp, a surgeon can estimate vault in units of corneal thickness, a useful clinical shorthand, but an estimate rather than a measurement. Because vault moves with lighting, it is worth asking under what conditions a given number was captured.
When is an ICL exchanged for vault?
Uncommonly. The trigger is usually a high vault that narrows the angle and keeps eye pressure elevated, or a low vault combined with a toric lens that will not stay on axis. The fix is exchanging the lens for a different size. Work from a high-volume US center has quantified how often exchanges and explants happen for sizing reasons (Clinical Ophthalmology, 2025), and the rate is low, but nearly all of it is decided before surgery, by the size that was chosen.
Vault is an outcome of sizing, not a separate decision
This is the point worth carrying away. You do not choose a vault; you choose a lens size, and vault is what that choice produces in your eye. Everything that makes vault go well happens beforehand, in how accurately the space inside the eye is measured and how well the resulting vault is predicted for each available size. That is the subject of how an ICL is sized, and it is what machine-learning vault prediction, including the VAULT and VAULT-OCT models behind ICLFit.com, is built to improve.
Common questions about ICL vault
What is ICL vault?
Vault is the small gap between the back surface of the ICL and the front surface of your natural crystalline lens, measured in microns. It exists because the ICL is designed to arch over your own lens rather than rest on it.
What is a normal ICL vault?
Most surgeons are comfortable across a broad range, often described as roughly 250 to 750 microns, with many eyes sitting somewhere in the middle. But there is no single correct number: vault differs from eye to eye and shifts within the same eye as the pupil changes, so the goal is a lens that fits your eye across conditions rather than a specific micron value.
Is a low ICL vault dangerous?
Usually not. The modern EVO ICL has a central port that keeps fluid flowing past your natural lens, so low vaults are tolerated far better than they were with older lens designs. A low vault is most often simply monitored rather than treated.
What happens if ICL vault is too high?
A very high vault pushes the iris forward and can narrow the eye’s drainage angle, which may raise eye pressure. If that happens and does not settle, the ICL can be exchanged for a smaller size, or in some cases rotated, to reduce the vault. This is uncommon.
Does ICL vault change with lighting?
Yes. Peer-reviewed research by Hirabayashi, Virdi and colleagues measured vault and the anterior chamber angle under different lighting and found both shift measurably as the pupil dilates and constricts. Vault is a dynamic value, not a fixed one, which is why a single clinic measurement is a snapshot, not the whole picture.
Does ICL vault change over time?
Vault tends to drift downward slowly over the years as the natural crystalline lens continues to thicken with age. This is expected and gradual, and it is one reason a modestly higher vault in a young patient is not a concern.
How is ICL vault measured?
Most commonly with anterior-segment OCT, which images a cross-section of the front of the eye and lets the gap be measured directly in microns. Ultrasound biomicroscopy (UBM) can also be used. At the slit lamp a surgeon can estimate vault in corneal-thickness units, but imaging is what produces a number.
Can an ICL be exchanged because of vault?
Yes, though it is uncommon. Published work from a high-volume US center quantified how often lenses are exchanged or explanted for sizing reasons and found the rate low, and largely preventable with more accurate sizing before surgery.
Next: how an ICL is sized, the peer-reviewed research behind vault prediction, or the risks of ICL surgery.
Educational content reviewed by ICL surgeons. Vault ranges are approximate and vary between surgeons and published series; only your surgeon can interpret your own measurements.