Scleral lenses can provide excellent vision and comfort for people with keratoconus, irregular corneas and other complex eye conditions.
But some wearers notice a frustrating pattern:
The lens is clear when they first put it in, but several hours later their vision becomes cloudy, hazy or “milky”.
Removing the lens, cleaning it, refilling it with preservative-free saline and reinserting it may restore clear vision—only for the problem to return later.
This is commonly called midday fogging.
Although it can be tempting to assume that the lens is dirty, fogging can occur for several different reasons. Sometimes the cloudiness is actually underneath the lens, while in other cases the problem is on the front surface of the lens.
Finding out which is happening is important because the solution may be completely different.
What Is Midday Fogging in Scleral Lenses?
A scleral lens does not sit directly on the cornea.
Instead, it vaults over the cornea and is filled with preservative-free saline before insertion. This creates a fluid reservoir between the lens and the eye.
During wear, particles can sometimes accumulate within this reservoir and make it progressively cloudy.
Research has identified cellular material and lipids within the post-lens fluid of scleral lens wearers experiencing fogging. However, midday fogging appears to be multifactorial rather than having one universal cause.
Patients may describe:
- cloudy or milky vision;
- a “dirty lens” sensation despite having cleaned the lens;
- reduced contrast;
- haze developing after several hours;
- vision that is clear in the morning but worse later in the day; or
- vision that improves immediately after removing, refilling and reinserting the lens.
If that sounds familiar, the first question is where the fogging is occurring.
Is the Fogging Under the Scleral Lens or on Its Surface?
This distinction is important.
Fogging underneath the lens
If debris is suspended in the fluid reservoir between the lens and cornea, the lens can appear cloudy from within.
Removing and refilling the lens usually improves the vision because the cloudy fluid reservoir has been replaced.
Front-surface fogging
Sometimes the reservoir underneath the lens is relatively clear, but the front surface of the scleral lens is not wetting properly.
The tear film over the lens may break up, or deposits can accumulate on its surface.
In this situation, patients may notice that vision fluctuates with blinking or temporarily improves after using an appropriate lubricating drop.
Recent clinical research found that front-surface non-wetting and diffuse haze were more common in scleral lens wearers reporting fogging symptoms.
This is why simply saying “my scleral lens is fogging” does not necessarily tell us what needs to be changed.
Why Does Debris Get Under a Scleral Lens?
There isn’t one answer for every patient.
Several factors may need to be considered.
1. The way the lens lands on the eye
The sclera (the white part of the eye) is not perfectly spherical.
If the landing zone of a scleral lens does not align appropriately with the underlying eye, there may be areas where tears and debris can move beneath the lens.
Modern scleral lenses can therefore incorporate toric, quadrant-specific or highly customised landing zones rather than assuming that every eye has a symmetrical shape.
At Westmead Eyes, more complex eyes can also be mapped using sMap3D scleral profilometry, which measures the shape of the sclera to assist with customised lens design.
2. Tear exchange
It was once tempting to think of every scleral lens as creating a completely sealed reservoir.
The reality can be more complicated.
A 2026 study of established scleral lens wearers found measurable tear exchange within five minutes in 64% of eyes. Interestingly, very rapid tear exchange was relatively specific for patient-reported fogging in that study.
This doesn’t mean that all tear exchange is bad.
It means that when someone has persistent fogging, we may need to assess how the lens is interacting with the eye, rather than simply changing the saline.
3. Excessive fluid-reservoir thickness
A scleral lens needs enough clearance to safely vault the cornea.
But more clearance is not automatically better.
Research has previously found an association between greater corneal clearance and increased odds of midday fogging, although subsequent studies have shown that lens-fit variables alone do not explain every case.
The goal is therefore not simply to make the reservoir as shallow as possible.
The lens needs to be assessed as a complete system – including corneal clearance, limbal clearance, landing-zone alignment, oxygen considerations, comfort and stability.
Could Dry Eye or Eyelid Problems Contribute?
Potentially.
Some scleral lens wearers with fogging also have underlying ocular-surface inflammation, meibomian gland dysfunction or poor tear-film quality.
One multicentre study found that scleral lens wearers reporting midday fogging were more likely to report redness or irritation. Another study found that patients experiencing fogging had substantially worse dry-eye symptom scores than those without fogging.
This means that repeatedly redesigning the scleral lens may not solve the problem if an important contributor is actually the ocular surface or eyelids.
In selected patients we may therefore examine:
- the meibomian glands;
- tear-film stability;
- eyelid inflammation;
- corneal and conjunctival staining;
- lens-surface wettability; and
- the type of debris present.
Treating the eye supporting the lens can sometimes be just as important as changing the lens itself.
Does the Scleral Lens Filling Solution Matter?
The lens should be completely filled with an appropriate preservative-free solution before insertion.
Different filling solutions can feel different to individual patients.
A small clinical study using a filling solution designed to better mimic the ionic composition of tears found improvements in patient-reported burning, dryness, grittiness and fluctuating vision, although the objective reduction in fogging itself was not statistically significant.
So changing filling solution can sometimes be worth considering, but it should not be presented as a guaranteed cure for midday fogging.
What About Putting a Thicker Lubricating Drop in the Scleral Lens?
Some scleral lens wearers use a small amount of a preservative-free viscous lubricant in the lens bowl before completing the fill with preservative-free saline.
At Westmead Eyes, we sometimes recommend this approach in selected patients. For example, our patients may insert several drops of preservative-free Celluvisc before completing the lens fill.
However, this is not the answer for every patient.
If the underlying problem is lens alignment, excessive clearance, inflammation or poor front-surface wetting, simply making the filling solution thicker may not address the cause.
It is best to discuss any change in filling solution with your scleral lens practitioner.
Why Does My Vision Clear When I Remove and Reinsert the Lens?
This is actually useful information.
If vision becomes progressively hazy during the day but becomes clear again immediately after you:
remove → clean → refill → reinsert
then clouding within the fluid reservoir becomes an important possibility.
If, instead, vision fluctuates rapidly between blinks or improves after wetting the front surface, we may be more suspicious of a surface-wetting problem.
Neither observation provides a complete diagnosis, but telling your practitioner exactly when the blur develops and what makes it clear again can help considerably.
Do I Need a New Scleral Lens?
Not necessarily.
Some patients can manage occasional fogging simply by removing and refilling their lenses once during a long wearing day.
But if you are regularly removing your lenses multiple times each day, or your vision is significantly limiting work, driving or daily activities, it is worth investigating why.
Depending on the cause, management could involve:
- modifying corneal or limbal clearance
- changing the scleral landing zone
- improving lens centration or stability
- changing the filling system
- improving front-surface wettability
- addressing deposits
- treating associated dry-eye or eyelid disease
- redesigning the lens using more customised scleral mapping
There isn’t a single “anti-fogging” scleral lens design that fixes every case. Research examining lens properties and solutions supports the idea that changing one isolated variable may not be enough.
When Should Scleral Lens Fogging Be Reassessed?
Consider having your lenses reviewed if:
- they repeatedly become cloudy after only a few hours
- you need to remove and reinsert them several times each day
- the problem is becoming progressively worse
- vision fluctuates significantly
- the lenses develop heavy deposits
- your eyes become increasingly red or irritated
- your current lenses have never provided stable all-day vision
Significant pain, redness, light sensitivity, discharge or a sudden reduction in vision should not simply be assumed to be normal scleral-lens fogging. Remove the lens and arrange prompt eye assessment. Scleral lenses are medical contact lenses and complications, including infection and corneal inflammation, can occur.
Scleral Lens Fogging Assessment in Sydney
At Westmead Eyes, we regularly assess people with keratoconus, corneal grafts, irregular corneas and previous unsuccessful scleral or RGP lens fittings.
When someone presents with persistent fogging, the aim isn’t simply to prescribe another lens.
We try to determine where the cloudiness is occurring and why.
Assessment may include examination of the lens after it has been worn for several hours, corneal and limbal clearance, landing-zone alignment, lens centration, front-surface wettability, tear-film and eyelid health, and whether a more customised lens design may be appropriate.
For complex fittings, we also have access to anterior OCT, corneal topography and sMap3D scleral profilometry.
If your scleral lenses are clear when you put them in but repeatedly become foggy during the day, you do not necessarily have to accept this as part of wearing scleral lenses.
Learn about our Scleral Lens Clinic and specialty lens fitting
Book a Scleral Lens Consultation or existing-lens review to investigate why your lenses are fogging.