Scleral Lenses: Are Your Eyes Getting Enough Oxygen?
"A new study explores tear exchange and mixing beneath scleral lenses, revealing insights into lens settling and ocular health."
Scleral lenses are increasingly popular for correcting vision, especially for individuals with irregular corneas or dry eye. Unlike traditional contact lenses, scleral lenses vault over the entire cornea and rest on the sclera (the white part of the eye). This creates a reservoir filled with tears between the lens and the cornea, which provides comfort and constant hydration.
However, this tear reservoir can also trap debris, inflammatory cells, and metabolic by-products. Efficient tear exchange – the process of fresh tears flowing into the reservoir and flushing out old tears – is crucial for maintaining a healthy corneal environment. Without adequate tear exchange, the cornea can be deprived of oxygen and nutrients, potentially leading to discomfort, irritation, and even more serious complications.
New research is shedding light on how tear exchange and mixing occur under scleral lenses. A study by Tse et al. (2018) investigated tear dynamics at different time points during scleral lens wear, providing valuable insights into optimizing lens fitting and promoting ocular health.
Tear Inflow and Exchange
Research on habitual scleral lens wearers has examined tear inflow into the lens system and the turnover of the tear reservoir beneath the lens. One pilot study used fluorophotometry to evaluate tear inflow in wearers with and without midday fogging (MDF). More recent work has investigated how peripheral scleral lens modifications affect tear exchange, including comparisons with a toric landing zone control condition using non-invasive imaging. Another study reapplied sodium fluorescein after 90 minutes of lens settling and analyzed central and peripheral fluorescence with customized MATLAB software.
Current Clinical Approach
Scleral lenses are generally discussed as devices that rest on the sclera while creating a tear-filled space over the cornea. In practice, clinicians must consider lens fit, the tear reservoir, oxygen transmission, and patient comfort together rather than treating any one feature as the sole measure of success. Because outcomes can vary with lens design, wear duration, and individual ocular conditions, broad claims about a single standard approach should be made cautiously.
From Fluidless Designs to Modern Vaults
Scleral lenses are large lenses that rest on the sclera and create a tear-filled vault over the cornea. Historical accounts describe scleral lenses as among the earliest manufactured contact lenses, with designs evolving substantially over time. By the 1930s, some designs had become “fluidless” lenses that used the patient’s own tear film rather than a filling solution and were primarily intended to correct more regular refractive errors. Modern reviews continue to examine how scleral lenses interact with the eyelids and tear film and identify areas requiring further research.
Tear Exchange and Lens Settling: What the Research Reveals
The study used a technique called the "Out-in method," where a small amount of fluorescent dye is placed on the conjunctiva (the clear membrane covering the white part of the eye). Researchers then measure the time it takes for the dye to appear in the tear reservoir under the lens. This indicates how quickly tears are flowing into the space.
- Tear Exchange: 60% of subjects experienced tear flow into the reservoir within 5 minutes after 5 hours of lens wear.
- Lens Settling: Lens settling, the gradual sinking of the lens onto the eye, also played a role in tear dynamics. About 27% of the change in fluorescence under the lens was due to settling.
- Tear Mixing: Roughly 13% was due to tear exchange and mixing, while the remaining 60% was a combination of the three factors: tear exchange, mixing and lens settling.
New Directions in Tear Exchange
Recent research has compared scleral lenses with toric landing zones against spherical designs and reported greater central and peripheral tear exchange with the toric design despite comparable lens settling. Another study is examining relationships among tear exchange, the optical density of the fluid reservoir, and patient-reported midday fogging in established scleral lens wearers. A Contact Lens Spectrum report also describes innovative channel modifications intended to enhance tear exchange and mitigate common complications, according to findings by Dr. Melissa Barnett.
Remaining Uncertainties
Scleral lenses can offer important optical and surface benefits, but they are not free of potential limitations. Tear exchange, lens settling, fluid-reservoir characteristics, and individual fit may influence performance and comfort. The available material does not establish that one design or modification consistently prevents every complication, so expectations should remain individualized and evidence-based.
Oxygen Transmission Tradeoffs
Modern scleral lenses are fabricated from high oxygen-permeable materials, but their relatively thick profiles and limited tear exchange may modestly reduce oxygen transmission to the central cornea. The cited comparative evaluation indicates that this concern may be particularly relevant during continuous wear. Thus, material oxygen permeability is only one part of the comparison; lens thickness, tear exchange, and wearing schedule also matter.
What This Means for Scleral Lens Wearers
The research suggests that tear exchange continues to occur under scleral lenses, even after several hours of wear. However, lens settling can impact tear dynamics, potentially reducing the flow of fresh tears to the cornea.
Designing for Better Exchange
The emerging discussion around scleral lenses increasingly emphasizes tear exchange alongside oxygen-permeable materials and optical performance. A Contact Lens Spectrum report highlights innovative channel modifications as a way to enhance tear exchange and mitigate common complications. The report attributes these recent findings to Dr. Melissa Barnett, suggesting that design changes may become an important focus of scleral lens refinement.
Expanding Designs and Applications
A 2026 overview describes scleral lenses as providing comfort and clarity for people with conditions such as keratoconus or severe dry eye. It also emphasizes the tear-filled reservoir as a feature that helps maintain eye moisture and reduce discomfort. A separate 2026–2031 market report identifies mini and large scleral lens designs, dry eye and keratoconus as key drivers, regional trends, and major players as areas of industry analysis.
Balancing Benefits and Constraints
Scleral lens care sits at the intersection of vision correction, ocular-surface management, fit quality, and ongoing monitoring. Benefits may be substantial for some users, but outcomes can depend on individual anatomy, lens design, wearing habits, and access to appropriate clinical follow-up. These factors make generalized promises difficult and support a cautious, personalized approach.
Patient Experience Matters
For patients, the practical value of a scleral lens is measured not only by visual performance but also by comfort, moisture, and the ability to manage daily wear. Experiences may differ because ocular conditions and responses to lens fit are individual. Clinicians and patients therefore need to weigh reported benefits against tolerance, handling demands, and any symptoms that arise during wear.
To promote optimal ocular health, it's crucial to have scleral lenses properly fitted by an eye care professional. A well-fitted lens will minimize settling and maintain an adequate tear reservoir, ensuring sufficient tear exchange.
If you wear scleral lenses and experience discomfort, dryness, or blurry vision, consult with your eye care provider. They can assess your lens fit, evaluate your tear dynamics, and recommend strategies to improve ocular surface health.