Illustration of tear exchange beneath a scleral lens.

Scleral Lenses: Are Your Eyes Getting Enough Oxygen?

Mira Elwood in Health & Wellness December 2025 • 4 min read.

"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 Exchange and Lens Settling: What the Research Reveals

Illustration of tear exchange beneath a scleral lens.

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.

In addition to the Out-in method, researchers used a modified slit-lamp technique called fluorography to observe tear dynamics under the lens. This involved taking snapshots of the tear reservoir at regular intervals and measuring the fluorescence intensity, which indicates the concentration of the dye. High-resolution optical coherence tomography (OCT) was also used to measure the thickness of the tear layer.

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.

The study also found that lens settling can affect tear exchange. As the lens settles, the tear reservoir thins, which can reduce the flow of fresh tears into the space. This highlights the importance of proper lens fitting to minimize settling and ensure adequate tear exchange. Some participants in the study experienced no tear flow after 5 hours of wear, with fluorescence decline due to lens settling.

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.

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.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.clae.2018.11.016, Alternate LINK

Title: Tear Dynamics Under Scleral Lenses

Subject: Optometry

Journal: Contact Lens and Anterior Eye

Publisher: Elsevier BV

Authors: Vivien Tse, Bo Tan, Young Hyun Kim, Yixiu Zhou, Meng C. Lin

Published: 2019-02-01

Everything You Need To Know

Why are scleral lenses different from regular contacts, and what is the significance of the tear reservoir they create?

Scleral lenses are unique because they vault over the cornea and rest on the sclera, creating a tear reservoir. This reservoir provides constant hydration, beneficial for individuals with dry eye or irregular corneas. However, it can also trap debris and metabolic by-products, which is why tear exchange is so vital. Without sufficient tear exchange, the cornea may not receive enough oxygen and nutrients, leading to discomfort or more serious issues.

What research methods like the 'Out-in method', fluorography, and optical coherence tomography (OCT) were used to study tear dynamics under scleral lenses?

The 'Out-in method' involves placing a fluorescent dye on the conjunctiva to measure how quickly tears flow into the reservoir under a scleral lens. Fluorography, a modified slit-lamp technique, takes snapshots of the tear reservoir to measure dye concentration. High-resolution optical coherence tomography (OCT) measures the thickness of the tear layer. These methods help researchers understand tear dynamics and optimize scleral lens fitting.

How does the settling of a scleral lens affect tear exchange and what implications does this have for lens fitting?

The research indicates that lens settling, the gradual sinking of the scleral lens onto the eye, can significantly affect tear dynamics. As the lens settles, the tear reservoir thins, potentially reducing the flow of fresh tears. Proper lens fitting is crucial to minimize settling and maintain adequate tear exchange. The study showed that in some participants, fluorescence decline was due to lens settling, with no tear flow after 5 hours of wear.

Why is proper tear exchange so important when wearing scleral lenses, and how does this relate to corneal health?

Tear exchange is crucial because it allows fresh tears to flow into the reservoir under a scleral lens, flushing out debris, inflammatory cells, and metabolic by-products. Without adequate tear exchange, the cornea may be deprived of necessary oxygen and nutrients. The study by Tse et al. (2018) revealed that tear exchange continues even after several hours of lens wear, but lens settling can impact tear dynamics.

What are the different factors that contribute to tear dynamics under scleral lenses, and what are the implications for lens design and wear?

The study indicates that tear exchange, mixing, and lens settling all play a role in tear dynamics under scleral lenses. Approximately 13% of the fluorescence change was attributed to tear exchange and mixing, while about 27% was due to lens settling. The remaining 60% was a combination of all three factors. These findings emphasize the importance of considering all these dynamics when fitting scleral lenses to promote ocular health. Further research could explore how different lens designs and materials impact these dynamics.