Scleral lenses are categorised as hard lenses, specifically a type of rigid gas permeable (RGP) lens.
However, they feel far more comfortable than traditional hard lenses due to their unique design and advanced technology.
If you’re exploring scleral lenses, chances are you’re curious about their material, function, and how they differ from soft contact lenses. This blog will take a deep look at whether scleral lenses are hard or soft, explain why they fall into the “hard lens” category, and uncover why they remain a popular and effective choice for various eye conditions.
Understanding the Material of Scleral Lenses
To answer the question directly, scleral lenses are considered hard lenses because they are made from rigid gas permeable (RGP) materials. Unlike soft lenses that are more flexible and conform to the surface of the eye, scleral lenses retain their shape even when handled.
- Rigid Gas Permeable Material
Scleral lenses are crafted using durable RGP materials with high oxygen permeability, designed to allow sufficient oxygen to pass through and keep the cornea healthy during wear. This is essential for maintaining healthy eyes when wearing lenses for extended periods.
- Why Not Soft Lenses?
Soft contact lenses are made from hydrogel or silicone hydrogel and are much more pliable. While they provide immediate comfort, soft lenses lack the structural rigidity that allows scleral lenses to vault over the cornea and correct complex eye issues like keratoconus or severe dry eye syndrome.
How Are Scleral Lenses Different from Traditional Hard Lenses?
Scleral lenses are technically hard, but they’re very different from the hard lenses of past generations. Here’s how:
Larger Diameter and Complete Corneal Coverage
While traditional hard lenses are small and rest directly on the cornea, scleral lenses have a much larger diameter. They rest on the sclera (the white part of the eye), bypassing direct contact with the sensitive corneal surface altogether.
- Comfort Factor
Despite being hard lenses, the larger size and scleral design reduce irritation by resting on less sensitive tissue and maintaining a fluid reservoir that cushions the eye.
- Stability
Traditional hard lenses often shift or move when you blink, causing discomfort or blurry vision. Scleral lenses stay securely in place due to their larger size, offering clearer vision and a stable wearing experience.
Customisable and Designed for Complexity
Scleral lenses are custom-fitted for each individual’s unique eye shape, making them ideal for those with hard-to-fit eyes.
- Tailored Design
Each scleral lens is meticulously customised to accommodate the specific contours of your eye, especially for irregular corneas caused by conditions like keratoconus or corneal scars.
- Therapeutic Benefits
The unique fluid reservoir created by the lens also acts as a protective layer to keep the cornea hydrated, offering therapeutic relief for severe dry eyes.
Why Are Scleral Lenses Categorised as Hard?
The rigidity of scleral lenses is what sets them apart from soft lenses. Here’s why the hard structure is advantageous:
- Enhanced Vision Correction
The rigid material allows scleral lenses to create a smooth refractive surface, correcting irregularities in the cornea and significantly improving vision clarity.
- Durability
Hard lenses last longer than soft lenses because they are scratch-resistant and less prone to wear and tear.
- Highly Permeable to Oxygen
Although hard, RGP materials allow oxygen to pass through, ensuring that your cornea stays healthy throughout the day.
- Maintenance of Shape
The rigidity ensures that the lens stays intact even under pressure, which is crucial for providing a stable, clear vision for the wearer.
How Do Scleral Lenses Compare to Soft Lenses?
Before opting for scleral lenses, it’s essential to know how they differ from their soft lens counterparts. Here’s a comparison based on key factors:
| Feature | Scleral Lenses | Soft Lenses |
| Material | Rigid Gas Permeable (RGP) | Hydrogel or Silicone Hydrogel |
| Structure | Hard and retains shape | Soft and flexible |
| Comfort | Higher comfort for complex eyes; rests on less sensitive sclera with fluid cushion | Immediate comfort on the cornea |
| Oxygen Permeability | High oxygen permeability due to RGP materials | Moderate to high (silicone hydrogel) |
| Suitable for Complex Cases | Yes (e.g., Keratoconus, dry eye) | Limited |
| Durability | Long-lasting | Shorter lifespan |
| Wearing Time | Longer (up to 12-14 hours) | Usually shorter (up to 8-12 hours) |
Who Benefits the Most from Scleral Lenses?
Given their unique structure and materials, scleral lenses are an excellent choice for individuals with specific eye conditions:
- Keratoconus
Scleral lenses effectively manage irregular corneas by creating a smooth optical surface, drastically improving vision.
- Severe Dry Eye
The fluid reservoir beneath the lens keeps the cornea continuously hydrated, providing much-needed relief for those with chronic dry eye.
- Corneal Scarring or Irregularities
For individuals with corneal scars or any irregularities, scleral lenses offer a non-surgical solution for improved visual acuity.
- Post-Surgery Vision
They are also ideal for those recovering from corneal surgeries or transplants.
What Makes Scleral Lenses Feel Comfortable If They Are Hard?
You might wonder how a hard lens can feel comfortable. Here’s why scleral lenses offer superior comfort:
- Scleral Placement
Unlike traditional hard lenses that rest on the sensitive corneal apex, scleral lenses sit on the sclera, an area with fewer nerve endings.
- Custom Fit
Each lens is tailored to your exact eye shape, eliminating pressure points and ensuring a perfect fit.
- Hydrating Cushion
The fluid layer trapped between the lens and the cornea acts as a cushion, reducing irritation and providing continuous moisture.
How to Care for Your Scleral Lenses?
Yes, scleral lenses are hard, but proper care ensures they stay effective and comfortable:
- Cleaning
Use only prescribed disinfecting solutions and avoid tap water to prevent contamination and infections.
- Filling with Saline Solution
Always fill your scleral lenses with preservative-free saline solution before inserting them to ensure hydration.
- Regular Check-Ups
Visit your optometrist regularly to ensure your lenses are still a good fit and your eyes remain healthy.
Final Thoughts on Whether Scleral Lenses Are Hard or Soft
To summarise, scleral lenses are hard lenses that offer the comfort and functionality often associated with soft lenses. Their advanced design makes them a go-to choice for those with specific vision or corneal needs, bridging the gap between hard structure and unmatched comfort.
If you’re considering scleral lenses, speak with an eye care professional to discuss how they can benefit your vision and overall eye health.
