Disclosures: Trattler reports he has relevant financial disclosures with CXLO, Glaukos, Oculus and Zeiss. Kramer reports she has numerous relevant financial disclosures with scleral lens companies.
September 22, 2020
7 min read
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Strategy of scleral lenses, cross-linking effective in treating keratoconus

William B. Trattler, MD, and Elise Kramer, OD, share their approaches in management of keratoconus and endothelial cell disease.

Disclosures: Trattler reports he has relevant financial disclosures with CXLO, Glaukos, Oculus and Zeiss. Kramer reports she has numerous relevant financial disclosures with scleral lens companies.
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Welcome to another edition of CEDARS/ASPENS Debates. CEDARS/ASPENS is a joint society of cornea, cataract and refractive surgery specialists, here to discuss some of the latest hot topics in ophthalmology.

Ken Beckman
Kenneth A. Beckman

Before the advent of corneal cross-linking and scleral lenses, many patients with keratoconus who developed significant steepening and poor vision required a corneal transplant, which has its own risks, and leads to a lifetime of maintenance and potentially multiple future procedures. Fortunately, many of these patients can now achieve excellent vision and long-term stability without this highly invasive procedure. In fact, unless there is a visually significant central scar, most of these patients can undergo cross-linking for stability and scleral lens fitting for visual rehabilitation and completely avoid a transplant.

This month, William B. Trattler, MD, and Elise Kramer, OD, discuss how they use corneal cross-linking and scleral lens fitting in their management of keratoconus. We hope you enjoy the discussion.

Kenneth A. Beckman, MD, FACS
OSN CEDARS/ASPENS Debates Editor

Cross-linking and scleral lenses go hand in hand

Treatments for keratoconus have improved remarkably over the last 15 years, both in the ability to stop progression of the disease and then also to improve vision, with the help of cross-linking to stop progression and scleral lenses to improve vision. There were other therapies in the past, with the most common treatment options being corneal transplants and rigid gas permeable (RGP) lenses, which both work. However, the ability to perform cross-linking to stabilize the cornea has made a significant difference for patients with keratoconus.

William B. Trattler, MD
William B. Trattler

Cross-linking can not only stabilize the corneal shape, but can in many cases improve corneal shape in patients with keratoconus. As a participant in the Avedro FDA clinical trial in 2008 to 2009, our patients experienced on average 1 D of flattening at 1 year after CXL. Further flattening and reshaping occur beyond 1 year, so many patients can experience improvement in their corneal shape and vision over many years after CXL. For patients with moderate to severe keratoconus, spectacles are typically not helpful. Instead, patients can benefit from scleral lenses, which are a huge improvement over RGP lenses, as they vault over the cornea and provide a bubble of protection and lubrication. They make a big difference by providing excellent vision as well as good comfort in patients with keratoconus.

Cross-linking and scleral lenses go hand in hand. For example, a patient with severe keratoconus may no longer be able to drive or work effectively. On consultation, I will recommend that they see a scleral lens expert for fitting, so that they can get scleral lenses, which will allow them to return to a more normal life. While cross-linking is a critical step in their treatment, it is important to not delay scheduling an appointment for them to see a scleral lens expert. Typically, they will see the scleral lens expert and then return in 4 to 6 weeks for CXL. Cross-linking is the long-term strategy, as CXL will result in improvement in the corneal shape over months and years. But for immediate improvement in vision, it is scleral lenses that will change the patient’s life with the significant improvement in functional vision.

On the other hand, if a patient with keratoconus is able to work, drive, etc, with their current correction, then the first step would be the CXL procedure. In my practice, most patients who present with keratoconus are functional with their current vision correction strategy. Patients would therefore undergo CXL first. If patients who have undergone CXL would potentially benefit from scleral lenses, I typically have them see a scleral lens specialist once their cornea has healed following CXL.

Patient education is critical for patients with keratoconus. Eye rubbing is a known risk factor, so we advise our patients to avoid eye rubbing. One concern is that patients who rub their eyes while wearing RGP lenses may hasten progression of keratoconus, as the hard RGP lens transmits the forces of eye rubbing directly onto the cornea. In contrast, scleral lenses vault over the cornea. If a patient with a scleral lens touches their eye and presses on the scleral lens, they are not actually pressing on their cornea, so the risk for progression is likely much less.

Patients with advanced keratoconus
Patients with advanced keratoconus can potentially experience improvement in corneal shape and improvement in BCVA. This patient underwent corneal cross-linking as part of a clinical study in 2014. Four years later, he has experienced significant corneal reshaping and improvement in vision.

Source: William B. Trattler, MD

Some patients who have endothelial disease, such as Fuchs’ corneal dystrophy, may also have weakness in the cornea. These patients may be experiencing thickening of their corneas due to their endothelial cell disease and at the same time may be experiencing weakening of their corneas from keratoconus. You can see these corneas start to get steeper over time and eventually develop keratoconus.

This is not a common occurrence, but when it does happen, there are a few approaches. First, determine the severity of the Fuchs’ corneal dystrophy to see if the patient would benefit from a procedure such as Descemet’s stripping endothelial keratoplasty or Descemet’s membrane endothelial keratoplasty. If the level of Fuchs’ is mild, physicians should proceed as they would normally with cross-linking and scleral lenses. Patients can achieve great vision with this approach.

If a patient has any issues after cross-linking or scleral lenses, they can always undergo a corneal transplant or a deep anterior lamellar keratoplasty procedure in the future. Consider cross-linking first, and if it fails or there are issues or complications, the next step would be a transplant. While some surgeons may jump straight to a transplant or DALK, they may be missing the opportunity to give the patient a chance to see with the combination of CXL plus scleral lenses. Even after a transplant or DALK, many patients with keratoconus may still need to use a scleral lens, so the less invasive strategy of CXL plus scleral lenses should be considered as a first step.

Scleral lens best nonsurgical technology to treat keratoconus

I am an optometrist who specializes in treating keratoconus and ocular surface disease. I have been working with scleral contact lenses for more than 10 years, and this type of lens is probably the best nonsurgical treatment for patients with keratoconus. Scleral lenses can correct vision in patients who are unable to wear regular contact lenses or glasses, especially for those whose keratoconus is moderate or severe and who can no longer see well with soft contact lenses or glasses.

Elise Kramer, OD
Elise Kramer

Glasses sit on the face; they do not sit on the eye and therefore cannot alter the shape of the cornea. Soft lenses mold to the same shape as the irregular cornea, and they too cannot correct vision if the cornea is highly irregular.

The scleral lens does not change shape when it goes onto the eye. It is filled with a preservative-free saline solution and smooths the irregular corneal surface. The scleral lens does not touch the cornea; instead, it vaults over it and sits on the scleral conjunctiva. It is safe and comfortable to use, even for the most irregular and sensitive corneas or for progressive keratoconus.

Some patients with poor corneal endothelial health may not tolerate scleral lenses, but scleral lenses are never contraindicated. Not every patient with an irregular cornea will do well with a scleral lens. You have to evaluate each patient to decide whether he or she will be a good candidate.

In the case of a patient with severe corneal endothelial disease, it may be difficult to maintain the integrity of the cornea with use of a scleral lens. In particular, patients with either a low cell count or poor endothelial cell quality may not do well with scleral lenses.

In such cases, you should determine the endothelial cell count using specular microscopy, but you should also assess the quality of the cells. You must evaluate polymegathism or pleomorphism. Some patients may have sufficient high-quality cells to tolerate a scleral lens. If you do not have the equipment to determine the quality and quantity of corneal epithelial cells, you can “challenge the cornea” by applying a scleral lens and waiting 4 to 6 hours to assess whether the patient develops a complication. The most common complication would be microcystic edema, which is temporary and reversible. The patient perceives a Sattler’s veil, consisting of rainbow-like colors around light sources.

Scleral lens in an eye
Scleral lens in an eye with advanced keratoconus with intrastromal ring segments providing 20/20 vision. The contralateral eye has a failed corneal transplant.

Source: Elise Kramer, OD, FAAO, FSLS

Even if the patient temporarily develops edema with a scleral lens, the transmission of oxygen to the cornea can be maximized with a scleral lens. Lenses with a high Dk or a highly oxygen-permeable material, minimal tear-film reservoir (to about 200 µm) and/or minimal thickness can be helpful in increasing oxygen transmission, which in turn will increase tolerability of the scleral lens.

If the patient develops edema despite these modifications, lens fenestrations can be added to allow oxygen to pass through. You can also ask the patient to reduce the number of hours that the lens is worn or switch to another type of lens.

Why should you want to fit a scleral lens in these patients? Because of the exceptional vision and comfort you can get with a scleral lens. Several studies have demonstrated their superior comfort vs other types of lenses when fit properly. Most patients, even those with a corneal transplant, can achieve good vision, even 20/25 or 20/20, with scleral lenses. So, they are definitely worth a try.

Another important thing about scleral lenses is that studies have demonstrated their potential for reducing the need for corneal transplants. In particular, the combination of corneal cross-linking and scleral lenses can help delay or avoid a corneal transplant. After corneal transplant surgeries, many patients still need specialty contact lenses, so avoiding this type of surgery in the first place is obviously preferable. Consider sending your patients for “hard lens over-refraction” to see if they can improve their vision. They can then decide if they want to go that route or get a corneal transplant.