The Developing Role of Scleral Lenses in Today's Society
The Developing Role of Scleral Lenses in Today’s Society
Scleral lenses are fast becoming a good fit for today’s “do it faster, do it better” way of life.
By Melissa Barnett, OD, FAAO, & Brooke Messer, OD
||Dr. Barnett is a principal optometrist at the UC Davis Medical Center in Sacramento, where she performs primary and medical eye examinations and fits contact lenses, including specialty contact lenses, in addition to teaching optics and contact lenses to ophthalmology residents. She is a consultant or advisor to Alcon, Allergan, and SynergEyes.
||Dr. Messer practices in Minneapolis, Minn. in a private optometry office focused on specialty contact lenses. She fits specialty contact lenses for keratoconus, post-surgical corneas, and other corneal diseases as well as multifocal contact lenses, orthokeratology contact lenses for myopia control, and pediatric contact lenses. She is a consultant or advisor to Precilens, has received research funding from Ciba/Alcon and Bausch + Lomb, and has received honoraria from Essilor.
As we enter the waiting and optical areas of our offices to greet patients, we often catch them doing a last-minute web search or text message on their smartphone. Many patients have to wrap up a business-related email on the way back to the exam room, and they check their phone during any spare moment of the exam for any updates. As we discuss patients’ health history, they mention a systemic condition, and we wonder about potential ocular complications. Without missing a beat, we perform an internet web search midconversation to instantly gain more information and start planning our exam before they can finish telling us about their grandmother’s cataracts. As the exam concludes, patients ask about their eye condition, and we’ll bring up patient education materials on our office tablet.
Our patients always want to know more about their corneal topography, fundus photos, and contact lens materials. We as practitioners need to be at the top of our game when it comes to on-the-spot interpretations and explanations of ocular data. That’s just a typical day at our offices, and probably something like yours, too.
Changing Times Require a New Way of Thinking
Now that the Internet, e-mail, and GPS are available instantly in the palm of our hands, the speed at which society moves is faster than ever. We want more technology, more information, and we want it now. The same goes for product performance. Can the new model do more, do it faster, and with better results? Why would we keep our fourth-generation smartphone when the fifth is faster and more efficient? We should adopt the same attitude when prescribing for our patients. Which model really will produce the best results?
Our patients are expecting the same mindset from their healthcare providers. They appreciate high-tech scans of their eyes and explanations about new spectacle and contact lens designs. This is especially true for patients who hope to obtain improved performance over their current modality, or those who simply want the best option out there. Why do we keep trying to “make it work” with soft toric contact lenses on these patients when they have moderate-to-high amounts of corneal cylinder? Why do we jump from one soft contact lens design to another on our patients who suffer from dry eye disease, while we watch them lose hope with each soft diagnostic lens that we hand out?
Now is the time for us to keep up with the rest of society and to start doing our jobs better and faster. With the addition of scleral contact lenses in our arsenal, we finally have the tools to do so.
Traditional Scleral Indications and Fitting Philosophies
Scleral GP contact lenses first hit the scene more than 100 years ago to correct vision and promote ocular surface healing in irregular corneas, but several hurdles made them short-lived. The material in which the original scleral lenses were made provided poor transmissibility of oxygen through the lens, which caused corneal hypoxia. The lenses were hand-made and impossible to replicate if broken or lost, and improper fitting techniques sacrificed corneal health.
But with the development of GP lens materials that are described as hyper-permeable to oxygen, as well as computer-driven lathes and better fitting techniques, scleral lenses are again back on the scene, changing lives for those patients who previously thought that they were no longer candidates for contact lens wear. We have nearly three decades of documentation and hundreds of scientific studies demonstrating the success and benefits of wearing scleral contact lenses. Our patients who have keratoconus, corneal transplants, ocular surface disease, and other types of irregular corneas are now enjoying healthy lens wear and great vision with similar initial comfort to that of soft contact lenses.
When modern scleral lenses first reappeared in the market, they were initially described as lenses that were 16.5mm or larger in overall diameter and rested solely on the sclera, with complete corneal and limbal clearance. Initially, an ideal fit included 200 microns to 300 microns of clearance over the apex of the cornea. Some practitioners utilized fenestrations in the optic zone of the lens to assist with tear exchange and oxygen transmission. The most common groups of scleral lens wearers were those who had corneal ectasias such as keratoconus and pellucid marginal degeneration. There was also a small percentage of patients wearing scleral lenses to promote healing of their ocular surface conditions.
A Shift in Mindset
Over the past three decades, the use of scleral lenses has become widespread across many ocular conditions, and the applications for them continue to grow. The largest group of scleral lens wearers continues to be those who have corneal ectasias, but their use in the ocular surface disease realm is expanding at a rapid pace. Scleral lenses are restoring vision in patients who have neurotrophic and exposure keratopathies, replacing the need for tarsorrhaphies and corneal transplants in many cases.
Laboratories are continuing to improve their designs and find ways to make more patients potential candidates for their lenses. In the last decade, developments in scleral contact lens technology have included front-surface toric lenses for residual astigmatism and toric peripheral curves for eyes that have greater-than-average scleral toricity. Reverse geometry designs and multifocal scleral lenses are also available from many laboratories. These options allow us to reach an entirely different group of patients and give us the opportunity to provide an amazing level of customized care for our entire patient base. These changes to scleral designs have improved vision, comfort, and overall quality of life for habitual and new lens wearers alike.
As the technology and designs of scleral lenses continue to change, so have the fitting techniques and the types of patients who can now be fitted with them. Patients who have normal corneas are now considered great candidates, especially when their visual needs are outside of typical soft lens parameters. The addition of normal eyes to the scleral lens-wearing population is a change in philosophy from years past and is gaining popularity. Certain lens laboratories are designing scleral lenses made specifically to vault normal corneas, and patients who have more than a few diopters of corneal astigmatism are ecstatic about their results. Those who have high astigmatism and desire a multifocal option are no longer restricted to corneal GP lenses (even though these remain a great option for lens wear in certain cases).
Another significant change in viewpoint focuses around the overall diameter of scleral contact lenses. The theory behind lens diameter selection remains the same, in that the more sagittal depth needed to vault the corneal apex, the larger the lens diameter should be. But now, diameters come as small as 14.3mm and still maintain a full corneal and limbal vault rather than resting partially on the cornea. While this design is not applicable for all irregular corneas, it has been greatly successful with normal corneas, and a vault of as little as 100 microns is considered acceptable in many cases. The smaller-diameter scleral contact lenses are less intimidating, easier for patients to handle, less expensive, and are typically more predictable to fit.
Small-diameter scleral lenses also require less modification to the peripheral curvatures of the lens. The scleral curvature is most regular and is relatively consistent near the cornea, but becomes more toric and variable further out on the sclera. The most important fitting factor to monitor while using smaller-diameter scleral lenses is to make certain that limbal clearance in maintained during lens wear, ensuring the health of limbal stem cells.
A final change in fitting technique worth discussing is the use of fenestrations. Fenestrations are used very selectively now, on a case-by-case basis. A common contemporary use of fenestrations is to release bubbles that are trapped under the scleral lens as a result of improper application technique, rather than their original uses of promoting the flow of oxygen and facilitating tear exchange.
Scleral lens fitting sets now offer more options for parameter changes to expedite the fitting process. In addition to numerous base curves, many fitting sets include lenses with different overall diameters, changes to the peripheral curve lifts, different curvatures to contour the limbus, and even different specifications in sagittal depth. Utilizing these lenses during the initial fitting process provides instant information to both patients and practitioners that helps us keep up with our “do it faster, do it better” society.
New Concepts for a New Patient Base
With all of the additions in scleral lens parameters and technology, nearly every patient in your office becomes a scleral lens candidate once their vision needs or contact lens frustrations surpass what soft contact lenses can correct. Sometimes, it’s up to us as practitioners to ensure lens satisfaction and to ask patients whether they are satisfied with their quality of vision. Some patients may think that their lenses are the best that they can get, so they do not bother asking about what is new in the contact lens world. Some common groups of patients that may fit into this category are those who have high astigmatism, residual refractive error post-LASIK surgery, and presbyopia.
Patients who have high astigmatism will especially love scleral lenses, because the lens can twist and rotate with no effect on their vision. As you explain the new lens to them, you may encounter some resistance. Most of these patients have been told that they should be wearing “hard lenses,” or perhaps they have already tried corneal GPs and tremble at the thought of attempting to adapt to the lenses again (because frankly, who has time to adapt anymore?). Thankfully, we can use fitting sets in the office on the day of the fitting to meet the “do it faster, do it better” mentality. Once the final diagnostic lens is applied, you are only a few minutes away from showing patients the best vision they’ve had in years through a quick over-refraction. With your astigmatic patients, keep in mind that if their topography shows limbus-to-limbus toricity, it may extend onto the sclera and produce some lens flexure. You’ll see with-the-rule astigmatism on retinoscopy, and patients may mention vision fluctuation or reduced acuity with a spherical over-refraction. I then recommend a sphero-cylindrical over-refraction and keratometry or topography over the lens to gain insight on how much flexure is occurring. Typically, increasing the center thickness of the lens by anywhere from 0.05mm to 0.20mm is my first adjustment, but decreasing the overall diameter is another option that may reduce flexure. A final option for decreasing flexure is to add toric peripheral curves to better contour the sclera.
Patients who struggle with refraction change or mild ectasia after LASIK surgery are another group that struggle to wear contact lenses successfully, especially if any amount of astigmatism is involved. The oblate-shaped cornea no longer fits well to toric soft lenses, and patients become frustrated with lens movement. Scleral lenses are an excellent option for these patients because they provide vision stability and a fluid layer for any residual dry eye. While they are not always necessary, reverse geometry scleral lenses fit post-LASIK corneas very well, as they keep the vault in the center of the cornea from becoming too deep and instead maintain an even tear film from limbus to limbus.
Many post-LASIK patients return to the office looking for contact lens options when presbyopia becomes a problem in their daily routine. But thanks to some hard work by our GP lens laboratories, many well-designed multifocal scleral lenses are on the market today, and we are able to keep these patients satisfied with one of the new lens options out there. Numerous companies are in the process of, or have recently released, multifocal scleral lenses. Table 1 lists some of these lenses.
New Patient Base, New Fitting Tips
After this review, perhaps the most common “new” candidates to consider fitting in scleral lenses are your patients who have normal corneas and wear soft lenses for astigmatism or presbyopia who complain of fluctuating vision or problems seeing at night. These groups will be motivated to switch out of their current lenses and try something new. To be successful at converting our soft lens-wearing patients, we have to prove to them that we can do it faster and with better results while maintaining good lens comfort.
Begin by assessing their current frustration level and their desire to change modalities and undergo a new contact lens fitting. Once patients have agreed to try new lenses, I like to use information from their topographies, corneal diameter, and palpebral fissure widths to help in selecting the lens design. We all know that scleral lenses are comfortable when compared to smaller-diameter corneal GP lenses, but with our soft contact lens wearers, we need to select an appropriate design to ensure a good first experience so that patients can remain excited about the vision potential with a new lens design. Since I started fitting normal corneas in scleral lenses, I have learned a few tips and tricks that help with the education and fitting process. Some of the most effective tips I’ve learned are as follows:
• Lens Diameter Selection The overall diameter of the scleral lens is my first decision, because that is the primary reason scleral lenses are more comfortable compared to corneal GP lenses. Many patients think that their soft lenses are more comfortable compared to GPs because the lenses are soft, but we know that it’s because they have a larger overall diameter. That is an important point to communicate to your patients. The larger lenses sit behind both lids, which minimizes the eyelid-lens interaction and promotes excellent comfort and lens stability. Once patients understand this concept, “hard” lenses are not nearly as intimidating.
|Some Multifocal Scleral Lens Designs
||Maxim Plus, Comfort SL Plus
|Advanced Vision Technologies
||Custom Stable 15 Near,
||Custom Stable 16 Near
But, just because larger lenses are more comfortable, that doesn’t mean that I jump for an 18mm lens for all of my patients. For normal corneas, 14mm to about 16mm scleral lenses work great because the lens size is similar to a habitual soft contact lens, and they fit most normal corneas.
• Observe Corneal Diameter and Palpebral Fissure Widths On the market today are probably 10 or more scleral lens fitting sets with overall diameters between 14mm and 16mm. How do we further choose the appropriate diameters for our patients? Corneal diameter and palpebral fissure width are my next secret weapons in achieving great lens comfort (notice we haven’t even thought about keratometry readings yet). When observing corneal diameter, which is often described as white to white, be on the lookout for larger-than-average corneas. If the cornea is 12mm or more in overall diameter, you may want to begin with a lens that is at least 14.5mm to 15mm so that the lens can appropriately vault both the central cornea and the limbus comfortably.
The same concept applies for when patients have larger-than-average palpebral fissure widths, which is the vertical distance between the upper and lower lids in primary gaze. An average palpebral fissure width is about 10mm. If a patient has an average-sized cornea with a small-to-average palpebral fissure width, lenses that are 14mm to 15mm in overall diameter will perform well, and the patient will appreciate how easy the lens is to apply and remove from his eye. Larger palpebral fissure widths call for a larger lens diameter to ensure that the edges of the lens are tucked behind both lids for good comfort.
These tips may seem self-explanatory, but remember that we are now fitting patients who habitually wear very comfortable soft lenses, and we need to find the scleral lens that will match this comfort or patients will ultimately end up back in their soft contact lenses. Patients who have habitually worn corneal GP lenses are typically easier to please because even a scleral lens that doesn’t fit quite perfectly can match the comfort of a corneal-sized lens, due to the adaptation of their eyelids to GP lens edges. If your patient notes that the lens is “a little uncomfortable,” you may want to apply or order a lens that is 0.3mm to 0.5mm larger to further push the lens edges behind the lids.
• Corneal Topography and Keratometry Readings While a Mayo Clinic study (Schornack and Patel, 2010) demonstrated that there is minimal to no relationship between corneal topography readings and scleral lens base curves, much information can still be taken from these scans to improve your fitting technique. Note that the study involved irregular corneas, but the take-home point is that appropriate scleral lens fitting is more about the amount of lens sagittal depth needed to vault the cornea and limbus, and less about matching lens base curves to the corneal curvatures. Topography maps are a great tool to assist in fitting scleral contact lenses. Knowledge about the shape of the overall cornea can be the deciding factor in your lens design selection.
For example, if the topography shows a moderate-to-large amount of limbus-to-limbus toricity, you might expect the sclera to have a greater-than-average amount of toricity as well. A proper choice of lens design may be one that is available with toric peripheral curves to match the patient’s toric sclera. However, if the corneal toricity is only in the central cornea, then you can be confident that a lens with toric peripheral curves is not needed. Topographic readings are also very useful in evaluating post-surgical corneas.
It’s the Same, But Different
With all of the changes in scleral lenses in the past decade, it can be confusing to keep all of the information straight. Remember that your lens consultants are a wealth of knowledge, as are organizations such as the Scleral Lens Education Society. There are new techniques to learn with newer scleral designs, but the patient communication remains the same. These lenses are healthy, comfortable, and can provide excellent vision correction. The fitting process does require some patience, as the lenses need to be customized to your patients’ eyes. But with clear communication and guidance from your laboratories, adding scleral lenses for normal corneas should be a booster in developing relationships and loyalty with your patients for years to come. CLS
To obtain references for this article, please visit http://www.clspectrum.com/references.asp and click on document #215.
Contact Lens Spectrum, Volume: 28 , Issue: October 2013, page(s): 40 - 55