FIVE TIPS FOR ACHIEVING SCLERAL LENS SUCCESS
Fitting scleral lenses is much simpler once you have the technology and a system in place.
CHAD M. ROSEN, OD, FAAO, & JOSH T. LOTOCZKY, OD, FAAO
Despite being in existence since the late 1800s, scleral contact lenses have only recently gained significant popularity. Based on data from ABB Optical Group, Nichols (2016) stated, “The dollar growth of scleral lenses is up 135% year-to-date compared to the same time frame last year.” This shows how quickly scleral lenses have risen to fame. We are seeing a shift from scleral lenses being used primarily on irregular eyes to their use on eyes that are described as “normal” in refractive error. As more practitioners become more interested in this type of contact lens, we, as educators, are being asked similar questions on a regular basis. The goal of this article is to highlight a few areas to improve the success rate in fitting scleral lenses for both novice and experienced contact lens fitters.
Not only are eyecare providers becoming more interested in scleral lenses, but patients are also starting to look into their use and to ask questions in the office. Website traffic on patient-oriented sites such as AllAboutVision.com show an increase in searches for scleral lens information over the past five years (Figure 1). This demonstrates a need for eyecare providers to have a method to screen for and fit this type of contact lens. Whether working in a solo practice, a group practice, or an academic institution, as we do, it is vital for consistent care to have a system in place with which everyone in the practice is on board.
Figure 1. Unique webpage views regarding scleral lenses. Courtesy of AllAboutVision.com
TIP 1: KNOW WHEN TO CONSIDER SCLERAL LENSES
As with managing any condition (i.e. glaucoma, dry eye, etc.), it is important to know when certain options are viable for patients. Patients who have irregular corneas have traditionally been, and are still considered to be, good candidates for sclerals due to the lenses’ ability to vault over the cornea and land on more regular scleral tissue. Wagner and Byrnes (2008) state, “Today’s rigid gas-permeable (GP) contact lenses mask the underlying irregular cornea and provide a new refractive surface for the eye.” A non-comprehensive list of eyes that fall within the category of “irregular” includes keratoconus, pellucid marginal degeneration, post-refractive surgery, post-corneal transplant, Salzmann’s nodular degeneration, Terrien’s marginal degeneration, and post-trauma. Simply utilizing the GP contact lens qualities can neutralize many optical aberrations at the anterior surface of the cornea and improve a patient’s visual acuity (Griffiths et al, 1998).
More recent studies report an increasing amount of evidence suggesting that patients who have irregularly shaped corneas would benefit from wavefront-guided optics incorporated into their lenses. This involves correcting for higher-order aberrations (HOAs), such as coma and trefoil, as opposed to just addressing the more common lower-order aberrations, such as myopia, hyperopia, and astigmatism. There does appear to be promise in this area, as wavefront-guided lenses can qualitatively improve vision in patients who have keratoconus whether they have large or small pupils (Marsack et al, 2014), and they have substantially reduced HOAs in patients who have advanced keratoconus (Sabesan et al, 2013).
One of the main reasons for the growth of scleral lenses over the last few years has been the increase in their use as a means of correction for patients who have regular corneas. While this practice has proven beneficial for these patients, slightly different considerations must be realized. Because patients who have regular corneas are used to consistently clear vision with glasses and more traditional contact lenses, a careful evaluation of lens prescription must be performed to achieve optimal results. Clinically, we see inferotemporal decentration of scleral lenses on-eye a majority of the time. In one study, a clinically significant amount of residual against-the-rule (ATR) astigmatism was present, creating questions as to the exact impact that inferiorly displaced scleral lenses have on inducing astigmatism (Ramdass et al, 2016). While this can be managed with toric optics on the front surface, practitioners must consider this when fitting scleral lenses to satisfy patients who have regular corneas. Due to high visual expectations, they may not be happy with spherical equivalent corrections.
To aid in the rotational stability of scleral lenses, front-surface toric correction is frequently manufactured in combination with toric haptics. Make sure to confirm that the lens rotates in a repeatable fashion to ensure that the axis of the cylinder correction is in the proper position for clear vision.
In addition, short-term experimental studies have demonstrated that less corneal edema is observed with eight hours of scleral contact lens wear (using high-Dk materials) than is typically observed with overnight eyelid closure (Schipper and Lotoczky, 2016; Vincent et al, 2016). This suggests that these lenses may be relatively safe for longer-term wear in this type of patient, but more studies are needed to confirm this.
TIP 2: USE TOOLS & INSTRUMENTS TO YOUR ADVANTAGE
Corneal Topography We have many tools at our disposal in caring for patients. When fitting corneal GP contact lenses, keratometry and topography readings play a key role in selecting the proper lens; these lenses land on the surface of the cornea, so it makes sense to obtain the corneal curvature measurements. Because scleral contact lenses don’t rest on the cornea, corneal curvature readings don’t play as big of a role in selecting these lenses. This doesn’t mean that the corneal topographer is useless for fitting scleral contact lenses, but understanding that it plays a different role in selecting lenses is important.
Modern scleral contact lenses focus on sagittal depth/height, rather than curvature. As such, some topographers have the ability to extract information from a scan and calculate sagittal depth. This can make the fitting process of scleral lenses similar to that of corneal GP lenses. Corneal topographers are also good at measuring the horizontal visible iris diameter (HVID) and the diagonal visible iris diameter (DVID). Depending on the instrument being used and how wide of an image it provides, HVID may not be obtainable. In these cases, it is recommended to use DVID. We have learned that HVID plays a larger role in sagittal height/depth than does the base curve (BC) of a lens (Young, 1992). By understanding that larger-diameter corneas may have greater sagittal depth compared to smaller-diameter corneas (in normal eyes), we at least have a starting point for how deep of a scleral lens may be needed.
Other studies have looked at large numbers of “normal” eyes, finding that the mean ocular sagittal height at a 15.0mm chord is approximately 3,700 microns (Hall et al, 2013). Using this information combined with desired lens vault for a particular design can help in selecting the initial lens.
Optical Coherence Tomography Optical coherence tomography (OCT) has done wonders for eye care. In addition to its use in evaluating the retina or optic nerve, we can also use it to determine sagittal height of the eye and to measure the vault of the lens over the corneal surface. This can be helpful for those who are unsure in their slit lamp evaluation or when getting started in fitting scleral lenses. If your office has a posterior-segment rather than an anterior-segment OCT instrument, a simple adjustment can be made on many instruments to focus the image on the cornea rather than on the retina.
Corneo-Scleral Topography Another type of instrument that has been developed recently is the corneo-scleral topographer/profiler. These instruments use fluorescence to capture information from the cornea and sclera, creating 3D images and providing sagittal depth calculations. They are different from traditional placido-based topographers, which generally capture a smaller area in one scan.
Slit Lamp Perhaps the most important tool to use when fitting and evaluating scleral lenses is the slit lamp. Utilizing various types of magnification and light combinations, it can provide all of the information necessary to properly manage these lenses and should not be overlooked.
TIP 3: DEVELOP A FITTING PROCESS FOR THE PRACTICE
For any practice, proper flow is a necessity for smooth operations. From office staff to technicians, scribes, and eyecare practitioners, it is vital to ensure that all members are on the same page for patient care. Just as an eyecare office has a protocol for fitting soft contact lenses, it is important to develop one for scleral lenses as well. Large practices that have numerous providers and staff members can create scleral lens management challenges, so having a protocol for fitting scleral lenses can be a lifesaver.
Whichever method is used to select an initial lens (i.e. topography, HVID, OCT, fitting guide recommendation, etc.), be consistent and train staff/technicians to follow the same process. We work in an academic setting with students. Because numerous providers fit scleral lenses, a consistent method of lens selection and evaluation has been created and taught to all involved. The following steps can be helpful for office flow:
1) Evaluate patients’ eyes and select scleral lenses based on their condition, HVID, and the manufacturers’ fitting guides.
2) Use sterile, nonpreserved saline solution to fill the lens prior to application. We prefer dipping a fluorescein strip into the filled lens bowl before placing it on a patient’s eye during the initial fitting; applying fluorescein to the front of the lens after application can enhance the lens surfaces during evaluation.
3) Use the slit lamp to ensure that no air bubbles are present and that there is adequate central and limbal clearance (~250 to 350 microns initially over the apex).
4) Allow the lens to settle, especially if there is movement with the blink.
5) Perform a sphero-cylindrical over-refraction; this can often be done while the lens is settling, but be sure to inform patients that the vision will continue to improve as the lens settles and once the fluorescein has been removed from behind the lens.
6) After the lens has had time to settle, use the slit lamp to re-evaluate the central clearance, limbal clearance, and the landing area 360° around the lens. It is important to note this because most lenses decenter slightly inferotemporally, creating vault that isn’t uniform; this does not usually cause major issues for patients.
7) Confirm the prior refraction and refine it if needed.
8) Use a suction cup tool to remove the lenses, making sure to grab the lens from the edge at either 6 o’clock or 12 o’clock to break suction (Figure 2).
Figure 2. Scleral removal at the bottom edge of the lens with a suction cup tool.
The total process can often be performed in 15 to 20 minutes, and technicians can help with many of the steps. The key is becoming proficient at evaluating the fit properly, as lenses will settle over time at different amounts based on the lens design (Kauffman et al, 2014), with one design showing 25% of total settling after 20 minutes on the eye (Bauer and Lotoczky, 2015). Examples of what to evaluate can be found in the Scleral Lens Fit Scales (Lotoczky et al, 2014). In addition, perceptive clinicians can provide thorough information to their manufacturing laboratory on where design adjustments are needed. This helps the lab consultants provide the most accurate advice for parameter changes.
Have patients return to the office after approximately one week of wearing their new lenses. It is important for them to wear the lenses for at least four hours prior to the appointment. Upon examination, it is essential to evaluate all areas of clearance and landing prior to removing the lenses, as this provides information on how the lenses sit once they have settled. Once the lenses are removed, a corneal health evaluation with the slit lamp and fluorescein helps determine whether the lens is landing on the cornea anywhere and causing staining.
TIP 4: UNDERSTAND COMMON LENS TENDENCIES
There are certain trends that are starting to emerge with scleral lenses, and being familiar with them can help with successful fitting. One of the common findings noted upon clinical evaluation of a scleral lens fit is lens decentration. If the lens doesn’t center, it tends to move inferiorly or inferotemporally (Ramdass et al, 2016), as has been found in studies of normal eyes. This is most likely due to the anatomy of the eye. When evaluated with anterior segment OCT, a significant difference in scleral curvature has been noted between the superonasal and superotemporal quadrants (Kasahara et al, 2014). Decentration may not have a major impact on visual performance with low spherical lenses, but it must be considered if desired results aren’t being achieved. This plays an even larger role when using high spherical powers, toric powers, and multifocal optics, as centration is key to proper visual correction. As lens designs progress more and multifocal optics become more prevalent in sclerals, this issue must be considered.
Another finding that comes up when using scleral lenses is clouding after a certain amount of wear time. This is often referred to as “midday fogging” (MDF) because it requires patients to remove lenses part-way through the day due to clouding or haziness in their vision (Figure 3). Once the lenses are removed, cleaned, and reapplied, the vision becomes clear again. This MDF has not been fully explained in scientific literature, but there are thoughts that the debris contains a lipid component (Walker et al, 2016), that it is more common in patients who have dry eye and inflammatory conditions (McKinney et al, 2013), or even that larger amounts of lens vault over the cornea contribute to this phenomenon. To lessen MDF, use thicker, preservative-free artificial tears to fill scleral lenses, decrease the vault of the tear reservoir, and ensure that no edge lift-off or tear exchange is present in the landing area.
Figure 3. OCT image showing clouding progression under a scleral lens starting at baseline (top image), four hours (middle image), and eight hours (bottom image).
A third finding that can present with scleral lens wear has been termed “conjunctival prolapse” due to the nature and appearance of the bulbar conjunctiva under a scleral lens. This can occur under areas in which there is significant lens clearance over the limbal area (Caroline and André, Aug. 2013) and can be seen in patients who have irregularly shaped corneas that extend onto the limbus. While not as common as lens decentration or MDF, it is still prevalent enough to be on practitioners’ radar. We have also encountered clinical cases of conjunctival prolapse in patients who have conjunctival chemosis secondary to seasonal allergies. In many instances, prolapse of the conjunctival tissue doesn’t appear to cause permanent changes to the eye. There are some cases, however, in which the conjunctival tissue anchors itself to the underlying cornea (Caroline and André, Sep. 2013). Because the corneal stem cells are located in the limbus, make sure to closely monitor patients who exhibit conjunctival prolapse.
TIP 5: STAY CURRENT ON CHANGES
As fast as scleral lenses are gaining popularity among eyecare providers and patients, the information regarding lens designs and the uses for them continues to evolve. One topic that has been discussed more frequently is the use of toric haptics. The haptic is the area that comes into contact with and lands on the sclera. Toric haptics are used when the shape of the ocular tissue is not rotationally symmetric. In fact, it has been stated that many scleras demonstrate a with-the-rule (WTR) shape and can benefit from toric haptic scleral lenses (Bennett and Henry, 2013).
For example, a 26-year-old white male presented to the University Eye Center at the Michigan College of Optometry. He had a history of unsuccessful soft contact lens fits and discomfort, but no ocular pathology. He was interested in being fit with scleral contact lenses and stated that he had been hearing a lot of positive comments about them. Topographical imaging of the right eye showed 1.30D of limbus-to-limbus corneal astigmatism. When an elevation map was used to evaluate the height differences between the horizontal and vertical meridians of the right eye, a 200-micron difference was noted in the cornea between the two meridians (Figure 4).
Figure 4. Corneal topography of right eye showing axial curvature (left) and elevation map (right).
When patients who have seemingly normal eyes are fit in a scleral lens that contains spherical haptics, they may return to the clinic after wearing the lens for a few days and note clouding of the vision. The elevation difference between the horizontal and vertical meridians could continue onto the sclera, creating improper alignment on landing and significant tear exchange that allows debris into the tear reservoir (Figure 5).
Figure 5. OCT image of scleral landing zone with spherical haptic (top) showing lift-off and then with toric haptic (bottom) showing aligned landing.
Utilizing toric haptics allows the lens to land more appropriately in an aligned pattern with the conjunctival tissue on top of the sclera. This also makes the lens rotationally stable, allowing for toric powers to be placed in the lens if necessary.
Work is increasingly being done to customize haptics even more by adjusting four quadrants independently of each other. These quadrant-variable back-surface designs provide practitioners even more options for fitting patients who have non-rotationally symmetric scleras, and we are seeing more options become available from manufacturers.
We know scleral lenses have many benefits and are wonderful tools when fitting patients with contact lenses, particularly those who have irregularly shaped corneas. Using available tools in your fitting process, developing a system for fitting sclerals, and understanding common lens tendencies can create financial benefits as well as improve practice flow and efficiency. It is difficult to create a single set of steps that works perfectly in every type of practice, but in our experience this article provides some important tips that can be utilized in any setting. With the advances in technologies for measuring the eyes and designing lenses, rapid changes are taking place within the area of scleral lenses. From solutions made specifically for scleral lenses with nutrients for ocular health to wavefront-guided corrections, it is an exciting time to be involved in advancing the industry and improving patient care. CLS
For references, please visit www.clspectrum.com/references and click on document #251.
Dr. Rosen is an assistant professor at the Michigan College of Optometry where he teaches in the classroom and as a clinical attending doctor. You can reach him at ChadRosen@ferris.edu. He has also received travel funding from CooperVision and X-Cel Specialty Contacts (X-Cel) and lecture or authorship honoraria from X-Cel and Art Optical.
Dr. Lotoczky is a professor at the Michigan College of Optometry where he serves as the chief of the Cornea and Contact Lens Service and teaches courses in contact lenses and anterior segment disease. He is a consultant for Valley Contax and has received travel funding from CooperVision. You can reach him at firstname.lastname@example.org.