SCLERAL FITTING SUCCESS
Improve Your Scleral Lens Fitting Success
A look at 10 things to consider to boost your proficiency when fitting sclerals.
By Gregory W. DeNaeyer, OD, FAAO
Specialty contact lens fitters primarily fit scleral lenses to manage cases of corneal irregularity or ocular surface disease (OSD). As scleral lens use has become more popular, practitioners are also starting to fit them on patients who have regular corneas and have failed with other contact lens modalities.
The functionality of scleral lenses is unique, and there is a learning curve for fitting them. The reward of utilizing scleral lenses is improved outcomes for challenging cases. This article will outline 10 ways to improve your scleral lens fitting success.
1. Streamline the Fitting Process
First, have diagnostic fitting sets readily available that will allow you to manage a variety of cases. Next, determine the geometry of the eye that you are fitting, which will help you with design selection. Some designs are specific for prolate or oblate corneas, while others fit either.
Follow the manufacturers’ guidelines for choosing an initial diagnostic lens. If in doubt, just choose the middle diagnostic lens in your fitting set. Use this lens as a sagittal depth gauge to determine whether you need a steeper or a flatter lens for more or less vault. When choosing the next diagnostic lens, make a relatively big step and then bracket the fit back as needed. Unless you are really close to the desired vault, this is more efficient than just choosing the next lens in your set.
During the fitting process, estimate the central corneal clearance (CCC) for your initial diagnostic lenses using the slit lamp beam. The Michigan College of Optometry Vision Research Institute has a Scleral Lens Fit Assessment Guide (available at www.ferris.edu/ScleraLensFitScales) that can improve accuracy of CCC estimation for both beginners and experienced scleral lens fitters (Dinardo et al, 2014). If available, use optical coherence tomography (OCT) to more accurately measure the CCC of the best-fitting diagnostic lens.
Many of the available diagnostic fitting sets for scleral designs vary by vault, but have standard haptic profiles. With this in mind, find the diagnostic lens that best vaults the cornea, then assess the haptic section. Follow the fitting guide or contact a consultant to make any adjustments as needed.
Finally, take photos of the diagnostic lenses. Images of fluorescein patterns, CCC, and haptic fitting can be invaluable for consultative help, and they may be used later for troubleshooting. Photographs can be taken using a standard digital camera or phone in conjunction with the slit lamp.
If you are having trouble getting clear images, you can take a video instead, which makes it easier to obtain in-focus images. Processing software on your computer will allow you to save a still image from the video (Figure 1) to cut down on file size when emailing. For fluorescein photos, make sure to use a Wratten filter.
Figure 1. A still image taken from a video of a fluid reservoir of a scleral lens.
Choosing scleral lens diameter is critical to success when managing corneal irregularity or OSD. Increasing diameter allows the scleral lens to create more vault, making it more forgiving in nature. However, increasing diameter also makes the scleral lens more difficult to apply. Additionally, because the sclera becomes increasingly more nonrotationally symmetrical with increasing distance from the limbus (van der Worp, 2010), scleral lenses that have large diameters (greater than 17mm) and spherical haptics will often misalign, which can lead to discomfort, reservoir debris, and bubbles.
For most cases, scleral lenses approximately 16mm in diameter provide sufficient vault while maintaining proper haptic alignment. Patients also will have an easier time with application, and they will complain less of reservoir debris. Utilize larger-diameter designs for extreme ectasia or if limbal clearance isn’t achieved after modifications have been attempted for corneas that have relatively large horizontal visible iris diameters.
Scleral lenses are defined as a GP lens that completely vaults the cornea. There isn’t a consensus on what constitutes an ideal CCC when fitting scleral lenses for patients who have corneal irregularity or OSD. Successfully fit patients may have CCC ranges from 50 to 300 microns. Sonsino and Mathe (2013) reported that CCC did not seem to be important when using scleral lenses to manage dry eye, and there was no correlation between vault and visual acuity. Short- and long-term scleral lens settling, which reduces vault, further complicates the matter.
A study by Caroline and André (2012) demonstrated that a 16.5mm scleral lens design had a range of settling between 70 to 180 microns after eight hours of wear. This seems reasonable considering that the average bulbar conjunctival thickness has been reported to be 240 microns (Zhang et al, 2013). In addition, long-term settling may occur secondary to adaptive changes of the bulbar conjunctiva. The risk of late-term settling is that the scleral lens will eventually bear on the corneal surface, causing irritation and corneal staining (Figure 2). If this happens, you will have no choice but to refit the patient.
Figure 2. Corneal impression stain secondary to a scleral lens that settled on the cornea.
When performing diagnostic lens fitting, it is best to assume that the lens will settle up to 200 microns. This means that during the fitting process, you would over-vault the cornea by 200 microns to achieve the desired CCC. Consider having patients wear scleral lenses for a full day to help accurately determine diurnal lens settling. If you are trying to decide between two trial lenses, it makes sense to err on the side of steep rather than flat.
4. Front Torics
Patients who are not meeting visual expectations with scleral lenses may have uncorrected residual astigmatism. It is important that you check for cylinder when doing an over-refraction during fitting or at follow ups. If residual astigmatism is measured, do an over-topography or over-keratometry to determine whether the residual astigmatism is secondary to lens flexure, which will result in an astigmatic reading. Increasing lens thickness can reduce lens flexure.
Residual astigmatism secondary to lenticular astigmatism can be corrected with glasses used in conjunction with scleral lenses or by designing a front-surface toric. Some practitioners may shy away from utilizing front-surface correction because of previous experiences with unstable front-toric GP designs. However, scleral lenses that are ballasted provide a predictable and stable platform to incorporate front-surface toricity. Patients will appreciate the improved visual result and will be grateful to not have to wear over-glasses to achieve their best vision.
5. Haptic Success
The haptic section of a well-fit scleral contact lens evenly rests on the bulbar conjunctiva without significant compression, impingement, or areas of edge lift. However, as stated earlier, the sclera is nonrotationally symmetrical, and a spherical haptic won’t always align perfectly. Small areas of blanching are acceptable as long as the patient is comfortable and there isn’t significant resistance when properly removing the scleral lens.
If a lens causes severe compression that results in seal-off, the lens haptic will exhibit 360º of peripheral blanching and associated paralimbal injection (Figure 3). This will cause the lens to be uncomfortable to wear and difficult to remove. Correct for this by significantly flattening the peripheral curves or switching designs.
Figure 3. A scleral lens that results in excessive compression.
Sometimes you can over-push a diagnostic lens onto the eye during fitting, which will cause temporary peripheral blanching. If the lens is allowed to settle, the blanching will dissipate if it is fitting appropriately. A quick test to differentiate a tight-fitting lens from a lens that has been pushed on too hard is to remove it and judge the amount of resistance. If it removes easily, then the lens is probably not too tight.
Areas of edge lift are unacceptable because they will not only induce bubbles (Figure 4) and debris, but they will cause the lens to be uncomfortable. Troubleshoot this complication by switching to a smaller-diameter lens or by using a toric back-surface haptic.
Figure 4. Bubbles under a scleral lens secondary to haptic-sclera misalignment.
6. Lens Notching
Any practitioner who fits soft contact lenses deals with scleral obstacles (e.g., pingueculae) on a daily basis. Soft contact lenses have the advantage in that they are able to successfully drape over most lumps and bumps found on the bulbar conjunctiva. The firm nature of GP scleral contact lenses prevents draping, and scleral obstacles can create a fitting complication.
Two of the most common obstacles that can interfere with a scleral contact lens include pingueculae and conjunctival blebs after trabeculectomy. Consider a corneal GP lens, specialty soft lens, or hybrid lens if a patient who requires a specialty contact lens has a significant scleral obstacle. However, if a scleral lens is the patient’s best option, then have the manufacturer create a small notch that will bypass the obstacle. A notch that is larger than 2mm wide and 2mm deep will likely induce bubbles. So, a relatively smaller-diameter scleral lens will require a relatively small notch, which will decrease the likelihood of bubble formation. Keep a notched trial lens in the office for diagnostic fitting.
Photographs of the diagnostic fitting will help with design consultation and modifications. At the dispensing visit, instruct the patient to apply the lens like a puzzle piece so that the notch matches up with the obstacle.
A successfully fit scleral contact lens will provide optimal vision, be comfortable to wear, and maintain or improve the health of the anterior ocular surface. If you are able to achieve all three of these objectives, then the fitting process is complete. In other words, a successful fit doesn’t always look picture perfect. One mistake during the fitting process is to make modifications too soon.
At the first dispensing visit, if vision and fit are acceptable, then send the patient home to start the adaptation process. Don’t send the patient home with the lenses if they are not meeting specific vision-related legal requirements, such as driving or flying. At the first follow-up visit, you will have a more complete assessment of what modifications to make with fit and power after receiving subjective input from the patient.
8. Education, Mentors, and Consultation
There is a learning curve for fitting scleral lenses. Thankfully, there are abundant resources and help that is readily accessible. Attending meetings, webinars, and workshops will get you started and inform you of more advanced options. Or, contact colleagues who already fit scleral contact lenses and ask them to be a mentor for you as you get started fitting patients. Manufacturing consultants also are an invaluable resource for troubleshooting fits and complications. Applying experience from other fits helps them to readily assess and resolve issues that you may have during the fitting process. Additionally, a forums page on the Scleral Lens Education Society’s website (www.sclerallens.org) is another place you can start a discussion or ask a question on a particular problem or topic.
9. Patient Education
Educating patients about the fitting and use of scleral lenses is important to success. Discuss why they are a good candidate for scleral lenses versus other modalities. Explain the nuances of wearing scleral lenses that are different from other lens designs. At the dispensing visit, they should be informed of contact lens risk and safety just like any other contact lens patient in your practice.
It’s helpful to send patients home with copies of instructions that review all aspects of lens care and risk. Another resource is a video (sponsored by Bausch + Lomb) on the Scleral Lens Education Society’s website that covers scleral lens application, removal, and care.
10. New Designs and Technology
The popularity of scleral lenses has ignited specialty lens manufacturers to introduce new designs and lens options. Reach out to various manufacturers’ representatives or explore their websites to learn about what they have to offer for your scleral lens fitting needs.
Practitioners have the option to customize the back surface with the EyePrintPro (www.eyeprintpro.com) when standard large scleral designs fail secondary to poor haptic fitting. In the next few years, other customization options will include the ability to improve optic zone centration, which will decrease aberrations and maximize multifocal optics (Figure 5). A future application is the addition of wavefront-guided optics to correct residual higher-order aberrations secondary to posterior surface corneal irregularity. Scleral topography also will be used to help with design and fitting. Using cutting-edge technology will not only improve your success, but it also gives you a competitive advantage in your local area.
Figure 5. Measuring the optic zone placement of a scleral contact lens relative to the pupil.
And One More ... 11. Practice!
The most important way to improve your success with scleral lenses is to fit more patients, which means attracting patients who need scleral lenses for improved vision or health. Update your website to include scleral lens fitting, because these patients often rely on the Internet for information and self referral.
Corneal specialists are the true pipeline for patients who need scleral lenses. Introduce yourself to ones in your area and let them know how you can help their challenging patients who have corneal irregularity or OSD. CLS
For references, please visit www.clspectrum.com/references and click on document #228.
Dr. DeNaeyer is the clinical director for Arena Eye Surgeons in Columbus, Ohio and is a consultant to Visionary Optics, B+L, and Aciont. He has financial interest in the Europa scleral lens and in a scleral lens for regular corneas currently in development with Visionary Optics. You can contact him at firstname.lastname@example.org.