Your patient is ready for their first scleral lens and maybe you are too…even if it’s been a minute. Whether your last fit was a few years ago or back in optometry school, don’t stress. We’re here to help you confidently and systematically evaluate your lenses every step of the way.
Set-Up Essentials: What You’ll Need Before You Begin
When approaching your first diagnostic lens fitting, make sure you have all the supplies needed and ready. This includes paper toweling (or an apron) for your patient’s chest and lap to prevent spills with fluorescein or saline on their clothes, a scleral lens applicator and remover, diagnostic set, gas permeable lens cleaner or conditioner, preservative free scleral lens saline and plenty of tissues.
A little preparation goes a long way. Having everything organized before the lens ever comes out of the case allows you to focus on the fit itself rather than searching for supplies during the examination.
Start Your Exam: Establishing Your Baseline Findings
Begin your examination as you normally would by taking a history and measuring best corrected acuity with habitual spectacles, contact lenses or a refraction. This way you can document appropriate information to demonstrate an improvement in acuity with a scleral lens.
Topographies are useful for scleral lens fitting but are not required. Sometimes the most valuable information comes before the patient even reaches the slit lamp. Simply observing the profile of the cornea can reveal a high sagittal height or the location of significant elevations that may influence your fitting strategy.
For example, if a patient has a corneal transplant, there may be an elevated graft-host junction, and it can be peripheral (Figure 1). Recognizing these elevations early will help guide your evaluation and identify areas where clearance should be examined particularly carefully.
Figure 1: Example of OCT that demonstrates elevated superior graft host junction. Care must be taken not only to bridge over central cornea, but elevations peripherally as well.
Europa Tangent Starting Points: Choosing Your Initial Diagnostic Lens
One of the advantages of the Europa Tangent design is its streamlined fitting philosophy. The diagnostic set was intentionally designed to fit a broad range of patients while reducing the number of trial lenses required to achieve a successful fit. Rather than making multiple interconnected changes, practitioners can independently adjust central clearance, limbal clearance, and the tangent landing zone, making the fitting process more efficient and predictable.
It is helpful to follow the fitting guide. For example, when using the Europa Tangent, you can begin with lens #3 in the top row for regularly shaped corneas or mild cones if you prefer beginning with spherical landing zones. If you prefer using a toric landing zone, then begin with lens T2 (200 microns of peripheral landing zone toricity) on the bottom row.
If the cone is moderate to advanced, then use #5 in the spherical row or T3 in the toric row. Reserve T4-T6 lenses only if 200 microns of toricity is insufficient as these lenses have 400 microns of peripheral toricity.
Remember that the diagnostic set is intended to provide an efficient starting point, not necessarily the final answer. Once the lens is applied, the Europa Tangent step system makes it straightforward to refine the fit based on your observations without significantly affecting other fitting characteristics.
Since all lenses are stored dry in the diagnostic set, it is important to condition the lenses before application. That can be done by rubbing a gas permeable conditioner into the lens or cleaning them with an alcohol-based cleaner but ensure they are rinsed very well with saline before application.
To Use Fluorescein or Not: Evaluating Clearance Without Guesswork
Some practitioners use sodium fluorescein to aid in determining central and limbal clearance. This can be especially helpful if you do not have access to OCT. You can determine areas of narrow clearance by examining the fluorescein pattern with cobalt light and low magnification (Figure 2).
You can see if there is sufficient (Figure 3A) or insufficient limbal clearance without measuring it on the OCT (Figure 3B). Sometimes what looks like corneal contact is actually just narrow clearance, so it is important to examine those areas with an optic section using white light and higher magnification. This allows the fluorescein in the reservoir to be viewed directly (Figure 4).
Figure 2: Overall assessment of fluorescein with cobalt light, Wratten filter and low magnification.
Figure 3: (A) Fluorescein clearance over the peripheral cornea and limbal zone. (B) Peripheral cornea and limbal zone contact with the lens where there is a black arc.
Figure 4: This shows increased magnification of the optic section near the limbus demonstrating clearance as evidenced by the green band.
Evaluating Clearance: What to Measure and Where
Whether you have fluorescein or not, you can measure the clearance using the surfaces of the scleral lens. You are measuring the gap between the cornea and the back surface of the lens relative to the center thickness of the lens.
It may be tricky to view the clearance without fluorescein but as long as you can see the back surface of the lens, you will be able to determine if the lens is touching or measure the clearance (Figure 5).
The center thickness of Europa and Europa Tangent diagnostic lenses is 400 microns (patient lenses are 300 microns). Ideally you would like to have at least 300-350 microns pre-settling, as settling varies and can be as much as 150-175 microns at times. Therefore, you are looking for a clearance-to-thickness ratio that is just shy of 1:1 prior to settling to build in additional space if needed.
Figure 5: The clearance is easily seen when the back surface of the lens is illuminated.
If you are examining a cornea with ectasia, make sure that you are measuring over the apex of the ectasia. If you only measure central clearance, you may underestimate the clearance at the apex as the apex may be more inferiorly decentered (Figure 6).
Figure 6: Here the apical clearance is less than the central clearance. If it is significantly less, the lens may settle and touch the apex of the ectasia while the central clearance may be acceptable.
Evaluating the Limbus: Ensuring Adequate Limbal Clearance
At the limbus, if you do not observe fluorescein crossing over the sclera, or OCT suggests limbal contact or low limbal clearance (Figure 7A), then order the lens with either a higher limbal height (Figure 7B) or increase the overall diameter by 0.5 mm (Figure 7C).
The goal is to maintain adequate clearance across this critical transition zone while preserving the overall fit of the lens. Depending on the clinical presentation, either approach may be appropriate.
Figure 7: (A) The limbal zone is defined by thick epithelial zone above the yellow dotted angle that is typically observed in OCT with the density of the cornea changing into the sclera. The diagnostic lens demonstrates 50 microns of clearance. If a clearance change is desired, it can be increased (B) as a limbal curve step change of 50 microns or (C) an overall diameter change of 0.5 mm which pulls the landing of the lens more peripheral to the limbus.
Evaluating the Landing Zone: Recognizing Compression, Impingement, and Edge Lift
Lastly, examine the landing zone. First, evaluate the landing zone in extreme gaze because compression and impingement will often be exaggerated. Then examine those same zones in primary gaze. If the finding is reduced but not eliminated, then you will typically order a looser landing zone.
If there is impingement at the very edge, then raise the toe up (Figure 8). Typically, a 75 µm change is clinically significant. If there is compression closer to the limbus, or heel-down compression, then lower the toe of the lens to release the compression. You can also flatten the limbal zone to prevent a harsh bend or elbow to the lens.
Figure 8: (A) An aligned scleral lens landing zone where vessels run smoothly and there is no “toe-down” edge impingement into the conjunctiva. (B) A lens that was constructed 300 µm tighter for demonstration shows the edge digging into the conjunctiva and the associated OCT image below.
In heel-down compression you will see a groove-like appearance in the contour of the conjunctiva on OCT (Figure 9).
Figure 9: An example of “heel down” compression where the shape of the conjunctival surface dips down resulting from the junction between the limbal and landing zone.
To determine if there is edge lift, simply apply fluorescein to the surface of the lens to see where it seeps in. It is important to apply the fluorescein behind the slit lamp so you can observe the pattern quickly. Figure 10 demonstrates the fluorescein highlighting the edge lift. Even if there is fluorescein in the reservoir of the lens you will be able to assess the edge lift after a few blinks as long as the fluorescein is applied with the patient at the slit lamp. Oftentimes, when a patient complains of lens awareness, it is most likely due to edge lift. Patients may report that their lenses are tight, but they probably exhibit edge lift. Patients will localize where their symptoms are. Pulling the lids away from the lens will alleviate the symptoms of edge lift. Tight lenses are typically comfortable initially unless they are extremely tight.
Figure 10: Example of edge lift. Always be sure the fluorescein is under the edge of the lens by having the patient blink to clear the fluorescein from the front surface.
If you use a toric lens, note where the hashmark is located (figure 11). The hashmark designates the steep meridian in Europa and Tangent lenses. Evaluate the steep meridian and the flat meridian (90 degrees away) for signs of compression, impingement and edge lift. We will modify each meridian independently to optimize your toric lens.
Figure 11: Example of the toric lens hashmark that can be observed with white or cobalt blue light. The hashmarks on Europa and Tangent lenses is on the steep meridian
If you use a spherical diagnostic lens, identify misalignment and see if it is present along the same axis and then check the opposite axis 90 degrees apart. If there is a difference, then you will most likely need a toric lens. You can either apply the toric diagnostic lens with a sag equal or greater or have consultation assist designing the lens for you.
Over-Refract: Refining Vision Without Overcomplicating the Fit
As with any contact lens evaluation, you will need to over-refract the patient. Some lenses may require high minus over-refractions, so do not be discouraged if the patient initially reports worse vision with the scleral lens on. This is not uncommon.
Continue adjusting in larger 3 diopter steps until the chart becomes clearer for the patient and then refine the result. It is helpful to perform a sphero-cylindrical over-refraction. However, typically the first lens will be designed with the spherical equivalent until the lens is worn and allowed to settle.
Once a lens has stabilized, the next lens can incorporate the cylinder into the optics if needed. Make sure to always document the location of the hashmarks at every examination, especially when front surface optical toricity is utilized. If you have a very high minus over-refraction, you can apply a high minus soft lens to the surface of the scleral and that can help reduce your over-refraction power. Please remember to tell consultation what power soft lens you used!
Piecing It All Together: From Clinical Findings to Lens Design
Once you have systematically evaluated the clearance, limbus, landing zone and over-refraction, it is time to plan your lens order.
By this point, you have gathered all the information needed to make informed lens design decisions. Remember, successful scleral lens fitting is rarely about finding the perfect lens on the first application. It is about following a systematic process that allows you to make thoughtful adjustments based on what you observe.
When you approach the fit methodically, even challenging cases become manageable.
When in doubt, request a consultation. If you have photos and OCTs, please send them along. Feel free to set up time with me if you have challenging cases or simply need a brush up on scleral lenses. We will figure this out together.
Lens ID:
Wearing time:
Rotation of hashmark:
Sag Height: Increase? Decrease? No change (in microns)
Limbus: Increase? Decrease? (in microns) No change? Or change diameter?
Diameter: Increase? Decrease? (in mm)
Landing zone: Flatten? Steepen? (in microns) No change?
Toricity: Increase? Decrease? (in microns and meridian axis in degrees)
Material: We offer many different materials, if you are unsure consultation will help
Material color: Clear for right? Blue for left?
Hydra-PEG:
Dots: Black, white, clear
Over-refraction: Be sure to mention if a power has already been vertexed
