Scleral Lens Technology: Wavefronts, Impressions, and More

Jan 25, 2022
7 min read
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Want to take your scleral lens practice to the next level with new technology? Here are my top three pieces of equipment and/or software to add to your office to help you fit specialty lenses more accurately and quickly.

Scleral topography and scan-based lens design software

At this point you’ve probably heard of scleral topography. It has been gaining in popularity and many doctors, including myself, have it and love it.  

Scleral topography takes scans of the cornea and the sclera. They typically use multiple scans of the eye (one newer version uses only single scan) and stitches them together to make a rendering of the eye to show scleral elevation data on a more “3-D” level.

I implemented this piece of technology (the scleral topographer) and software (to design and order scan-based scleral lens designs) because I knew it would help fit my patients more efficiently and reduce the amount of lens remakes, especially with difficult-to-fit patients.. 

In my experience so far, my patients love seeing this technology. I use it to explain to them that they need customized peripheral curves and use the data to order conventional lenses with toric and quadrant-specific peripheral curves, as well as lenses with toric limbal elevations.

This technology can also tell you what trial lens to choose, depending on the diameter of lens you prefer. Some can even inform you of what peripheral curves to order based on integration with lens manufacturers. It is truly amazing technology to reduce chair time, impress your patients, and hone your clinical skills. 

The software to design scan-based scleral lenses can be integrated to use with many different manufacturers, each with their own scan-based lens design. This creates a more customized lens for the patient which can result in improved comfort, centration, and fit of the lens. 

Patient case:

Here is an example of how this technology helped me fit a lens for a patient with an extremely toric sclera:

This patient has a history of radial keratotomy and through scleral topography, we learned that they had an incredibly irregular sclera. If you look at their scleral topography below, you can see that their scleral elevation is 42 degrees temporally, 46 superiorly, 29 nasally, and 46 degrees inferiorly.

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For this patient, we used quadrant specific meridians on his left scleral lens.

Superiorly and inferiorly, we fit them with peripheral curves that are classified in this particular lens as Steep 12 (12 steps or 360 microns steeper than standard), nasally was Flat 12 (360 microns flatter than standard), and temporally they have a Flat 2 (60 microns flatter than standard).

The final lens parameters were:

Zenlens / Oblate / 5030 Sagittal Depth / 17.0 Diameter / 8.08 Base Curve / +1.25 -4.75 x 162 / HydraPEG / Clear / 0 (temporally)-Flat 2, 90 (superiorly) Stp10, 180 (nasally) Flat 12, 270 (inferiorly)- Steep 10, FC 0 / 0.41CT

This patient had a lot of redness on their conjunctiva before these changes were made, especially nasally, but they have a white and quiet eye with a well centered lens.

Wavefront aberration correction

Wavefront aberrometers are machines that observe rays of light as they travel through the eye, bounce off the retina, and come back to the machine to quantify the amount of aberration (spreading of light from a point) in the visual system.

Lower order aberrations are the well-known refractive errors such as sphere and cylinder. Scleral lenses easily correct these. Higher order aberrations such as coma and trefoil (remember learning about these from first year optometry school?!) can cause complaints such as “glare”, “halos”, or “comet-like tails on lights.”1

People who have these types of complaints are often those who achieve 20/20 vision with scleral lenses but are what I call "20/20 unhappy.” In patients who are still very symptomatic for visual aberrations, even with a well-fit scleral lens, this is my next recommendation for them.

Higher order aberrations are now able to be corrected with a scleral lens. The way that this works is that different corrections are specified throughout the lens. A simplified explanation is that if you have a lens that has a -5.00 prescription, the lens with wavefront aberrations will incorporate many small areas of slightly different correction throughout the lens (-5.00 centrally, -5.15 superior nasally, -5.20 inferiorly, etc). They will also decenter the central optics by measuring the higher order aberration profile once the scleral lens is on the eye.

These can be fit for patients with and without corneal conditions. One study of 11 patients with keratoconus fit with scleral lenses, showed that when they introduced higher order aberration correction, they were able to reduce the root-mean-square of higher order aberrations by 3.1x on average, improved visual acuity by an average of 1.9 lines, and increased contrast sensitivity.2

I would recommend considering this piece of equipment if you fit an incredibly high amount of scleral lenses and are interested in offering the highest level of optical correction.

Impression-based scleral lenses

Having a tough time getting the perfect fit for some incredibly difficult eyes? This is another great piece of technology to introduce if you fit a large volume of scleral lenses and have severe ocular surface disease.

Impression-based scleral lenses are scleral lenses that are designed by taking an impression of the eye using a molding material, scanning the impression into software, and cutting the lens. This creates a highly customized and incredibly specific, comfortable, and stable scleral lens for the patient.

After implementing this technology in my office in early 2020, impression-based lenses quickly became one of my most popular lenses. It is a great tool to have for those patients with highly irregular scleras or large tissue mounds who find conventional scleral lenses still uncomfortable, even after many iterations. Patients with large pingueculas, glaucoma surgeries, or post-surgical scleral abnormalities can benefit from the specificity of using a direct impression to design the lens.

Using this technology requires an in-office training by members of the manufacturing team who fly out to your office and see patients with you for a day. You will have impression material, molding cups, and tips as well as the software necessary to order lenses. After taking impressions you send the impressions to the lab where the molds are scanned into a digital file and cut by a lathe. 

These are extremely custom lenses which mean they can be used for those who have “failed” other types of scleral lenses due to discomfort. Because of their centration, vision with these lenses can also be better than conventional scleral lenses due to better centration of the optics over the visual axis. This is compared to most scleral lenses which have a slight inferior temporal decentration (even with the best fitting lens) and will decenter the optics slightly.

Conclusion

I hope this helped narrow down the vast array of incredible instrumentation and tools that we have available to us. Going the extra mile for hard-to-fit cases can help foster lifelong doctor-patient relationships while also improving practice profitability. Clinicians who routinely fit scleral and specialty contact lenses should consider updating their scleral lens technology to better suit their patient’s visual needs. Patients of mine have benefited immensely by some of these tools.

References

  1. Maeda N. Clinical applications of wavefront aberrometry – a reiew. Clinical & Experimental Ophtahlmology. 2009 37(1); 118-129.
  2. Sabesan R, Johns L, Tomashevskaya O, et al. Wavefront-Guided Scleral Lens Prosthetic Device for Keratoconus. Optom Vis Sci 2013 Apr; 90(4): 314-323.
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About Caitlin Morrison, OD, FAAO, FSLS

Dr. Morrison is residency trained in cornea and contact lens and is the owner of In Focus: Specialty Contact Lens & Vision Solutions, a private practice in Scottsdale, Arizona specializing in contact lenses for advanced ocular conditions and comprehensive …

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