Depth Matters: Why Dual Sagittal Depth Scleral Lenses Make a Difference
By CharliRae Edmunds, NCLEC, Valley Contax Professional Services Director
🧪 Clinical Challenge
You’ve been working on a scleral lens fit, and you just keep steepening and steepening the vertical meridian of the lens edge to no avail; there is still vertical movement, tear exchange, or the lens is still riding inferiorly. How many times has this happened to you during a fit? As a scleral lens consultant, I come across this issue multiple times a day. The normal ‘tricks’ aren’t working to eliminate the problem, so something deeper must be going on with the fit that needs to be addressed.
📊 Understanding the Limits of Toric SLZ
The average scleral toricity is approximately 210 µm; however, there are some cases where there is more toricity and even more elevation differential at the lens edge. Most scleral lens designs have a toric landing zone available, and this feature does a great job of fitting the average eye because the toricity aligns with the two meridians via the angle and depth.
But what if the angles are correct, but the depth is off on that vertical meridian?
If you continue steepening the angle of the lens edge, you may inevitably end up with some impingement at the very outer edge and still have a lens that is not centered well or stable. That is because the lens is virtually teetering on the horizontal meridian, and no matter how steep an angle you make the edges in the vertical, you are still not getting good, full-edge alignment.
🌀 Introducing the Dual Sagittal Depth Concept
By adding more sagittal depth to the vertical meridian, we can create more lens contact with the sclera from the heel to the toe of the edge. This is the Dual Sagittal Depth concept. By addressing this issue, you will find your lens fits are more stable and center better, which is important if you are incorporating custom optics such as front toric, multifocal, eccentricity, or HOA correction.
🖥️ Profilometry Assistance
Profilometry is a great way to determine how much toricity to incorporate into the lens edges versus the sagittal depth. Valley Contax currently works with the Eaglet ESP to design Dual Sagittal lenses via their DirectConnect system. We can also use the Pentacam CSP reports to empirically design a Dual Sagittal lens. In both cases, a trial lens and thorough evaluation are always needed to help determine lens behavior, rotation, and final lens power.
🔄 Quad-Specific Sagittal Depths
Going a step further, you can use quadrant-specific depths to better center and align the lens with a highly irregular sclera. If a lens is dramatically decentered temporally and the nasal sclera is more elevated than the temporal, it makes sense to adjust the depth in those areas to better center and align the lens optics. You can do the same for the superior and inferior quadrants. It is best to make these types of adjustments with the help of profilometry and lens consultant to get exact measurements.
❓ How Do You Know if Incorporating Dual Sagittal Features Is the Right Way to Go?
🚩 The lens is riding low despite efforts to center it with lower overall vault and edge changes.
🚩 Tear exchange in the vertical/steeper meridian of the edge, even after steepening it.
🚩 Excessive vertical movement in the lens, again despite efforts to adjust edges alone.
🚩 Midday fogging, again despite efforts to even out the clearance and stop tear exchange.
🚩 If any of the above issues are paired with the fact that the patient has high corneal astigmatism.
📞 Let Us Help!
If you are running into any of these issues, we highly recommend reaching out to a contact lens consultant for assistance with incorporating Dual Sagittal Depths into the lens fit. Our consultants are available Monday–Friday, 5:30 a.m.–5:15 p.m. Pacific time. Feel free to email us after hours, and we will get back to you the next business day. To share your profilometry data, photos and videos, you can upload it securely to our file share portal here.
✉️ Don’t Hesitate to Reach Out
As always, I am happy to discuss this topic further.
If you have any questions about this topic or anything else, feel free to email me directly at [email protected].