The question I'd like to ask is: Yes, you can get good results with wavefront, but again, what is the practicality of the matter?
I'M NOT TALKING ABOUT IRREGULAR CORNEAS from cones or grafts. I'm talking about HOA from mother nature and possibly from lenticular changes.
Withe spectacles, just how much position of wear "registration error" exists to offset it, and, for that matter, fingerprints or even scratch coat or AR coat uneveness or even lens stress from lens/frame sizing errors? And how would we reliably even check in such jobs? To me it sounds like folly.
As to CLs, your scleral platform makes sense, but I continue to be skeptical because don't the lenses film, fog, warp, and do everything else my spherical RGPs do?
What's more, is how much "chasing of the HOA" we'd be doing. If it's from lenticular change, is that going to change annually? A pair of glasses should last awhile. If you pay a "HOA premium" in year one (say $200), and the benefit evaporates in 12 months, you can do the math.
And if there are concurrent lower-order aberrations progressing over time, doesn't that wipe out the relatively miniscule gains from HOA correction?
Doesn't "scleral settling" screw things up, too?
I.e., are we hitting a very moving target? I really don't know.
Ah, good questions. Unquestionably the contact lens platform makes infinitely more sense than the spectacle platform. I don't even think about wavefront-guided spectacles except perhaps in reducing spherical aberration. You can always sell a feature, and maybe even convince the patient they can tell the difference. Think placebo effect here. However, wavefront-guided contact lenses are the real deal. Also, there are wavefront readers and one can always measure the wavefront error through the lens in front of the eye with an aberrometer.
Let me answer questions with a couple of examples. Recently I had a patient whose HOA were on the low end of the abnormal scale, and possibly in the normal range depending on the data source. He was 20/20 uncorrected. WG sclerals improved his vision to 20/10. While not everybody is correctable to 20/10, it is much less rare in my practice than it used to be. Maybe this speaks to your more "normal' patients. Think about improving visual performance. Wouldn't an aspiring baseball player love that?
Now, I have a really challenging KC patient who lives in New Zealand. KC is very prevalent down there. He had been having some GPC problems with the sclerals I made for him a year ago. We worked so much on the optics that we neglected to fine-tune the edges on his lenses. He wants to come see me but needs to be out of his Kerasofts for awhile. So, I made him a duplicate set of lenses, this time with the modified edges, and sent them. They were more comfortable. He dutifully had them checked out by his local optometrist and his visual acuity was still the same as before with the other lenses. This should speak to the reproducibility and longevity of both the lenses and the correction. Really this has not been an issue I have had to deal with.
Filming isn't a big problem. Fogging is. But we know why it happens and we know what steps to take to minimize it, but it requires a flexible lens platform - with more design flexibility than currently exists. Scleral settling does happen, in both the Y and Z dimensions. The Z-dimension settling, i.e. lens settles into the conjunctiva, is something that doesn't seem to effect the correction. The Y settling, or the lens dropping down, does matter. This has to be corrected by repositioning the optics. Same with lens rotation. Flexure needs to be controlled, and that is a design issue. Sclerals probably flex less than corneal lenses because they are thicker - typically 250 microns CT minimally.
Prescriptions do change, and so do aberrations over time. However, I haven't found this to be a deal breaker. After all, it is a major reason why we are in business. Most of my KC patients continue to see well. I just had one in the office post one-year sclerals. She is still seeing great with them and chose not to replace them.
Let me add that even if the magnitude of change only converts to a fraction of a diopter, it is enough to improve acuity from 20/20 to 20/10. Think about it. It's very subtle, but very powerful.
