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The annual congress of the Netherlands Ophthalmological Society (NOG) – the scientific professional association for ophthalmologists – took place on April 2, 2025.
For the second year in a row, Chrétien took the stage to share his passion and expertise around keratoconus. With his presentation he took the attending ophthalmologists through the latest insights and groundbreaking developments he works with.
A great opportunity to create more awareness about keratoconus and to show what the Keratoconus Center NL now makes possible for patients.
Below is an excerpt from the presentation, in which Chrétien explains the added value of a wavefront-corrected scleral lens.
Keratoconus patients see better with scleral lenses with wavefront correction.
Scleral lenses make vision better, but vision is not yet perfect:
Scleral lenses are increasingly being fitted to patients with keratoconus. The insights and possibilities for improving the fit of this lens type have improved significantly in recent years. Yet, in keratoconus (KC), many higher order aberrations (HOAs) remain uncorrected after fitting standard scleral lenses. As the degree of KC increases, the result gets worse and worse. Very typically a KC patient, after correction with scleral lenses sees shadows (ghosting) at the top of the optotypes.
By no means all KC patients will complain of a suboptimal end result. They see significantly better with scleral lenses than without correction. Nevertheless, it is very easy to demonstrate a suboptimal result with the stenopean orifice (this is 1 or more small holes of 1mm diameter in a (metal) plate). When KC patients have better vision stenopically, it is highly plausible that uncorrected HOAs are the reason for the lower vision. “Can I take this glass?” is an oft-asked question. Unfortunately, it is not that simple.
What the KC patient is not properly informed of is the announcement that 95% vision has been achieved. This percentage is scored when vision rule 1.0 is read almost completely correctly. However, vision 1.0 is not the same as 100 percent. What percentage is seen when vision rule 1.2 or 1.5 is read?’ So far it can be said that no KC patient with scleral lens correction could see 100% or more again. An ordinary vision test also says nothing about contrast loss, monocular diplopia, photophobia and starburst complaints in this regard.
Research shows that vision can be significantly improved:
Ray tracing aberrometry currently seems to be the best method to investigate the uncorrected higher order aberrations. Through 256 consecutive infrared laser measurements, it is possible to measure the vergence differences in the pupil plane. See Fig1. After this, it is possible to construct a refraction map, where after correction with a scleral lens, a negative vergence is seen in the upper part of the pupil and a positive vergence is seen in the lower part of the pupil. See fig.2
Even so, even this technology does not provide an easy answer to the question, how to fully restore visual performance. A 2013 study on the effect of wavefront-guided scleral lenses shows that it is already technically possible to correct all higher-order aberrations. Vision was found to improve significantly with this correction, but still these patients scored 2.2 lines below average vision compared to patients without keratoconus. Apparently, there is more to it. In fact, the study by the Keratoconus Center Netherlands shows that when 40% of the eye error coma is corrected there appeared to be more vision gain than when the HOAs are completely corrected. The path to ever better correction may lie between these two solutions. The big question is: where are our thinking errors and how do we get better results. Now that the biggest bumps of fitting problems with scleral lenses have been overcome, it is time to improve optical performance. Work to be done, then.
