In Focus Blog

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SynergEyes In Focus Blog

At SynergEyes, we pride ourselves in delivering contact lens products that improve vision and ultimately enhance the quality of everyday life.

This blog is geared towards practitioners to highlight case studies from your peers and covers topics such as fitting & troubleshooting, as well helpful articles on practice management and the handling and care of SynergEyes lenses like Duette and UltraHealth.

Why Shape Matters: Impact of Cornea and Sclera Shape in Specialty Contact Lenses

By Amy Hellem

Our deep understanding of corneal shape has driven contact lenses design since its very beginnings, resulting in the development of outstanding options for vision correction. However, as scleral lenses gained popularity, researchers began to question how applicable their knowledge of corneal shape is when designing a lens that lands beyond the cornea.

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What they discovered is that it is not possible to make assumptions about the shape of the whole eye based on the cornea. On the contrary, the anterior ocular surface is unique and, to truly optimize scleral lens design, it is necessary to integrate principles of scleral anatomy as well.

Corneal Shape Scleral Shape

It was once assumed that, like the cornea, the sclera features a curved shape.[1] As researchers looked more closely at maps and molds of the eye, they discovered that from the peripheral cornea onward, the sclera often continues in a straight line, otherwise known as a tangential.[2]  

Researchers at Pacific University College of Optometry took measurements of 96 eyes and found that the shape of the transition area between cornea and sclera was straight in most cases, with only one-quarter of cases exhibiting concave shapes as well as few convex shapes.[3] 

The anterior scleral shape was also tangential in most cases.[4] This is valuable insight that can have a tremendous impact when designing lenses that are meant to rest on these zones.

The Nonspherical Sclera

Another interesting discovery that is having a big impact on emerging scleral lens designs relates to the fact that, even within the same eye, scleral shape is inconsistent from one meridian to the next. Additionally, researchers have now discovered that the ocular surface is not rotationally symmetric outside the corneal borders.[5]

Interestingly, although it is not often taken into consideration here in the United States, this awareness of scleral shape is not brand new. In fact, it was described back in 2006 by Esther-Simone Visser,[6][7][8] MSc. PhD. Optometrist.

Shape and Scleral Lens Performance

Why continue to design scleral lenses to fit corneal shape when that is not where they rest?

Consider the impact of a nonrotationally symmetric sclera on scleral lens design and fitting. Is this ideal for fit and comfort? Current thinking implies that it is not.[9][10][11][12] 

Knowing this, Visser and many of her colleagues have been fitting nonrotationally symmetric toric scleral lens designs at 24 Visser Contact Lens Practices located primarily in eye hospitals in the Netherlands.

Here in the United States, eye care professionals now have access to the lenses designed and used by the Visser practices in Europe. The SynergEyes VS lens is an innovative scleral lens with a bi-tangential periphery that aligns with the flatter more toric sclera, creating ease of landing and stability. This exciting new lens is poised to shift the way practitioners fit scleral lenses, while simultaneously changing the way patients experience life while wearing them.

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Amy Hellem is an independent writer and researcher who specializes in ophthalmology and optometry. Previously, she served as editor-in-chief of Review of Optometry and Review of Cornea & Contact Lenses and directed the custom publishing division for Review of Ophthalmology.

References

[1] Van der Worp E, Graf T, Caroline P. Exploring beyond the corneal borders. Contact Lens Spectrum 2010;6:26-32.
[2] Van der Worp E, Graf T, Caroline P. Exploring beyond the corneal borders. Contact Lens Spectrum 2010;6:26-32.
[3] Van der Worp E, Graf T, Caroline P. Exploring beyond the corneal borders. Contact Lens Spectrum 2010;6:26-32.
[4] Van der Worp E, Graf T, Caroline P. Exploring beyond the corneal borders. Contact Lens Spectrum 2010;6:26-32.
[5] Van der Worp E, Graf T, Caroline P. Exploring beyond the corneal borders. Contact Lens Spectrum 2010;6:26-32.
[6] Visser ES, Visser R, Van Lier HJ. Advantages of toric scleral lenses. Optom Vis Sci 2006;83:233Y6.
[7] Visser ES, Visser R, van Lier HJ, Otten HM. Modern scleral lenses. Part I: clinical features. Eye Contact Lens 2007;33:13Y20.
[8] Visser ES, Visser R, van Lier HJ, Otten HM. Modern scleral lenses. Part II: patient satisfaction. Eye Contact Lens 2007;33:21Y5.
[9] Van der Worp E, Graf T, Caroline P. Exploring beyond the corneal borders. Contact Lens Spectrum 2010;6:26-32.
[10] Visser ES, Visser R, Van Lier HJ. Advantages of toric scleral lenses. Optom Vis Sci 2006;83:233Y6.
[11] Visser ES, Visser R, van Lier HJ, Otten HM. Modern scleral lenses. Part I: clinical features. Eye Contact Lens 2007;33:13Y20.
[12] Visser ES, Visser R, van Lier HJ, Otten HM. Modern scleral lenses. Part II: patient satisfaction. Eye Contact Lens 2007;33:21Y5.