Ehlers-Danlos cornea new insights

New insights into Ehlers-Danlos syndrome

Researchers from ELZA, the ETH Zurich, the University of Zurich and the University of South Florida investigate corneal biomechanics in a mouse model for Ehlers-Danlos syndrome

Having a weak cornea can be bad for your sight – and can ultimately lead to blindness, which is why there are intense research efforts into understanding why some corneas become weak, and others not. But there’s a problem. In most other diseases, transgenic mouse models can be used to understand diseases better but assessing corneal strength – or “biomechanics” – in mouse eyes is a big challenge. Methods that measure corneal strength, such as extensometry, which involves cutting a strip from the cornea and stretching it in one dimension, and assessing the rate at which it stretches, and how much force is required to break the strip are much harder to perform accurately and reproducibly in mouse eyes than in eyes from larger animals like pigs.

But researchers from both the ETH Zurich (www.ethz.ch), the University of Zurich (www.cabmm.uzh.ch), the University of South Florida, and clinicians from the ELZA Institute, Zurich (www.elza-institute.com), previously adapted this approach for extra-small eye dimensions1, and now added one innovative technique: optical coherence elastography (OCE), and one advanced imaging method, Second Harmonic Generation (SHG) microscopy, in order to compare mice with a genetic collagen V deficiency 2, a model for Ehlers-Danlos syndrome. Collagen V is an important component of the structural part of the cornea, called the stroma, but transgenic mice where both copies of the Col5a1 gene are knocked out fail to develop beyond embryonic day 10-11. However, heterozygotic mice (Col5a1+/-) do survive, with the corneas of these mice having fewer collagen fibrils than their wild-type (WT) littermates.

With the applied experimental techniques, the investigators could assess the strain in the cornea – in other words, how much and how fast the cornea changes in shape and size in response to a force applied to it. The small-dimension extensometry experiments showed differences between the two groups. Compared with WT corneas, heterozygote corneas were 25–30% more likely to rupture during the extensometry experiments – something that is seen in the clinic, where approximately 35% of patients with Ehlers–Danlos syndrome experience corneal ruptures either spontaneously 3 or in response to minimal trauma, a condition termed “oculus fragilis”  4. Furthermore, the corneas became significantly more relaxed after a load was applied. For elastography, the entire experimental set-up was contained in a sealed pressure chamber, and the force applied was a change in chamber pressure. The OCE experiments showed that the heterozygote corneas were significantly thinner than WT corneas, yet able to carry the same amount of axial strain as wild-type corneas. After adjusting for corneal thickness, this meant that the heterozygote corneas had a higher mechanical stiffness than the wild-type corneas. SHG imaging indicated that the heterozygotic corneas displayed “fibril disorganization, increased fibril density and abnormalities in the hierarchical organization”, compared to wild-type corneas.

The study’s first author, Dr. Sabine Kling of the ETH Zurich explained the significance of their work “We have demonstrated that tissues can show a distinct deformation behavior depending on the type and speed a load is applied. Therefore, a single characterisation test could not have provided these insights on the mechanical impact of col5 on corneal tissue as we obtained here.”

Farhad Hafezi, MD PhD states that “our findings provide more insights and might help develop therapeutic approaches in brittle corneas”.

The full text of the article is available to read here: https://rdcu.be/cwlU1

 

References

  1. Hammer A, Kling S, Boldi M-O, et al. Establishing corneal cross-linking with riboflavin and uv-a in the mouse cornea in vivo: biomechanical analysis. Invest Ophthalmol Vis Sci. 56(11):6581-6590 (2015).
  2. Kling S, Torres-Netto EA, Abdshahzadeh H, Espana EM, Hafezi F. Collagen V insufficiency in a mouse model for Ehlers Danlos‑syndrome affects viscoelastic biomechanical properties explaining thin and brittle corneas. Sci Rep 11(1):17362. (2021).
  3. Cameron, J. A. Corneal abnormalities in Ehlers–Danlos syndrome type VI. Cornea 12, 54–59 (1993).

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Thunder Shiviah
14:05 23 Nov 21
After some research on local options I decided to go with ELZA since it stood out as the best. The operation and the... post-operation recovery went extremely smooth (something I was worried about with PRK). Now my vision is much better than I had hoped and I have no side effects such as dry eye or night vision problems. Thank you!read more
Squitieri Elias
Squitieri Elias
12:43 08 Sep 21
Die Behandlungen waren bei mir erfolgreich, alle waren sehr nett und haben mein Leben vereinfacht.Danke
Eliane Bossart
Eliane Bossart
13:01 05 Sep 21
Vor einem Jahr war ich einer ganz verzweifelten Situation und total im Stich gelassen. Meine Augen wurden aufgrund... eines ausgeprägten Kerakotonus immer schlechter, ich hatte Angst und war alleine mit meinen Problemen. Zudem vertrug ich die Kontaktlinsen nur noch ganz schlecht und hatte jeden Tag Schmerzen.Professor Hafezi hat mir mit zwei Operationen wieder das auf Grund der Situation mögliche an Lebensqualität zurückgebracht. Es war ein starpaziöses Jahr mit vielen Entbehrungen aber es hat sich gelohnt! Herzlichen Dank fuer die Unterstützung.read more
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18:32 22 Aug 21
Ich wurde von meiner Optikerin auf Prof. Dr. Dr. Hafezi aufmerksam gemacht. Es war mir vorher nicht bewusst, dass meine... Augenkrankheit (Keratokonus) operativ mittels Cross Linking behandelt und so gestoppt werden kann. Die Beratung und Behandlung war sehr kompetent und ich fühlte mich jederzeit wohl. Die Operation verlief gut und das Ergebnis ist einwandfrei.read more
Naomi
Naomi
11:38 11 Aug 21
Ich bin sehr glücklich, dass ich das Elza Institute gefunden habe. Ich wurde von anderen Augenärzten abgewiesen, da... meine Augen zu kompliziert/schwierig zu behandeln waren. Prof. Dr. Dr. Hafezi konnte mir jedoch helfen und ich bin sehr glücklich und zufrieden mit dem Resultat. Vielen Dank!read more
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08:30 19 Jul 21
Ich habe eine überaus kompetente Beratung und Behandlung erlebt. Die gesamte Betreuung war sehr freundlich und... professionell. Herzlichen Dank!read more
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Thomas S.
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My left eye had to be operated on because of a cataract. As I had an Artiflex lens implanted a few years ago, it had to... be removed first before a modern lens could be implanted to correct the cataract. Prof. Hafezi treated me in an very competent and friendly manner. I am very happy with the result.read more
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Prof. F. Hafezi s expertise is enormous and he has a very pleasant and calm nature which gives the patient... security.Thank youread more
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Totally creepy, very arrogant Prof.He just want your money.It may explain, why this Prof. is not in the center of the... city of Zürich and why he has been thrown away from University of Geneva.read more
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Elena Churilova
10:06 17 Nov 20
At the moment, 3 months have passed since the moment I made laser vision correction in this clinic. and I can say that... I am happy that I chose this particular clinic and Prof. F. Hafezi. The entire staff of the clinic is very friendly, treats patients with sympathy and patience if they are nervous before surgery (my big gratitude to Aida Alili for all support and patience). The doctor Hafezi and other doctors of the clinic are very professional and ready to explain to you as many times as you need. I can only recommend!read more
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