Différentes études cliniques se sont intéressées aux modifications de la cornée chez la femme :
. Changements de l’épaisseur de la cornée pendant la grossesse (Weinreb, 1988).
. Les femmes auraient 13,5 fois plus de risque d’avoir des problèmes de réfraction après PRK si elles prennent un contraceptif oral (Corbett, 1996)
. Après Lasik, les femmes sous un traitement hormonal substitutif (THS ou HRT) auraient un risque plus élevé d’avoir des problèmes cornéens. (O‘Doherty, 2006)
. Les femmes auraient 9 fois plus de risque d’avoir une ectasie cornéenne après Lasik (Randelman, 2003)
En parcourant un CD, je suis tombé sur un Pdf du Pr Spoerl qui est le co-inventeur du traitement du kératocône par cross-linking (CCL).
http://www.keratocone.eu/estrogen.pdf
On sait que la diminution de la rigidité de la cornée est responsable d'ectasies cornéennes. Le Pr Spoerl et son équipe ont conduit une étude afin de savoir si la prise d’oestrogène n’induisait pas des modifications biomécaniques de la cornée responsables d’ectasies ou de kératocônes iatrogènes :
Estrogen-induced changes in biomechanics of the cornea as possible reason for keratectasia. (E. Spoerl, F. Raiskup-Wolf, V. Zubaty Department of Ophthalmology Carl Gustav Carus University Hospital Dresden).
AIM: The risk of regression after PRK and the tendency to develop keratectasia after LASIK procedure is higher in women. Currently interest is focused on the influence of estrogen on corneal stability after corneal refractive surgery. The aim of this experimental study was to investigate the change in biomechanical properties of the cornea induced by estrogen
METHODS: The influence of estrogen was investigated in 12 fresh porcine corneas incubated in culture medium with 10microM of beta-estradiol for 7 days. A group of 12 porcine corneas incubated in culture medium without estradiol for the same time served as a control group. Strips of cornea were cut and the stress-strain was measured in a biomaterial tester. The Young's modulus was calculated.
RESULTS: During incubation the thickness of the cornea changed in the control group by only 6.4% and in the estradiol group by 12%. However, the difference in the biomechanical stress values at 10% strain was significantly larger. In the control group was the stress value measured 120.18 +/- 28.93 kPa and in the estradiol group 76.87 +/- 34.63 kPa (p=0.002), representing a reduction of the corneal stiffness by 36% due to the estradiol treatment.
CONCLUSION: Estrogen is a modulating factor of the biomechanical properties of the cornea which is not explainable only by an increased swelling. The significance of the hormone status of patients and its influence on the biomechanical stability of the cornea, a determining factor after refractive surgery, have been underestimated and may contribute to the development of keratectasia.
Pour son étude, le Pr Spoerl a utilisé du beta-estradiol, estrogène utilisé dans le Diane 35 (Bayer Schering Pharma) qui est indiqué dans le traitement de l’acné. Il est également utilisé en contraceptif. Dans la notice anglo-saxonne ont peut lire ceci :
• Estrogen have been reported to produce keratoconus (steepening of corneal curvature) and intolerance to contact lenses.
• Pharmacology: Cyproterone Acetate--Ethinyl Estradiol. Diane-35 is a combination antiandrogen-estrogen
for use in the treatment of androgen-dependent dermatological conditions in females.
• Indications: For the treatment of women with severe acne, unresponsive to oral antibiotic and other available treatments, with associated symptoms of androgenization, including seborrhea and mild hirsutism.
• Precautions: Ocular Disease: Progressive astigmatic error, possibly leading to keratoconus, has been noted in some myopic women receiving drugs of the estrogen/progestogen class. In women who developed myopia at or near puberty, and in whom myopia stabilized in adult life, estrogen/progestogen combinations after some 6 months of use have increased the refractive error 2- to 3-fold. Women with a family history of myopic astigmatism or keratoconus who are using such therapy may experience rapid advancement of the ocular disorder.
http://www.cbc.ca/consumers/market/file ... update.pdf
A noter que la notice d’utilisation française ne précise pas cette précaution d’emploi, le Vidal non plus :
http://www.bayerscheringpharma.fr/scrip ... iane35.php